Functional Characterization of a CruP-Like Isomerase in Dunaliella.

Dunaliella bardawil is a marine unicellular green algal that produces large amounts of ß-carotene and is a model organism for studying the carotenoid synthesis pathway. However, there are still many mysteries about the enzymes of the D. bardawil lycopene synthesis pathway that have not been revealed. Here, we have identified a CruP-like lycopene isomerase, named DbLyISO, and successfully cloned its gene from D. bardawil. DbLyISO showed a high homology with CruPs. We constructed a 3D model of DbLyISO and performed molecular docking with lycopene, as well as molecular dynamics testing, to identify the functional characteristics of DbLyISO. Functional activity of DbLyISO was also performed by overexpressing gene in both E. coli and D. bardawil. Results revealed that DbLyISO acted at the C-5 and C-13 positions of lycopene, catalyzing its cis-trans isomerization to produce a more stable trans structure. These results provide new ideas for the development of a carotenoid series from engineered bacteria, algae, and plants.

Advancement of Carotenogenesis of Astaxanthin from Haematococcus pluvialis: Recent Insight and Way Forward.

The demand for astaxanthin has been increasing for many health applications ranging from pharmaceuticals, food, cosmetics, and aquaculture due to its bioactive properties. Haematococcus pluvialis is widely recognized as the microalgae species with the highest natural accumulation of astaxanthin, which has made it a valuable source for industrial production. Astaxanthin produced by other sources such as chemical synthesis or fermentation are often produced in the cis configuration, which has been shown to have lower bioactivity. Additionally, some sources of astaxanthin, such as shrimp, may denature or degrade when exposed to high temperatures, which can result in a loss of bioactivity. Producing natural astaxanthin through the cultivation of H. pluvialis is presently a demanding and time-consuming task, which incurs high expenses and restricts the cost-effective industrial production of this valuable substance. The production of astaxanthin occurs through two distinct pathways, namely the cytosolic mevalonate pathway and the chloroplast methylerythritol phosphate (MEP) pathway. The latest advancements in enhancing product quality and extracting techniques at a reasonable cost are emphasized in this review. The comparative of specific extraction processes of H. pluvialis biological astaxanthin production that may be applied to large-scale industries were assessed. The article covers a contemporary approach to optimizing microalgae culture for increased astaxanthin content, as well as obtaining preliminary data on the sustainability of astaxanthin production and astaxanthin marketing information.

Biophotoelectrochemical process co-driven by dead microalgae and live bacteria.

Anaerobic reduction processes in natural waters can be promoted by dead microalgae that have been attributed to nutrient substances provided by the decomposition of dead microalgae for other microorganisms. However, previous reports have not considered that dead microalgae may also serve as photosensitizers to drive microbial reduction processes. Here we demonstrate a photoelectric synergistic linkage between dead microalgae and bacteria capable of extracellular electron transfer (EET). Illumination of dead Raphidocelis subcapitata resulted in two-fold increase in the rate of anaerobic bioreduction by pure Geobacter sulfurreducens, suggesting that photoelectrons generated from the illuminated dead microalgae were transferred to the EET-capable microorganisms. Similar phenomena were observed in NO3- reduction driven by irradiated dead Chlorella vulgaris and living Shewanella oneidensis, and Cr(VI) reduction driven by irradiated dead Raphidocelis subcapitata and living Bacillus subtilis. Enhancement of bioreduction was also seen when the killed microalgae were illuminated in mixed-culture lake water, suggesting that EET-capable bacteria were naturally present and this phenomenon is common in post-bloom systems. The intracellular ferredoxin-NADP+-reductase is inactivated in the dead microalgae, allowing the production and extracellular transfer of photoelectrons. The use of mutant strains confirmed that the electron transport pathway requires multiheme cytochromes. Taken together, these results suggest a heretofore overlooked biophotoelectrochemical process jointly mediated by illumination of dead microalgae and live EET-capable bacteria in natural ecosystems, which may add an important component in the energetics of bioreduction phenomena particularly in microalgae-enriched environments.

Effect of the seed coating with biomass of Dunaliella salina on early plant growth and in the secondary metabolites content of Coriandrum sativum.

The environmental and health risks associated with the application of synthetic chemical inputs in agriculture increased the demand for technologies that allow higher performance and quality of vegetable crops by implementing synergistic materials with the principles of sustainability. In this work, the seed coating with the biomass of Dunaliella salina incorporated in a bioplastic film of Manihot esculenta (cassava) was evaluated as an initial growth and secondary compounds stimulator of Coriandrum sativum (coriander) plants. The obtained results demonstrated that the coating stimulated an increase in the germination percentage (28.75%) and also in concentration of bioactive compounds, such as the six-fold increment of caffeic acid (13.33 mg 100 g-1). The carbohydrates, lipids, and proteins present in the microalgae biomass seem to be responsible for these increments once they are known for providing energy to the seedling development and coordinating the secondary metabolites synthesis. As conclusion, we consider the coating with biomass of D. salina an alternative for crop improvement that contributes to the development of sustainable agricultural practices.

Optimization of Extraction Conditions of Carotenoids from Dunaliella parva by Response Surface Methodology.

Extraction conditions can exert a remarkable influence on extraction efficiency. The aim of this study was to improve the extraction efficiency of carotenoids from Dunaliella parva (D. parva). Dimethyl sulfoxide (DMSO) and 95% ethanol were used as the extraction solvents. The extraction time, extraction temperature and the proportions of mixed solvent were taken as influencing factors, and the experimental scheme was determined by Central Composite Design (CCD) of Design Expert 10.0.4.0 to optimize the extraction process of carotenoids from D. parva. The absorbance values of the extract at 665 nm, 649 nm and 480 nm were determined by a microplate spectrophotometer, and the extraction efficiency of carotenoids was calculated. Analyses of the model fitting degree, variance and interaction term 3D surface were performed by response surface analysis. The optimal extraction conditions were as follows: extraction time of 20 min, extraction temperature of 40 °C, and a mixed solvent ratio (DMSO: 95% ethanol) of 3.64:1. Under the optimal conditions, the actual extraction efficiency of carotenoids was 0.0464%, which was increased by 18.19% (the initial extraction efficiency of 0.03926%) with a lower extraction temperature (i.e., lower energy consumption) compared to the standard protocol.

Phenolic compounds and antioxidant capacity of Pediastrum boryanum (Chlorococcales) biomass.

Bioactive compounds, synthesized by photosynthetic microorganisms, have drawn the attention of the pharmaceutical field. This study aimed at evaluating synthesis and in vitro antioxidant capacity of phenolic compounds produced by a microalgae species P. boryanum, which was grown in six different culture media (standard BG11, modified BG11/MBG11, standard WC, modified WC, WC*2 and basal). The highest concentrations of biomass (1.75 ± 0.01 g.L-1) and phenolic content (3.18 ± 0.00 mg.g-1) were obtained when P. boryanum was grown in MBG11 and phenolic acids were identified: gallic, protocatechuic, chlorogenic, hydroxybenzoic and vanillic ones. All extracts exhibited scavenger activity in the ABTS assay and inhibited peroxidase. However, phenolic compounds from P. boryanum grown in BG11 and MBG11 had the most potent scavenger activity in the DPPH assay. In sum, P. boryanum can be a new source of free phenolic compounds with potential antioxidant activity when grown in MBG11, since it yields high amounts of biomass and phenolic compounds.

Comparison of Different Methods for Extracting the Astaxanthin from Haematococcus pluvialis: Chemical Composition and Biological Activity.

In this study, the impact of different cell disruption techniques (high-pressure micro fluidization (HPMF), ionic liquids (ILs), multi-enzyme (ME), and hydrochloric acid (HCl)) on the chemical composition and biological activity of astaxanthin (AST) obtained from Haematococcus pluvialis was investigated. Results indicated that all cell disruption techniques had a significant effect on AST composition, which were confirmed by TLC and UPC2 analysis. AST recovery from HCl (HCl-AST) and ILs (ILs-AST) cell disruption techniques was dominant by free and monoesters AST, while AST recovery from HPMF (HPMF-AST) and ME (ME-AST) cell disruption techniques was composed of monoesters, diesters, and free AST. Further biological activity analysis displayed that HCl-AST showed the highest ABTS and DPPH activity, while ILs-AST showed better results against the ORAC assay. Additionally, ILs-AST exhibits a stronger anti-proliferation of HepG2 cells in a dose-dependent manner, which was ascribed to AST-induced ROS in to inhibit the proliferative of cancer cells.

Tuning Dunaliella tertiolecta for Enhanced Antioxidant Production by Modification of Culture Conditions.

Microalgae, a popular source of food and bioactive compounds, accumulate antioxidants in response to culture condition stresses. Using a factorial design (3 × 3), the effect of light, temperature, and nitrogen level on chlorophyll and carotenoids, total protein, total phenolic, ascorbate and glutathione content, and enzyme (catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD)) activities in Dunaliella tertiolecta was studied. Data were analysed using Design of Experiments (DoE), and recommendations are made for optimum cultivation conditions to achieve the highest antioxidant content (phenolics, ascorbate and glutathione) or enzyme (CAT, SOD, and POD) activities. This is the first study to apply three levels of three factors during cultivation to tune Dunaliella tertiolecta for optimal antioxidant production.

Characterization of Astaxanthin Nanoemulsions Produced by Intense Fluid Shear through a Self-Throttling Nanometer Range Annular Orifice Valve-Based High-Pressure Homogenizer.

Stable, oil-in-water nanoemulsions containing astaxanthin (AsX) were produced by intense fluid shear forces resulting from pumping a coarse reagent emulsion through a self-throttling annular gap valve at 300 MPa. Compared to crude emulsions prepared by conventional homogenization, a size reduction of over two orders of magnitude was observed for AsX-encapsulated oil droplets following just one pass through the annular valve. In krill oil formulations, the mean hydrodynamic diameter of lipid particles was reduced to 60 nm after only two passes through the valve and reached a minimal size of 24 nm after eight passes. Repeated processing of samples through the valve progressively decreased lipid particle size, with an inflection in the rate of particle size reduction generally observed after 2-4 passes. Krill- and argan oil-based nanoemulsions were produced using an Ultra Shear Technology™ (UST™) approach and characterized in terms of their small particle size, low polydispersity, and stability.

Comparison of neutral lipid fatty acid composition in organisms from different trophic levels.

The profiles of total fatty acids (TFAs) and the neutral lipid fatty acids (NLFAs) were compared for the bacterium Rhodopirellula rubra and the alga Raphidocelis subcapitata (conventional food source for Daphnia magna). D. magna NLFAs were assessed when this crustacean was fed with bacterium and alga, individually or in combination. After NLFA extraction, the profiles of the various organisms were characterized by gas chromatography. Results evidenced the relevance of the different composition of the fatty acid (FAs) fractions in the different organisms, R. rubra and R. subcapitata. In these species, the NFLA analyses revealed high amounts of long chain FAs (C19). The FA profile of D. magna was influenced by the different diets provided although the preferred diet was the alga. D. magna showed the capacity to adapt to the available food resources as it defines its FA profile according to its needs, namely for the long chain FAs (C19).

Microalgal extract from thermotolerant Coelastrella sp. F50 retards the liver tumor progression by targeting hepatic cancer stem cells.

Microalgae extracts have shown antitumor activities. However, the antitumor mechanism of them is not yet completely clear, especially the effect on cancer stem cells (CSCs). This study aimed to elucidate the antitumor activity and mechanism of microalgal extract from thermotolerant Coelastrella sp. F50 (F50) in hepatocellular carcinoma (HCC). Oncogenic behaviors were analyzed using cell proliferation, colony formation, invasion, sphere formation, and side population cells (SPCs) assays in HCC cells after F50 treatment. The molecular mechanism was further studied by quantitative real-time PCR, immunoblot, and immunofluorescence analyses. The chemopreventive efficacy of F50 was evaluated in rat orthotopic hepatoma, and the hepatic pathologies were investigated by immunohistochemical, immunoblot, and immunofluorescence analyses. F50 specifically suppressed hepatic CSCs (tumor spheres, drug efflux, CD133/ABCG2 CSCs markers) with no cytotoxicity in vitro. In the animal experiments, prophylactic F50 administration significantly attenuated tumor progression and improved liver function in HCC-bearing rats. In the mechanistic analysis, F50 potentially inhibited cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2 ) axis in HCC cells and rat hepatoma, and exogenous PGE2 restored CSCs properties in F50-treated HCC cells. In summary, F50 extract inhibits hepatic CSCs by COX-2/PGE2 downregulation and may facilitate a novel phytotherapy for HCC prevention.

Haematococcus pluvialis Carotenoids Enrich Fractions Ameliorate Liver Fibrosis Induced by Thioacetamide in Rats: Modulation of Metalloproteinase and Its Inhibitor.

Hepatic fibrosis is a consequence of chronic liver diseases. Metalloproteinase and its inhibitor have crucial roles in the resolution of liver fibrosis. The current relevant study is aimed to evaluate the therapeutic effect of Haematococcus pluvialis (H. pluvialis) extract, astaxanthin-rich fraction, astaxanthin ester-rich fraction, and ß-carotene-rich fraction as well as their mechanisms of action in curing hepatic fibrosis induced by thioacetamide (TAA). Liver fibrosis was induced using TAA (intraperitoneal injection, two times a week for 6 weeks), in a rat model and H. pluvialis extract (200 mg/kg), and other fractions (30 mg/kg) were orally administered daily for 4 weeks after the last TAA injection. Based on HPLC analysis, H. pluvialis extract contains ß-carotene (12.95 mg/g, extract) and free astaxanthin (10.85 mg/g, extract), while HPLC/ESI-MS analysis revealed that H. pluvialis extract contains 28 carotenoid compounds including three isomers of free astaxanthin, α or ß-carotene, lutein, 14 astaxanthin mono-esters, 5 astaxanthin di-esters, and other carotenoids. H. pluvialis and its fractions reduced liver enzymes, nitric oxide, collagen 1, alpha-smooth muscle actin, and transforming growth factor-beta as well as elevated catalase antioxidant activity compared to the TAA group. Also, H. pluvialis extract and its fractions exceedingly controlled the balance between metalloproteinase and its inhibitor, activated Kupffer cells proliferation, and suppressed liver apoptosis, necrobiosis, and fibrosis. These findings conclude that H. pluvialis extract and its fractions have an antifibrotic effect against TAA-induced liver fibrosis by regulating the oxidative stress and proinflammatory mediators, suppressing multiple profibrogenic factors, and modulating the metalloproteinase and its inhibitor pathway, recommending H. pluvialis extract and its fractions for the development of new effective medicine for treating hepatic fibrosis disorders.

Cholinesterase inhibitory activity, antioxidant properties, and phytochemical composition of Chlorococcum sp. extracts.

In this study, Chlorococcum sp. was investigated for its cholinesterase inhibitory potentials and antioxidant activity. The algal sample was cultivated, harvested, and extracted sequentially using n-hexane, dichloromethane, and ethanol. The extracts were characterized using Fourier transmission infra-red (FTIR) and Gas Chromatography-Mass Spectrometry. The metal chelating, radical scavenging activities, as well as anticholinesterase potentials of the algal extract, was also investigated. FTIR characterization of the microalgal biomass revealed the presence of phenolic compounds, alkaloids, polysaccharides, and fatty acids. The extracts showed the presence of phytol, neophytadiene, butylated hydroxyl toluene, and 3-tert-butyl-4-hydroxyanisole. The ethanol extract showed the highest DPPH (IC50  = 147.40 µg/ml) and OH (IC50  = 493.90 µg/ml) radical scavenging and metal chelating (IC50  = 83.25 µg/ml) activities. Similarly, the ethanol extract (IC50  = 13.83 µg/ml) exhibited the highest acetylcholinesterase inhibitory activity, while the dichloromethane extract showed the highest butyrylcholinesterase inhibitory activity. All the extracts exhibited antioxidant properties and inhibitory effects against butyrylcholinesterase and acetylcholinesterase; however, ethanol extracts showed better activity. PRACTICAL APPLICATIONS: Biomass obtained from some microalgal species is commonly used as dietary supplements and nutraceuticals due to the presence of high-valued products. However, the antioxidant and anticholinesterase activities of biomass from Chlorococcum sp. have not been explored. Chlorococcum sp. extracts contain some antioxidants such as 3-tert-Butyl-4-hydroxyanisole, butylated hydroxytoluene, phytol, and neophytadiene. Characterization of the extracts also revealed the presence of phenolic compounds, polysaccharides, and fatty acids. These compounds may contribute to the observed antioxidant and anticholinesterase activities of Chlorococcum sp. The result of this study suggests that Chlorococcum sp. may contain some nutraceuticals which could be used as antioxidants and cholinesterase inhibitors.

Effect of CO2 Flow Rate on the Extraction of Astaxanthin and Fatty Acids from Haematococcus pluvialis Using Supercritical Fluid Technology.

Haematococcus pluvialis is the largest producer of natural astaxanthin in the world. Astaxanthin is a bioactive compound used in food, feed, nutraceutics, and cosmetics. In this study, astaxanthin extraction from H. pluvialis by supercritical fluid extraction was evaluated. The effects of temperature (40 and 50 °C), pressure (40 and 50 MPa), and CO2 flow rate (2 and 4 L/min) were investigated. The results showed that the highest astaxanthin recovery was obtained at 50 °C/50 MPa and the CO2 flow rates evaluated had no significant effect. It was possible to achieve astaxanthin recoveries of 95% after 175 min for a CO2 flow rate of 2 L/min, and 95 min for CO2 flow rate of 4 L/min. The ω-6/ω-3 ratios obtained were similar in all conditions, reaching 0.87, demonstrating that the extracts from H. pluvialis by SFE are rich in unsaturated fatty acids (UFA) which increases their positive effects when used as a functional ingredient in food.

Effects of supplementing natural astaxanthin from Haematococcus pluvialis to laying hens on egg quality during storage at 4°C and 25°C.

The objective of this study was to evaluate the effects of different levels of dietary natural astaxanthin (ASTA) (from the microalga Haematococcus pluvialis) and storage at 4°C and 25°C on the quality of eggs from laying hens. Nongda No. 3 laying hens (n = 450) were randomly allocated to 1 of 5 dietary treatments. Each treatment had 6 replicates of 15 hens each. All birds were assigned to a corn-soybean meal-based diet containing 0, 20, 40, 80, or 160 mg/kg natural ASTA for 4 wk. A total of 540 eggs were collected at the end of the 4-week feeding trial. Sixty fresh eggs were collected and measured for egg quality within 24 h after collection. The other 480 eggs were used in a factorial arrangement with 5 dietary ASTA levels, 4 storage times, and 2 storage temperatures. During the 8-week storage period at 4°C and 25°C, egg quality measurements were performed every 2 wk on 12 eggs per treatment. No significant effects (P > 0.05) on yolk index, yolk pH, Haugh units, weight loss, or eggshell strength were observed with increasing concentrations of dietary ASTA. Yolk color darkened linearly with increasing dose of ASTA (P < 0.05). During storage of eggs, yolk index and Haugh units decreased significantly (P < 0.05), whereas yolk pH and weight loss increased (P < 0.05). An interaction was observed between dietary ASTA level and storage time on yolk index, yolk color, and Haugh units (P < 0.05). These results demonstrated that dietary ASTA from H. pluvialis delayed the decrease in yolk index and yolk color during storage at 4°C and 25°C. Therefore, we speculate that there may be a combined effect of dietary ASTA level and storage time on egg internal quality; this information may provide additional options by which to extend the storage time of eggs.

Effects of dietary supplementation of natural astaxanthin from Haematococcus pluvialis on antioxidant capacity, lipid metabolism, and accumulation in the egg yolk of laying hens.

The present study evaluated the effects of natural astaxanthin (ASTA) from Haematococcus pluvialis on the antioxidant capacity, lipid metabolism, and ASTA accumulation in the egg yolk of laying hens. Hy-Line Brown layers (n = 288, 50 wk old) were randomly assigned to 1 of 4 dietary treatment groups. Each group had 6 replicates of 12 hens each. All birds were given a corn-soybean meal-based diet containing 0, 25, 50, or 100 mg/kg ASTA for 6 wk. The results showed that the total antioxidant capacity, superoxide dismutase level, and glutathione peroxidase level in the plasma, livers, and egg yolks were significantly increased in the ASTA groups compared with those of the control group (P < 0.05), whereas the content of malondialdehyde linearly decreased (P < 0.05). The plasma levels of high-density and very-low-density lipoprotein cholesterol in the ASTA groups were significantly higher than those in the control group (P < 0.05). In addition, ASTA supplementation decreased low-density lipoprotein cholesterol and triglyceride plasma levels (P < 0.05). However, there were no significant differences in the other lipid metabolism parameters among the ASTA-supplemented groups relative to the control group except for an increase in high-density lipoprotein cholesterol in the liver. Compared with the control, dietary ASTA supplementation significantly increased the enrichment of ASTA in egg yolks at the end of week 2, 4, and 6 (P < 0.05). The mRNA expression of scavenger receptor class B type 1 (SCARB1) and very-low-density lipoprotein receptor (VLDLR) in the ASTA groups was markedly higher (P < 0.05) than that in the control group in the liver and ovaries, respectively. In conclusion, these results suggest that dietary ASTA enhances the antioxidant capacity and regulates lipid metabolism in laying hens. ASTA enrichment in egg yolks may be closely related to the upregulation of SCARB1 and VLDLR gene expression.

Incorporation of Magnetic Nanoparticles into Protoplasts of Microalgae Haematococcus pluvialis: A Tool for Biotechnological Applications.

Intensive research on the use of magnetic nanoparticles for biotechnological applications of microalgae biomass guided the development of proper treatment to successfully incorporate them into these single-cell microorganisms. Protoplasts, as cells lacking a cell wall, are extensively used in plant/microalgae genetic manipulation as well as various biotechnological applications. In this work, a detailed study on the formation of protoplasts from Haematococcus pluvialis with the use of enzymatic and mechanical procedures was performed. The optimization of several parameters affecting the formation of protoplasmic cells and cell recovery was investigated. In the enzymatic treatment, a solution of cellulase was studied at different time points of incubation, whereas in the mechanical treatment, glass beads vortexing was used. Mechanical treatment gave better results in comparison to the enzymatic one. Concerning the cell recovery, after the protoplast formation, it was found to be similar in both methods used; cell viability was not investigated. To enhance the protoplast cell wall reconstruction, different "recovery media" with an organic source of carbon or nitrogen were used. Cell morphology during all treatments was evaluated by electron microscopy. The optimal conditions found for protoplast formation and cell reconstruction were successfully used to produce Haematococcus pluvialis cells with magnetic properties.

Functional Characterization of Long-Chain Acyl-CoA Synthetase Gene Family from the Oleaginous Alga Chromochloris zofingiensis.

Long-chain acyl-coenzyme A (CoA) synthetase (LACS) catalyzes the formation of acyl-CoAs from free fatty acids, which is pivotal for lipid metabolism. Here, we confirmed the presence of six CzLACS genes in Chromochloris zofingiensis. Functional complementation and in vitro enzymatic assay indicated that CzLACS2 through CzLACS5 rather than CzLACS1 or CzLACS6 are bona fide LACS enzymes and they have overlapping yet distinct substrate preference. The results of the subcellular colocalization experiment and different expression patterns under three triacylglycerol (TAG)-inducing conditions showed that CzLACS2 through CzLACS4 reside at endoplasmic reticulum (ER) and are involved in TAG biosynthesis, while CzLACS5 resides in peroxisome and participates in fatty acid ß-oxidation. The yeast one-hybrid assay using a library of 50 transcription factors (TFs) constructed in our study identified 12 TFs potentially involved in regulating the expression of CzLACSs. Moreover, heterologous expression of CzLACSs demonstrated their engineering potential for modulating TAG synthesis in yeast and algal cells.

Structure of a minimal photosystem I from the green alga Dunaliella salina.

Solar energy harnessed by oxygenic photosynthesis supports most of the life forms on Earth. In eukaryotes, photosynthesis occurs in chloroplasts and is achieved by membrane-embedded macromolecular complexes that contain core and peripheral antennae with multiple pigments. The structure of photosystem I (PSI) comprises the core and light-harvesting (LHCI) complexes, which together form PSI-LHCI. Here we determined the structure of PSI-LHCI from the salt-tolerant green alga Dunaliella salina using X-ray crystallography and electron cryo-microscopy. Our results reveal a previously undescribed configuration of the PSI core. It is composed of only 7 subunits, compared with 14-16 subunits in plants and the alga Chlamydomonas reinhardtii, and forms the smallest known PSI. The LHCI is poorly conserved at the sequence level and binds to pigments that form new energy pathways, and the interactions between the individual Lhca1-4 proteins are weakened. Overall, the data indicate the PSI of D. salina represents a different type of the molecular organization that provides important information for reconstructing the plasticity and evolution of PSI.

Potential Use of Marine Seaweeds as Prebiotics: A Review.

Human gut microbiota plays an important role in several metabolic processes and human diseases. Various dietary factors, including complex carbohydrates, such as polysaccharides, provide abundant nutrients and substrates for microbial metabolism in the gut, affecting the members and their functionality. Nowadays, the main sources of complex carbohydrates destined for human consumption are terrestrial plants. However, fresh water is an increasingly scarce commodity and world agricultural productivity is in a persistent decline, thus demanding the exploration of other sources of complex carbohydrates. As an interesting option, marine seaweeds show rapid growth and do not require arable land, fresh water or fertilizers. The present review offers an objective perspective of the current knowledge surrounding the impacts of seaweeds and their derived polysaccharides on the human microbiome and the profound need for more in-depth investigations into this topic. Animal experiments and in vitro colonic-simulating trials investigating the effects of seaweed ingestion on human gut microbiota are discussed.