Functional properties of carotenoids originating from algae

Harnessing marine resources for Alzheimer's therapy: A review integrating bioactivity and molecular docking

Alzheimer's disease (AD) is a neurodegenerative condition resulting in cognitive impairment and the formation of neurofibrillary tangles and plaques in the brain. The drivers of AD's molecular progression and pathology include the accumulation of amyloid β protein (Aβ); thus, Aβ is an intervention target. However, the limitations in clinical trials of Aβ-targeted medicine and the failure to intervene in disease progression have raised concerns about the use of this drug and its veracious route. In particular, we comprehensively reviewed the potential effect of marine compounds and the mechanism of isolation and extraction from marine organisms resulting in the optimization of AD treatment. Furthermore, the hub compounds were docked with Beta-secretase receptors to strengthen the extrapolation of mechanistic interactions thus inhibiting the activity of an enzyme. An extensive review revealed that marine aquaculture and its byproducts are a promising source and isolated with green methods or less investment, ensuring their sustainability. MNPs harbor specific pharmacological features that enable them to exert neuroprotective effects by minimizing events such as Aβ peptide formation and reactive oxygen species (ROS) generation.

Metabolic engineering and cultivation strategies for efficient production of fucoxanthin and related carotenoids

Fucoxanthin, a bioactive carotenoid derived from algae, has attracted considerable attention for its applications in health, cosmetics, and nutrition. Advances in metabolic engineering, such as the overexpression of pathway-specific enzymes and enhancement of precursor availability, have shown promising results in improving production efficiency. However, despite its high value, the biosynthetic pathway of fucoxanthin remains only partially elucidated, posing significant challenges for metabolic engineering efforts. Recent studies have identified previously unknown enzymes and regulatory elements within the pathway, providing opportunities for further productivity enhancements through targeted metabolic modifications. Additionally, adaptive evolution, mutagenesis-driven strain development, and optimized cultivation conditions have demonstrated significant potential to boost fucoxanthin yields. This review consolidates the latest insights into the biosynthetic pathway of fucoxanthin and highlights metabolic engineering strategies aimed at enhancing the production of fucoxanthin and related carotenoids, offering approaches to design high-yielding strains. Furthermore, recent advancements in random mutagenesis and cultivation technology are discussed. By integrating these developments, more economically viable and environmentally sustainable fucoxanthin production systems can be achieved. KEY POINTS : • Insights into fucoxanthin biosynthesis enable targeted metabolic engineering. • ALE and cultivation strategies complement metabolic engineering efforts. • Balanced push-pull-block strategies improve fucoxanthin production efficiency.

Enhancing biomass and lipid productivities of Haematococcus pluvialis for industrial raw materials products

For biofuels and nutraceuticals, the green microalga Haematococcus pluvialis (Chlorophyceae) is a prospective source of biomass and lipids. This study examined how biomass production and lipid accumulation were affected by temperature (10 °C, 20 °C, and 30 °C) and potassium nitrate (KNO₃) concentrations (0.41 g/L, 0.31 g/L, 0.21 g/L, 0.10 g/L, and 0). The findings showed that the largest biomass (0.665 ± 0.200 g/L) was produced at a potassium nitrate concentration of 0.21 g/L at 20 °C, whereas the highest lipid content (46.31 ± 0.026% dry weight) was produced at a temperature without nitrate. Notably, a balanced result was obtained with a modest nitrate content (0.10 g/L) at 20 °C, yielding significant biomass (0.560 ± 0.136 g/L) and lipids (40.30 ± 0.012% dry weight). These results highlight how crucial it is to optimize cultivation settings in order to increase H. pluvialis's dual productivity, offering important new information for its industrial-scale use. By adjusting growing conditions, this research helps meet the need for renewable resources worldwide by promoting the production of high-value bioproducts and sustainable, commercially viable algae-based biofuels.

Biosorption Ability of Pharmaceutically Active Compounds by Anabaena sp. and Chroococcidiopsis thermalis

Drug overuse harms the biosphere, leading to disturbances in ecosystems' functioning. Consequently, more and more actions are being taken to minimise the harmful impact of xenopharmaceuticals on the environment. One of the innovative solutions is using biosorbents-natural materials such as cells or biopolymers-to remove environmental pollutants; however, this focuses mainly on the removal of metal ions and colourants. Therefore, this study investigated the biosorption ability of selected pharmaceuticals-paracetamol, diclofenac, and ibuprofen-by the biomass of the cyanobacteria Anabaena sp. and Chroococcidiopsis thermalis, using the LC-MS/MS technique. The viability of the cyanobacteria was assessed by determining photosynthetic pigments in cells using a UV-VIS spectrophotometer. The results indicate that both tested species can be effective biosorbents for paracetamol and diclofenac. At the same time, the tested compounds did not have a toxic effect on the tested cyanobacterial species and, in some cases, stimulated their cell growth. Furthermore, the Anabaena sp. can effectively biotransform DCF into its dimer.

Physicochemical properties of wild and cultivated Saccharina latissima macroalgae harvested in the Canadian boreal-subarctic transition zone

Saccharina latissima is a brown seaweed used as a food ingredient. The aim of this work was to study possible differences between S. latissima chemical composition, color, mode of cultivation, harvesting period and site and its environmental conditions. Water temperature, salinity, radiation, and fluorescence were monitored in each harvesting site. Chemical composition of S. latissima varied greatly with period and site, with a high content of carbohydrates and ash. Crude protein content varied from 3.7 % to 12.8 %, with a higher concentration observed in wild samples harvested in Bas-St. Laurent (11.1-12.8 %). Cultivated seaweed also presented a high crude protein (12.2 %) and ash (52 % against 27 % in wild samples) concentrations, but crude fiber and carbohydrates concentrations were lower, reaching up to 2.7 and 1.9-fold, respectively, than those in wild seaweeds. S. latissima presented a more intense yellow color in June. A trend of darker and more green-colored seaweeds when cultivated in the end of summer was confirmed. Our results suggest that variations in chemical components and chromaticity of this species are probably affected by complex interactions of environmental conditions.

Haematococcus lacustris Carotenogensis: A Historical Event of Primary to Secondary Adaptations to Earth's Oxygenation

(1) Background: Oxygen has exerted a great effect in shaping the environment and driving biological diversity in Earth's history. Green lineage has evolved primary and secondary carotenoid biosynthetic systems to adapt to Earth's oxygenation, e.g., Haematococcus lacustris, which accumulates the highest amount of secondary astaxanthin under stresses. The two systems are controlled by lycopene ε-cyclase (LCYE) and β-cyclase (LCYB), which leave an important trace in Earth's oxygenation. (2) Objectives: This work intends to disclose the underlying molecular evolutionary mechanism of Earth's oxygenation in shaping green algal carotenogensis with a special focus on lycopene cyclases. (3) Methods: The two kinds of cyclases were analyzed by site-directed mutagenesis, phylogeny, divergence time and functional divergence. (4) Results: Green lineage LCYEs appeared at ~1.5 Ga after the first significant appearance and accumulation of atmospheric oxygen, the so-called Great Oxygenation Event (GOE), from which LCYBs diverged by gene duplication. Bacterial β-bicyclases evolved from β-monocyclase. Enhanced catalytic activity accompanied evolutionary transformation from ε-/β-monocyclase to β-bicyclase. Strong positive selection occurred in green lineage LCYEs after the GOE and in algal LCYBs during the second oxidation, the Neoproterozoic Oxygenation Event (NOE). Positively selected sites in the catalytic cavities of the enzymes controlled the mono-/bicyclase activity, respectively. Carotenoid profiling revealed that oxidative adaptation has been wildly preserved in evolution. (5) Conclusions: the functionalization of the two enzymes is a result of primary to secondary adaptations to Earth's oxygenation.

The effect of PK gene overexpression on content and antioxidant properties of carotenoids in marine microalga Dunaliella parva

Dunaliella parva can extensively accumulate carotenoids, which is a promising raw material for carotenoids production. Carotenoids have important medicinal value. D. parva is an ideal organism for studying the mechanism of carotenoid synthesis. Our previous study identified a transcription factor DpAP2 which could regulate carotenoid synthesis in D. parva. In addition, DpAP2 could interact with three proteins with different activities (DNA binding transcription factor activity, protein kinase activity, and alpha-D-phosphohexomutase). To investigate the function of PK gene encoding interacting protein of DpAP2 with protein kinase activity in D. parva, PK gene was cloned into vector pBI221-GFP-UbiΩ-CAT and transformed into D. parva in this study. The results showed that overexpression of PK gene enhanced the contents of carotenoids, total sugars, proteins, and antioxidant activities of carotenoid extract such as superoxide radical scavenging activity, reducing power, hydroxyl radical scavenging activity in transgenic D. parva with overexpression of PK gene. This study explored the function of PK gene, and improved the medicinal value of D. parva.

Bet hedging in a unicellular microalga

Understanding how organisms have adapted to persist in unpredictable environments is a fundamental goal in biology. Bet hedging, an evolutionary adaptation observed from microbes to humans, facilitates reproduction and population persistence in randomly fluctuating environments. Despite its prevalence, empirical evidence in microalgae, crucial primary producers and carbon sinks, is lacking. Here, we report a bet-hedging strategy in the unicellular microalga Haematococcus pluvialis. We show that isogenic populations reversibly diversify into heterophenotypic mobile and non-mobile cells independently of environmental conditions, likely driven by stochastic gene expression. Mobile cells grow faster but are stress-sensitive, while non-mobile cells prioritise stress resistance over growth. This is due to shifts from growth-promoting activities (cell division, photosynthesis) to resilience-promoting processes (thickened cell wall, cell enlargement, aggregation, accumulation of antioxidant and energy-storing compounds). Our results provide empirical evidence for bet hedging in a microalga, indicating the potential for adaptation to current and future environmental conditions and consequently conservation of ecosystem functions.

Intelligent and active biodegradable biopolymeric films containing carotenoids

There is growing interest in the use of natural bioactive compounds for the development of new bio-based materials for intelligent and active food packaging applications. Several beneficial effects have been associated with the antioxidant and antimicrobial potentials of carotenoid compounds. In addition, carotenoids are sensitive to pH changes and oxidation reactions, which make them useful bioindicators of food deterioration. This review summarizes the current research on the application of carotenoids as novel intelligent and active biodegradable food packaging materials. Carotenoids recovered from food processing by-products can be used in the development of active food packaging materials due to their antioxidant properties. They help maintain the stability of lipid-rich foods, such as vegetable oils. Additionally, when incorporated into films, carotenoids can monitor food oxidation, providing intelligent functionalities.

Trends and challenges of fruit by-products utilization: insights into safety, sensory, and benefits of the use for the development of innovative healthy food: a review

A significant portion of the human diet is comprised of fruits, which are consumed globally either raw or after being processed. A huge amount of waste and by-products such as skins, seeds, cores, rags, rinds, pomace, etc. are being generated in our homes and agro-processing industries every day. According to previous statistics, nearly half of the fruits are lost or discarded during the entire processing chain. The concern arises when those wastes and by-products damage the environment and simultaneously cause economic losses. There is a lot of potential in these by-products for reuse in a variety of applications, including the isolation of valuable bioactive ingredients and their application in developing healthy and functional foods. The development of novel techniques for the transformation of these materials into marketable commodities may offer a workable solution to this waste issue while also promoting sustainable economic growth from the bio-economic viewpoint. This approach can manage waste as well as add value to enterprises. The goal of this study is twofold based on this scenario. The first is to present a brief overview of the most significant bioactive substances found in those by-products. The second is to review the current status of their valorization including the trends and techniques, safety assessments, sensory attributes, and challenges. Moreover, specific attention is drawn to the future perspective, and some solutions are discussed in this report.

Microalgae as a Sustainable Source of Antioxidants in Animal Nutrition, Health and Livestock Development

Microalgae are a renewable and sustainable source of bioactive compounds, such as essential amino acids, polyunsaturated fatty acids, and antioxidant compounds, that have been documented to have beneficial effects on nutrition and health. Among these natural products, the demand for natural antioxidants, as an alternative to synthetic antioxidants, has increased. The antioxidant activity of microalgae significantly varies between species and depends on growth conditions. In the last decade, microalgae have been explored in livestock animals as feed additives with the aim of improving both animals' health and performance as well as product quality and the environmental impact of livestock. These findings are highly dependent on the composition of microalgae strain and their amount in the diet. The use of carbohydrate-active enzymes can increase nutrient bioavailability as a consequence of recalcitrant microalgae cell wall degradation, making it a promising strategy for monogastric nutrition for improving livestock productivity. The use of microalgae as an alternative to conventional feedstuffs is becoming increasingly important due to food-feed competition, land degradation, water deprivation, and climate change. However, the cost-effective production and use of microalgae is a major challenge in the near future, and their cultivation technology should be improved by reducing production costs, thus increasing profitability.

Beneficial effect of ζ-carotene-like compounds on acute UVB irradiation by alleviating inflammation and regulating intestinal flora

ζ-Carotene is a key intermediate in the carotenoid pathway, but owing to its low content and difficulties in isolation, its application is restricted. In this study, three genes (pnCrtE, pnCrtB, and pnCrtP) in the carotenoid pathway of Antarctic moss were identified, recombined, and expressed in Escherichia coli (E. coli) BL21(DE3). The expression product was identified as one of the ζ-carotenes by UV absorbance spectrum, thin layer chromatography (TLC), and super-high-performance liquid chromatography-mass spectrum (UPLC-MS), and was called a ζ-carotene-like compound (CLC). Excessive exposure to ultraviolet B (UVB) irradiation is one of the main risk factors for skin photodamage. The purpose of this study was to investigate the preventive and therapeutic effects of CLC on UVB-induced skin photodamage in mice. In this paper, through histological examinations (hematoxylin-eosin, HE; Masson and TdT-mediated dUTP Nick-End Labeling, Tunel), biochemical index detection (reactive oxygen species, ROS; inflammatory factors; cyclobutyl pyrimidine dimers, CPDs and hyaluronic acid, HA), quantitative real time polymerase chain reaction (qRT-PCR), immunohistochemistry and intestinal content flora, etc., it is concluded that CLC has the potential to enhance skin antioxidant capacity by activating the nuclear transcription factor/antioxidant reaction element (Nrf2/ARE) pathway and also reduce skin inflammation and aging by inhibiting the mitogen-activated protein kinase (MAPK) pathway. Moreover, the regulation of intestinal flora may potentially mitigate skin damage induced by UVB radiation. This research not only developed a green and sustainable platform for the efficient synthesis of CLC but also laid a foundation for its application in functional food and medicine for skin resistance against UVB damage.

Metabolomic and physiological changes of acid-tolerant Graesiella sp. MA1 during long-term acid stress

Algae plays a significant role for the primary production in the oligotrophic ecosystems such as the acid mine pit lakes. Graesiella sp. MA1 was a new acid-tolerant photosynthetic protist isolated from an acid mine pit lake. To understand the acid responses of Graesiella sp. MA1, its physiological changes and metabolomics were studied during long-term acid stress. Photosynthetic pigments, soluble proteins, and antioxidant systems of Graesiella sp. MA1 cells displayed two phases, the adaptation phase and the growth phase. During the adaptation phase, both photosynthetic pigments and soluble proteins were inhibited, while antioxidant activity of SOD, APX, and GSH were promoted to response to the organism's damage. Metabolomics results revealed lipids and organic acids were abundant components in Graesiella sp. MA1 cells. In response to acid stress, the levels of acid-dependent resistant amino acids, including glutamate, aspartate, arginine, proline, lysine, and histidine, accumulated continuously to maintain orderly intracellular metabolic processes. In addition, fatty acids were mainly unsaturated, which could improve the fluidity of the cell membranes under acid stress. Metabolomic and physiological changes showed that Graesiella sp. MA1 had tolerance during long-term acid stress and the potential to be used as a bioremediation strain for the acidic wastewater.

Ultrasonic-Assisted Extraction of Astaxanthin from Shrimp By-Products Using Vegetable Oils

BACKGROUND

The use of conventional astaxanthin extraction methods, typically involving organic solvents, leads to a heightened environmental impact. The aim of this study was to explore the potential use of environmentally friendly extraction solvents, such as vegetable oils, for recovering the shrimp by-product astaxanthin.

METHODS

Ultrasound-assisted extraction (UAE) in vegetable oils, including olive oil (OO), sunflower oil (SO), and flaxseed oil (FO), was employed to extract astaxanthin. The astaxanthin antioxidant activity was evaluated using an ABTS assay, and a mixture of gum Arabic and soy lecithin was used to form coacervates to produce astaxanthin encapsulation.

RESULTS

A by-product-vegetable oil ratio of 1:60, extraction time of 210 min, 60% amplitude of the extraction process, and the use of OO as the extracting medium resulted in an astaxanthin yield of 235 ± 4.07 μg astaxanthin/g by-products. The astaxanthin encapsulation efficiency on day 0 and astaxanthin recovery on day 1 were recorded at 66.6 ± 2.7% and 94.4 ± 4.6%, respectively.

CONCLUSIONS

The utilization of OO as an extraction solvent for astaxanthin from shrimp by-products in UAE represents a novel and promising approach to reducing the environmental impact of shrimp by-products. The effective astaxanthin encapsulation efficiency highlights its potential application in food industries.

An unexpected hydratase synthesizes the green light-absorbing pigment fucoxanthin

The ketocarotenoid fucoxanthin and its derivatives can absorb blue-green light enriched in marine environments. Fucoxanthin is widely adopted by phytoplankton species as a main light-harvesting pigment, in contrast to land plants that primarily employ chlorophylls. Despite its supreme abundance in the oceans, the last steps of fucoxanthin biosynthesis have remained elusive. Here, we identified the carotenoid isomerase-like protein CRTISO5 as the diatom fucoxanthin synthase that is related to the carotenoid cis-trans isomerase CRTISO from land plants but harbors unexpected enzymatic activity. A crtiso5 knockout mutant in the model diatom Phaeodactylum tricornutum completely lacked fucoxanthin and accumulated the acetylenic carotenoid phaneroxanthin. Recombinant CRTISO5 converted phaneroxanthin into fucoxanthin in vitro by hydrating its carbon-carbon triple bond, instead of functioning as an isomerase. Molecular docking and mutational analyses revealed residues essential for this activity. Furthermore, a photophysiological characterization of the crtiso5 mutant revealed a major structural and functional role of fucoxanthin in photosynthetic pigment-protein complexes of diatoms. As CRTISO5 hydrates an internal alkyne physiologically, the enzyme has unique potential for biocatalytic applications. The discovery of CRTISO5 illustrates how neofunctionalization leads to major diversification events in evolution of photosynthetic mechanisms and the prominent brown coloration of most marine photosynthetic eukaryotes.

Copper multifaceted interferences during swine wastewater treatment in high-rate algal ponds: alterations on nutrient removal, biomass composition and resource recovery

Microalgae cultivation in swine wastewater (SW) allows the removal of nutrients and biomass production. However, SW is known for its Cu contamination, and its effects on algae cultivation systems such as high-rate algal ponds (HRAPs) are poorly understood. This gap in the literature limits the proposition of adequate concentrations of Cu to optimise SW treatment and resource recovery in HRAPs. For this assessment, 12 HRAPs installed outdoors were operated with 800 L of SW with different Cu concentrations (0.1-4.0 mg/L). Cu's interferences on the growth and composition of biomass and nutrient removal from SW were investigated through mass balance and experimental modelling. The results showed that the concentration of 1.0 mg Cu/L stimulated microalgae growth, and above 3.0 mg Cu/L caused inhibition accompanied by an accumulation of H₂O₂. Furthermore, Cu affected the contents of lipids and carotenoids observed in the biomass; the highest concentration was observed in the control (16%) and 0.5 mg Cu/L (1.6 mg/g), respectively. An innovative result was verified for nutrient removal, in which increased Cu concentration reduced the N-NH₄⁺ removal rate. In contrast, the soluble P removal rate was enhanced by 2.0 mg Cu/L. Removal of soluble Cu in treated SW reached 91%. However, the action of microalgae in this process was not associated with assimilation but with a pH increase resulting from photosynthesis. A preliminary evaluation of economic viability showed that the commercialisation of biomass considering the concentration of carotenoids obtained in HRAPs with 0.5 mg Cu/L could be economically attractive. In conclusion, Cu affected the different parameters evaluated in this study in a complex way. This can help managers consort nutrient removal, biomass production, and resource recovery, providing information for possible industrial exploitation of the generated bioproducts.

Study on bioactive compounds of microalgae as antioxidants in a bibliometric analysis and visualization perspective

Natural antioxidants are more attractive than synthetic chemical oxidants because of their non-toxic and non-harmful properties. Microalgal bioactive components such as carotenoids, polysaccharides, and phenolic compounds are gaining popularity as very effective and long-lasting natural antioxidants. Few articles currently exist that analyze microalgae from a bibliometric and visualization point of view. This study used a bibliometric method based on the Web of Science Core Collection database to analyze antioxidant research on bioactive compounds in microalgae from 1996 to 2022. According to cluster analysis, the most studied areas are the effectiveness, the antioxidant mechanism, and use of bioactive substances in microalgae, such as carotene, astaxanthin, and tocopherols, in the fields of food, cosmetics, and medicine. Using keyword co-occurrence and keyword mutation analysis, future trends are predicted to improve extraction rates and stability by altering the environment of microalgae cultures or mixing extracts with chemicals such as nanoparticles for commercial and industrial applications. These findings can help researchers identify trends and resources to build impactful investigations and expand scientific frontiers.

Astaxanthin as a King of Ketocarotenoids: Structure, Synthesis, Accumulation, Bioavailability and Antioxidant Properties

Astaxanthin (3,3-dihydroxy-β, β-carotene-4,4-dione) is a ketocarotenoid synthesized by Haematococcus pluvialis/lacustris, Chromochloris zofingiensis, Chlorococcum, Bracteacoccus aggregatus, Coelastrella rubescence, Phaffia rhodozyma, some bacteria (Paracoccus carotinifaciens), yeasts, and lobsters, among others However, it is majorly synthesized by Haematococcus lacustris alone (about 4%). The richness of natural astaxanthin over synthetic astaxanthin has drawn the attention of industrialists to cultivate and extract it via two stage cultivation process. However, the cultivation in photobioreactors is expensive, and converting it in soluble form so that it can be easily assimilated by our digestive system requires downstream processing techniques which are not cost-effective. This has made the cost of astaxanthin expensive, prompting pharmaceutical and nutraceutical companies to switch over to synthetic astaxanthin. This review discusses the chemical character of astaxanthin, more inexpensive cultivating techniques, and its bioavailability. Additionally, the antioxidant character of this microalgal product against many diseases is discussed, which can make this natural compound an excellent drug to minimize inflammation and its consequences.

Overexpression of 18S rRNA methyltransferase CrBUD23 enhances biomass and lutein content in Chlamydomonas reinhardtii

Post-transcriptional modification of nucleic acids including transfer RNA (tRNA), ribosomal RNA (rRNA) and messenger RNA (mRNA) is vital for fine-tunning of mRNA translation. Methylation is one of the most widespread post-transcriptional modifications in both eukaryotes and prokaryotes. HsWBSCR22 and ScBUD23 encodes a 18S rRNA methyltransferase that positively regulates cell growth by mediating ribosome maturation in human and yeast, respectively. However, presence and function of 18S rRNA methyltransferase in green algae are still elusive. Here, through bioinformatic analysis, we identified CrBUD23 as the human WBSCR22 homolog in genome of the green algae model organism Chlamydonomas reinhardtii. CrBUD23 was a conserved putative 18S rRNA methyltransferase widely exited in algae, plants, insects and mammalians. Transcription of CrBUD23 was upregulated by high light and down-regulated by low light, indicating its role in photosynthesis and energy metabolism. To characterize its biological function, coding sequence of CrBUD23 fused with a green fluorescence protein (GFP) tag was derived by 35S promoter and stably integrated into Chlamydomonas genome by glass bead-mediated transformation. Compared to C. reinhardtii wild type CC-5325, transgenic strains overexpressing CrBUD23 resulted in accelerated cell growth, thereby leading to elevated biomass, dry weight and protein content. Moreover, overexpression of CrBUD23 increased content of photosynthetic pigments but not elicit the activation of antioxidative enzymes, suggesting CrBUD23 favors growth and proliferation in the trade-off with stress responses. Bioinformatic analysis revealed the G1177 was the putative methylation site in 18S rRNA of C. reinhardtii CC-849. G1177 was conserved in other Chlamydonomas isolates, indicating the conserved methyltransferase activity of BUD23 proteins. In addition, CrTrm122, the homolog of BUD23 interactor Trm112, was found involved in responses to high light as same as CrBUD23. Taken together, our study revealed that cell growth, protein content and lutein accumulation of Chlamydomonas were positively regulated by the 18S rRNA methyltransferase CrBUD23, which could serve as a promising candidate for microalgae genetic engineering.

A comprehensive review on algal nutraceuticals as prospective therapeutic agent for different diseases

Ongoing research in the food supplement sector provides insightful information regarding algae as a new-generation nutritional supplement and is also referred to as a superfood. Due to the diverse nutritional components, algae have documented numerous health benefits like fighting microbial diseases, hypertension, obesity, and diabetes. Therefore, algae-derived nutraceuticals account for a rapidly expanding market in the food supplements sector. The concept of algal prebiotics and their role in modulating gut microbiota have also been a chief contributor to this. This review evaluates the use of possible algal species and their specific bioactive compounds for the management of several chronic diseases. Proteins, peptides, polysaccharides, phenolics, and vitamins give an insight into the significance of algae in boosting the immune system and improving the body's nutritional makeup. In addition, phyco-compounds such as polysaccharides and polyphenols are also receiving a lot more interest in cosmeceutical applications for protecting skin from photodamage. The incorporation of algae in the diet for the management and prevention of chronic diseases like cancer, lung, and heart disease has been discussed in this review along with their action mechanism. This review provides a brief overview of several bioactive compounds present in micro and macroalgae and their therapeutic effect on lifestyle diseases, gastrointestinal diseases as well as neurodegenerative diseases.

Testing for terrestrial and freshwater microalgae productivity under elevated CO2 conditions and nutrient limitation

BACKGROUND

Microalgae CO₂ fixation results in the production of biomass rich in high-valuable products, such as fatty acids and carotenoids. Enhanced productivity of valuable compounds can be achieved through the microalgae's ability to capture CO₂ efficiently from sources of high CO₂ contents, but it depends on the species. Culture collections of microalgae offer a wide variety of defined strains. However, an inadequate understanding of which groups of microalgae and from which habitats they originate offer high productivity under increased CO₂ concentrations hampers exploiting microalgae as a sustainable source in the bioeconomy.

RESULTS

A large variety of 81 defined algal strains, including new green algal isolates from various terrestrial environments, were studied for their growth under atmospheres with CO₂ levels of 5-25% in air. They were from a pool of 200 strains that had been pre-selected for phylogenetic diversity and high productivity under ambient CO₂. Green algae from terrestrial environments exhibited enhanced growth up to 25% CO₂. In contrast, in unicellular red algae and stramenopile algae, which originated through the endosymbiotic uptake of a red algal cell, growth at CO₂ concentrations above 5% was suppressed. While terrestrial stramenopile algae generally tolerated such CO₂ concentrations, their counterparts from marine phytoplankton did not. The tests of four new strains in liquid culture revealed enhanced biomass and chlorophyll production under elevated CO₂ levels. The 15% CO₂ aeration increased their total carotenoid and fatty acid contents, which were further stimulated when combined with the starvation of macronutrients, i.e., less with phosphate and more with nitrogen-depleted culture media.

CONCLUSION

Green algae originating from terrestrial environments, Chlorophyceae and Trebouxiophyceae, exhibit enhanced productivity of carotenoids and fatty acids under elevated CO₂ concentrations. This ability supports the economic and sustainable production of valuable compounds from these microalgae using inexpensive sources of high CO₂ concentrations, such as industrial exhaust fumes.

Potential of Spirulina platensis as a feed supplement for poultry to enhance growth performance and immune modulation

Increase in drug resistance as well as ineffective immunization efforts against various pathogens (viruses, bacteria and fungi) pose a significant threat to the poultry industry. Spirulina is one of the most widely used natural ingredients which is becoming popular as a nutritional supplement in humans, animals, poultry and aquaculture. It contains protein, vitamins, minerals, fatty acids, pigments, and essential amino acids. Moreover, it also has considerable quantities of unique natural antioxidants including polyphenols, carotenoids, and phycocyanin. Dietary supplementation of Spirulina can beneficially affect gut microbial population, serum biochemical parameters, and growth performance of chicken. Additionally, it contains polyphenolic contents having antibacterial effects. Spirulina extracts might inhibit bacterial motility, invasion, biofilm formation, and quorum sensing in addition to acting directly on the bacterium by weakening and making the bacterial cell walls more porous, subsequently resulting in cytoplasmic content leakage. Additionally, Spirulina has shown antiviral activities against certain common human or animal viruses and this capability can be considered to exhibit potential benefits against avian viruses also. Spirulan, a calcium-rich internal polysaccharide of Spirulina, is potentially responsible for its antiviral effect through inhibiting the entry of several viruses into the host cells, boosting the production of nitric oxide in macrophages, and stimulating the generation of cytokines. Comparatively a greater emphasis has been given to the immune modulatory effects of Spirulina as a feed additive in chicken which might boost disease resistance and improve survival and growth rates, particularly under stress conditions. This manuscript reviews biological activities and immune-stimulating properties of Spirulina and its potential use as a dietary supplement in poultry to enhance growth, gut health and disease resistance.

Asterarcys quadricellulare (Chlorophyceae) protects H9c2 cardiomyoblasts from H2O2-induced oxidative stress

Oxidative stress has recently been identified as an important mediator of cardiovascular diseases. The need to find efficient antioxidant molecules is essential in the disease's prevention. Therefore, the present study aimed to evaluate the potential of microalgae bioactive in protecting H9c2 cardiomyoblasts from H₂O₂-induced oxidative stress. Four microalgal species were investigated for their antioxidant capacity. A qualitative assessment of oxidative stress in H9c2 cardiomyoblasts stained with DCFH-DA, treated with the highly active microalgae extracts, was performed. The protein expression of total caspase-3 was also examined to investigate whether the extract protects H9c2 cardimyoblasts from H₂O₂-induced apoptosis. High antioxidant activity was observed for the hexanoic extracts after 10 days of cultivation. Asterarcys quadricellulare exhibited the highest antioxidant capacity of 110.59 ± 1.75 mg TE g^-1 dry weight and was tested against H9c2 cardiomyoblasts, which were initially subjected to H₂O₂-induced oxidative stress. This hexanoic extract protected against H₂O₂ induced oxidative stress with a similar scavenging capacity as N-Acetylcysteine. Furthermore, total caspase-3 was increased following treatment with the hexanoic extract, suggesting that A. quadricellulare also had anti-apoptotic properties. The outcome of our study highlighted the possible use of the local A. quadricellulare strain QUCCCM10 as a natural, safe, and efficient antioxidant to prevent cardiovascular diseases.

Cryptochrome-mediated blue-light signal contributes to carotenoids biosynthesis in microalgae

Microalgae are considered as ideal cell factories for producing natural carotenoids which display favorable biological activities. As the most important abiotic factor, light not only provides energy for photosynthetic metabolism, but also regulates numerous biological processes. Blue light is the main wavelength of light that can travel through water. Previous studies have shown that blue light triggered carotenoid accumulation in several microalgae species, but the molecular mechanism remains unclear. Cryptochromes were blue-light-absorbing photoreceptors that have been found in all studied algal genomes. In this study, several different types of cryptochrome genes were cloned from Haematococcus pluvialis and Phaeodactylum tricornutum. Among them, cryptochrome genes HpCRY4 from H. pluvialis and PtCPF1 from P. tricornutum were upregulated under blue light treatment, in correlation with the increase of astaxanthin and fucoxanthin contents. Besides, heterologous expression and gene knockout was performed to verify the function of HpCRY4 and PtCPF1 in regulating carotenoid biosynthesis in microalgae. These results indicate that carotenoid biosynthesis in microalgae promoted by blue light was mediated by cryptochromes as photoreceptors.

Aquaculture sustainability through alternative dietary ingredients: Microalgal value-added products

Aquaculture contributes remarkably to the global economy and food security through seafood production, an important part of the global food supply chain. The success of this industry depends heavily on aquafeeds, and the nutritional composition of the feed is an important factor for the quality, productivity, and profitability of aquaculture species. The sustainability of the aquaculture industry depends on the accessibility of quality feed ingredients, such as fishmeal and fish oil. These traditional feedstuffs are under increasing significant pressure due to the rapid expansion of aquaculture for human consumption and the decline of natural fish harvest. In this review, we evaluated the development of microalgal molecules in aquaculture and expanded the use of these high-value compounds in the production of aquaculture diets. Microalgae-derived functional ingredients emerged as one of the promising alternatives for aquafeed production with positive health benefits. Several compounds found in microalgae, including carotenoids (lutein, astaxanthin, and β-carotene), essential amino acids (leucine, valine, and threonine), β-1-3-glucan, essential oils (docosahexaenoic acid and eicosapentaenoic acid), minerals, and vitamins, are of high nutritional value to aquaculture.

Improvement in the Sequential Extraction of Phycobiliproteins from Arthrospira platensis Using Green Technologies

Arthrospira platensis (commercially known as Spirulina) is an excellent source of phycobiliproteins, especially C-phycocyanin. Phycobiliproteins are significant bioactive compounds with useful biological applications. The extraction process plays a significant role in downstream microalga production and utilisation. The important pigments found in A. platensis include chlorophyll and carotenoids as nonpolar pigments and phycobiliproteins as polar pigments. Supercritical fluid extraction (SFE) as a green extraction technology for the high-value metabolites of microalgae has potential for trends in food and human health. The nonpolar bioactive compounds, chlorophyll and carotenoids of A. platensis, were primarily separated using supercritical carbon dioxide (SC-CO₂) solvent-free fluid extraction pressure; the temperature and ethanol as cosolvent conditions were compared. The residue from the A. platensis cells was subjected to phycobiliprotein extraction. The phosphate and water extraction of A. platensis SFE residue were compared to evaluate phycobiliprotein extraction. The SFE results exhibited higher pressure (350 bar) and temperature extraction (50 °C) with ethanol-free extraction and increased nonpolar pigment. Phycobiliprotein yield was obtained from A. platensis SFE residue by ethanol-free buffer extraction as a suitable process with antioxidant properties. The C-phycocyanin was isolated and enhanced to 0.7 purity as food grade. This developed method can be used as a guideline and applied as a sustainable process for important pigment extraction from Arthrospira microalgae.

Environmental impacts due to the use of sunscreen products: a mini-review

Sunscreen use has increased in recent years, as sunscreen products minimize the damaging effects of solar radiation. Active ingredients called ultraviolet (UV) filters or UV agents, either organic or inorganic, responsible for defending skin tissue against harmful UV rays, are incorporated in sunscreen formulations. UV agents have a serious impact on many members of bio communities, and they are transferred to the environment either directly or indirectly. Many organic UV filters are found to be accumulated in marine environments because of high values of the octanol/water partition coefficient. However, due to the fact that UV agents are not stable in water, unwanted by-products may be formed. Experimental studies or field observations have shown that organic UV filters tend to bioaccumulate in various aquatic animals, such as corals, algae, arthropods, mollusks, echinoderms, marine vertebrates. This review was conducted in order to understand the effects of UV agents on both the environment and marine biota. In vivo and in vitro studies of UV filters show a wide range of adverse effects on the environment and exposed organisms. Coral bleaching receives considerable attention, but the scientific data identify potential toxicities of endocrine, neurologic, neoplastic and developmental pathways. However, more controlled environmental studies and long-term human use data are limited. Several jurisdictions have prohibited specific UV filters, but this does not adequately address the dichotomy of the benefits of photoprotection vs lack of eco-friendly, safe, and approved alternatives.

Innovative binary sorption of Cobalt(II) and methylene blue by Sargassum latifolium using Taguchi and hybrid artificial neural network paradigms

The present investigation has been designed by Taguchi and hybrid artificial neural network (ANN) paradigms to improve and optimize the binary sorption of Cobalt(II) and methylene blue (MB) from an aqueous solution, depending on modifying physicochemical conditions to generate an appropriate constitution for a highly efficient biosorption by the alga; Sargassum latifolium. Concerning Taguchi's design, the predicted values of the two responses were comparable to actual ones. The biosorption of Cobalt(II) ions was more efficient than MB, the supreme biosorption of Cobalt(II) was verified in run L21 (93.28%), with the highest S/N ratio being 39.40. The highest biosorption of MB was reached in run L22 (74.04%), with a S/N ratio of 37.39. The R2 and adjusted R2 were in reasonable values, indicating the validity of the model. The hybrid ANN model has exclusively emerged herein to optimize the biosorption of both Cobalt(II) and MB simultaneously, therefore, the ANN model was better than the Taguchi design. The predicted values of Cobalt(II) and MB biosorption were more obedience to the ANN model. The SEM analysis of the surface of S. latifolium showed mosaic form with massive particles, as crosslinking of biomolecules of the algal surface in the presence of Cobalt(II) and MB. Viewing FTIR analysis showed active groups e.g., hydroxyl, α, β-unsaturated ester, α, β-unsaturated ketone, N-O, and aromatic amine. To the best of our knowledge, there are no reports deeming the binary sorption of Cobalt(II) and MB ions by S. latifolium during Taguchi orthogonal arrays and hybrid ANN.

Green diatom mutants reveal an intricate biosynthetic pathway of fucoxanthin

Fucoxanthin is a major light-harvesting pigment in ecologically important algae such as diatoms, haptophytes, and brown algae (Phaeophyceae). Therefore, it is a major driver of global primary productivity. Species of these algal groups are brown colored because the high amounts of fucoxanthin bound to the proteins of their photosynthetic machineries enable efficient absorption of green light. While the structure of these fucoxanthin-chlorophyll proteins has recently been resolved, the biosynthetic pathway of fucoxanthin is still unknown. Here, we identified two enzymes central to this pathway by generating corresponding knockout mutants of the diatom Phaeodactylum tricornutum that are green due to the lack of fucoxanthin. Complementation of the mutants with the native genes or orthologs from haptophytes restored fucoxanthin biosynthesis. We propose a complete biosynthetic path to fucoxanthin in diatoms and haptophytes based on the carotenoid intermediates identified in the mutants and in vitro biochemical assays. It is substantially more complex than anticipated and reveals diadinoxanthin metabolism as the central regulatory hub connecting the photoprotective xanthophyll cycle and the formation of fucoxanthin. Moreover, our data show that the pathway evolved by repeated duplication and neofunctionalization of genes for the xanthophyll cycle enzymes violaxanthin de-epoxidase and zeaxanthin epoxidase. Brown algae lack diadinoxanthin and the genes described here and instead use an alternative pathway predicted to involve fewer enzymes. Our work represents a major step forward in elucidating the biosynthesis of fucoxanthin and understanding the evolution, biogenesis, and regulation of the photosynthetic machinery in algae.

Influence of exogenous phytohormone supplementation on the pigment and fatty acid content of three marine diatoms

Diatoms are ubiquitous photosynthetic microorganisms with great potential for biotechnological applications. However, their commercialisation is hampered by production costs, requiring hence optimisation of cultivation methods. Phytohormones are plant growth regulators which may be used to influence physiological processes in microalgae, including diatoms. In this study, the model species Phaeodactylum tricornutum (Phaeodactylaceae) and two Irish isolates of Stauroneis sp. (Stauroneidaceae) and Nitzschia sp. (Bacillariaceae) were grown with varying amounts of the phytohormones indoleacetic acid (IAA), gibberellic acid (GA3), methyl jasmonate (MJ), abscisic acid (ABA) or salicylic acid (SA), and their influence on pigment and fatty acid profiles was monitored. The application of GA3 (200 mg/l) stimulated the growth of P. tricornutum which accumulated 52% more dry biomass compared to the control and concomitantly returned the highest eicosapentaenoic acid (EPA) yield (0.6 mg/l). The highest fucoxanthin yield (0.18 mg/l) was obtained for P. tricornutum cultivated with GA3 (2 mg/l) supplementation. In Stauroneis sp., SA (1 mg/l) had the most positive effect on EPA, the content of which was enhanced up to 45.7 μg/mg (4.6% of total dry weight). The SA (1 mg/l) treatment also boosted carotenogenesis in Nitzschia sp., leading to 1.7- and 14-fold increases in fucoxanthin and β-carotene compared to the control, respectively. Of note, MJ (0.5 mg/l) increased the EPA content of all diatom species compared to their controls. These results indicate that phytohormone-based treatments can be used to alter the pigment and lipid content of microalgae, which tend to respond in dose- and species-specific manners to individual compounds.Key points• Response to phytohormones was investigated in diatoms from distinct families.• MJ (0.5 mg/l) caused an increase in EPA cellular content in all three diatoms.• Phytohormones mostly caused dose-dependent and species-specific responses.

Biological Potential, Gastrointestinal Digestion, Absorption, and Bioavailability of Algae-Derived Compounds with Neuroprotective Activity: A Comprehensive Review

Currently, there is no known cure for neurodegenerative disease. However, the available therapies aim to manage some of the symptoms of the disease. Human neurodegenerative diseases are a heterogeneous group of illnesses characterized by progressive loss of neuronal cells and nervous system dysfunction related to several mechanisms such as protein aggregation, neuroinflammation, oxidative stress, and neurotransmission dysfunction. Neuroprotective compounds are essential in the prevention and management of neurodegenerative diseases. This review will focus on the neurodegeneration mechanisms and the compounds (proteins, polyunsaturated fatty acids (PUFAs), polysaccharides, carotenoids, phycobiliproteins, phenolic compounds, among others) present in seaweeds that have shown in vivo and in vitro neuroprotective activity. Additionally, it will cover the recent findings on the neuroprotective effects of bioactive compounds from macroalgae, with a focus on their biological potential and possible mechanism of action, including microbiota modulation. Furthermore, gastrointestinal digestion, absorption, and bioavailability will be discussed. Moreover, the clinical trials using seaweed-based drugs or extracts to treat neurodegenerative disorders will be presented, showing the real potential and limitations that a specific metabolite or extract may have as a new therapeutic agent considering the recent approval of a seaweed-based drug to treat Alzheimer’s disease.

Integrated marine microalgae biorefineries for improved bioactive compounds: A review

Marine microalgae offer a promising feedstock for biofuels and other valuable compounds for biorefining and carry immense potential to contribute to a clean energy and environment future. However, it is currently not economically feasible to use marine algae to produce biofuels, and the potential bioactive chemicals account for only a small market share. The production of algal biomass with multiple valuable chemicals is closely related to the algal species, cultivation conditions, culture systems, and production modes. Thus, higher requirements for screening of dominant algal strains, developing integrated technologies with the optimum culture conditions, efficient cultivation systems, and production modes to exploit algal biomass for biorefinery applications, are all needed. This review summarizes the screening of dominant microalgae, discusses the environmental conditions that may affect the growth, as well as the culture systems and production modes, and further emphasizes the valorization options of the algal biomass, which should help to offer a sustainable approach to run a profitable marine algae production system.

Up-to-Date Overview of the Use of Natural Ingredients in Sunscreens

The photoprotective skincare segment is in high demand to meet consumer concerns on UV-induced skin damage, with a recent trend towards sunscreen alternatives with a natural origin. In this study, the use of natural ingredients, either from terrestrial or marine origin, in a panel of 444 sunscreen commercial formulations (2021) was analyzed. Ingredients from terrestrial organisms represent the large majority found in the analyzed sunscreen formulations (48%), whereas marine ingredients are present only in 13% of the analyzed products. A deeper analysis regarding the most prevalent families of ingredients from terrestrial and marine organisms used as top ingredients is also presented, as well as their mechanisms of action. This study provides an up-to-date overview of the sunscreen market regarding the use of natural ingredients, which is of relevance for scientists involved in the development of new sunscreens to identify opportunities for innovation.

A Review on Biodegradable Packaging Films from Vegetative and Food Waste

Plastics around the globe have been a matter of grave concern due to the unavoidable habits of human mankind. Taking waste statistics in India for the year 2019-20 into account, the data of 60 major cities show that the generation of plastic waste stands tall at around 26,000 tonnes/day, of which only about 60 % is recycled. A majority of the non-recycled plastic waste is petrochemical-based packaging materials that are non-biodegradable in nature. Vegetative/food waste is another global issue, evidenced by vastly populated countries such as China and India accounting for 91 and 69 tonnes of food wastage, respectively in 2019. The mitigation of plastic packaging issues has led to key scientific developments, one of which is biodegradable materials. However, there is a way that these two waste-related issues can be fronted as the analogy of "taking two shots with the same arrow". The presence of various bio-compounds such as proteins, cellulose, starch, lipids, and waxes, etc., in food and vegetative waste, creates an opportunity for the development of biodegradable packaging films. Although these flexible packaging films have limitations in terms of mechanical, permeation, and moisture absorption characteristics, they can be fine-tuned in order to convert the biobased raw material into a realizable packaging product. These strategies could work in replacing petrochemical-based non-biodegradable packaging plastics which are used in enormous quantities for various household and commercial packaging applications to combat the ever-increasing pollution in highly populated countries. This paper presents a systematic review based on modern scientific tools of the literature available with a major emphasis on the past decade and aims to serve as a standard resource for the development of biodegradable packaging films from food/vegetative waste.

Seaweeds' pigments and phenolic compounds with antimicrobial potential

Recently, there has been increased interest in the development of novel antimicrobial compounds for utilization in a variety of sectors, including pharmaceutical, biomedical, textile, and food. The use, overuse, and misuse of synthetic compounds or derivatives have led to an increase of pathogenic microorganisms gaining resistance to the traditional antimicrobial therapies, which has led to an increased need for alternative therapeutic strategies. Seaweed are marine organisms that can be cultivated sustainably, and they are a source of polar molecules, such as pigments and phenolic compounds, which demonstrated antimicrobial potential. This review focuses on current knowledge about pigments and phenolic compounds isolated from seaweeds, their chemical characteristics, antimicrobial bioactivity, and corresponding mechanism of action.

Coelastrella terrestris for Adonixanthin Production: Physiological Characterization and Evaluation of Secondary Carotenoid Productivity

A novel strain of Coelastrella terrestris (Chlorophyta) was collected from red mucilage in a glacier foreland in Iceland. Its morphology showed characteristic single, ellipsoidal cells with apical wart-like wall thickenings. Physiological characterization revealed the presence of the rare keto-carotenoid adonixanthin, as well as high levels of unsaturated fatty acids of up to 85%. Initial screening experiments with different carbon sources for accelerated mixotrophic biomass growth were done. Consequently, a scale up to 1.25 L stirred photobioreactor cultivations yielded a maximum of 1.96 mg·L-1 adonixanthin in free and esterified forms. It could be shown that supplementing acetate to the medium increased the volumetric productivity after entering the nitrogen limitation phase compared to autotrophic control cultures. This study describes a promising way of biotechnological adonixanthin production using Coelastrella terrestris.

Algae and Their Metabolites as Potential Bio-Pesticides

An increasing human population necessitates more food production, yet current techniques in agriculture, such as chemical pesticide use, have negative impacts on the ecosystems and strong public opposition. Alternatives to synthetic pesticides should be safe for humans, the environment, and be sustainable. Extremely diverse ecological niches and millions of years of competition have shaped the genomes of algae to produce a myriad of substances that may serve humans in various biotechnological areas. Among the thousands of described algal species, only a small number have been investigated for valuable metabolites, yet these revealed the potential of algal metabolites as bio-pesticides. This review focuses on macroalgae and microalgae (including cyanobacteria) and their extracts or purified compounds, that have proven to be effective antibacterial, antiviral, antifungal, nematocides, insecticides, herbicides, and plant growth stimulants. Moreover, the mechanisms of action of the majority of these metabolites against plant pests are thoroughly discussed. The available information demonstrated herbicidal activities via inhibition of photosynthesis, antimicrobial activities via induction of plant defense responses, inhibition of quorum sensing and blocking virus entry, and insecticidal activities via neurotoxicity. The discovery of antimetabolites also seems to hold great potential as one recent example showed antimicrobial and herbicidal properties. Algae, especially microalgae, represent a vast untapped resource for discovering novel and safe biopesticide compounds.

Dietary supplementation with microalgae enhances the zebrafish growth performance by modulating immune status and gut microbiota

Microalgae are known to be abundant in various habitats around the globe, and are rich in high value-added products such as fatty acids, polysaccharides, proteins, and pigments. Microalgae can be exploited as the basic and primitive food source of aquatic animals. We investigated the effects of dietary supplementation with Schizochytrium sp., Spirulina platensis, Chloroella sorokiniana, Chromochloris zofingiensis, and Dunaliella salina on the growth performance, immune status, and intestinal health of zebrafish (Danio rerio). The results showed that these five microalgae diets could improve the feed conversion rate (FCR), especially the D. salina (FCR = 1.02%) and Schizochytrium sp. (FCR = 1.20%) additive groups. Moreover, the microalgae diets decreased the gene expression level of the pro-inflammatory cytokines IL6, IL8, and IL1β at a normal physiological state of the intestine, especially the Schizochytrium sp., S. platensis, and D. salina dietary groups. The expression of neutrophil marker b7r was increased in the C. sorokiniana diet group; after, the zebrafish were challenged with Vibrio anguillarum, improving the ability to resist this disease. We also found that microalgae diets could regulate the gut microbiota of fish as well as increase the relative abundance of probiotics. To further explain, Cetobacterium was significantly enriched in the S. platensis additive group and Stenotrophomonas was higher in the Schizochytrium sp. additive group than in the other groups. Conversely, harmful bacteria Mycoplasma reduced in all tested microalgae diet groups. Our study indicated that these microalgae could serve as a food source supplement and benefit the health of fish. KEY POINTS: • Microalgae diets enhanced the growth performance of zebrafish. • Microalgae diets attenuated the intestinal inflammatory responses of zebrafish. • Microalgae diets modulated the gut microbiota composition to improve fish health.

The role of seaweed as a potential dietary supplementation for enteric methane mitigation in ruminants: Challenges and opportunities

Seaweeds are macroalgae, which can be of many different morphologies, sizes, colors, and chemical profiles. They include brown, red, and green seaweeds. Brown seaweeds have been more investigated and exploited in comparison to other seaweed types for their use in animal feeding studies due to their large sizes and ease of harvesting. Recent in vitro and in vivo studies suggest that plant secondary compound-containing seaweeds (e.g., halogenated compounds, phlorotannins, etc.) have the potential to mitigate enteric methane (CH4) emissions from ruminants when added to the diets of beef and dairy cattle. Red seaweeds including Asparagopsis spp. are rich in crude protein and halogenated compounds compared to brown and green seaweeds. When halogenated-containing red seaweeds are used as the active ingredient in ruminant diets, bromoform concentration can be used as an indicator of anti-methanogenic properties. Phlorotannin-containing brown seaweed has also the potential to decrease CH4 production. However, numerous studies examined the possible anti-methanogenic effects of marine seaweeds with inconsistent results. This work reviews existing data associated with seaweeds and in vitro and in vivo rumen fermentation, animal performance, and enteric CH4 emissions in ruminants. Increased understanding of the seaweed supplementation related to rumen fermentation and its effect on animal performance and CH4 emissions in ruminants may lead to novel strategies aimed at reducing greenhouse gas emissions while improving animal productivity.

Abiotic and Biotic Damage of Microalgae Generate Different Volatile Organic Compounds (VOCs) for Early Diagnosis of Algal Cultures for Biofuel Production

Open microalgal ponds used in industrial biomass production are susceptible to a number of biotic and abiotic environmental stressors (e.g., grazers, pathogens, pH, temperature, etc.) resulting in pond crashes with high economic costs. Identification of signature chemicals to aid in rapid, non-invasive, and accurate identification of the stressors would facilitate targeted and effective treatment to save the algal crop from a catastrophic crash. Specifically, we were interested in identifying volatile organic compounds (VOCs) that can be used to as an early diagnostic for algal crop damage. Cultures of Microchloropsis gaditana were subjected to two forms of algal crop damage: (1) active grazing by the marine rotifer, Brachionus plicatilis, or (2) repeated freeze–thaw cycles. VOCs emitted above the headspace of these algal cultures were collected using fieldable solid phase microextraction (SPME) fibers. An untargeted analysis and identification of VOCs was conducted using gas chromatography-mass spectrometry (GC-MS). Diagnostic VOCs unique to each algal crop damage mechanism were identified. Active rotifer grazing of M. gaditana was characterized by the appearance of carotenoid degradation products, including β-cyclocitral and various alkenes. Freeze–thaw algae produced a different set of VOCs, including palmitoleic acid. Both rotifer grazing and freeze–thawed algae produced β-ionone as a VOC, possibly suggesting a common stress-induced cellular mechanism. Importantly, these identified VOCs were all absent from healthy algal cultures of M. gaditana. Early detection of biotic or abiotic environmental stressors will facilitate early diagnosis and application of targeted treatments to prevent algal pond crashes. Thus, our work further supports the use of VOCs for monitoring the health of algal ponds to ultimately enhance algal crop yields for production of biofuel.

R-Phycoerythrin from Colaconema formosanum (Rhodophyta), an Anti-Allergic and Collagen Promoting Material for Cosmeceuticals

R-phycoerythrin (R-PE), a pigment complex found in red algae, was extracted and purified from a newly identified red alga, Colaconema formosanum, and its bioactivities were examined. It was revealed that R-PE treatment resulted in high cell viability (>70%) to the mammalian cell lines NIH-3T3, RBL-2H3, RAW264.7, and Hs68, and had no effect on cell morphology in NIH-3T3 cells. Its suppression effect was insignificant on the production of IL-6 and TNF-α in lipopolysaccharides-stimulated RAW264.7 cells. However, calcium ionophore A23187-induced β-hexosaminidase release was effectively inhibited in a dose-dependent manner in RBL-2H3 cells. Additionally, it was revealed to be non-irritating to bionic epidermal tissues. Notably, procollagen production was promoted in Hs68 cells. Overall, the data revealed that R-PE purified from C. formosanum exhibits anti-allergic and anti-aging bioactivities with no observed consequential toxicity on multiple mammalian cell lines as well as epidermal tissues, suggesting that this macromolecule is a novel material for potential cosmetic use.

Continuous measurements of volatile gases as detection of algae crop health

Algae cultivation in open raceway ponds is considered the most economical method for photosynthetically producing biomass for biofuels, chemical feedstocks, and other high-value products. One of the primary challenges for open ponds is diminished biomass yields due to attack by grazers, competitors, and infectious organisms. Higher-frequency observations are needed for detection of grazer infections, which can rapidly reduce biomass levels. In this study, real-time measurements were performed using chemical ionization mass spectrometry (CIMS) to monitor the impact of grazer infections on cyanobacterial cultures. Numerous volatile gases were produced during healthy growth periods from freshwater Synechococcus elongatus Pasteur Culture Collection (PCC) 7942, with 6-methyl-5-hepten-2-one serving as a unique metabolic indicator of exponential growth. Following the introduction of a Tetrahymena ciliate grazer, the concentrations of multiple volatile species were observed to change after a latent period as short as 18 h. Nitrogenous gases, including ammonia and pyrroline, were found to be reliable indicators of grazing. Detection of grazing by CIMS showed indicators of infections much sooner than traditional methods, microscopy, and continuous fluorescence, which did not detect changes until 37 to 76 h after CIMS detection. CIMS analysis of gases produced by PCC 7942 further shows a complex temporal array of biomass-dependent volatile gas production, which demonstrates the potential for using volatile gas analysis as a diagnostic for grazer infections. Overall, these results show promise for the use of continuous volatile metabolite monitoring for the detection of grazing in algal monocultures, potentially reducing current grazing-induced biomass losses, which could save hundreds of millions of dollars.

Molecular analysis of a fungal disease in the habitat-forming brown macroalga Phyllospora comosa (Fucales) along a latitudinal gradient

Infectious diseases affecting habitat-forming species can have significant impacts on population dynamics and alter the structure and functioning of marine ecosystems. Recently, a fungal infection was described as the causative agent of necrotic lesions on the stipe of the forest-forming macroalga Phyllospora comosa, a disease named "stipe rot" (SR). Here, we developed a quantitative PCR (qPCR) method for rapid detection and quantification of this pathogen, which was applied to evaluate the level of SR infection in eight P. comosa populations spanning the entire latitudinal distribution of this species along southeastern Australia. We also investigated the relationship between the abundance and prevalence of Stipe Rot Fungus (SRF) and potential host chemical defenses as well as its relationship with morphological and ecophysiological traits of P. comosa. qPCR estimates of SRF abundance reflected the levels of infection estimated by visual assessment, with higher numbers of SRF copies being observed in individuals showing high or intermediate levels of visual symptoms of SR. Concordance of conventional PCR and visual assessments was 92 and 94%, respectively, compared to qPCR detection. SRF prevalence was positively related to fucoxanthin content and herbivory, but not significant related to other traits measured (phlorotannin content, total length, thallus diameter, stipe width, number of branches, frond width, fouling, bleaching, gender, and photosynthetic efficiency). These results provide confidence for previous reports of this disease based upon visual assessments only, contribute to the development of monitoring and conservation strategies for safeguarding P. comosa forests, and generate insights into potential factors influencing host-pathogen interactions in this system.

Applying Seaweed Compounds in Cosmetics, Cosmeceuticals and Nutricosmetics

The interest in seaweeds for cosmetic, cosmeceutics, and nutricosmetics is increasing based on the demand for natural ingredients. Seaweeds offer advantages in relation to their renewable character, wide distribution, and the richness and versatility of their valuable bioactive compounds, which can be used as ingredients, as additives, and as active agents in the formulation of skin care products. Bioactive compounds, such as polyphenols, polysaccharides, proteins, peptides, amino acids, lipids, vitamins, and minerals, are responsible for the biological properties associated with seaweeds. Seaweed fractions can also offer technical features, such as thickening, gelling, emulsifying, texturizing, or moistening to develop cohesive matrices. Furthermore, the possibility of valorizing industrial waste streams and algal blooms makes them an attractive, low cost, raw and renewable material. This review presents an updated summary of the activities of different seaweed compounds and fractions based on scientific and patent literature.