Bioactivity and applications of sulphated polysaccharides from marine microalgae

Structural insights and bioactivity of a cell wall sulfated polysaccharide from the marine diatom Cyclotella cryptica

Sulfated Polysaccharides (SPs) are abundant in marine organisms, where they play an essential role in the mechanisms of adaptation to saline environments. SPs from macro- and microalgae possess unique structural features, which often correlate to taxonomy, and are under active investigation due to their various potential fields of application. We have investigated the structure of the sulfated polysaccharide isolated from the cell wall of the marine diatom Cyclotella cryptica (CcSP), finding that it consisted of a homopolysaccharide with a backbone of (1 → 4)-⍺-d-Manp carrying, in the most abundant form, sulfation at O-6. CcSP exhibited promising antiviral activity against Herpes Simplex Virus-1 (HSV-1), which was likely associated with a mechanism involving steric hindrance and/or electrostatic repulsion, preventing viral attachment to host cells. In addition, we have also proved the binding of CcSP to the innate human receptor Langerin, a well-known C-type lectin that recognizes sulfated polysaccharides and is involved in virus entry in cells. We attempted to partially reconstruct the biosynthetic pathway of CcSP: analysis of C. cryptica genome revealed the presence of several putative carbohydrate 6-O sulfotransferases (CH-STs) with homology to the human enzymes involved in glycosaminoglycans sulfation. Our results suggest an ancient evolutionary origin for the regioselective specialization of CH-STs, and could pave the way for future research on diatom cell wall biogenesis, as well as for biotechnological applications relying on the manipulation of the sulfation levels in CcSP for enhanced activity.

The microalgal sector in Europe: Towards a sustainable bioeconomy

Microalgae are a diverse group of photosynthetic microorganisms that can be exploited to produce sustainable food and feed products, alleviate environmental pollution, or sequester CO2 to mitigate climate change, among other uses. To optimize resource use and integrate industrial waste streams, it is essential to consider factors such as the biology and cultivation parameters of the microalgal strains, as well as the cultivation system and processing technologies employed. This paper reviews the main commercial applications of microalgae (including cyanobacteria) and examines the biological and biotechnological aspects critical to the sustainable processing of microalgal biomass and its derived compounds. We also provide an up-to-date overview of the microalgal sector in Europe considering the strain, cultivation system and commercial application. We have identified 146 different microalgal-derived products from 66 European microalgae producers, and 49 additional companies that provide services and technologies, such as optimization and scalability of the microalgal production. The most widely cultivated microalga is 'spirulina' (Limnospira spp.), followed by Chlorella spp. and Nannochloropsis spp., mainly for human consumption and cosmetics. The preferred cultivation system in Europe is the photobioreactor. Finally, we discuss the logistic and regulatory challenges of producing microalgae at industrial scale, particularly in the European Union, and explore the potential of new genomic techniques and bioprocessing to foster a sustainable bioeconomy in the microalgal sector.

Microalgae: A Promising Source of Bioactive Polysaccharides for Biotechnological Applications

Polysaccharides (PSs) are the most abundant carbohydrates in nature, performing essential biological functions such as immune system regulation, structural support, and cell communication. PSs from marine microalgae have gained increasing attention due to their diverse biological activities and potential applications in various fields, including the human health sector. These natural macromolecules, primarily composed of glucose, xylose, galactose, rhamnose, and fucose, exhibit bioactive properties influenced by their molecular weight, sulfation degree, and structural complexity. Microalgal PSs can function as antiviral, antimicrobial, antioxidant, immunomodulatory, and antitumor agents, making them promising candidates for pharmaceutical and nutraceutical applications. Additionally, their physicochemical properties make them valuable as bioactive ingredients in cosmetics, serving as hydrating agents, UV protectants, and anti-ageing compounds. The production of PSs from microalgae presents a sustainable alternative to terrestrial plants, as microalgae can be cultivated under controlled conditions, ensuring high yield and purity while minimizing environmental impact. Despite their potential, challenges remain in optimizing extraction techniques, enhancing structural characterization, and scaling up production for commercial applications. This review provides an overview of the principal biological activities of PSs from eukaryotic microalgae and their possible use as ingredients for cosmetic applications. Challenges to address to implement their use as products to improve human health and wellbeing are also discussed.

Tetrastigma hemsleyanum polysaccharide protects against "two-hit" induced severe pneumonia via TLR4/NF-κB signaling pathway

Severe pneumonia, frequently accompanied by cytokine storms, stands as a perilous respiratory condition with alarmingly high mortality rates. Tetrastigma hemsleyanum polysaccharide (THP), a pivotal constituent derived from Tetrastigma hemsleyanum Diels et Gilg (TH), has demonstrated efficacy in treating lung inflammation. However, its precise efficacy and underlying mechanisms in the context of severe pneumonia remain elusive. Our research aims to elucidate THP's protective effects in a "two-hit" severe pneumonia model. Our observations indicate that THP administration markedly shields the lungs from injury, reduces pulmonary apoptosis, balances the formation of immune thrombus and alleviates oxidative stress in pneumonia-induced mice. Furthermore, THP significantly decreases the levels of pro-inflammatory cytokines, suggesting its robust anti-inflammatory capabilities. Notably, THP also plays a crucial role in normalizing gut microbiota imbalance, which is vital in the pathogenesis of severe pneumonia. Metabolomic analysis further validates THP's restorative effects on plasma metabolites, indicating its involvement in regulating energy metabolism and immune homeostasis. Mechanistically, THP targets the TLR4/NF-κB signaling pathway, a core mediator of inflammation, thereby dampening the inflammatory cascade. In summary, our findings underscore that THP, through its multifaceted actions targeting inflammation, oxidative stress, immune thrombus formation, gut microbiota regulation, and metabolic modulation, emerges as a promising therapeutic approach for severe pneumonia. This study provides invaluable insights into the potential applications of natural polysaccharides in treating severe pneumonia and highlights the significance of the TLR4/NF-κB pathway in the disease's progression.

Innovation in Osteogenesis Activation: Role of Marine-Derived Materials in Bone Regeneration

Marine-derived biomaterials are emerging as promising candidates for tissue regeneration due to their sustainability, biocompatibility, bioactivity, and unique chemical structure. This review provides an overview of different marine-derived inorganic and organic materials, such as calcium carbonate, magnesium salts, silica, polysaccharides, bioactive peptides, and lipid-based compounds, and their effects in promoting osteogenesis. Specifically, the osteoinductive, osteoconductive, and osteointegrative activities of traditional and innovative materials that influence key molecular pathways such as BMP/Smad and Wnt/β-catenin signaling underlying bone formation will be evaluated. This review also prospects innovative approaches, i.e., phage display technology, to optimize marine-derived peptides for targeted bone regeneration. In the context of innovative and sustainable materials, this review suggests some interesting applications of unusual materials able to overcome the limitations of conventional ones and stimulate cellular regeneration of bone tissue by activating specific molecular pathways.

Microalgae in health care and functional foods: β-glucan applications, innovations in drug delivery and synthetic biology

Microalgae are emerging as a key player in healthcare, functional foods, and sustainable biotech due to their capacity to produce bioactive compounds like β-glucans, omega-3 fatty acids, and antioxidants in an eco-friendly manner. This review comprehensively discusses the role of microalgae in healthcare and functional foods, focusing particularly on β-glucan therapeutics, drug delivery innovations, and synthetic biology applications. In healthcare, microalgae-derived compounds show immense promise for treating diseases, boosting immunity, and tackling oxidative stress. Euglena-derived paramylon, a type of β-glucan, has shown potential in various medical applications, including immunomodulation and anticancer therapy. Synthetic biology and bioprocess engineering are enhancing microalgae's therapeutic and nutritional value, with applications in drug delivery and personalized medicine. To maximize the potential of microalgae, further research and development are needed to address scalability, regulatory alignment, and consumer acceptance, with a focus on interdisciplinary collaboration and sustainable practices to align healthcare innovation with environmental conservation.

Exploring Marine Biomineralization on the Al-Mg Alloy as a Natural Process for In Situ LDH Growth to Improve Corrosion Resistance

This study provides a detailed characterization of the AA5083 aluminum alloy, surface, and interface over 6 months of immersion in seawater, employing techniques such as SEM/EDX, GIXRD, μ-Raman and XPS. The purpose was to evaluate the evolution of the biomineralization process that occurs on the Al-Mg alloy. By investigating the specific conditions that favor the in situ growth of layered double hydroxide (LDH) during seawater immersion as a result of biomineralization, this research provides insights into marine biomineralization, highlighting its potential as an innovative and sustainable strategy for corrosion protection.

Wound Healing, Antioxidant, and Antiviral Properties of Bioactive Polysaccharides of Microalgae Strains Isolated from Greek Coastal Lagoons

Microalgae have gained significant attention as sustainable sources of high value compounds, such as bioactive polysaccharides that are usually rich in sulfated groups and exhibit antioxidant properties. Here, 14 new microalgae strains of the genera Tetraselmis, Dunaliella, and Nannochloropsis, isolated from Greek coastal lagoons were analyzed to quantify and characterize their polysaccharide content. Heterogeneity was observed regarding the content of their total sugars (5.5-40.9 g/100 g dry biomass). The strains with a total sugar content above 20% were analyzed concerning the content of total, α- and β-glucans. Tetraselmis verrucosa f. rubens PLA1-2 and T. suecica T3-1 were rich in β-glucans (11%, and 8.1%, respectively). The polysaccharides of the two Tetraselmis strains were isolated and they were mainly composed of glucose and galactose. The isolated polysaccharides were fractionated using ion-exchange-chromatography. The anionic fraction from T. verrucosa f. rubens PLA1-2 was rich in sulfated polysaccharides, had antioxidant capacity, and exhibited healing properties. The anionic polysaccharides from the two Tetraselmis strains did not negatively influence the viability of human cells, while exhibiting antiviral properties against the replication of Hepatitis C Virus (HCV), with median efficient concentrations (EC50) at a range of 210-258 μg/mL.

Amphora coffeiformis extracellular polymeric substances and their potential applications in lead removal

Microorganisms producing extracellular polymeric substances (EPS) are of great potential in numerous environmental applications. The present study explores the production and properties of extracellular polymeric substances (EPS) from Amphora coffeiformis diatom strain and their potential applications in environmental remediation. EPS were composed of a complex mixture of polysaccharides, proteins, humic substances and nucleic acids, with polyanionic characteristics as revealed by FTIR, Raman and zeta potential analyses. EPS showed high flocculation efficiency against kaolin clay at low dosages (5 mg/L) through a charge neutralization mechanism involving both polysaccharides and proteins. EPS also exhibited strong emulsification activity for various nonpolar substrates, mainly olive oil, corn oil, soybean oil, essence and diesel, with emulsification indexes above 80%. The emulsions were stable for 72 h under different NaCl concentrations (1-10% w/v). Moreover, EPS demonstrated remarkable adsorption capacity for lead, reaching a maximum of 1699.33 ± 89.61 mg/g under optimized conditions using Box-Behnken design. The adsorption mechanism involved multiple functional groups such as hydroxyl, carbonyl, carboxyl, phosphoric and sulfhydryl. Therefore, EPS from A. coffeiformis are a promising candidate for restoring environments contaminated by heavy metals.

Antimicrobial Activities of Polysaccharide-Rich Extracts from the Irish Seaweed Alaria esculenta, Generated Using Green and Conventional Extraction Technologies, Against Foodborne Pathogens

A rise in antimicrobial resistance coupled with consumer preferences towards natural preservatives has resulted in increased research towards investigating antimicrobial compounds from natural sources such as macroalgae (seaweeds), which contain antioxidant, antimicrobial, and anticancer compounds. This study investigates the antimicrobial activity of compounds produced by the Irish seaweed Alaria esculenta against Escherichia coli and Listeria innocua, bacterial species which are relevant for food safety. Microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), ultrasound-microwave-assisted extraction (UMAE), and conventional extraction technologies (maceration) were applied to generate extracts from A. esculenta, followed by their preliminary chemical composition (total phenolic content, total protein content, total soluble sugars) and antimicrobial activity (with minimum inhibitory concentration determined by broth microdilution methods), examining also the molecular weight distribution (via high performance size exclusion chromatography) and oligosaccharide fraction composition (via high-performance liquid chromatography) of the polysaccharides, as they were the predominant compounds in these extracts, aiming to elucidate structure-function relationships. The chemical composition of the extracts demonstrated that they were high in total soluble sugars, with the highest total sugars being seen from the extract prepared with UAE, having 32.68 mg glucose equivalents/100 mg dried extract. Extracts had antimicrobial activity against E. coli and featured minimum inhibitory concentration (MIC) values of 6.25 mg/mL (in the case of the extract prepared with UAE) and 12.5 mg/mL (in the case of the extracts prepared with MAE, UMAE, and conventional maceration). No antimicrobial activity was seen by any extracts against L. innocua. An analysis of molar mass distribution of A. esculenta extracts showed high heterogeneity, with high-molecular-weight areas possibly indicating the presence of fucoidan. The FTIR spectra also indicated the presence of fucoidan as well as alginate, both of which are commonly found in brown seaweeds. These results indicate the potential of antimicrobials from seaweeds extracted using green technologies.

Characterization and Otoprotective Effects of Polysaccharides from Arthrospira platensis

Hearing loss is one of the most common sensory disorders in humans, and a large number of cases are due to ear cell damage caused by ototoxic drugs including anticancer agents, such as cisplatin. The recent literature reported that hearing loss is promoted by an excessive generation of reactive oxygen species (ROS) in cochlea cells, which causes oxidative stress. Recently, polysaccharides from the cyanobacterium Arthrospira platensis showed many biological activities, including antioxidant activity, suggesting their potential use to combat hearing loss. On these bases, this study describes the extraction, purification, and characterization of water-soluble polysaccharides from A. platensis (SPPs) and the investigation of their protective role against cisplatin toxicity on House Ear Institute-Organ of Corti (HEI-OC1) cells. The results showed that SPPs (5-80 µg/mL) induced a dose-dependent increase in viability, statistically significant at 40 µg/mL and 80 µg/mL. Moreover, SPPs, evaluated at 80 µg/mL, inhibited the cisplatin-induced ROS level increase in HEI-OC1. This evidence highlights the potential of SPPs as natural candidates to protect cochlear ear cells against ototoxic oxidative agents. Moreover, in view of the potential use of microalgal polysaccharides to realize hydrogels, SPPs could also represent a healthy carrier for other topically administered otoprotective agents.

Efficacy of β-Glucan From Microalgae on the Intestinal Health and Growth of Nursery Pigs

This study aimed to investigate the efficacy of β-glucan from microalgae (Algamune, Algal Scientific, Plymouth, MI, USA) on the intestinal health and growth of nursery pigs. One hundred sixty nursery pigs (6.0 ± 1.6 kg BW) were assigned to four treatments arranged in a 2 × 2 factor: antibiotic use and β-glucan supplementation (0.02% Algamune). Diets were fed for 5 weeks, at which eight pigs from each treatment were selected for tissue sample collection. During the overall experimental period, antibiotics improved (p < 0.05) ADG and G:F. In Week 5, β-glucan supplementation increased (p < 0.05) the ADG of pigs without antibiotics, whereas β-glucan supplementation had no effect in pigs with antibiotics. In Phase 3, β-glucan supplementation tended to increase (p = 0.061) ADFI of pigs without antibiotics, whereas β-glucan supplementation had no effect in pigs with antibiotics. Both antibiotics and β-glucan increased (p < 0.05) villus height in the duodenum. Supplementation of β-glucan reduced (p < 0.05) IgA in the jejunum and tended to reduce (p = 0.053) IgA in the ileum. In conclusion, β-glucan from microalgae may encourage growth and feed intake of nursery pigs by improving intestinal health when antibiotics are not used in the diets.

Anti-arthritic potential of crude sulfated polysaccharide from marine macroalgae Sargassum ilicifolium (Turner) C. Agardh: Regulation of cytokine cascade

Seaweeds have been utilized as food, fodder, fertilizer, and medicine since ancient times; nevertheless, they have received only a little attention. In the current work, we extracted the sulfated polysaccharide from a marine source and investigated its anti-arthritic potential in vivo. The isolated and freeze-dried polysaccharide was tested for acute oral toxicity based on OECD 423. This step was followed by investigations on clinical signs and gross pathological alterations seen. A complete Freund's adjuvant-induced arthritis was used to test the in vivo activity in female Sprague-Dawley rats, which were divided into five groups: (1) normal control, (2) arthritic control, (3) methotrexate treatment (0.1 mg/kg), (4) crude sulfated polysaccharide (CSP) (5 mg/kg), and (5) CSP (10 mg/kg). CSP was from the marine brown algae Sargassum ilicifolium from the Gulf of Mannar. The body weight, paw volume, and biochemical markers (alanine aminotransferase, aspartate aminotransferase, creatinine, urea, and C-reactive protein levels) were also measured for each group coupled with histopathological and immunohistochemistry studies. The acute toxicity investigation indicated that the lethal dose of 50% (LD50) of the polysaccharide was more than 2,000 mg/kg. In addition, animals from the methotrexate and CSP (5 mg/kg, p.o.) groups had a substantial reduction in paw volume compared to other treatment groups. Methotrexate and CSP treatment dramatically decreased the levels of the investigated marker enzymes. Histopathology revealed that low-dose CSP (5 mg/kg, p.o.) significantly reduced the severity of synovitis, panniculitis, liver necrosis, inflammatory cell infiltration, and cortical and paracortical necrotic foci in node, compared to the high dose (10 mg/kg, p.o.). Immunohistochemical studies revealed that CSP (5 mg/kg) significantly inhibited pro-inflammatory cytokines such as tumor necrosis factor-alpha, interleukin-2, and CD4 cells. Overall, it can be concluded that a low-dose CSP (5 mg/kg) is an efficient anti-arthritic agent that confers its effects via the cytokine pathway.

Impact of recharge water source quality on Chlorella vulgaris growth and biomass: Strategies for eutrophication control in urban landscape lakes

Understanding the relationship between recharge water quality and algal metabolism is critical for managing eutrophication in urban landscape water bodies. This study investigates six landscape water bodies in Xi'an City, utilizing natural and reclaimed water recharge sources to cultivate and evaluate the growth and biomass composition of Chlorella vulgaris. The findings revealed that the growth and metabolic rate of C. vulgaris were faster in reclaimed water sources, whereas nitrogen (N) and phosphorus (P) conversion rates were higher in natural water sources. Redundancy and statistical analyses indicated that total nitrogen (TN) in reclaimed water was a major factor influencing C. vulgaris growth, contributing 74.3 % to its growth dynamics. In contrast, natural water sources did not significantly affect the growth characteristics of C. vulgaris. The biomass characteristics of C. vulgaris across different recharge water sources were similar, exhibiting a strong correlation with water quality. Environmental factors such as COD, N/P ratio, and PO4-P contributed most significantly to biomass accumulation. These findings provide a strategy for preventing and controlling eutrophication in landscape water bodies that utilize reclaimed water recharge sources in Xi'an City.

Anticoagulant Activity of the Polysaccharide Fromgonad of Abalone Haliotis discus hannai Ino: The Role of Conjugate Protein

Few studies are concerned with the effect of the conjugat protein on the bioactivities of the abalone gonad polysaccharide (AGP). In this study, a series of treatments, including raw material (female and male) defatting, extraction temperature (25-121 °C), proteolysis, ultrafiltration, and ethanol precipitation, was conducted to investigate the role of the conjugate protein on AGP anticoagulant activity. All AGP extracts significantly prolonged activated partial thromboplastin time (APTT) and thrombin time (TT). The strongest was observed in the female AGPs prepared at 50 and 121 °C. The most active is located at 30-300 kDa by ultrafiltration. After being exposed to neutral protease, quick shortening of APTT and TT was found in all AGPs. Further ethanol precipitating of found the longest APTT in the sediment, which contains most polysaccharides and proteins. Defatting lowered the activity of female AGP but increased that of males. Proteolysis also significantly weakened the clotting factor inhibition effect of the 50 °C female AGP, but heating seemed not affect the effect. Five fractions were obtained after the 50 °C female AGP was subjected to ion exchange column. Fraction V, with the highest protein and medium polysaccharide content, showed the strongest anticoagulant effect and was also much higher than AGSP, which was obtained by multi-step proteolysis. The findings supported positive effect of the conjugate protein in AGP anticoagulant activity.

Exploring the versatility of Porphyridium sp.: A comprehensive review of cultivation, bio-product extraction, purification, and characterization techniques

Interest in red microalgae of the Porphyridium genus has surged due to their richness in phycobiliproteins, polyunsaturated fatty acids, and sulfated polysaccharides. These biomasses and their derivatives find applications across food, feed, nutraceutical, pharmaceutical, and cosmetic industries. A deeper understanding of their properties and extraction methods is essential to optimize downstream processing. This paper comprehensively reviews Porphyridium sp., focusing on cultivation techniques, bioproduct extraction, purification, and characterization. It delves into protein, lipid, and polysaccharide extraction, considering the influence of culture conditions on biomass yield. Various methods like chromatography, electrophoresis, and membrane-based techniques for cell lysis and bioproduct recovery are explored, highlighting their pros and cons. By offering diverse insights, this review aims to inspire innovative research and industry progress in red microalgae biotechnology, contributing to sustainable solutions across sectors.

Growth potential, biochemical properties and nutrient removal efficiency of some freshwater microalgae and their consortia from wastewater

Impact of varying nitrate (NO3-N) and phosphate (PO4-P) concentrations and sewage water (SW) on the growth, nutrient removal, lipid accumulation, enzymatic antioxidant activity and phytochemical contents of the microalgae Scenedesmus dimorphus, Coelastrella tenuitheca, Chroococcus turgidus and Parachlorella kessleri under monoculture and their consortia have been investigated. High growth rates were observed for all the four algae in both mono and mixed culture conditions at enhanced concentrations of N (1500 mg/L NO3-N) and P (40 mg/L PO4-P). The species Scenedesmus dimorphus outperformed other microalgae growing in SW in efficiently removing nitrogen. The algal consortia of mixed species was found to be more effective in phosphorus removal. The carbohydrate and protein contents were highest in Parachlorella kessleri, about 37% and 44%, respectively, in SW cultivation. The algal consortia demonstrated highest starch content (4%) in nitrogen deprived growth medium. Highest lipid production (43%) was observed in the SW culture. The species Coelastrella tenuitheca, Chroococcus turgidus and Scenedesmus dimorphus irrespective of the growth media indicated significant accumulation of phenol, flavonoid and tannin. The DPPH, catalase and ascorbic peroxidase assay showed pronounced antioxidant activity. Nutrient (N and P) enrichment exhibited enhanced antioxidant enzymatic activity and accumulation of cell storage products.

Size fractionation informs microbial community composition and interactions in the eastern tropical North Pacific Ocean

Marine microorganisms are drivers of biogeochemical cycles in the world's oceans, including oxygen minimum zones (OMZs). Using a metabarcoding survey of the 16S rRNA gene, we investigated prokaryotic communities, as well as their potential interactions with fungi, at the coastal, offshore, and peripheral OMZ of the eastern tropical North Pacific. Water samples were collected along a vertical oxygen gradient, and large volumes were filtered through three size fractions, 0.22, 2, and 22 µm. The changes in community composition along the oxygen gradient were driven by Planctomycetota, Bacteroidota, Verrucomicrobiota, and Gammaproteobacteria; most are known degraders of marine polysaccharides and usually associated with the large particle-associated (LPA) community. The relative abundance of Nitrososphaerota, Alphaproteobacteria, Actinomycetota, and Nitrospinota was high in free-living and small particle-associated (SPA) communities. Network analyses identified putative interactions between fungi and prokaryotes in the particle-associated fractions, which have been largely overlooked in the ocean. In the SPAnetwork analysis, fungal amplicon sequence variants (ASVs) had exclusively negative connections with SAR11 nodes. In the LPA network analysis, fungal ASVs displayed both negative and positive connections with Pseudomonadota, SAR324, and Thermoplasmatota. Our findings demonstrate the utility of three-stage size-fractioned filtration in providing novel insights into marine microbial ecology.

Synthesis of polysaccharides by microalgae Chlorella sp

Microalgae are known to be the richest natural source of polysaccharides. The study aimed to evaluate the ability of microalgae from the Chlorella sp. genus to synthesize polysaccharides. Brody & Emerson max medium proved to be the most effective; the average cell content in the culture fluid at the beginning and at the end of cultivation for IPPAS Chlorella pyrenoidosa Chick was 1.23 ± 0.03 g/L and 1.71 ± 0.20 g/L, respectively. With a high average dry weight of IPPAS Chlorella pyrenoidosa Chick (4.45 ± 0.10 g/L), it produced the least amount of neutral sugars (0.75 ± 0.02 g/L) and uronic acids (0.14 ± 0.01 mg/L). The microalga IPPAS Chlorella vulgaris with the lowest average dry weight (1.18 ± 0.03 g/L) produced 0.80 ± 0.02 g/L of neutral sugars and 0.17 ± 0.01 mg/L of uronic acids. Microalgal polysaccharides have the potential to be used as a source for biologically active food additives, as they contain various types of polysaccharides that can be beneficial to human health.

Microalgal extracellular polymeric substances (EPS) and their roles in cultivation, biomass harvesting, and bioproducts extraction

Microalgae extracellular polymeric substances (EPS) are complex high-molecular-weight polymers and the physicochemical properties of EPS strongly affect the core features of microalgae cultivation and resource utilization. Revealing the key roles of EPS in microalgae life-cycle processes in an interesting and novelty topic to achieve energy-efficient practical application of microalgae. This review found that EPS showed positive effect in non-gas uptake, extracellular electron transfer, toxicity resistance and heterotrophic symbiosis, but negative impact in gas transfer and light utilization during microalgae cultivation. For biomass harvesting, EPS favored biomass flocculation and large-size cell self-flocculation, but unfavored small size microalgae self-flocculation, membrane filtration, charge neutralization and biomass dewatering. During bioproducts extraction, EPS exhibited positive impact in extractant uptake, but the opposite effect in cellular membrane permeability and cell rupture. Future research on microalgal EPS were also identified, which offer suggestions for comprehensive understanding of microalgal EPS roles in various scenarios.

Subcritical Water Extraction of Undaria pinnatifida: Comparative Study of the Chemical Properties and Biological Activities across Different Parts

The subcritical water extraction of Undaria pinnatifida (blade, sporophyll, and root) was evaluated to determine its chemical properties and biological activities. The extraction was conducted at 180 °C and 3 MPa. Root extracts exhibited the highest phenolic content (43.32 ± 0.19 mg phloroglucinol/g) and flavonoid content (31.54 ± 1.63 mg quercetin/g). Sporophyll extracts had the highest total sugar, reducing sugar, and protein content, with 97.35 ± 4.23 mg glucose/g, 56.44 ± 3.10 mg glucose/g, and 84.93 ± 2.82 mg bovine serum albumin (BSA)/g, respectively. The sporophyll contained the highest fucose (41.99%) and mannose (10.37%), whereas the blade had the highest galactose (48.57%) and glucose (17.27%) content. Sporophyll had the highest sulfate content (7.76%). Key compounds included sorbitol, glycerol, L-fucose, and palmitic acid. Root extracts contained the highest antioxidant activity, with IC50 values of 1.51 mg/mL (DPPH), 3.31 mg/mL (ABTS+), and 2.23 mg/mL (FRAP). The root extract exhibited significant α-glucosidase inhibitory activity with an IC50 of 5.07 mg/mL, indicating strong antidiabetic potential. The blade extract showed notable antihypertensive activity with an IC50 of 0.62 mg/mL. Hence, subcritical water extraction to obtain bioactive compounds from U. pinnatifida, supporting their use in functional foods, cosmetics, and pharmaceuticals is highlighted. This study uniquely demonstrates the variation in bioactive compound composition and bioactivities across different parts of U. pinnatifida, providing deeper insights. Significant correlations between chemical properties and biological activities emphasize the use of U. pinnatifida extracts for chronic conditions.

Anti-Vasculogenic, Antioxidant, and Anti-Inflammatory Activities of Sulfated Polysaccharide Derived from Codium tomentosum: Pharmacokinetic Assay

The purpose of this paper was to investigate the anti-inflammatory and anti-angiogenic activities of sulfated polysaccharide from C. tomentosum (PCT) using carrageenan (CARR)-induced paw edema in a rat model and anti-vasculogenic activity on a chorioallantoic membrane assay (CAM) model. Based on in vitro tests of anti-radical, total antioxidant, and reducing power activities, PCT presents a real interest via its antioxidant activity and ability to scavenge radical species. The in vivo pharmacological tests suggest that PCT possesses anti-inflammatory action by reducing paw edema and leukocyte migration, maintaining the redox equilibrium, and stabilizing the cellular level of several pro-/antioxidant system markers. It could significantly decrease the malondialdehyde levels and increase superoxide dismutase, glutathione peroxidase, and glutathione activities in local paw edema and erythrocytes during the acute inflammatory reaction of CARR. PCT pretreatment was effective against DNA alterations in the blood lymphocytes of inflamed rats and reduced the hematological alteration by restoring blood parameters to normal levels. The anti-angiogenic activity results revealed that CAM neovascularization, defined as the formation of new vessel numbers and branching patterns, was decreased by PCT in a dose-dependent manner, which supported the in silico bioavailability and pharmacokinetic findings. These results indicated the therapeutic effects of polysaccharides from C. tomentosum and their possible use as anti-proliferative molecules based on their antioxidant, anti-inflammatory, and anti-angiogenic activities.

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.

Bilayer coatings for extension of the shelf life of fish fillets: Incorporating seaweed sulfated polysaccharides in chitosan-alginate LbL structures

The aim of this study was to develop a new active coating of layer-by-layer (LbL) structure composed of alginate (as polyanions) and chitosan (as a polycation) containing sulfated polysaccharide (fucoidan) from Sargassum angustifolium, to protect rainbow trout fillets during refrigerated storage. Chitosan and alginate do not combine with each other as a homogeneous solution, so they are suitable for multilayer coatings. The results demonstrated that coating samples with chitosan and fucoidan significantly improved the quality of fish fillets and extended their shelf life from 6 to 16 days. The chemical values (TBARS and TVB-N) and bacterial growth (total viable count (TVC), total psychrophilic count (PTC), and lactic acid bacteria (LAB)) indicated lower levels in the LbL coating samples containing fucoidan compared to the alginate and control samples. Among the different coating samples, the LbL coating with fucoidan (AChF1) exhibited lower weight loss, improved chromaticity (L*, a*, and b*), and minimal changes in mechanical and sensory evaluations. Based on the findings, AChF1 was the most effective treatment for increasing the shelf life of rainbow trout fillets during refrigerated storage. Therefore, it has potential applications in the food packaging industry.

Physicochemical surface properties of Chlorella vulgaris: a multiscale assessment, from electrokinetic and proton uptake descriptors to intermolecular adhesion forces

Given the growing scientific and industrial interests in green microalgae, a comprehensive understanding of the forces controlling the colloidal stability of these bioparticles and their interactions with surrounding aqueous microenvironment is required. Accordingly, we addressed here the electrostatic and hydrophobic surface properties of Chlorella vulgaris from the population down to the individual cell levels. We first investigated the organisation of the electrical double layer at microalgae surfaces on the basis of electrophoresis measurements. Interpretation of the results beyond zeta-potential framework underlined the need to account for both the hydrodynamic softness of the algae cells and the heterogeneity of their interface formed with the outer electrolyte solution. We further explored the nature of the structural charge carriers at microalgae interfaces through potentiometric proton titrations. Extraction of the electrostatic descriptors of interest from such data was obscured by cell physiology processes and dependence thereof on prevailing measurement conditions, which includes light, temperature and medium salinity. As an alternative, cell electrostatics was successfully evaluated at the cellular level upon mapping the molecular interactions at stake between (positively and negatively) charged atomic force microscopy tips and algal surface via chemical force microscopy. A thorough comparison between charge-dependent tip-to-algae surface adhesion and hydrophobicity level of microalgae surface evidenced that the contribution of electrostatics to the overall interaction pattern is largest, and that the electrostatic/hydrophobic balance can be largely modulated by pH. Overall, the combination of multiscale physicochemical approaches allowed a drawing of some of the key biosurface properties that govern microalgae cell-cell and cell-surface interactions.

Immunomodulation by xylan and carrageenan-type polysaccharides from red seaweeds: Anti-inflammatory, wound healing, cytoprotective, and anticoagulant activities

The immunomodulatory properties of the polysaccharides (carrageenan, xylan) from Chondrus crispus (CC), Ahnfeltiopsis devoniensis (AD), Sarcodiotheca gaudichaudii (SG) and Palmaria palmata (PP) algal species were studied. Using RAW264.7 macrophages, we investigated the proliferation and migration capacity of different extracts along with their immunomodulatory activities, including nitric oxide (NO) production, phagocytosis, and secretion of pro-inflammatory cytokines. Polysaccharides from C. crispus and S. gaudichaudii effectively mitigated inflammation and improved scratch-wound healing. Polysaccharide fractions extracted under cold conditions (25 °C), including CC-1A, SG-1A and SG-1B stimulated cell proliferation, while fractions extracted under hot conditions (95 °C), including CC-3A, CC-2B and A. devoniensis (AD-3A), inhibited cell proliferation after 48 h. Furthermore, RAW264.7 cells treated with the fractions CC-3A, AD-1A, and SG-2A significantly reduced LPS-stimulated NO secretion over 24 h. Phagocytosis was significantly improved by treatment with C. crispus (CC-2B, CC-3B) and A. devoniensis (AD-3A) fractions. RAW264.7 cells treated with the CC-2A and SG-1A fractions showed elevated TGF-β1 expression without affecting TNF-α expression at 24 h. Polysaccharide fractions of A. devoniensis (ι/κ hybrid carrageenan; AD-2A, AD-3A) showed the highest anti-coagulation activity. CC-2A and SG-1A fractions enhanced various bioactivities, suggesting they are candidates for skin-health applications. The carrageenan fractions (CC-3A: λ-, μ-carrageenan, SG-2A: ν-, ι-carrageenan) tested herein showed great potential for developing anti-inflammatory and upscaled skin-health applications.

Challenges in Functional Food Products with the Incorporation of Some Microalgae

Much attention has been given to the use of microalgae to produce functional foods that have valuable bioactive chemicals, including essential amino acids, polyunsaturated fatty acids, vitamins, carotenoids, fiber, and minerals. Microalgal biomasses are increasingly being used to improve the nutritional values of foods because of their unique nutrient compositions that are beneficial to human health. Their protein content and amino acid composition are the most important components. The microalgal biomass used in the therapeutic supplement industry is dominated by bio-compounds like astaxanthin, β-carotene, polyunsaturated fatty acids like eicosapentaenoic acid and docosahexaenoic acid, and polysaccharides such as β-glucan. The popularity of microalgal supplements is growing because of the health benefits of their bioactive substances. Moreover, some microalgae, such as Dunaliella, Arthrospira (Spirulina), Chlorella, and Haematococcus, are commonly used microalgal species in functional food production. The incorporation of microalgal biomass leads not only to enhanced nutritional value but also to improved sensory quality of food products without altering their cooking or textural characteristics. Microalgae, because of their eco-friendly potential, have emerged as one of the most promising and novel sources of new functional foods. This study reviews some recent and relevant works, as well as the current challenges for future research, using different methods of chemical modification in foods with the addition of a few commercial algae to allow their use in nutritional and sensory areas. It can be concluded that the production of functional foods through the use of microalgae in foods has become an important issue.

Biochemical responses of freshwater microalgae Chlorella sorokiniana to combined exposure of Zn(Ⅱ) and estrone with simultaneous pollutants removal

With the development of livestock industry, contaminants such as divalent zinc ions (Zn (Ⅱ)) and estrone are often simultaneously detected in livestock wastewater. Nevertheless, the combined toxicity of these two pollutants on microalgae is still unclear. Moreover, microalgae have the potential for biosorption and bioaccumulation of heavy metals and organic compounds. Thus, this study investigated the joint effects of Zn (Ⅱ) and estrone on microalgae Chlorella sorokiniana, in terms of growth, photosynthetic activity and biomolecules, as well as pollutants removal by algae. Interestingly, a low Zn (Ⅱ) concentration promoted C. sorokiniana growth and photosynthetic activity, while the high concentration experienced inhibition. As the increase of estrone concentration, chlorophyll a content increased continuously to resist the environmental stress. Concurrently, the secretion of extracellular polysaccharides and proteins by algae increased with exposure to Zn (Ⅱ) and estrone, reducing toxicity of pollutants to microalgae. Reactive oxygen species and superoxide dismutase activity increased as the increase of pollutant concentration after 96 h cultivation, but high pollutant concentrations resulted in damage of cells, as proved by increased MDA content. Additionally, C. sorokiniana displayed remarkable removal efficiency for Zn (Ⅱ) and estrone, reaching up to 86.14% and 84.96% respectively. The study provides insights into the biochemical responses of microalgae to pollutants and highlights the potential of microalgae in pollutants removal.

Microalgae's polysaccharides, are they potent antioxidants? Critical review

The scientific community continue to explore novel bioactive molecules by investigating natural origins; microalgae are photosynthetic organisms considered as a sustainable resource to use in many fields. They present a high diversity in species and richness in terms of attractive bio-compounds. The aim of this review is to (1) provide first an overview of current issues related to oxidative stress, and propose a natural metabolite derived from eukaryotic and prokaryotic microalgae; 'polysaccharides' as a powerful antioxidant agent, then, (2) organize the available data on the antioxidant potential of polysaccharides derived from the main microalgal groups (red microalgae, green microalgae, and cyanobacteria) and especially highlighted the key species of each group (Porphyridium sp., Chlorella sp., and Arthrospira sp., respectively), meanwhile, (3) we described the chemical composition of polysaccharides from each class, and (4) we cite briefly the most factors affecting the antioxidant activity of these molecules. Finally, we explored the major challenges and gaps found to require more investigation.

Polysaccharides from Spirulina platensis (PSP): promising biostimulants for the green synthesis of silver nanoparticles and their potential application in the treatment of cancer tumors

Photosynthetic cyanobacterial components are gaining great economic importance as prospective low-cost biostimulants for the green synthesis of metal nanoparticles with valuable medical and industrial applications. The current study comprises the biological synthesis of silver nanoparticles (Ag-NPs) using soluble polysaccharides isolated from Spirulina platensis (PSP) as reducing and capping agents. FTIR spectra showed major functional groups of PSP and biogenic silver nanoparticles including O-H, C-H (CH2), C-H (CH3), C=O, amide, and COO- groups. The UV/Vis spectroscopy scan analyses of the extracted PSP showed absorption spectra in the range of 200-400 nm, whereas the biogenic Ag-NPs showed a maximum spectrum at 285 nm. Transmission electron microscopy (TEM) analysis of the synthesized Ag-NPs showed spherical nanoparticles with mean size between 12 and 15.3 nm. The extracted PSP and Ag-NPs exhibited effective cytotoxic activity against Hep-G2 (human hepatocellular carcinoma). The IC50 for PSP and Ag-NPs were 65.4 and 24.5 µg/mL, respectively. Moreover, cell apoptosis assays for PSP and Ag-NPs against the growth of Hep-G2 cells revealed superior growth inhibitory effects of the green synthesized Ag-NPs that encouraged tracing the apoptotic signalling pathway. In conclusion, the current study demonstrated an unprecedented approach for the green synthesis of silver nanoparticles (NPs), using the polysaccharide of Spirulina platensis as reducing and capping agents, with superior anticancer activity against a hepatocellular carcinoma cell line.

Tropical Seaweeds as a Sustainable Resource Towards Circular Bioeconomy: Insights and Way Forward

Seaweeds are photosynthetic marine macroalgae known for their rapid biomass growth and their significant contributions to global food and feed production. Seaweeds play a crucial role in mitigating various environmental issues, including greenhouse gases, ocean acidification, hypoxia, and eutrophication. Tropical seaweeds are typically found in tropical and subtropical coastal zones with warmer water temperatures and abundant sunlight. These tropical seaweeds are rich sources of proteins, vitamins, minerals, fibers, polysaccharides, and bioactive compounds, contributing to their health-promoting properties and their diverse applications across a range of industries. The productivity, cultivability, nutritional quality, and edibility of tropical seaweeds have been well-documented. This review article begins with an introduction to the growth conditions of selected tropical seaweeds. Subsequently, the multifunctional properties of tropical seaweeds including antioxidant and anti-inflammatory, anti-coagulant, anti-carcinogenic and anti-proliferative, anti-viral, therapeutic and preventive properties were comprehensively evaluated. The potential application of tropical seaweeds as functional foods and feeds, as well as their contributions to sustainable cosmetics, bioenergy, and biofertilizer production were also highlighted. This review serves as a valuable resource for researchers involved in seaweed farming as it provides current knowledge and insights into the cultivation and utilization of seaweeds.

Bioprospecting for new exopolysaccharide-producing microalgae of marine origin

Microalgae are photosynthetic organisms that can produce biomolecules with industrial interest, including exopolysaccharides (EPS). Due to their structural and compositional diversity, microalgae EPS present interesting properties that can be considered in cosmetic and/or therapeutic areas. Seven microalgae strains from three different lineages, namely Dinophyceae (phylum Miozoa), Haptophyta, and Chlorophyta, were investigated as EPS producers. All strains were found to be EPS producers, though the highest EPS yield was obtained for Tisochrysis lutea, followed by Heterocapsa sp. (126.8 and 75.8 mg L-1, respectively). Upon assessment of the polymers' chemical composition, significant contents of unusual sugars, including fucose, rhamnose, and ribose, were found. Heterocapsa sp. EPS stood out due to its high content of fucose (40.9 mol%), a sugar known to confer biological properties to polysaccharides. The presence of sulfate groups (10.6-33.5 wt%) was also noticed in the EPS produced by all microalgae strains, thus contributing to the possibility that these EPS might have biological activities worth exploring.

Environmental modulation of exopolysaccharide production in the cyanobacterium Synechocystis 6803

Microorganisms produce extracellular polymeric substances (EPS, also known as exopolysaccharides) of diverse composition and structure. The biochemical and biophysical properties of these biopolymers enable a wide range of industrial applications. EPS from cyanobacteria are particularly versatile as they incorporate a larger number and variety of building blocks and adopt more complex structures than EPS from other organisms. However, the genetic makeup and regulation of EPS biosynthetic pathways in cyanobacteria are poorly understood. Here, we measured the effect of changing culture media on titre and composition of EPS released by Synechocystis sp. PCC 6803, and we integrated this information with transcriptomic data. Across all conditions, daily EPS productivity of individual cells was highest in the early growth phase, but the total amount of EPS obtained from the cultures was highest in the later growth phases due to accumulation. Lowering the magnesium concentration in the media enhanced per-cell productivity but the produced EPS had a lower total sugar content. Levels of individual monosaccharides correlated with specific culture media components, e.g. xylose with sulfur, glucose and N-acetyl-galactosamine with NaCl. Comparison with RNA sequencing data suggests a Wzy-dependent biosynthetic pathway and a protective role for xylose-rich EPS. This multi-level analysis offers a handle to link individual genes to the dynamic modulation of a complex biopolymer. KEY POINTS: • Synechocystis exopolysaccharide amount and composition depends on culture condition • Production rate and sugar content can be modulated by Mg and S respectively • Wzy-dependent biosynthetic pathway and protective role proposed for xylose-rich EPS.

The osteogenic and mineralogenic potential of the microalgae Skeletonema costatum and Tetraselmis striata CTP4 in fish models

Skeletal disorders are problematic aspects for the aquaculture industry as skeletal deformities, which affect most species of farmed fish, increase production costs and affect fish welfare. Following recent findings that show the presence of osteoactive compounds in marine organisms, we evaluated the osteogenic and mineralogenic potential of commercially available microalgae strains Skeletonema costatum and Tetraselmis striata CTP4 in several fish systems. Ethanolic extracts increased extracellular matrix mineralization in gilthead seabream (Sparus aurata) bone-derived cell cultures and promoted osteoblastic differentiation in zebrafish (Danio rerio) larvae. Long-term dietary exposure to both extracts increased bone mineralization in zebrafish and upregulated the expression of genes involved in bone formation (sp7, col1a1a, oc1, and oc2), bone remodeling (acp5a), and antioxidant defenses (cat, sod1). Extracts also improved the skeletal status of zebrafish juveniles by reducing the incidence of skeletal anomalies. Our results indicate that both strains of microalgae contain osteogenic and mineralogenic compounds, and that ethanolic extracts have the potential for an application in the aquaculture sector as dietary supplements to support fish bone health. Future studies should also identify osteoactive compounds and establish whether they can be used in human health to broaden the therapeutic options for bone erosive disorders such as osteoporosis.

Characterization and anticancer effects of extracellular polysaccharide from DHA-producing microalga Crypthecodinium sp. SUN

The Characterization and anticancer effects of extracellular polysaccharide (EPS) from DHA-producing microalga Crypthecodinium sp. SUN were studied in the present research. Results showed that EPS from C. sp. SUN have a molecular weight of 1.118 × 106 g/mol. EPS significantly inhibited the proliferation and migration of LA795 lung adenocarcinoma cells, and the apoptosis rate decreased in a concentration-dependent manner, reached 52 % at 15 mg/mL. C. sp. SUN EPS also significantly decreased reactive oxygen species (ROS) level by over 50 %, superoxide dismutase (SOD) activity by 76 %, and catalase (CAT) activity by 34 % at 10 mg/mL, indicating that EPS may inhibit tumor cell growth instead of killing tumor cells. Additionally, C. sp. SUN EPS suppressed cell proliferation by downregulating the expression of adhesion proteins and cyclin D1 in LA795 cells. In vivo experiments demonstrated that C. sp. SUN EPS inhibited the growth of lung adenocarcinoma tumors without affecting the normal body weight of nude mice. Collectively, the present study showed that C. sp. SUN EPS could be a potential substance for cancer treatment, which provided a research basis for future study on EPS and expanded the application of Crypthecodinium.

The role of bacterial exopolysaccharides (EPS) in the synthesis of antimicrobial silver nanomaterials: A state-of-the-art review

The emergence of multi-drug resistant (MDR) pathogens poses a significant global health concern due to the failure of conventional medical treatment. As a result, the development of several metallic (Ag, Au, Zn, Ti, etc.) nanoparticles, has gained prominence as an alternative to conventional antimicrobial therapies. Among these, green-synthesized silver nanoparticles (AgNPs) have gained significant attention due to their notable efficiency and broad spectrum of antimicrobial activity. Bacterial exopolysaccharides (EPS) have recently emerged as a promising biological substrate for the green synthesis of AgNPs. EPS possess polyanionic functional groups (hydroxyl, carboxylic, sulfate, and phosphate) that effectively reduce and stabilize AgNPs. EPS-mediated AgNPs exhibit a wide range of antimicrobial activity against various pathogenic microbes, including Gram-positive and Gram-negative bacteria, as well as fungi. The extraction and purification of bacterial EPS play a vital role in obtaining high-quality and -quantity EPS for industrial applications. This study focuses on the comprehensive methodology of EPS extraction and purification, encompassing screening, fermentation optimization, pretreatment, protein elimination, precipitation, and purification. The review specifically highlights the utilization of bacterial EPS-mediated AgNPs, covering EPS extraction, the synthesis mechanism of green EPS-mediated AgNPs, their characterization, and their potential applications as antimicrobial agents against pathogens. These EPS-mediated AgNPs offer numerous advantages, including biocompatibility, biodegradability, non-toxicity, and eco-friendliness, making them a promising alternative to traditional antimicrobials and opening new avenues in nanotechnology-based approaches to combat microbial infections.

Extraction and application of extracellular polymeric substances from fungi

Extracellular polymeric substances (EPS) are extracellular metabolites of microorganisms, highly associated with microbial function, adaptation, and growth. The main compounds in EPS have been revealed to be proteins, polysaccharides, nucleic acids, humic substances, lipids, etc. EPS are not only biomass, but also a biogenic material. EPS have high specific surface, abundant functional groups, and excellent degradability. In addition, they are more extensible to the environment than the microbial cells themselves, which exhibits their huge advantages. Therefore, they have been applied in many fields, such as the environment, ecosystem, basic commodities, and medicine. However, the functions of EPS highly depend on the suitable extraction process, as different extraction methods have different effects on their composition, structure, and function. There are many types of EPS extraction methods, in which physical and chemical methods have been widely utilized. This review summarizes the extraction methods and applications of EPS. In addition, it considers some important gaps in current knowledge, and indicates perspectives of EPS for their future study.

Exploring Bioactive Compounds in Brown Seaweeds Using Subcritical Water: A Comprehensive Analysis

In this study, we characterized the bioactive properties of three important brown seaweed species, Sargassum thunbergii, Undaria pinnatifida, and Saccharina japonica, by subcritical water extraction (SWE), as these species are well known for their beneficial health effects. Their physiochemical properties, including potential antioxidant, antihypertensive, and α-glucosidase inhibitory activity, and the antibacterial activity of the hydroysates were also analyzed. The highest total phlorotannin, total sugar content, and reducing sugar content in the S. thunbergii hydrolysates were 38.82 ± 0.17 mg PGE/g, 116.66 ± 0.19 mg glucose/g dry sample, and 53.27 ± 1.57 mg glucose/g dry sample, respectively. The highest ABTS⁺ and DPPH antioxidant activities were obtained in the S. japonica hydrolysates (124.77 ± 2.47 and 46.35 ± 0.01 mg Trolox equivalent/g, respectively) and the highest FRAP activity was obtained in the S. thunbergii hydrolysates (34.47 ± 0.49 mg Trolox equivalent/g seaweed). In addition, the seaweed extracts showed antihypertensive (≤59.77 ± 0.14%) and α-glucosidase inhibitory activity (≤68.05 ± 1.15%), as well as activity against foodborne pathogens. The present findings provide evidence of the biological activity of brown seaweed extracts for potential application in the food, pharmaceutical, and cosmetic sectors.

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.

Effect of mussel polysaccharide on glucolipid metabolism and intestinal flora in type 2 diabetic mice

BACKGROUND

Type 2 diabetes (T2D) mellitus is a major metabolic disease, and its incidence and lethality have increased significantly in recent years, making it a serious threat to human health. Among numerous previous studies, polysaccharides have been shown to alleviate the adverse effects of T2D, but there are still problems such as insufficient analysis and poor understanding of the mechanisms by which polysaccharides, especially those of marine origin, regulate T2D.

METHODS

In this study, we used multiple allosteric approaches to further investigate the regulatory effects of mussel polysaccharides (MPs) on T2D and gut microbiota disorders in mice by identifying changes in genes, proteins, metabolites and target organs associated with glucolipid metabolism using an animal model of T2D fed with high-fat diets, and to explore the underlying molecular mechanisms.

RESULTS

After MP intervention, serum levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and high-density lipoprotein cholesterol (HDL-C) were up-regulated, and blood glucose and lipid levels were effectively reduced in T2D mice. Activation of signaling molecules related to the upstream and downstream of the insulin PI3K/Akt signaling pathway reduced hepatic insulin resistance. The relative abundance of short-chain fatty acid (SCFA)-producing bacteria (including Akkermansia, Siraeum Eubacterium and Allobaculum) increased and harmful desulfurizing Vibrio decreased. In addition, the levels of SCFAs were increased.

CONCLUSION

These results suggest that MP can increase SCFA levels by altering the abundance of intestinal flora, thereby activating the PI3K/Akt signaling pathway and exerting hypoglycemic effects. © 2023 Society of Chemical Industry.

Exploring the potential of Halomonas levan and its derivatives as active ingredients in cosmeceutical and skin regenerating formulations

Demand on natural products that contain biological ingredients mimicking growth factors and cytokines made natural polysaccharides popular in pharmaceutical and cosmetic industries. Levan is the β-(2-6) linked, nontoxic, biocompatible, water-soluble, film former fructan polymer that has diverse applications in pharmacy and cosmeceutical industries with its moisturizing, whitening, anti-irritant, anti-aging and slimming activities. Driven by the limited reports on few structurally similar levan polymers, this study presents the first systematic investigation on the effects of structurally different extremophilic Halomonas levan polysaccharides on human skin epidermis cells. In-vitro experiments with microbially produced linear Halomonas levan (HL), its hydrolyzed, (hHL) and sulfonated (ShHL) derivatives as well as enzymatically produced branched levan (EL) revealed increased keratinocyte and fibroblast proliferation (113-118 %), improved skin barrier function through induced expressions of involucrin (2.0 and 6.43 fold changes for HL and EL) and filaggrin (1.74 and 3.89 fold changes for hHL and ShHL) genes and increased type I collagen (2.63 for ShHL) and hyaluronan synthase 3 (1.41 for HL) gene expressions together with fast wound healing ability within 24 h (100 %, HL) on 2D wound models clearly showed that HL and its derivatives have high potential to be used as natural active ingredients in cosmeceutical and skin regenerating formulations.

Structural Characterization and Anti-Inflammatory Effects of 24-Methylcholesta-5(6), 22-Diene-3β-ol from the Cultured Marine Diatom Phaeodactylum tricornutum; Attenuate Inflammatory Signaling Pathways

In the present investigation, 24-methylcholesta-5(6), 22-diene-3β-ol (MCDO), a major phytosterol was isolated from the cultured marine diatom, Phaeodactylum tricornutum Bohlin, and in vitro and in vivo anti-inflammatory effects were determined. MCDO demonstrated very potent dose-dependent inhibitory effects on the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) against lipopolysaccharide (LPS)-induced RAW 264.7 cells with minimal cytotoxic effects. MCDO also demonstrated a strong and significant suppression of pro-inflammatory cytokines of interleukin-1β (IL-1β) production, but no substantial inhibitory effects were observed on the production of cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) at the tested concentrations against LPS treatment on RAW macrophages. Western blot assay confirmed the suppression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expressions against LPS-stimulated RAW 264.7 cells. In addition, MCDO was assessed for in vivo anti-inflammatory effects using the zebrafish model. MCDO acted as a potent inhibitor for reactive oxygen species (ROS) and NO levels with a protective effect against the oxidative stress induced by LPS in inflammatory zebrafish embryos. Collectively, MCDO isolated from the cultured marine diatom P. tricornutum exhibited profound anti-inflammatory effects both in vitro and in vivo, suggesting that this major sterol might be a potential treatment for inflammatory diseases.

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.

Assessing the Antitumor Potential of Variants of the Extracellular Carbohydrate Polymer from Synechocystis ΔsigF Mutant

Cancer is a leading cause of death worldwide with a huge societal and economic impact. Clinically effective and less expensive anticancer agents derived from natural sources can help to overcome limitations and negative side effects of chemotherapy and radiotherapy. Previously, we showed that the extracellular carbohydrate polymer of a Synechocystis ΔsigF overproducing mutant displayed a strong antitumor activity towards several human tumor cell lines, by inducing high levels of apoptosis through p53 and caspase-3 activation. Here, the ΔsigF polymer was manipulated to obtain variants that were tested in a human melanoma (Mewo) cell line. Our results demonstrated that high molecular mass fractions were important for the polymer bioactivity, and that the reduction of the peptide content generated a variant with enhanced in vitro antitumor activity. This variant, and the original ΔsigF polymer, were further tested in vivo using the chick chorioallantoic membrane (CAM) assay. Both polymers significantly decreased xenografted CAM tumor growth and affected tumor morphology, by promoting less compact tumors, validating their antitumor potential in vivo. This work contributes with strategies for the design and testing tailored cyanobacterial extracellular polymers and further strengths the relevance of evaluating this type of polymers for biotechnological/biomedical applications.

Biological active metabolites from microalgae for healthcare and pharmaceutical industries: A comprehensive review

Microalgae are photoautotrophic microorganisms which comprise of species from several phyla. Microalgae are promising in producing a varieties of products, including food, feed supplements, chemicals, and biofuels. Medicinal supplements derived from microalgae are of a significant market in which compounds such as -carotene, astaxanthin, polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), and polysaccharides such as -glucan, are prominent. Microalgae species which are commonly applied for commercial productions include Isochrysis sp., Chaetoceros (Chlorella sp.), Arthrospira sp. (Spirulina Bioactive) and many more. In this present review, microalgae species which are feasible in metabolites production are being summarized. Metabolites produced by microalgae as well as their prospective applications in the healthcare and pharmaceutical industries, are comprehensively discussed. This evaluation is greatly assisting industrial stakeholders, investors, and researchers in making business decisions, investing in ventures, and moving the production of microalgae-based metabolites forward.

Bioactive Molecules from Marine Diatoms and Their Value for the Nutraceutical Industry

The search for novel sources of nutrients is among the basic goals for achievement of sustainable progress. In this context, microalgae are relevant organisms, being rich in high-value compounds and able to grow in open ponds or photobioreactors, thus enabling profitable exploitation of aquatic resources. Microalgae, a huge taxon containing photosynthetic microorganisms living in freshwater, as well as in brackish and marine waters, typically unicellular and eukaryotic, include green algae (Chlorophyceae), red algae (Rhodophyceae), brown algae (Phaeophyceae) and diatoms (Bacillariophyceae). In recent decades, diatoms have been considered the most sustainable sources of nutrients for humans with respect to other microalgae. This review focuses on studies exploring their bio-pharmacological activities when relevant for human disease prevention and/or treatment. In addition, we considered diatoms and their extracts (or purified compounds) when relevant for specific nutraceutical applications.

Microalgal bioactive metabolites as promising implements in nutraceuticals and pharmaceuticals: inspiring therapy for health benefits

The rapid increase in global population and shrinkage of agricultural land necessitates the use of cost-effective renewable sources as alternative to excessive resource-demanding agricultural crops. Microalgae seem to be a potential substitute as it rapidly produces large biomass that can serve as a good source of various functional ingredients that are not produced/synthesized inside the human body and high-value nonessential bioactive compounds. Microalgae-derived bioactive metabolites possess various bioactivities including antioxidant, anti-inflammatory, antimicrobial, anti-carcinogenic, anti-hypertensive, anti-lipidemic, and anti-diabetic activities, thereof rapidly elevating their demand as interesting option in pharmaceuticals, nutraceuticals and functional foods industries for developing new products. However, their utilization in these sectors has been limited. This demands more research to explore the functionality of microalgae derived functional ingredients. Therefore, in this review, we intended to furnish up-to-date knowledge on prospects of bioactive metabolites from microalgae, their bioactivities related to health, the process of microalgae cultivation and harvesting, extraction and purification of bioactive metabolites, role as dietary supplements or functional food, their commercial applications in nutritional and pharmaceutical industries and the challenges in this area of research.

Graphical abstract

Enhancement of Cell Behavior by the Polysaccharide Extract of Arthrospira and Potential Biomedical Applications

Arthrospira is one of the most studied cyanobacteria and has been reported with practical applications. Among the substances derived from Arthrospira, polysaccharides have received relatively less attention than phycocyanins, though they have more abundant structural variations and specific properties. Herein, a new Arthrospira-derived sulfated polysaccharide was explored for its potential bioactive functions. The ability of this sulfated polysaccharide to promote the behavior of neural stem cells (NSCs) in three-dimensional hydrogel was examined for the first time. NSCs encapsulated in the sulfated polysaccharide-containing hydrogel showed better proliferation than the control hydrogel as well as a unique cell clustering behavior, i.e., formation of multicellular spherical clusters (40-60 μm). The sulfated polysaccharide, in an appropriate range of concentration (5 mg/mL), also maintained the stemness of NSCs in hydrogel and facilitated their differentiation. In addition, the potentials of the new sulfated polysaccharide as a coating material and as a component for drug carrier were verified. The sulfated polysaccharide-modified substrate exhibited superhydrophilicity (contact angle ~9°) and promoted cell adhesion to the substrate. Composite nanoparticles composed of the sulfated polysaccharide and other differently charged polysaccharides were produced with an average diameter of ~240 nm and estimated drug loading of ~18%. The new Arthrospira-derived sulfated polysaccharide is a promising candidate for cell culture, surface-modification, and drug-delivery applications in the biomedical field.

Elaboration and Characterization of a New Heavy Metal Sensor Functionalized by Extracellular Polymeric Substances Isolated from a Tunisian Thermophilic Microalga Strain Graesiella sp

The present study aimed to develop and characterize new heavy metal sensors functionalized by extracellular polymeric substances (EPSs) isolated from a Tunisian thermophilic microalga strain Graesiella sp. The elaborated sensor showed a highly homogeneous character and revealed a microstructural lamellar arrangement, high crystalline nature, and several functional groups. Electrochemical impedance spectroscopy (EIS) and acoustic wave sensing were used as sensing techniques to explore the ability of microalgae-EPS-functionalized sensors to detect cadmium and mercury as heavy metals. For impedimetric measurements, a two-dipole circuit was adopted and showed good-fitted results with a low total error. The acoustic sensor platforms showed good compatibility with EPS in adjacent water. For both EPS-functionalized sensors, metal ions (Cd2+, Hg2+) were successfully detected in the concentration range from 10-10 M to 10-4 M. Impedimetric sensor was more sensitive to Cd2+ at low concentrations before saturation at 10-7 M, while the acoustic sensor exhibited more sensitivity to Hg2+ over the full range. The results highlight a new potential alternative to use microalgae EPSs as a sensitive coating material for the detection of heavy metals. However, its use in a real liquid medium requires further investigation of its selectivity in the presence of other compounds.