Potential of microalgae as a sustainable feed ingredient for aquaculture

An overall study on efficient Cr (VI) adsorbents for improving of the application value of Chlorella pyrenoidosa

Chromium (Cr) is one of the most common pollutants in aquatic ecosystems, posing a serious threat to environmental protection and biological survival. In this study, the adsorbents, prepared from the residue of extracting lipids, polysaccharides and proteins from Chlorella pyrenoidosa, are investigated for effectively purring the Cr (VI)-containing wastewater. The lipid, polysaccharide and protein are identified to having potential for the preparation of biodiesel, food component substitution and feed production, respectively. Meanwhile, Cr (VI) adsorbents are achieved from these extracted residues. The results show that a porous structure with sufficient active functional groups (O-H, pyrrole N, CO, C-O-C, C-O and pyridine N) and remarkable surface area can be well realized. All active functional groups present the effective adsorption performance for removing the Cr (VI) ions from the wastewater due to their active negative adsorption energies, especially -OH and pyrrole N (O-H = -2.86 eV > pyrrole N = -2.80 eV > CO = -2.30 eV > C-O = -2.16 eV > C-O-C = -2.14 eV > pyridine N = -1.87 eV). Under the conditions of high Cr (VI) concentration of 300 mg/L, the amount of absorbent needed for adsorption is reduced from 8 g/L (original algal residue) to 4 g/L (modified biochar). And removal rate of Cr (VI) is dramatically increased from 60.94 % (L), 60.57 % (S) and 46.48 % (P) to 98.99 % (LC800K2), 96.39 % (SC800K2) and 94.73 % (PC800K2). This study provides an achievable approach for the comprehensive utilization of Chlorella pyrenoidosa from extracting valuable biomass to effectively treating Cr (VI)-containing wastewater.

The Fate of Dietary Tryptophan in Fish: Unveiling Its Sources, Transport, Metabolism, and Multifaceted Impacts

The rising need for sustainable protein sources has made aquaculture vital for securing food supply. A balanced protein-rich diet is essential to support the optimal growth, health, and productivity of farmed aquatic species. Tryptophan, an essential amino acid, plays a crucial role in protein synthesis and serves as a precursor for neurotransmitters such as serotonin (5-hydroxytryptamine) and melatonin, which regulate reproduction, appetite, stress, and aggression in fish. The shift toward sustainable feed solutions emphasizes the need for tryptophan supplementation to address the deficiencies in alternative protein sources. Tryptophan supplementation promotes growth by enhancing protein synthesis, muscle development, and nutrient absorption while mitigating stress and inflammation through serotonin and melatonin synthesis. Its antioxidant properties help regulate oxidative stress, protect against environmental damage, and improve fish resilience. Tryptophan also modulates immune functions and reproductive processes, highlighting its multifaceted significance in aquaculture. Tryptophan interacts synergistically with other nutrients to enhance growth and immune responses. However, imbalanced tryptophan levels can impair growth, immune function, and productivity, thus requiring precise dietary formulations. The optimal tryptophan requirement varies among species and target functions. This review aims to highlight the pivotal role of tryptophan in fish health, growth, stress regulation, immune responses, oxidative damage, reproduction, cannibalism and its interaction with other nutrients, demonstrating its potential to further enhance immune function and support metabolic regulation.

Microchloropsis gaditana as a Natural Antimicrobial with a One Health Approach to Food Safety in Farmed Salmon

Sustainably farmed Atlantic salmon could drive global food system solutions by contributing essential nutrients to the human diet while delivering high-quality protein. One of the biggest obstacles to sustainable salmon aquaculture in Chile is the prevalence of piscirickettsiosis disease caused by the Gram-negative bacteria Piscirickettsia salmonis and the excessive amount of antibiotics used to eradicate this disease. Farmed salmon products can be consumed without prior processing and therefore present a substantial risk for the transfer of resistant pathogens to humans. Antibiotics also carry the risk of antibiotic residues and damage to the environment. An alternative to antibiotics is the use of natural antimicrobials without the negative influence on the consumer's microbiome. Here, we evaluate the potential antimicrobial activity against P. salmonis of the marine microalgae Microchloropsis gaditana. A non-genetically modified M. gaditana was grown with nitrogen deprivation to improve the synthesis of the eicosapentaenoic fatty acid (EPA). A spray-dried M. gaditana concentrate (Mg) was elaborated and given to Atlantic salmon for a period of 49 days, and serum and fillet samples were collected. Our results showed a significant increase in the nutritional quality improving the levels of EPA+ Docosapentaenoic acid (DPA) (23%) and Vitamin D3 (106%) of the fillets treated with Mg. Fish fed serum were challenged with P. salmonis, and serum antibacterial activity was measured. Sera from fish fed Mg-enriched diets showed a significant increase in antibacterial activity (85.68%) against P. salmonis. Our results indicate that Mg can be used as a viable alternative to address the critical problem of microbial resistance and to assure consumers that farm-raised Atlantic salmon is safe.

Integrative biomonitoring in Litopenaeus vannamei: Metal analysis and biochemical markers

Contaminants are a major cause of seafood export rejections in foreign markets and have significantly impacted consumer health. This investigation addresses the issues of metal contamination and biochemical markers in Litopenaeus vannamei from East Midnapore, West Bengal, India. The analyzed metals included vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), silver (Ag), gallium (Ga), germanium (Ge), arsenic (As), selenium (Se), strontium (Sr), tin (Sn), cadmium (Cd), mercury (Hg), and lead (Pb), using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Samples were collected from the muscle and hepatopancreas of L. vannamei, as well as from soil sediments and water at 19 sampling sites. The trace element levels detected were within the safety limits recommended by national and international regulatory agencies. A risk assessment, based on the Total Hazard Quotient (THQ) and cancer risk factors, indicated that L. vannamei cultured in this region is safe for human consumption. Additionally, oxidative enzymes such as catalase, superoxide dismutase, and glutathione s-transferase were measured as biomarkers. Other biochemical markers, including lipid peroxidation and acetylcholinesterase activity, were also assessed. Enzymes such as alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and malate dehydrogenase were identified as key biochemical indicators of pollution in this study. In conclusion, the findings suggest that the consumption of L. vannamei from East Midnapore is safe according to FAO/WHO guidelines. The study also highlights the utility of biochemical markers as reliable indicators of pollution in open water systems.

Towards Sustainable Aquafeeds: Microalgal (Nannochloropsis sp. QH25) Co-Product Biomass Can Fully Replace Fishmeal in the Feeds for Rainbow Trout (Oncorhynchus mykiss)

Aquaculture, one of the world's most rapidly growing food sectors, faces several concerns about its sustainability. A major concern is using fishmeal and fish oil from ocean-derived small pelagic fish (sardine, anchovy, etc.) in aquaculture feed. The aquafeed industry is seeking new sustainable ingredients to replace fish meal. This study focused on microalgal co-product, Nannochloropsis sp. QH25 co-product (leftover after oil extraction for nutraceuticals) is a novel aquafeed ingredient that can replace fishmeal in rainbow trout diets. A nutritional feeding experiment was conducted and compared fishmeal-containing rainbow trout diets with microalgal co-products that replaced fishmeal as follows: 0% replacement in reference diet (fishmeal, no microalgal co-product) and test diets with 33%, 66%, and 100% replacement of fishmeal using microalgal-product. Results showed the complete replacement diet yielded fish growth, feed conversion, and survival similar to the reference diet. Depositions of macronutrients, amino acids, fatty acids, macro minerals, and several trace elements in the filet were not significantly different across diets. Economic conversion ratio (ECR) analysis showed that the rainbow trout fed the 100% replacement diet had the lowest feed cost per kg of fish produced. Microalgal co-products can fully replace fishmeal in trout feed while maintaining fish performance, flesh composition, and cost-effectiveness.

Effects of Chlorella protothecoides-derived polydeoxyribonucleotides on skin regeneration and wound healing

The skin acts as a crucial barrier and, upon injury, initiates complex wound-healing processes involving various cell types. Polydeoxyribonucleotides (PDRNs) are well-known for their efficacy in enhancing skin regeneration and wound healing. This study sought to investigate the effectiveness of PDRNs derived from Chlorella protothecoides, a sustainable and scalable microalgal source, in promoting skin regeneration and wound healing. Keratinocytes and fibroblasts were used for assessing the impact of PDRNs on cell proliferation, migration, collagen synthesis, and angiogenesis. Gene expression and associated signaling pathways were also examined using RT-qPCR and Western blot analyses. Our findings demonstrated that PDRNs significantly enhanced the proliferation and migration of skin cells, upregulated growth arrest specific 6 (GAS6) and hepatocyte growth factor (HGF) expression, and increased collagen synthesis by modulating collagen type I alpha 1 (COLIA1) expression. Additionally, PDRNs enhanced angiogenesis by promoting vascular endothelial growth factor (VEGF) expression and activation of ERK, AKT, β-catenin and STAT3 pathways via an adenosine A2A receptor (A2AR)-dependent mechanism. These findings suggest that microalgal-derived PDRNs have significant potential as sustainable and effective agents for clinical and cosmetic applications aimed at improving skin health and wound healing.

Unleashing the power of microalgae: a pioneering path to sustainability and achieving the sustainable development goals

This study explores the remarkable potential of algae in addressing global sustainability challenges. Microalgae, in particular, emerge as sustainability champions. Their applications span an impressive array of industries and processes, including food and feed production, biofuels, cosmetics, pharmaceuticals, and environmental remediation. This versatility positions algae as key players in achieving over 50% of UN Sustainable Development Goals (SDGs) simultaneously, addressing issues such as climate action, clean water and sanitation, affordable and clean energy, and zero hunger. From sequestering carbon, purifying wastewater, and producing clean energy to combating malnutrition, algae demonstrates unparalleled potential. Their ability to flourish in extreme conditions and their rapid growth rates further enhance their appeal for large-scale cultivation. As research advances, innovative applications continue to emerge, such as algae-based bioplastics and dye-sensitized solar cells, promising novel solutions to pressing global issues. This study illuminates how harnessing the power of algae can drive us towards a more resilient, sustainable world. By leveraging algae's multifaceted capabilities, we can tackle climate change, resource scarcity, and economic development concurrently. The research highlights the critical role of algae in promoting circular economy principles and achieving a harmonious balance between human needs and environmental preservation, paving the way for a greener, more sustainable future.

Untapping the potential of algae for β-glucan production: A review of biological properties, strategies for enhanced production and future perspectives

β-Glucan, a naturally occurring polymer of glucose, is found in bacteria, algae, fungi, and higher plants (barley, oats, cereal seeds). Recently, β-glucan has gained attention due to its multiple biological roles, like anticancer, anti-inflammatory, and immunomodulatory effects. Globally, bacteria, mushrooms, yeast and cereals are used as conventional sources of β-glucan. However, obtaining it from these sources is challenging due to low quantity, complex branched structure, and costly extraction process. Algae have emerged as a potential sustainable alternative source of β-glucan to conventional sources due to several advantages including unique structural and functional advantages, higher yields, faster growth rates, and large-scale production in a controlled environment. Additionally, extracting β-glucan from microalgal sources is relatively easy and can be done without altering the structure of β-glucan. Some algal species, such as Euglena spp., are reported to contain higher β-glucan content than conventional β-glucan sources. This review highlights the current research and opportunities associated with algae-derived β-glucan and their biological roles. The challenges, research gaps and strategies to enhance algae-based β-glucan production and the need for further research in this promising area are also discussed. Future research can be extended to comprehend the cellular and molecular mechanisms via which β-glucan functions.

Algal lipids: A review on current status and future prospects in food processing

The consumer demand for functional foods derived from natural sources has been enhanced due to health-promoting effects. Algae are widely available globally as a sustainable source of proteins, lipids, and carbohydrates. Algal lipids are underexplored natural sources that exhibit several nutraceutical effects and applications in fortification, cosmetics, and pharmaceuticals. Both macro- and microalgae are composed of high-quality lipids. These latter involve polar lipids, nonpolar lipids, and essential fatty acids. Therefore, this review aimed to bring out knowledge on the chemistry of various lipids isolated and identified from micro- and macroalgae. Further, their extraction using traditional thermal (solid-liquid, and liquid-liquid) and advanced nonthermal (supercritical fluid, microwave-, ultrasound-, and enzyme-assisted) techniques has been explored. Along with this, bioactivities of algal lipids have been discussed. This study explored algal lipids in advancing sustainable food processing technologies that contribute positively to environmental sustainability and global health, in line with United Nations Sustainable Development GroupUnited Nations Sustainable Development Group UNSDGs.

Microbial diversity and community structure of microalgae (Nannochloropsis oculata) and rotifer (Brachionus plicatilis) in aquaculture by 16S rRNA amplicon-based sequencing

Live cultures, including Nannochloropsis oculata and Brachionus plicatilis, are essential in aquaculture due to its economic and nutritional value for commercial fish species. Pathogens and probiotics can be introduced to aquaculture systems by live feed, with variations in abundance influenced by environmental physicochemical parameters. To investigate this, amplicon sequencing of the V3-V4 region of the 16S rRNA was conducted using Illumina MiSeq to elucidate bacterial abundances and their variations in response to changes in physicochemical parameters in live feed cultures. Results revealed that pathogens like, Tenacibaculum, predominantly found in rotifer cultures, was inhibited under dissolved oxygen levels of 6.87-8.19 mg/L and pH levels of 8.63-9.23. Winogradskyella, mainly present on day 1 of the microalgae culture, thrived under these same conditions. Potential probiotics were also analyzed. Phaeodactylibacter, primarily found on day 1 of microalgae cultures, was favored by dissolved oxygen levels of 7.11-7.68 mg/L and pH levels of 8.63-9.23 but was inhibited by nitrite levels of 0.46-0.5 mg/L. Overall, dissolved oxygen was the key parameter modulating microbial diversity. This study shows that optimizing environmental parameters can enhance culture health by promoting probiotics and reducing harmful bacteria.

Harnessing algal biomass for sustainable energy: cultivation, strain improvement, and biofuel production

The world faces pressing environmental challenges, including greenhouse gas emissions, global warming, climate change, and rising sea levels. Alongside, these issues, the depletion of fossil fuels has intensified the search for alternative energy sources. Algal biomass presents a promising long-term solution to these global problems. The quest for sustainable energy has driven significant research into algal biofuels as a viable alternative to fossil fuels. Algae offers several advantages as a feedstock for biofuel production, including high biomass yield, rapid growth rates, cost-effective cultivation, carbon dioxide fixation capabilities, and the potential to grow on non-arable land using non-potable water. This manuscript provides an overview of algal biomass cultivation using renewable feedstocks, identifies potential algal strains for biofuel production, and explores bioengineering advancements in algae. Additionally, strain improvement strategies to enhance biofuel yields are discussed. The review also addresses large-scale algal biomass cultivation for biofuel production, assesses its commercial viability, examines challenges faced by the biofuel industry, and outlines prospects for biofuel production using highly potent algal strains. By overcoming and addressing these challenges, algal biofuels have the potential to become a cornerstone of sustainable energy solutions.

Transgenic Schizochytrium as a Promising Oral Vaccine Carrier: Potential Application in the Aquaculture Industry

Schizochytrium limacinum SR21, a kind of eukaryotic heterotrophic organism rich in unsaturated fatty acids, is an emerging microbial alternative to fish oil. The dietary inclusion of 15% SR21 was optimal for the growth performance of zebrafish. Previous studies demonstrated that fructose-1,6-bisphosphate aldolase (FBA) of Edwardsiella tarda is a valuable broad-spectrum antigen against various pathogens in aquaculture (e.g., Aeromonas hydrophila, Vibro anguillarum, Vibro harveyi, Vibro alginolyticus). We pioneered the development of stable S. limacinum SR21 transformants expressing the antigen protein FBA, exploring their potential as a novel oral vaccine for the aquaculture industry. The model animal zebrafish (Danio rerio) and ornamental fish koi carp (Cyprinus carpio koi) were harnessed to assess the immunoprotective effect, respectively. According to the quantitative expression analysis, zebrafish fed with recombinant Schizochytrium expressing FBA exhibited specific immune responses in the intestine. The expression levels of MHC-I and MHC-II, involved in cell-mediated adaptive immune responses, were significantly upregulated on the 14th and 28th days post-immunization. Additionally, the expression of highly specialized antibody genes IgZ1 and IgZ2 in mucosal immunity were significantly triggered on the 14th day post-immunization. Feeding koi carp with recombinant S. limacinum SR21-FBA increased the production of myeloperoxidase and FBA-specific antibodies in the sera. Furthermore, the sera of koi fed with recombinant S. limacinum SR21-FBA exhibited significant bactericidal activities against pathogen E. tarda. Thus, S. limacinum SR21 is a natural and highly promising oral vaccine carrier that not only provides essential nutrients as a functional feed ingredient but also offers specific immune protection to aquatic animals. This dual application is vital for promoting the sustainable development of the aquaculture industry.

Light emitting diodes as alternative light source for growth and carotenoid enhancement in Chlorococcum humicola Cultured in airlift photobioreactors

This study compares the performance of white light emitting diodes (LEDs) and fluorescent lamps for cultivating Chlorococcum humicola (C. humicola) as aquaculture feed. Results demonstrate that daylight LEDs are seen to yield the highest biomass concentration at 1,010 ± 11 mg/L, exceeding fluorescent lamps by 36 %. Switching to daylight LEDs increased carotenoid content in algal biomass from 2.97 ± 0.23 to 3.86 ± 0.15 mg/g and carotenoid concentration from 2.21 ± 0.16 to 3.90 ± 0.27 mg/L: increases of 36 % and 76 %, respectively. Blue and daylight LEDs proved to be most effective for lutein induction, with less impact on beta-carotene. Biomass under daylight LEDs shows promising values for protein and lipid contents of 32 % and 11 % dry weight, respectively. Daylight LEDs consumed less than half the energy of fluorescent lamps. Daylight LEDs significantly enhance the growth and carotenoid content of C. humicola, offering a sustainable alternative for aquaculture feed production.

The need for high-resolution gut microbiome characterization to design efficient strategies for sustainable aquaculture production

Microbiome-directed dietary interventions such as microbiota-directed fibers (MDFs) have a proven track record in eliciting responses in beneficial gut microbes and are increasingly being promoted as an effective strategy to improve animal production systems. Here we used initial metataxonomic data on fish gut microbiomes as well as a wealth of a priori mammalian microbiome knowledge on α-mannooligosaccharides (MOS) and β-mannan-derived MDFs to study effects of such feed supplements in Atlantic salmon (Salmo salar) and their impact on its gut microbiome composition and functionalities. Our multi-omic analysis revealed that the investigated MDFs (two α-mannans and an acetylated β-galactoglucomannan), at a dose of 0.2% in the diet, had negligible effects on both host gene expression, and gut microbiome structure and function under the studied conditions. While a subsequent trial using a higher (4%) dietary inclusion of β-mannan significantly shifted the gut microbiome composition, there were still no biologically relevant effects on salmon metabolism and physiology. Only a single Burkholderia-Caballeronia-Paraburkholderia (BCP) population demonstrated consistent and significant abundance shifts across both feeding trials, although with no evidence of β-mannan utilization capabilities or changes in gene transcripts for producing metabolites beneficial to the host. In light of these findings, we revisited our omics data to predict and outline previously unreported and potentially beneficial endogenous lactic acid bacteria that should be targeted with future, conceivably more suitable, MDF strategies for salmon.

Supercritical CO2 extraction increases the recovery levels of omega-3 fatty acids in Tetraselmis chuii extracts

Tetraselmis chuii is a microalgae marketed as ingredient meeting the acceptance criteria for novel foods established by the European Union and can be an important source of healthy fatty acids (FA). The aim of this research was to characterize the FA profile of T. chuii fractions obtained by supercritical carbon dioxide (SCCO2) extraction operating with two sequential co-solvents and to evaluate the effect of biomass pretreatment (freeze/thaw cycles followed by ultrasounds). T. chuii biomass was confirmed to be an important source of omega-3 FA, mainly due to the abundance of α-linolenic acid, and pre-treatment significantly improved the lipid yield. Other omega-3 FA, such as 16:3, 16:4, 18:4, 18:5, 20:3 and 20:5, were also detected in different proportions. When SCCO2 extraction of pretreated and un-pretreated T. chuii was compared with conventional solvent extraction, the nutritional quality indices of the extracts were improved by the use of SCCO2.

Alternative protein sources in aquafeed: Current scenario and future perspectives

Fish meal represents the main protein source for most commercially farmed aquatic species, as it is characterized by high nutritional value and lack of anti-nutritional factors. However, its availability and the market price have been recognized as serious problems at least for over a decade, making it necessary to search for non-conventional protein sources, as an alternative to fish meals. This review aims to comprehensively examine and critically revise the use of fish meal and all alternative protein sources explored to date on the health, welfare, and growth performance of the major aquatic species commercially interesting from a global scenario. The investigation revealed that the inclusion levels of the different protein sources, plant- and animal-derived, ranged from 10 to 80 % and from 2 to 100 % respectively, in partial or complete replacement of fish meal, and generated positive effects on health, welfare, growth performance, and fillet quality. However, the results showed that above a certain level of inclusion, each protein source can negatively affect fish growth performance, metabolic activities, and other biological parameters. Moreover, it is likely that by mixing different protein sources, the combination of each ingredient causes a synergistic effect on the nutritional properties. Therefore, the future of aquatic feed formulation is expected to be based on the blend of different protein sources. Overall, the analysis highlighted the need for additional research in the field of replacing fish meals with new protein sources, given that many knowledge gaps are still to be filled on aquatic species, which deserve to be investigated.

Green microbes: Potential solutions for key sustainable development goals

The latest assessment of progress towards the Sustainable Development Goals (SDGs) has identified major obstacles, such as climate change, global instability and pandemics, which threaten efforts to achieve the SDGs even by 2050. Urgent action is needed, particularly to reduce poverty, hunger and climate change. In this context, microalgae are emerging as a promising solution, particularly in the context of food security and environmental sustainability. As versatile organisms, microalgae offer nutritional benefits such as high-quality proteins and essential fatty acids, and can be cultivated in non-arable areas, reducing competition for resources and improving the sustainability of food systems. The role of microalgae also includes other applications in aquaculture, where they serve as sustainable alternatives to animal feed, and in agriculture, where they act as biofertilizers and biostimulants. These microorganisms also play a key role in interventions on degraded land, stabilizing soils, improving hydrological function and increasing nutrient and carbon availability. Microalgae therefore support several SDGs by promoting sustainable agricultural practices and contributing to land restoration and carbon sequestration efforts. The integration of microalgae in these areas is essential to mitigate environmental impacts and improve global food security, highlighting the need for increased research and development, as well as public and political support, to exploit their full potential to advance the SDGs.

A comprehensive review on versatile microalga Tetraselmis: Potentials applications in wastewater remediation and bulk chemical production

Microalgae are considered sustainable resources for the production of biofuel, feed, and bioactive compounds. Among various microalgal genera, the Tetraselmis genus, containing predominantly marine microalgal species with wide tolerance to salinity and temperature, has a high potential for large-scale commercialization. Until now, Tetraselmis sp. are exploited at smaller levels for aquaculture hatcheries and bivalve production. However, its prolific growth rate leads to promising areal productivity and energy-dense biomass, so it is considered a viable source of third-generation biofuel. Also, microbial pathogens and contaminants are not generally associated with Tetraselmis sp. in outdoor conditions due to faster growth as well as dominance in the culture. Numerous studies revealed that the metabolite compositions of Tetraselmis could be altered favorably by changing the growth conditions, taking advantage of its acclimatization or adaptation ability in different conditions. Furthermore, the biorefinery approach produces multiple fractions that can be successfully upgraded into various value-added products along with biofuel. Overall, Tetraselmis sp. could be considered a potential strain for further algal biorefinery development under the circular bioeconomy framework. In this aspect, this review discusses the recent advancements in the cultivation and harvesting of Tetraselmis sp. for wider application in different sectors. Furthermore, this review highlights the key challenges associated with large-scale cultivation, biomass harvesting, and commercial applications for Tetraselmis sp.

Effects of nitrogen starvation on growth and biochemical composition of some microalgae species

Nitrogen is one of the most important nutrient sources for the growth of microalgae. We studied the effects of nitrogen starvation on the growth responses, biochemical composition, and fatty acid profile of Dunaliella tertiolecta, Phaeodactylum tricornutum, and Nannochloropsis oculata. The lack of nitrogen caused changes in carbohydrate, protein, lipid, and fatty acid composition in all examined microalgae. The carbohydrate content increased 59% in D. tertiolecta, while the lipid level increased 139% in P. tricornutum under nitrogen stress conditions compared to the control groups. Nitrogen starvation increased the oligosaccharide and polysaccharide contents of D. tertiolecta 4.1-fold and 3.6-fold, respectively. Furthermore, triacylglycerol (TAG) levels in N. oculata and P. tricornutum increased 2.3-fold and 7.4-fold, respectively. The dramatic increase in the amount of TAG is important for the use of these microalgae as raw materials in biodiesel. Nitrogen starvation increased the amounts of oligosaccharides and polysaccharides of D. tertiolecta, while increased eicosapentaenoic acid (EPA) in N. oculata and docosahexaenoic acid (DHA) content in P. tricornutum. The amount of polyunsaturated fatty acids (PUFAs), EPA, DHA, oligosaccharides, and polysaccharides in microalgal species can be increased without using the too costly nitrogen source in the culture conditions, which can reduce the most costly of living feeding.

Vitamin Solutions Effects on Reproduction of Broodstock, Growth Performance, and Survival Rate of Pangasius Catfish Fingerlings

This study evaluates the effect of different diets supplemented with vitamin solutions on Pangasius catfish broodstock reproduction, growth performances, and the survival rates of fish larvae and fingerling. The growth and reproductive performances of breeders fed with different test diets showed significant differences among the six tested diets (p < 0.05). The highest final body weight (FBW), weight gain (WG), daily weight gain (DWG), specific growth rate (SGR) of broodstock, and survival rate of Pangasius fingerlings were found in Treatment 5, which contained 0.6% H-OVN mixed with 12.6% algal oil, and Treatment 3, which contained 0.6% vitamin premix H-OVN. The average gonadosomatic index (GSI), relative fecundity index (RFI), fertilized eggs, hatching rates of eggs, and survival rate of fingerlings was 9.1 ± 2.8 (6.7-12.8%), 133,224 ± 39,090 (104,267-199,512 eggs/kg), 77.9 ± 22.2 (62.2-93.6%), and 45.3 ± 17.4 (22.0-66.3%), respectively. The findings of this study showed that the diet containing 35% CP contents supplemented with 0.6% vitamin premix H-OVN mixed with algal oils showed the highest results in terms of growth, reproductive performance indices, and survival rates of Pangasius catfish fingerlings.

Towards cleaner environment: recycling microalgal co-product to reduce emissions and impacts while eliminating fishmeal in rainbow trout feed for sustainable aquaculture

The rapid increase in aquaculture over the last several decades has led to concerns about the environmental impact of fish feeds relying on marine resources for fishmeal (FM). We aim to assess Nannochloropsis sp. QH25 co-product as a viable and sustainable replacement for FM in juvenile rainbow trout, Oncorhynchus mykiss, feeds. We formulated four experimental diets: a reference (FM based), 33N, 66N, and 100N diet (33%, 66%, and 100% co-product replacement). Rainbow trout were randomly assigned to one of 16 tanks and randomly assigned an experimental diet to consume throughout the experiment (64 days total), with four replicate tanks per diet. We compared the phosphorus (P) and nitrogen (N) digestibility, emissions, and growth between diets and, compared six environmental impacts (biotic resource use (BRU), global warming potential (GWP), water use, land use, marine eutrophication potential (MEP), and freshwater eutrophication potential (FEP)) of each diet. Our results indicate that replacing FM with co-product did not significantly alter growth. P digestibility of the experimental and reference diets was comparable. BRU conversion ratio was significantly lower in the experimental diets. However, there were significantly higher water and land use conversion ratios but insignificantly higher results in GWP, MEP, and FEP between the reference and 100N diet.

Modulation of gut microbiota composition and predicted metabolic capacity after nutritional programming with a plant-rich diet in Atlantic salmon (Salmo salar): insights across developmental stages

To promote sustainable aquaculture, the formulation of Atlantic salmon (Salmo salar) feeds has changed in recent decades, focusing on replacing standard marine-based ingredients with plant-based alternatives, increasingly demonstrating successful outcomes in terms of fish performance. However, little is known about how these plant-based diets may impact the gut microbiota at first feeding and onwards. Nutritional programming (NP) is one strategy applied for exposing fish to a plant-based (V) diet at an early stage in life to promote full utilisation of plant-based ingredients and prevent potential adverse impacts of exposure to a plant-rich diet later in life. We investigated the impact of NP on gut microbiota by introducing fish to plant ingredients (V fish) during first feeding for a brief period of two weeks (stimulus phase) and compared those to fish fed a marine-based diet (M fish). Results demonstrated that V fish not only maintained growth performance at 16 (intermediate phase) and 22 (challenge phase) weeks post first feeding (wpff) when compared to M fish but also modulated gut microbiota. PERMANOVA general effects revealed gut microbiota dissimilarity by fish group (V vs. M fish) and phases (stimulus vs. intermediate vs. challenge). However, no interaction effect of both groups and phases was demonstrated, suggesting a sustained impact of V diet (nutritional history) on fish across time points/phases. Moreover, the V diet exerted a significant cumulative modulatory effect on the Atlantic salmon gut microbiota at 16 wpff that was not demonstrated at two wpff, although both fish groups were fed the M diet at 16 wpff. The nutritional history/dietary regime is the main NP influencing factor, whereas environmental and host factors significantly impacted microbiota composition in M fish. Microbial metabolic reactions of amino acid metabolism were higher in M fish when compared to V fish at two wpff suggesting microbiota played a role in digesting the essential amino acids of M feed. The excessive mucin O-degradation revealed in V fish at two wpff was mitigated in later life stages after NP, suggesting physiological adaptability and tolerance to V diet. Future studies are required to explore more fully how the microbiota functionally contributes to the NP.

Eco-friendly and safe alternatives for the valorization of shrimp farming waste

The seafood industry generates waste, including shells, bones, intestines, and wastewater. The discards are nutrient-rich, containing varying concentrations of carotenoids, proteins, chitin, and other minerals. Thus, it is imperative to subject seafood waste, including shrimp waste (SW), to secondary processing and valorization for demineralization and deproteination to retrieve industrially essential compounds. Although several chemical processes are available for SW processing, most of them are inherently ecotoxic. Bioconversion of SW is cost-effective, ecofriendly, and safe. Microbial fermentation and the action of exogenous enzymes are among the significant SW bioconversion processes that transform seafood waste into valuable products. SW is a potential raw material for agrochemicals, microbial culture media, adsorbents, therapeutics, nutraceuticals, and bio-nanomaterials. This review comprehensively elucidates the valorization approaches of SW, addressing the drawbacks of chemically mediated methods for SW treatments. It is a broad overview of the applications associated with nutrient-rich SW, besides highlighting the role of major shrimp-producing countries in exploring SW to achieve safe, ecofriendly, and efficient bio-products.

Data on growth performance and nutritional composition of common carp (Cyprinus carpio) fry fed with Chlamydomonas sp

A feeding trial spanning two months was conducted to evaluate the effects of Chlamydomonas sp. on growth performance, water quality, survival, proximate composition and biochemical profile of common carp (Cyprinus carpio) where fishmeal was partially replaced using Chlamydomonas sp. in the diet. Twenty uniform-sized common carp fries were distributed into triplicate groups and placed in 40-liter rectangular glass tanks. Chlamydomonas sp. was added at different levels in the diet: 0 % (control), 5 % (C5), 10 % (C10), 15 % (C15) along with the commercial feed (CMF). After the experiment, random sampling of fish was performed to conduct all the analyses. Significant variations (p < 0.05) were found in the chemical water quality parameters. The highest survival rate was recorded from C15 (81.67 %) followed by C10 (71.67 %), CMF (63.33 %) and C5 (58.33 %) respectively compared with the control (43.2 %). There were significant differences (p < 0.05) observed among all the treatments in terms of Average Daily Gains (ADG), Specific Growth Rate (SGR) and length increments. Protein content ranged the highest and the lowest in C15 (35.6 %) and control (24.8 %) respectively. The C15 group showed the highest lipid content (15.7 %) and the control group showed the lowest lipid (8.4 %). The inclusion of Chlamydomonas sp. in the diet had a significant positive impact on the fatty acid and amino acid profile of whole common carp. Present data revealed that substituting a portion of fishmeal with Chlamydomonas sp. powder could provide higher growth performance, offering both nutritional benefits and higher survival rate in common carp (Cyprinus carpio).

Recovery of nutrients from fish sludge to enhance the growth of microalga Chlorella sorokiniana CMBB276

Intensive aquaculture production generates large amounts of sludge. This waste could be considered as a potential source of nutrients that can be recovered and utilized. Little attention has been paid to nutrient recovery from fish sludge. In this study, bioconversion of sludge was evaluated in lab scale under anaerobic (AN), facultative anaerobic (FA) and aerobic (AE) conditions. After 40 days of fermentation, AN recovered the highest values of dissolved total nitrogen (82.7 mg L-1), while AE showed the highest dissolved total phosphorus (11.8 mg L-1) and the highest reduction of total suspended solids (36.0 %). Microbial analysis showed that AN exhibited a distinct bacterial community than that of FA and AE. Furthermore, C. sorokiniana grown in AN effluents collected after 12 days of fermentation achieved the highest biomass production (1.96 g L-1). These results suggest that AN has the best potential to recover nutrients from sludge for production of C. sorokiniana.

Sustainable microalgal biomass as a potential functional food and its applications in food industry: a comprehensive review

Microalgae (MA) are the most abundant seaweeds with high nutritional properties. They are accepted as potential biocatalysts for the bioremediation of wastewater. They are widely used in food, feed, and biofuel industries and can potentially be food for future generations. MA-based purification of wastewater technology could be a universal alternative solution for the recovery of resources from wastewater for low-cost biomass feedstock for industry. They provide a wide range of functional components, viz. omega-3 fatty acids, along with a plenteous number of pigments such as ß-carotene, astaxanthin, lutein, phycocyanin, and chlorophyll, which are used extensively as food additives and nutraceuticals. Further, proteins, lipids, vitamins, and carbohydrates are described as nutritional characteristics in MA. They are investigated as single-cell protein, thickening/stabilizing agents, and pigment sources in the food industry. The review emphasizes the production and extraction of nutritional and functional components of algal biomass and the role of microalgal polysaccharides in digestion and nutritional absorption in the gastrointestinal tract. Further, the use of MA in the food industry was also investigated along with their potential therapeutic applications.

Life cycle assessment on environmental feasibility of microalgae-based wastewater treatment for shrimp recirculating aquaculture systems

This life cycle assessment (LCA) study analyzed the environmental consequences of integrating microalgae-based wastewater treatment into a shrimp farm with recirculating aquaculture systems (RAS). Microalgae treatment produced <10 % of the system's freshwater eutrophication potential (FEP), marine eutrophication potential (MEP) and global warming potential, which was dominantly contributed by electricity use. Microalgae treatment performed comparably to activated sludge treatment for FEP reduction, and was more effective in remediating marine eutrophication. Replacing coal in electricity mix, particularly with renewables, reduced the system's impacts by up to 90-99 %. Performing the LCA based on system expansion generally obtained higher impacts compared to allocation. Utilizing algal biomass for biogas production reduced the MEP; however, production of feed ingredient and biodiesel were not environmentally beneficial. This study proved the use of microalgae for aquaculture wastewater treatment to be environmentally feasible, the results can guide more sustainable RAS operations and design of full-scale microalgae treatment.

A Holistic Approach to Circular Bioeconomy Through the Sustainable Utilization of Microalgal Biomass for Biofuel and Other Value-Added Products

Emissions from transportation and industry primarily cause global warming, leading to floods, glacier melt, and rising seas. Widespread greenhouse gas emissions and resulting global warming pose significant risks to the environment, economy, and society. The need for alternative fuels drives the development of third-generation feedstocks: microalgae, seaweed, and cyanobacteria. These microalgae offer traits like rapid growth, high lipid content, non-competition with human food, and growth on non-arable land using brackish or waste water, making them promising for biofuel. These unique phototrophic organisms use sunlight, water, and carbon dioxide (CO2) to produce biofuels, biochemicals, and more. This review delves into the realm of microalgal biofuels, exploring contemporary methodologies employed for lipid extraction, significant value-added products, and the challenges inherent in their commercial-scale production. While the cost of microalgae bioproducts remains high, utilizing wastewater nutrients for cultivation could substantially cut production costs. Furthermore, this review summarizes the significance of biocircular economy approaches, which encompass the utilization of microalgal biomass as a feed supplement and biofertilizer, and biosorption of heavy metals and dyes. Besides, the discussion extends to the in-depth analysis and future prospects on the commercial potential of biofuel within the context of sustainable development. An economically efficient microalgae biorefinery should prioritize affordable nutrient inputs, efficient harvesting techniques, and the generation of valuable by-products.

An ex vivo Approach in European Seabass Leucocytes Supports the in vitro Regulation by Postbiotics of Aip56 Gene Expression of Photobacterium damselae subsp. piscicida

Shewanella putrefaciens Pdp11 (SpPdp11) is a probiotic strain assayed in aquaculture; however, its postbiotic potential is unknown. Postbiotics are bacterial metabolites, including extracellular products (ECPs) that improve host physiology and immunity. Their production and composition can be affected by different factors such as the growing conditions of the probiotics. Photobacterium damselae subsp. piscicida strain Lg 41/01 (Phdp) is one of the most important pathogens in marine aquaculture. The major virulent factor of this bacterium is the exotoxin aip56, responsible for inducing apoptosis of fish leucocytes. Viable SpPdp11 cells have been reported to increase resistance to challenges with Phdp. This work aimed to evaluate the effect of two ECPs, T2348-ECP and FM1548-ECP, obtained from SpPdp11 grown under different culture conditions that previously demonstrated to exert different degradative and non-cytotoxic activities, as well as the effect on pathogens biofilm formation. These SpPdp11-ECPs were then analyzed by their effect on the viability, phagocytosis, respiratory burst and apoptogenic activity against European sea bass leucocytes infected or not with Phdp supernatant. Both ECPs, T2348-ECP and FM1548-ECP, were not cytotoxic against leucocytes and significantly reduced their apoptosis. Phagocytosis and respiratory burst of leucocytes were significantly reduced by incubation with Phdp supernatant, and not influenced by incubation with T2348-ECP or FM1548-ECP. However, both activities were significantly increased after leucocyte incubation with combined T2348-ECP and FM1548-ECP with Phdp supernatant, compared to those incubated only with Phdp supernatant. Finally, both T2348-ECP and FM1548-ECP significantly reduced the relative in vitro expression of the Phdp aip56 encoding gene.

Screening of Microalgae for Bioactivity with Antiviral, Antibacterial, Anti-Inflammatory and Anti-Cancer Assays

Marine microalgae are a rich reservoir of natural compounds, including bioactives. Nonetheless, these organisms remain fairly unexplored despite their potential biotechnological applications. Culture collections with diverse taxonomic groups and lifestyles are a good source to unlock this potential and discover new molecules for multiple applications such as the treatment of human pathologies or the production of aquaculture species. In the present work extracts from thirty-three strains (including twenty dinoflagellates, four diatoms and nine strains from seven other algal classes), cultivated under identical conditions, were examined for their antiviral, antibacterial, anti-inflammatory and anti-cancer activities. Among these, antiviral and anti-inflammatory activities were detected in a few strains while the antibacterial tests showed positive results in most assays. In turn, most trials did not show any anti-cancer activity. Significant differences were observed between species within the same class, in particular dinoflagellates, which were better represented in this study. These preliminary findings pave the way for an in-depth characterization of the extracts with highest signals in each test, the identification of the compounds responsible for the biological activities found and a further screening of the CCVIEO culture collection.

Unlocking the potential of forage fish to reduce the global burden of disease

Red meat consumption is associated with an elevated risk of mortality from non-communicable diseases (NCDs). In contrast, forage fish, as highly nutritious, environmentally friendly, affordable, and the most abundant fish species in the ocean, are receiving increasing interest from a global food system perspective. However, little research has examined the impact of replacing red meat with forage fish in the global diet on diet-related NCDs.

METHODS

We based our study on datasets of red meat projections in 2050 for 137 countries and forage fish catches. We replaced the red meat consumption in each country with forage fish (from marine habitats), without exceeding the potential supply of forage fish. We used a comparative risk assessment framework to investigate how such substitutions could reduce the global burden of diet-related NCDs in adults.

RESULTS

The results of our study show that forage fish may replace only a fraction (approximately 8%) of the world's red meat due to its limited supply, but it may increase global daily per capita fish consumption close to the recommended level. Such a substitution could avoid 0.5-0.75 million deaths and 8-15 million disability-adjusted life years, concentrated in low- and middle-income countries. Forage fish as an alternative to red meat could double (or more) the number of deaths that could be avoided by simply reducing red meat consumption.

CONCLUSIONS

Our analysis suggests that forage fish is a promising alternative to red meat. Policies targeting the allocation of forage fish to regions where they are needed, such as the Global South, could be more effective in maximising the potential of forage fish to reduce the global burden of disease.

Microalgae as fishmeal alternatives in aquaculture: current status, existing problems, and possible solutions

Fishmeal is an indispensable ingredient for most aquatic animals. However, the finite supply and escalating price of fishmeal seriously limit its use in aquaculture. Thus the development of new, sustainable protein ingredients has been a research focus. Microalgae are potential fishmeal alternatives owing to their high protein content and balanced amino acid profile. Studies suggest that suitable replacement of fishmeal with microalgae is beneficial for fish growth performance, but excessive replacement would induce poor growth and feed utilization. Therefore, this paper aims to review research on the maximum substitutional level of fishmeal by microalgae and propose the main issues and possible solutions for fishmeal replacement by microalgae. The maximum replacement level is affected by microalgal species, fish feeding habits, quality of fishmeal and microalgal meals, and supplemental levels of fishmeal in the control group. Microalgae could generally replace 100%, 95%, 95%, 64.1%, 25.6%, and 18.6% fishmeal protein in diets of carp, shrimp, catfish, tilapia, marine fish, and salmon and trout, respectively. The main issues with fishmeal replacement using microalgae include low production and high production cost, poor digestibility, and anti-nutritional factors. Possible solutions to these problems are recommended in this paper. Overall, microalgae are promising fishmeal alternatives in aquaculture.

Features of the microalga Raphidocelis subcapitata: physiology and applications

The microalga Raphidocelis subcapitata was isolated from the Nitelva River (Norway) and subsequently deposited in the collection of the Norwegian Institute of Water Research as "Selenastrum capricornutum Printz". This freshwater microalga, also known as Pseudokirchneriella subcapitata, acquired much of its notoriety due to its high sensitivity to different chemical species, which makes it recommended by different international organizations for the assessment of ecotoxicity. However, outside this scope, R. subcapitata continues to be little explored. This review aims to shed light on a microalga that, despite its popularity, continues to be an "illustrious" unknown in many ways. Therefore, R. subcapitata taxonomy, phylogeny, shape, size/biovolume, cell ultra-structure, and reproduction are reviewed. The nutritional and cultural conditions, chronological aging, and maintenance and preservation of the alga are summarized and critically discussed. Applications of R. subcapitata, such as its use in aquatic toxicology (ecotoxicity assessment and elucidation of adverse toxic outcome pathways) are presented. Furthermore, the latest advances in the use of this alga in biotechnology, namely in the bioremediation of effluents and the production of value-added biomolecules and biofuels, are highlighted. To end, a perspective regarding the future exploitation of R. subcapitata potentialities, in a modern concept of biorefinery, is outlined. KEY POINTS: • An overview of alga phylogeny and physiology is critically reviewed. • Advances in alga nutrition, cultural conditions, and chronological aging are presented. • Its use in aquatic toxicology and biotechnology is highlighted.

Role of Algal-derived Bioactive Compounds in Human Health

Algae is emerging as a bioresource with high biological potential. Various algal strains have been used in traditional medicines and human diets worldwide. They are a rich source of bioactive compounds like ascorbic acid, riboflavin, pantothenate, biotin, folic acid, nicotinic acid, phycocyanins, gamma-linolenic acid (GLA), adrenic acid (ARA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), etc. Beta-carotene, astaxanthin, and phycobiliproteins are different classes of pigments that are found in algae. They possess antioxidant, anti-inflammatory and anticancer properties. The sulfur-coated polysaccharides in algae have been used as an anticancer, antibacterial, and antiviral agent. Scientists have exploited algal-derived bioactive compounds for developing lead molecules against several diseases. Due to the surge in research on bioactive molecules from algae, industries have started showing interest in patenting for the large-scale production of bioactive compounds having applications in sectors like pharmaceuticals, food, and beverage. In the food industry, algae are used as a thickening, gelling, and stabilizing agent. Due to their gelling and thickening characteristics, the most valuable algae products are macroalgal polysaccharides such as agar, alginates, and carrageenan. The high protein, lipid, and nutrient content in microalgae makes it a superfood for aquaculture. The present review aims at describing various non-energy-based applications of algae in pharmaceuticals, food and beverage, cosmetics, and nutraceuticals. This review attempts to analyze information on algal-derived drugs that have shown better potential and reached clinical trials.

Decreasing resilience of China's coupled nitrogen-phosphorus cycling network requires urgent action

The coupled nature of the nitrogen (N) and phosphorus (P) cycling networks is of critical importance for sustainable food systems. Here we use material flow and ecological network analysis methods to map the N-P-coupled cycling network in China and evaluate its resilience. Results show a drop in resilience between 1980 and 2020, with further decreases expected by 2060 across different socio-economic pathways. Under a clean energy scenario with additional N and P demand, the resilience of the N-P-coupled cycling network would suffer considerably, especially in the N layer. China's socio-economic system may also see greater N emissions to the environment, thus disturbing the N cycle and amplifying the conflict between energy and food systems given the scarcity of P. Our findings on scenario-specific synergies and trade-offs can aid the management of N- and P-cycling networks in China by reducing chemical fertilizer use and food waste, for example.

Economic analysis of global microalgae biomass energy potential

With the increasing demand for renewable energy, microalgae, as a renewable biomass energy, can fix carbon dioxide and have broad application prospects in alleviating the energy crisis and improving the environment. In this paper, the potential biomass of global microalgae is calculated based on the mathematical growth model of microalgae proposed by predecessors. Based on this, this study further uses Newton's gravity model as the basic model of economic analysis and calculates the economic potential coefficient of microalgae production in various regions of the world by using the data of the world's top 20 cities in terms of urban population and urban GDP in 2020. The study has obtained the current global unused land with the high economic value of large-scale microalgae production areas, such as western North America, northern Africa, and northwest China, etc., which can provide guidance for the future site selection and development of microalgae biomass energy.

The proximate composition, amino acid profile, fatty acid content, and mineral content of scale flour from three fish species as potential feeds for fish fry

BACKGROUND

Fish scale waste is highly valued both as a functional food ingredient and a potential feed source for farmed fish. This study aimed to analyse the chemical composition, fatty acid profile, and mineral content in fish scale flour of Osphronemus (O) goramy, Cyprinus (C) carpio, and Oreochromis (O) niloticus as potential feed for fish fry.

METHODS

Fish scales were cleaned with 10% w/v NaCl solution at a ratio of 1:10 (w/w) for 24 hours at 4 °C. Agitation was used every eight hours to remove excess protein. Fish scales were evenly arranged in a cooker and cooked at 121 °C for 10 minutes with 15 psi pressure. After cooking, 100 grams of wet fish scales was dried at 50 °C for four hours. Dried fish scales were transformed into flour for proximate composition analysed via standard AOAC method, amino acid and fatty acid assessment employing HPLC and GC-MS, while mineral content was determined using AAS.

RESULTS

The examined fish scale flour from three species displayed significant variations in chemical components, amino acids, and minerals (p<0.01). Crude protein content spanned 49.52% to 72.94%, and fat content ranged from 0.11% to 0.23%. Magnesium levels varied between 767.82 mg/kg and 816.50 mg/kg, calcium content ranged from 3.54 mg/kg to 12.16 mg/kg, iron content was within 40.46 mg/kg to 44.10 mg/kg, and zinc content ranged from 45.80 mg/kg to 139.19 mg/kg. Predominantly, glycine emerged as the main free amino acid (FAA), varying from 13.70% to 16.08%, while histidine had the lowest content, at 0.39% to 0.71%. Conversely, fatty acid content was low in all species examined ranging from 6.73% to 9.48%.

CONCLUSIONS

Flour from three farmed fish types has potential for fish fry feed due to its chemical composition, amino acid, and mineral content. Further validation is needed for amino acid comparison to fish meal.

The proximate composition, amino acid profile, fatty acid content, and mineral content of scale flour from three fish species as potential feeds for fish fry

Background

Fish scale waste is highly valued both as a functional food ingredient and a potential feed source for farmed fish. This study aimed to analyse the chemical composition, fatty acid profile, and mineral content in fish scale flour of Osphronemus (O) goramy, Cyprinus (C) carpio, and Oreochromis (O) niloticus as potential feed for fish fry.

Methods

Fish scales were cleaned with 10% w/v NaCl solution at a ratio of 1:10 (w/w) for 24 hours at 4 °C. Agitation was used every eight hours to remove excess protein. Fish scales were evenly arranged in a cooker and cooked at 121 °C for 10 minutes with 15 psi pressure. After cooking, 100 grams of wet fish scales was dried at 50 °C for four hours. Dried fish scales were transformed into flour for proximate composition analysed via standard AOAC method, amino acid and fatty acid assessment employing HPLC and GC-MS, while mineral content was determined using AAS.

Results

The examined fish scale flour from three species displayed significant variations in chemical components, amino acids, and minerals (p<0.01). Crude protein content spanned 49.52% to 72.94%, and fat content ranged from 0.11% to 0.23%. Magnesium levels varied between 767.82 mg/kg and 816.50 mg/kg, calcium content ranged from 3.54 mg/kg to 12.16 mg/kg, iron content was within 40.46 mg/kg to 44.10 mg/kg, and zinc content ranged from 45.80 mg/kg to 139.19 mg/kg. Predominantly, glycine emerged as the main free amino acid (FAA), varying from 13.70% to 16.08%, while histidine had the lowest content, at 0.39% to 0.71%. Conversely, fatty acid content was low in all species examined ranging from 6.73% to 9.48%.

Conclusions

Flour from three farmed fish types has potential for fish fry feed due to its chemical composition, amino acid, and mineral content. Further validation is needed for amino acid comparison to fish meal.

Effects of microalgae as dietary supplement on palatability, digestibility, fecal metabolites, and microbiota in healthy dogs

The current trend of dog owners increasingly favoring the functional value of food to assure preventive health and wellbeing of their pets has been raising the interest in microalgae as natural additives with bioactive properties. However, scientific studies addressing the effects of microalgae supplementation in diets for dogs are scarce. This study aimed to evaluate the effects of dietary supplementation with three microalgae species (Chlorella vulgaris, Nannochloropsis oceanica, and Tetradesmus obliquus) on diet palatability, total tract digestibility, metabolizable energy content, fecal metabolites and microbiota of dogs. Twelve adult Beagle dogs were used in three two-bowl tests to compare the palatability of a commercial complete diet for adult dogs without (reference diet) and with 1.5% supplementation of each microalgae. From the results obtained, three digestibility trials were performed according to a replicated Latin square 3 × 3, with six adult Beagle dogs, three experimental periods of 10 days each, and three dietary supplementation levels of microalgae (0.5, 1.0, and 1.5%). In each trial, effects of microalgae supplementation levels on total tract digestibility, metabolizable energy content, fecal metabolites and microbiota of dogs were evaluated. First diet approached or tasted was not significantly affected by microalgae inclusion, but dogs showed a preference for the reference diet over the diets with 1.5% inclusion of C. vulgaris and N. oceanica, no difference being observed with 1.5% T. obliquus. In all digestibility trials, dietary supplementation with microalgae up to 1.5% did not greatly affected the dietary chemical composition and kept unaffected food intake, fecal output and metabolites, and digestibility of nutrients and energy. Compared with the reference diet, supplementation with C. vulgaris increased protein digestibility. Fecal characteristics and metabolites were affected by microalgae supplementation, being the effects dependent on the species. Fecal microbiota composition of dogs fed with microalgae-supplemented diets was modified by promoting the beneficial Turicibacter and Peptococcus genera associated with gut health and activation of the immune system. Overall, the results support C. vulgaris, N. oceanica, and T. obliquus as sustainable functional supplements that potentially enhance gastrointestinal health of dogs through the selective stimulation of microbiota without detrimental effects on food intake and digestibility.

Effect of feed enriched by products formulated from coconut water, palm sap sugar, and mushroom on the chemical composition of feed and carcass, growth performance, body indices, and gut micromorphology of giant gourami, Osphronemus goramy (Lacepède, 1801), juveniles

Background: Giant gourami, Osphronemus goramy is the most important freshwater fish species produced by aquaculture in Indonesia. This study aimed to the effects of various newly formulated products on the amino acid composition of the diet and whole-body carcass, and to analyse the growth coefficient, body indices, and gut micromorphology. Methods: One hundred gram of palm sap sugar was cooked in 1.1 litre of fresh water for fifteen minutes, to create 1 litre of 11% palm sap sugar solution (after some of it had been boiled off). Two litres of coconut water were then mixed with the litre of palm sugar solution. One litre of this product was added in turn to 2 g of Aspergillus niger (CP2), 2 g of Rhizopus oligosporus (CP3), and 2 g of Saccharomyces cerevisiae (CP4), while freshwater was used as a control (labeled CP1). Aquafeed was added to CP1, CP2, CP3, and CP4, to make diets labeled KP1, KP2, KP3, and KP4. The dosage was 150 ml/kg of feed. Juvenile giant gourami (initial weight 50±0.25 g and length 13.2±0.07 cm) were reared in triplicate net frames (2×1×1 m; water volume 1.5 m 3) in a freshwater concrete pond with a stocking density of 30 juveniles/net. Results: The results supported our hypothesis that different product formulations have a significant effect (P < 0.05) on aquafeed nutrition and the whole-body carcass, growth coefficient, feed utilization, body indices, and gut micromorphology of giant gourami juveniles. The thermal growth coefficient strongly correlated with the daily growth coefficient (r 2 = 92%), condition factor (r 2 = 77%), protein efficiency ratio (r 2 = 75%), while a moderate relationship with the feed intake ( r 2 = 69%). Conclusions: Diet KP3 contains higher total amino acids in diets and carcasses and leads to feed efficiency and better growth for giant gourami.

Effect of feed enriched by products formulated from coconut water, palm sap sugar, and mushroom on the chemical composition of feed and carcass, growth performance, body indices, and gut micromorphology of giant gourami, Osphronemus goramy (Lacepède, 1801), juveniles

Background: Giant gourami, Osphronemus goramy is the most important freshwater fish species produced by aquaculture in Indonesia. This study aimed to the effects of various newly formulated products on the amino acid composition of the diet and whole-body carcass, and to analyse the growth coefficient, body indices, and gut micromorphology. Methods: One hundred gram of palm sap sugar was cooked in 1.1 litre of fresh water for fifteen minutes, to create 1 litre of 11% palm sap sugar solution (after some of it had been boiled off). Two litres of coconut water were then mixed with the litre of palm sugar solution. One litre of this product was added in turn to 2 g of Aspergillus niger (CP2), 2 g of Rhizopus oligosporus (CP3), and 2 g of Saccharomyces cerevisiae (CP4), while freshwater was used as a control (labeled CP1). Aquafeed was added to CP1, CP2, CP3, and CP4, to make diets labeled KP1, KP2, KP3, and KP4. The dosage was 150 ml/kg of feed. Juvenile giant gourami (initial weight 50±0.25 g and length 13.2±0.07 cm) were reared in triplicate net frames (2×1×1 m; water volume 1.5 m 3) in a freshwater concrete pond with a stocking density of 30 juveniles/net. Results: The results supported our hypothesis that different product formulations have a significant effect (P < 0.05) on aquafeed nutrition and the whole-body carcass, growth coefficient, feed utilization, body indices, and gut micromorphology of giant gourami juveniles. The thermal growth coefficient strongly correlated with the daily growth coefficient (r 2 = 92%), condition factor (r 2 = 77%), protein efficiency ratio (r 2 = 75%), while a moderate relationship with the feed intake ( r 2 = 69%). Conclusions: Diet KP3 contains higher total amino acids in diets and carcasses and leads to feed efficiency and better growth for giant gourami.

The Gill-Associated Bacterial Community Is More Affected by Exogenous Chlorella pyrenoidosa Addition than the Bacterial Communities of Water and Fish Gut in GIFT Tilapia (Oreochromis niloticus) Aquaculture System

Microalgae has been widely used in aquaculture to improve both the water environment and fish growth; however, the current understanding of the effects of microalgae addition on the key players involved in regulating the water environment and fish health, such as microorganisms, remains limited. Here, a 50-day mesocosm experiment was set up to simulate the culture of Genetic Improvement of Farmed Tilapia (GIFT, Oreochromis niloticus) with an average weight of 14.18 ± 0.93 g and an average length of 82.77 ± 2.80 mm. Different amounts of Chlorella pyrenoidosa were added into these artificial systems to investigate dynamics of bacterial communities in aquaculture water, fish gill, and gut using amplicon-based high-throughput sequencing technology. Our results showed that Chlorella pyrenoidosa addition increased diversity and network complexity of gill-associated bacterial communities rather than those of the water and gut. Furthermore, more biomarkers in the gill-associated bacterial communities were detected in response to Chlorella pyrenoidosa addition than the water and fish gut samples. These findings highlighted the high sensitivity of gill-associated bacterial communities in response to the Chlorella pyrenoidosa addition, implying Chlorella pyrenoidosa addition could play important roles in regulating the fish mucosal immunity by altering the gill-associated microbiota.

Effect of dietary inclusion of microalgae (Nannochloropsis gaditana and Schizochytrium spp) on non-specific immunity and erythrocyte maturity in Atlantic salmon fingerlings

The parr-smolt transformation in salmonids involves a critical period characterized by systemic changes associated with the fish's immune response. In this context, as a dietary ingredient in functional diets, microalgae offer an alternative due to their nutritional and bioactive compounds that could strengthen the immune status. This study evaluated the effect of a diet supplemented with Schizochytrium spp and Nannochloropsis gaditana on the expression of genes associated with the antibacterial response. Additionally, the study assessed the effect on the leukocyte population and erythrocyte maturity in Salmo salar blood. Fish were fed for 30 days with a microalgal mixture (1:1) at a 10% inclusion. Each diet was randomly assigned to a tank using a completely randomized design (CRD) with four replications. Each tank was stocked with 70 Atlantic salmon fingerlings with an initial mean weight of 78.87 ± 0.84. Transcription levels were quantified and analyzed by qRT-PCR from cell isolates and mucus tissue. Furthermore, cell count and identification of leukocytes and classification of cellular maturity of erythrocytes using a neural network with a multilayer perceptron (MLP) were performed. Our results showed a significant (p < 0.05) increase in fold change expression of C3 (2.54 ± 0.65) and NK-Lysine (6.84 ± 0.94) in erythrocytes of microalgae-supplemented fish. Moreover, a significant increase of 1.59 and 2.35 times in monocytes and immature erythrocytes, respectively, was observed in the same group of fish (p < 0.05). This study's results indicate that dual microalgae (Schizochytrium spp and N. gaditana) supplementation can increase innate humoral antibacterial components, particularly in erythrocyte tissue, and increase phagocytic cells and immature erythrocytes in S. salar blood.

Identification of Marine Biotechnology Value Chains with High Potential in the Northern Mediterranean Region

Marine (blue) biotechnology is an emerging field enabling the valorization of new products and processes with massive potential for innovation and economic growth. In the Mediterranean region, this innovation potential is not exploited as well as in other European regions due to a lack of a clear identification of the different value chains and the high fragmentation of business innovation initiatives. As a result, several opportunities to create an innovative society are being missed. To address this problem, eight Northern Mediterranean countries (Croatia, France, Greece, Italy, Montenegro, Portugal, Slovenia and Spain) established five national blue biotechnology hubs to identify and address the bottlenecks that prevent the development of marine biotechnology in the region. Following a three-step approach (1. Analysis: setting the scene; 2. Transfer: identification of promising value chains; 3. Capitalization: community creation), we identified the three value chains that are most promising for the Northern Mediterranean region: algae production for added-value compounds, integrated multi-trophic aquaculture (IMTA) and valorization aquaculture/fisheries/processing by-products, unavoidable/unwanted catches and discards. The potential for the development and the technical and non-technical skills that are necessary to advance in this exciting field were identified through several stakeholder events which provided valuable insight and feedback that should be addressed for marine biotechnology in the Northern Mediterranean region to reach its full potential.

High-Level Expression of Recombinant VHSV Glycoprotein Using Transformed C. vulgaris and Verification of Vaccine Efficacy

The demand for aquaculture is increasing, but production is declining due to high feed costs and disease outbreaks. Viral hemorrhagic septicemia (VHS) is a viral disease that seriously affects seawater and freshwater fish in aquaculture, including the olive flounder (Paralichthys olivaceus), a major aquaculture fish in Korea. However, very few vaccines are currently available for viral hemorrhagic septicemia virus (VHSV). The nutrient-rich microalga Chlorella vulgaris has been used as a feed additive in aquaculture and as a host for the industrial production of recombinant VHSV glycoprotein as an oral vaccine. In this study, VHSV glycoprotein was cloned with a salt-inducible promoter, and high levels of expression up to 41.1 mg/g wet C. vulgaris, representing 27.4% of total extracted soluble protein, were achieved by growing the transformed C. vulgaris for 5 days in the presence of 250 mM NaCl. The production of a neutralizing antibody was detected in the serum of fish given feed containing 9% VHSV glycoprotein-expressing C. vulgaris. Furthermore, relative survival rates of 100% and 81.9% were achieved following challenges of these fish with VHSV at 10⁶ and 10⁷ pfu/fish, respectively, indicating that C. vulgaris could be used as a platform for the production of recombinant proteins for use as oral vaccines in the control of viral diseases in aquaculture.

Microalgal bioremediation of brackish aquaculture wastewater

Rapid aquaculture industry development contributed to a major increase in aquaculture wastewater generation. In the context of a circular economy, aquaculture wastewater treatment should simultaneously recover nutrients from the wastewater. Among many treatment methods, bioremediation using microalgae could be a cost-effective and environmentally friendly system that can be applied to treat aquaculture wastewater and simultaneously produce high-value microalgal biomass. This study explored the feasibility of treating brackish wastewater (0.8 % NaCl) generated from a Qatari commercial tilapia farm by microalgae. At first, 10 strains were grown using wastewater from the local farm in an indoor experiment. Based on nitrogen assimilation, biomass yield, biomass quality, and ease of harvesting, 4 candidate strains (Haematococcus sp., Neochloris sp., Monoraphidium sp., and Nostoc sp.) were shortlisted for outdoor growth experiments. Although Nostoc sp. could not grow outdoor in the wastewater, the other three strains were able to assimilate at least 70.5 % of the total nitrogen in the wastewater. Haematococcus sp. and Neochloris sp. could be harvested using self-settling, whereas Monoraphidium required an energy-intensive tangential flow filtration membrane process. Hence, the overall energy requirement for bioremediation, including biomass dewatering, for Haematococcus sp., Neochloris sp., and Monoraphidium sp. were determined as 0.64, 0.78, and 5.68 MJ/m³, respectively. Neochloris sp. had almost twice the biomass yield compared to Haematococcus sp. - suggesting that Neochloris sp. could be a potential candidate for aquaculture wastewater treatment.

Microalgae-Sustainable Source for Alternative Proteins and Functional Ingredients Promoting Gut and Liver Health

Dietary proteins derived from animal sources, although containing well-balanced profiles of essential amino acids, have considerable environmental and adverse health effects associated with the intake of some animal protein-based products. Consuming foods based on animal proteins carries a higher risk of developing non-communicable diseases such as cancer, heart disease, non-alcoholic fatty liver disease (NAFLD), and inflammatory bowel disease (IBD). Moreover, dietary protein consumption is increasing due to population growth, posing a supply challenge. There is, therefore, growing interest in discovering novel alternative protein sources. In this context, microalgae have been recognized as strategic crops that can provide a sustainable source of protein. Compared to conventional high-protein crops, using microalgal biomass for protein production presents several advantages in food and feed in terms of productivity, sustainability, and nutritional value. Moreover, microalgae positively impact the environment by not exploiting land or causing water pollution. Many studies have revealed the potential of microalgae as an alternative protein source with the added value of positive effects on human health due to their anti-inflammatory, antioxidant, and anti-cancer properties. The main emphasis of this review is on the potential health-promoting applications of microalgae-based proteins, peptides, and bioactive substances for IBD and NAFLD.

Exposure to oxyfluorfen-induced hematobiochemical alterations, oxidative stress, genotoxicity, and disruption of sex hormones in male African catfish and the potential to confront by Chlorella vulgaris

The present study evaluated the effect of chronic exposure to oxyfluorfen (OXY) on different physiological responses of male African catfish, Clarias gariepinus, and the ameliorative effect of Chlorella vulgaris. The fish (160 ± 5.10 g) were exposed to 1/20 LC₅₀ of OXY (0.58 mg/L) for 60 consecutive days with or without co-administration of C. vulgaris (25 g/kg diet) in triplicate groups. The results revealed that chronic exposure to a sublethal level of OXY induced severe anemia and leukopenia. OXY-exposed fish experienced hypoproteinemia, marked lower AchE levels, and a significant increase in glucose, liver, and kidney function biomarkers. The DNA fragmentation of the liver increased by 15 % in fish compared to the control. On the other hand, lipid peroxidation, superoxide dismutase, and catalase activities were markedly increased in the liver and testes homogenates of the OXY-exposed fish. Meanwhile, total antioxidant capacity and glutathione S-transferase levels declined in the same tissues. Exposure to OXY induced a significant reduction in testosterone and luteinizing hormone levels and a significant increase in follicle stimulating hormone and estradiol. Meanwhile, C. vulgaris dietary supplementation succeeded in alleviating the negative impact of OXY on hematobiochemical parameters and restoring the antioxidant balance in the liver and testes. Furthermore, it ameliorated endocrine disruption and repaired sex hormone levels. In conclusion, exposure to OXY could induce systemic stress, oxidative stress, and endocrine disruption in male C. gariepinus. The dietary supplementation of C. vulgaris could be a potential protective strategy against the toxicity of OXY.

Recent developments in the production and utilization of photosynthetic microorganisms for food applications

The growing use of photosynthetic microorganisms for food and food-related applications is driving related biotechnology research forward. Increasing consumer acceptance, high sustainability, demand of eco-friendly sources for food, and considerable global economic concern are among the main factors to enhance the focus on the novel foods. In the cases of not toxic strains, photosynthetic microorganisms not only provide a source of sustainable nutrients but are also potentially healthy. Several published studies showed that microalgae are sources of accessible protein and fatty acids. More than 400 manuscripts were published per year in the last 4 years. Furthermore, industrial approaches utilizing these microorganisms are resulting in new jobs and services. This is in line with the global strategy for bioeconomy that aims to support sustainable development of bio-based sectors. Despite the recognized potential of the microalgal biomass value chain, significant knowledge gaps still exist especially regarding their optimized production and utilization. This review highlights the potential of microalgae and cyanobacteria for food and food-related applications as well as their market size. The chosen topics also include advanced production as mixed microbial communities, production of high-value biomolecules, photoproduction of terpenoid flavoring compounds, their utilization for sustainable agriculture, application as source of nutrients in space, and a comparison with heterotrophic microorganisms like yeast to better evaluate their advantages over existing nutrient sources. This comprehensive assessment should stimulate further interest in this highly relevant research topic.

Optimum Temperature and Salinity Conditions for Growth, Lipid Contents, and Fatty Acids Composition of Centric Diatoms Chaetoceros Calcitrans and Thaassiosira Weissflogii

Microalgae are very important organisms as primary producers and have a wide range of applications in areas such as aquaculture, pharmaceuticals, medicine, biofuels, and others. In this study, the effect of temperature and salinity on growth, biomass, proximate composition, and lipid production of Chaetoceros calcitrans (Paulsen) and Thalassiosira weissflogii (Grunow) were investigated. The best growth rate (SGR) and highest biomass production were observed at 30°C and 30 ppt for C. calcitrans and at 30°C and 25 ppt for T. weissflogii. At these optimum temperature and salinity combinations, the maximum cell density was accomplished by day 12 for C. calcitrans (6.74 × 106 cells ml˗1) and by day 10 for T. weissflogii (3.45 × 106 cells ml˗1). The proximate composition during this period was 38.25 ± 0.99% protein, 16.96 ± 0.90% lipid, and 9.39 ± 0.59% carbohydrate in C. calcitrans, compared to 13.49 ± 0.28% protein, 10.43% ± 0.25% lipid and 16.49 ± 0.47% carbohydrate in T. weissflogii. Furthermore, over 35% of lipids in C. calcitrans were palmitic acid (C16), while in T. weissflogii, over 24% of lipids were myristic acid (C14). Although C. calcitrans exhibited higher lipid content than T. weissflogii, both species displayed higher levels of saturated (SFA) and monounsaturated (MUFAs) fatty acids and low levels of polyunsaturated fatty acids (PUFAs). The findings illustrated that under their optimum temperature and salinity combinations, both species might produce significant sources of lipids, which can be utilised in various activities such as aquaculture, pharmaceuticals, medicine, biofuels and others.