Beneficial effects of three brown seaweed polysaccharides on gut microbiota and their structural characteristics: An overview

Structural characterization and human gut microbiota fermentation in vitro of a polysaccharide from Fucus vesiculosus

In this study, an acidic polysaccharide (FVP-7 A) was isolated from Fucus vesiculosus by DEAE-Sepharose™ fast flow. The chemical composition, glycosidic bonds and in vitro fecal fermentation characteristics of FVP-7 A were studied. Results shown that FVP-7 A was a homogenous polysaccharide with average molecular weight of 30.94 kDa. Combined with FT-IR, monosaccharide composition, methylation and NMR analysis, the glycosidic bonds of FVP-7 A mainly composed of →4)-β-D-Manp-(1→, →3)-α-L-Fucp-(1→, α-D-Manp-(1→, →3)-β-D-Manp-(1 → and →4,6)-α-D-Manp-(1→. The zeta potential and atomic force microscopy images indicated that FVP-7 A could exist stably as a single chain-like structure in dilute solution. After gut fermentation, FVP-7 A was utilized and promoted multiple short-chain fatty acids production, especially acetic acid, butyric acid and valeric acid. For prebiotics, FVP-7 A significantly increased the relative abundance of short-chain fatty acids producing bacteria such as Bacteroides, Lachnospira, Faecalibacterium, Ruminococcus, Oscillospira and Dialister, and inhiited the growth of the harmful bacteria Shigella. These results indicated that FVP-7 A could be used as a potential dietary supplement to improve intestinal health.

Relationship between dietary fiber content and prebiotic potential of polysaccharides from the seaweeds of the North west coast of India

The macroalgae are a sustainable bioresource that can be harnessed for their functional food and nutraceutical applications. This study characterized the biochemical composition and bioactive potential of natural biological macromolecules, such as macroalgal polysaccharides extracted using a green, aqueous extraction process. The in-vitro antioxidant and antiglycemic activity of these polysaccharides were evaluated using model, free radical and antiglycemic compounds. The prebiotic potential of macroalgal polysaccharides were analysed based on their ability to promote the growth of two potential probiotic bacteria Lactobacillus acidophilus and L. bulgaricus and suppress the growth of enteric bacteria, Escherichia coli. Among the polysaccharides studied, the brown algal polysaccharide MPS8 MPS9 and MPS10 exhibited good antioxidant, antiglycemic and prebiotic activity. Based on infrared spectroscopy, the functional groups sulfation and carboxylation were identified in potential polysaccharides. The monosaccharide composition in the bioactive polysaccharides was determined using High Performance Anion Exchange Chromatography Pulse Amperometric detector (HPAEC-PAD). These bioactive polysaccharides were fractionated using ion exchange chromatography to purify it and further characterized using gel permeation chromatography and NMR spectroscopy. The results these polysaccharides are mainly composed of fucose and glucose which is due to the fucoidan and laminarin, respectively. Such macromolecules with high dietary fiber content and bioactivity are in global demand as functional food, nutraceutical and pharmaceutical formulations.

In Vitro Characterization of Polysaccharides from Fresh Tea Leaves in Simulated Gastrointestinal Digestion and Gut Microbiome Fermentation

Tea plants have a long cultivation history in the world, but there are few studies on polysaccharides from fresh tea leaves. In this study, tea polysaccharides (TPSs) were isolated from fresh tea leaves. Then, we investigated the characteristics of TPSs during in vitro simulated digestion and fermentation; moreover, the effects of TPSs on gut microbiota were explored. The results revealed that saliva did not significantly affect TPSs' molecular weight, monosaccharide composition, and reducing sugar content, indicating that TPSs cannot be digested in the oral cavity. However, TPSs were partially decomposed in the gastrointestinal tract after gastric and intestinal digestion, resulting in the release of a small amount of free glucose monosaccharides. Our in vitro fermentation experiments demonstrated that TPSs are degraded by gut microbiota, leading to short-chain fatty acid (SCFA) production and pH reduction. Moreover, TPSs increased the abundance of Bacteroides, Lactobacillus, and Bifidobacterium but reduced that of Escherichia, Shigella, and Enterococcus, demonstrating that TPSs can regulate the gut microbiome. In conclusion, TPSs are partially decomposed by gut microbiota, resulting in the production of SCFAs and the regulation of gut microbiota composition and function. Therefore, TPSs may be used to develop a prebiotic supplement to regulate the gut microbiome and improve host health.

Chitosan and its oligosaccharide accelerate colonic motility and reverse serum metabolites in rats after excessive protein consumption

Excessive protein consumption (EPC) could increase the gastrointestinal burden and impair gut motility. The present study was designed to explore the improvement of chitosan (CTS) and chitosan oligosaccharide (COS) on colonic motility and serum metabolites in rats after EPC. The results of in vivo experiments fully proved that CTS and COS could improve gut motility and reverse the serum metabolites in rats as indicated by LC-MS/MS analysis, and the COS group even showed a better effect than the CTS group. Furthermore, short-chain fatty acids (SCFAs), which could promote gut motility, were also increased to alleviate EPC-induced constipation after supplementation with CTS or COS. In addition, CTS and COS could decrease the concentration of ammonia in serum and down-regulate the levels of H2S and indole. In summary, the present study revealed that CTS and COS could produce SCFAs, improve the colonic motility in rats, reverse the levels of valine, adenosine, cysteine, 1-methyladenosine, indole, and uracil, and enhance aminoacyl-tRNA biosynthesis and valine, leucine and isoleucine degradation. The present study provides novel insights into the potential roles of CTS and COS in alleviating the adverse effects of EPC.

Dietary seaweed (Saccharina latissima) supplementation in pigs induces localized immunomodulatory effects and minor gut microbiota changes during intestinal helminth infection

Brown seaweeds have a rich bioactive content known to modulate biological processes, including the mucosal immune response and microbiota function, and may therefore have the potential to control enteric pathogens. Here, we tested if dietary seaweed (Saccharina latissima) supplementation could modulate pig gut health with a specific focus on parasitic helminth burdens, gut microbiota composition, and host immune response during a five week feeding period in pigs co-infected with the helminths Ascaris suum and Oesophagostomum dentatum. We found that inclusion of fermented S. latissima (Fer-SL) at 8% of the diet increased gut microbiota α-diversity with higher relative abundances of Firmicutes, Tenericutes, Verrucomicrobia, Spirochaetes and Elusimicrobia, and lower abundance of Prevotella copri. In the absence of helminth infection, transcription of immune-related genes in the intestine was only moderately influenced by dietary seaweed. However, Fer-SL modulated the transcriptional response to infection in a site-specific manner in the gut, with an attenuation of infection-induced gene expression in the jejunum and an amplification of gene expression in the colon. Effects on systemic immune parameters (e.g. blood lymphocyte populations) were limited, indicating the effects of Fer-SL were mainly localized to the intestinal tissues. Despite previously documented in vitro anti-parasitic activity against pig helminths, Fer-SL inclusion did not significantly affect parasite egg excretion or worm establishment. Collectively, our results show that although Fer-SL inclusion did not reduce parasite burdens, it may modify the gut environment during enteric parasite infection, which encourages continued investigations into the use of seaweeds or related products as novel tools to improve gut health.

Soluble dietary fiber and cellulose from Saccharina japonica by-product ameliorate Loperamide-induced constipation via modulating enteric neurotransmitters, short-chain fatty acids and gut microbiota

The effects of soluble dietary fiber (SDF) and cellulose (IDF) from Saccharina japonica by-product and their differences in improving constipation were further clarified in the present study. We demonstrated that SDF was mainly made up of d-mannuronic acid and d-mannose while IDF consisted of d-glucose , which is different from other reported dietary fibers of terrestrial plants. In this research, both SDF and IDF improved fecal-related indicators, gastrointestinal transit rate and histological morphology in Lop-induced mice. Moreover, they could increase the level of antioxidant enzymes (SOD and GSH-Px), restore the expression of enteric neurotransmitters, and maintain the function of ZO-1, JAM-1 as well as Occludin. Interestingly, SDF and IDF had a significant up-regulated effect on the proportion of Muribaculacea, Prevotellaceaen and Lachnospiraceae, which are critical to preserving intestinal immune homeostasis. Besides, they promoted the biosynthesis of short-chain fatty acids (SCFAs). The overall index showed that SDF is more effective for constipation due to its better water retention capacity. Thus, they can be used as a safe dietary supplement for the treatment of chronic or occasional constipation in humans.

Application of microbial organic fertilizers promotes the utilization of nutrients and restoration of microbial community structure and function in rhizosphere soils after dazomet fumigation

Introduction

Soil fumigant dazomet is a broad-spectrum nematicide and fungicide that can kill non-target microbes. Fungicides or organic fertilizers are often added after fumigation to improve the recovery of soil microbes. However, the effect of adding microbial organic fertilizers (MOF) after fumigation on the structure and function of rhizosphere soil microbial communities of crops is unclear.

Methods

Therefore, we investigated the effects of adding Junweinong and Junlisu MOFs after dazomet fumigation on the structure and function of rhizosphere microbial communities and its relationship with soil properties and enzyme activities.

Results and discussion

The results showed that the addition of these two MOFs after dazomet fumigation significantly reduced the rhizosphere soil available phosphorus, available potassium, organic matter content, and urease, alkaline phosphatase, and catalase activities, but increased the soil pH compared with the fumigation treatment. The application of MOFs after fumigation resulted in significant enrichment of bacteria such as Gaiella, norank_f_Vicinamibacteraceae, and Flavisolibacter and fungi such as Peroneutypa, Olpidium, and Microascus in the rhizosphere soil of the crop and increased the relative abundance of functional genes of 13 kinds of amino acids metabolism, pyruvate metabolism, TCA cycle, and pentose phosphate pathway as well as endophytic and epiphytic functional groups in the rhizosphere soil. In particular, NH₄ ⁺-N, pH, and AK had the greatest effect on rhizosphere microorganisms. Overall, the addition of MOFs after fumigation promoted crop root nutrient uptake, enhanced rhizosphere soil microbial metabolism, allowed more beneficial communities to colonize the roots, and promoted soil microbiological health.

Advancement in Therapeutic Intervention of Prebiotic-Based Nanoparticles for Colonic Diseases

Intestinal flora has become a therapeutic target for the intervention of colonic diseases (CDs) with better understanding of the interplay between microbiota and CDs. Depending on unique properties and prominent ability of regulating the intestinal flora, prebiotics can not only achieve a colon-specific drug delivery but also maintain the intestinal homeostasis, thus playing a positive role in the intervention of CDs. Currently, different studies on prebiotic-based nanoparticles have been contrived for colonic drug delivery and have shown great potential in curing various CDs, such as colitis and colorectal cancer. Nevertheless, there is a lack of systematic survey on the use of prebiotic nanoparticles for the treatment of CDs. This review aims to generalize the state-of-the-art of prebiotic nanomedicines specific for CDs. The species and function of intestinal flora and various kinds of prebiotics available as well as their regulating effects on intestinal flora were expounded. A variety of prebiotic nanoparticles pertinent to colon-targeted drug delivery systems were illustrated with particular emphasis on their curative activities on CDs. The efficacy and safety of prebiotic-based colonic drug delivery systems (p-CDDs) were also analyzed. In conclusion, the synergy between prebiotic nanoparticles and their cargos may hold promise for the treatment and intervention of CDs.

Effects of Auricularia auricula Polysaccharides on Gut Microbiota and Metabolic Phenotype in Mice

Personalized diets change the internal metabolism of organisms, which, in turn, affects the health of the body; this study was performed to explore the regulatory effects of polysaccharides extracted from Auricularia auricula on the overall metabolism and gut microbiota in normal C57BL/6J mice. The study was conducted using metabolomic and microbiomic methods to provide a scientific basis for further development and use of Auricularia auricula resources in the Qinba Mountains and in nutritional food with Auricularia auricula polysaccharides (AAP) as the main functional component. Based on LC-MS/MS metabolomic results, 51 AAP-regulated metabolites were found, mainly enriched in the arginine biosynthesis pathway, which had the highest correlation, followed by the following metabolisms: arginine and proline; glycine, serine and threonine; and glycerophospholipid, along with the sphingolipid metabolism pathway. Furthermore, supplementation of AAP significantly changed the composition of the mice intestinal flora. The relative abundance levels of Lactobacillus johnsonii, Weissella cibaria, Kosakonia cowanii, Enterococcus faecalis, Bifidobacterium animalis and Bacteroides uniformis were markedly up-regulated, while the relative abundance of Firmicutes bacterium M10-2 was down-regulated. The bioactivities of AAP may be related to the regulatory effects of endogenous metabolism and gut microbiota composition.

Potential Food and Nutraceutical Applications of Alginate: A Review

Alginate is an acidic polysaccharide mainly extracted from kelp or sargassum, which comprises 40% of the dry weight of algae. It is a linear polymer consisting of β-D-mannuronic acid (M) and α-L-guluronic acid (G) with 1,4-glycosidic linkages, possessing various applications in the food and nutraceutical industries due to its unique physicochemical properties and health benefits. Additionally, alginate is able to form a gel matrix in the presence of Ca²⁺ ions. Alginate properties also affect its gelation, including its structure and experimental conditions such as pH, temperature, crosslinker concentration, residence time and ionic strength. These features of this polysaccharide have been widely used in the food industry, including in food gels, controlled-release systems and film packaging. This review comprehensively covers the analysis of alginate and discussed the potential applications of alginate in the food industry and nutraceuticals.

An insight to the therapeutic potential of algae-derived sulfated polysaccharides and polyunsaturated fatty acids: Focusing on the COVID-19

Covid-19 pandemic severely affected human health worldwide. The rapidly increasing COVID-19 cases and successive mutations of the virus have made it a major challenge for scientists to find the best and efficient drug/vaccine/strategy to counteract the virus pathogenesis. As a result of research in scientific databases, regulating the immune system and its responses with nutrients and nutritional interventions is the most critical solution to prevent and combat this infection. Also, modulating other organs such as the intestine with these compounds can lead to the vaccines' effectiveness. Marine resources, mainly algae, are rich sources of nutrients and bioactive compounds with known immunomodulatory properties and the gut microbiome regulations. According to the purpose of the review, algae-derived bioactive compounds with immunomodulatory activities, sulfated polysaccharides, and polyunsaturated fatty acids have a good effect on the immune system. In addition, they have probiotic/prebiotic properties in the intestine and modulate the gut microbiomes; therefore, they can increase the effectiveness of vaccines produced. Thus, they with respectable safety, immune regulation, and modulation of microbiota have potential therapeutic against infections, especially COVID-19. They can also be employed as promising candidates for the prevention and treatment of viral infections, such as COVID-19.

Preparation and potential applications of alginate oligosaccharides

Alginate, a linear polymer consisting of β-D-mannuronic acid (M) and α-L-guluronic acid (G) with 1,4-glycosidic linkages and comprising 40% of the dry weight of algae, possesses various applications in the food and nutraceutical industries. However, the potential applications of alginate are restricted in some fields because of its low water solubility and high solution viscosity. Alginate oligosaccharides (AOS) on the other hand, have low molecular weight which result in better water solubility. Hence, it becomes a more popular target to be researched in recent years for its use in foods and nutraceuticals. AOS can be obtained by multiple degradation methods, including enzymatic degradation, from alginate or alginate-derived poly G and poly M. AOS have unique bioactivity and can bring human health benefits, which render them potentials to be developed/incorporated into functional food. This review comprehensively covers methods of the preparation and analysis of AOS, and discussed the potential applications of AOS in foods and nutraceuticals.

Algal Metabolites Can Be an Immune Booster against COVID-19 Pandemic

The world has faced the challenges of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) for the last two years, first diagnosed at the end of 2019 in Wuhan and widely distributed worldwide. As a result, the WHO has proclaimed the illness brought on by this virus to be a global pandemic. To combat COVID-19, researcher communities continuously develop and implement rapid diagnoses, safe and effective vaccinations and other alternative therapeutic procedures. However, synthetic drug-related side effects and high costs have piqued scientists’ interest in natural product-based therapies and medicines. In this regard, antiviral substances derived from natural resources and some medicines have seen a boom in popularity. For instance, algae are a rich source of compounds such as lectins and sulfated polysaccharides, which have potent antiviral and immunity-boosting properties. Moreover, Algae-derived compounds or metabolites can be used as antibodies and vaccine raw materials against COVID-19. Furthermore, some algal species can boost immunity, reduce viral activity in humans and be recommended for usage as a COVID-19 preventative measure. However, this field of study is still in its early stages of development. Therefore, this review addresses critical characteristics of algal metabolites, their antioxidant potential and therapeutic potential in COVID-19.

The Algal Polysaccharide Ulvan and Carotenoid Astaxanthin Both Positively Modulate Gut Microbiota in Mice

The intestinal microbial community (microbiota) is dynamic and variable amongst individuals and plays an essential part in gut health and homeostasis. Dietary components can modulate the structure of the gut microbiota. In recent years, substantial efforts have been made to find novel dietary components with positive effects on the gut microbial community structure. Natural algal polysaccharides and carotenoids have been reported to possess various functions of biological relevance and their impact on the gut microbiota is currently a topic of interest. This study, therefore, reports the effect of the sulfated polysaccharide ulvan and the carotenoid astaxanthin extracted and purified from the aquacultured marine green macroalgae Ulva ohnoi and freshwater green microalgae Haematococcus pluvialis, respectively, on the temporal development of the murine gut microbiota. Significant changes with the increase in the bacterial classes Bacteroidia, Bacilli, Clostridia, and Verrucomicrobia were observed after feeding the mice with ulvan and astaxanthin. Duration of the treatments had a more substantial effect on the bacterial community structure than the type of treatment. Our findings highlight the potential of ulvan and astaxanthin to mediate aspects of host-microbe symbiosis in the gut, and if incorporated into the diet, these could assist positively in improving disease conditions associated with gut health.

Potential Prebiotic and Anti-Obesity Effects of Codium fragile Extract

Polysaccharides from marine algae exhibit beneficial biological activities. In this study, we examined the effect of Codium fragile extract (CFE) on prebiotic and anti-obesity activity through in vitro experiments. CFE increases the growth of specific beneficial microbial populations with concomitant decrease in pathogenic microbes. Further, total phenolic content (TPC), total flavonoid content (TFC), and DPPH radical scavenging activity (DPPH activity) after fermentation with CFE as the carbon source were higher than for glucose as the control. Moreover, CFE inhibited adipocyte differentiation by inducing differentiation-related factors when the induction of 3T3-L1 preadipocytes into adipocytes was induced. Therefore, we suggest that CFE can be used as a prebiotic material with an anti-obesity effect for human health.

Structural characterization and protective effects of polysaccharide from Gracilaria lemaneiformis on LPS-induced injury in IEC-6 cells

This study was aimed to characterize Gracilaria lemaneiformis polysaccharides and evaluate their protective effects on Lipopolysaccharide-induced injury in IEC-6 cells. The G. lemaneiformis polysaccharide was degraded by UV/H₂O₂ treatment and purified to three fractions named GLP-1.0 M, GLP-1.4 M and GLP-1.6 M. The purified fractions were mainly composed of galactose, glucose and xylose. The structural analysis showed that GLP-1.6 M was a typical sulfated red alga polysaccharide containing the linear backbone of β-(1 → 3)- and α-(1 → 4)-linked galactosyl residues, anhydro-galactose units. In the Lipopolysaccharide-induced IEC-6 cells model, GLP-1.6 M exerted the strongest in vitro anti-inflammatory activity by inhibiting the release and expressions of tumor necrosis factor-α, interleukin-6 and interleukin-1β by 89.93%, 67.82% and 38.06%, respectively. Meanwhile, GLP-1.6 M enhanced the intestinal barrier function via up-regulating the expressions of tight junctions and mucin. Therefore, the purified polysaccharide from G. lemaneiformis could be a promising candidate for maintaining intestinal health in the food and pharmaceutical industries.

Low molecular weight fucoidan fraction LF2 improves metabolic syndrome via up-regulating PI3K-AKT-mTOR axis and increasing the abundance of Akkermansia muciniphila in the gut microbiota

Metabolic syndrome (MetS) is a pathological condition of a variety of metabolic abnormalities, which requires more urgent treatment and intervention. Fucoidan has been recommended as a supplement for health enhancement and disease management. Here, we first propose that the beneficial effect of low molecular weight fucoidan fraction LF2 in regulating metabolic syndrome induced by high-fat diet is similar to that of metformin, in terms of molecular mechanism and gut microbiota. The study found that LF2 significantly reduces fasting blood glucose, enhances insulin sensitivity and restores insulin homeostasis and lipid homeostasis. Moreover, LF2 reduced liver oxidative stress and inflammation, and improved hepatocyte steatosis. To decipher the mechanism behind this therapeutic effect, both the molecular mechanisms and gut microbiota were further analyzed. LF2 inhibited the activation of PI3K-Akt-mTOR axis and decreased the expression of SREBP-1c and PPARγ in liver. Interestingly, we found that LF2 and metformin have similar effects on gut microbiota, increasing the proportion of Verrucomicrobia and enriching the abundance of Akkermansia muciniphila, which is beneficial to host health. Collectively, our research clarifies the new application of fucoidan as a functional food for anti-MetS, and provides a new insight for fucoidan to exert systemic therapeutic effects from the perspective of molecular mechanism and gut microbiota.

Low-molecular alginate improved diet-induced obesity and metabolic syndrome through modulating the gut microbiota in BALB/c mice

Alginate is the most abundant polysaccharide in brown seaweed, which is widely used as a food additive, but its high viscosity and gel property limit its applications in foods as a functional ingredient. In this study, low-molecular alginate from Laminaria japonica (L-LJA) was prepared, and its effect on obesity and metabolic syndrome was analyzed in high-fat diet (HFD)-fed mice. L-LJA reduced weight gain, fat accumulation in the liver and epididymal adipose tissue, lipid abnormality and inflammation in HFD-fed mice accompanied with the improvement of gut microbiota. L-LJA modulated the structure of gut microbiota, increased some Bacteroidales members, and reduced some Clostridiales members in mice, which were positively correlated with the improvement of physiological status. Fecal transplant from L-LJA-fed mice reduced fat accumulation in body tissues and lipid abnormality in the serum and liver and increased short chain fatty acids production in HFD-fed mice, confirming that L-LJA-induced gut microbiota alteration played an important role in its bioactivity. L-LJA has better solubility and can be utilized in food systems in high dose, implying that it can be developed as a prebiotic agent to increase both economic value and nutritive value of alginate.

Comparative Study of Sargassum fusiforme Polysaccharides in Regulating Cecal and Fecal Microbiota of High-Fat Diet-Fed Mice

Seaweed polysaccharides represent a kind of novel gut microbiota regulator. The advantages and disadvantages of using cecal and fecal microbiota to represent gut microbiota have been discussed, but the regulatory effects of seaweed polysaccharides on cecal and fecal microbiota, which would benefit the study of seaweed polysaccharide-based gut microbiota regulator, have not been compared. Here, the effects of two Sargassum fusiforme polysaccharides prepared by water extraction (SfW) and acid extraction (SfA) on the cecal and fecal microbiota of high-fat diet (HFD) fed mice were investigated by 16S rRNA gene sequencing. The results indicated that 16 weeks of HFD dramatically impaired the homeostasis of both the cecal and fecal microbiota, including the dominant phyla Bacteroidetes and Actinobacteria, and genera Coriobacteriaceae, S24-7, and Ruminococcus, but did not affect the relative abundance of Firmicutes, Clostridiales, Oscillospira, and Ruminococcaceae in cecal microbiota and the Simpson's index of fecal microbiota. Co-treatments with SfW and SfA exacerbated body weight gain and partially reversed HFD-induced alterations of Clostridiales and Ruminococcaceae. Moreover, the administration of SfW and SfA also altered the abundance of genes encoding monosaccharide-transporting ATPase, α-galactosidase, β-fructofuranosidase, and β-glucosidase with the latter showing more significant potency. Our findings revealed the difference of cecal and fecal microbiota in HFD-fed mice and demonstrated that SfW and SfA could more significantly regulate the cecal microbiota and lay important foundations for the study of seaweed polysaccharide-based gut microbiota regulators.

Seaweed Components as Potential Modulators of the Gut Microbiota

Macroalgae, or seaweeds, are a rich source of components which may exert beneficial effects on the mammalian gut microbiota through the enhancement of bacterial diversity and abundance. An imbalance of gut bacteria has been linked to the development of disorders such as inflammatory bowel disease, immunodeficiency, hypertension, type-2-diabetes, obesity, and cancer. This review outlines current knowledge from in vitro and in vivo studies concerning the potential therapeutic application of seaweed-derived polysaccharides, polyphenols and peptides to modulate the gut microbiota through diet. Polysaccharides such as fucoidan, laminarin, alginate, ulvan and porphyran are unique to seaweeds. Several studies have shown their potential to act as prebiotics and to positively modulate the gut microbiota. Prebiotics enhance bacterial populations and often their production of short chain fatty acids, which are the energy source for gastrointestinal epithelial cells, provide protection against pathogens, influence immunomodulation, and induce apoptosis of colon cancer cells. The oral bioaccessibility and bioavailability of seaweed components is also discussed, including the advantages and limitations of static and dynamic in vitro gastrointestinal models versus ex vivo and in vivo methods. Seaweed bioactives show potential for use in prevention and, in some instances, treatment of human disease. However, it is also necessary to confirm these potential, therapeutic effects in large-scale clinical trials. Where possible, we have cited information concerning these trials.

In vitro fermentation characteristics of polysaccharide from Sargassum fusiforme and its modulation effects on gut microbiota

In this study, polysaccharides from Sargassum fusiforme (SFP) were obtained by cellulase assisted hot water extraction. The chemical composition, structural characteristics, and in vitro fermentation properties of SFP were investigated. Results showed that the contents of total carbohydrate, protein, uronic acid and sulfate in SFP were 83.25%, 1.42%, 12.80% and 7.81%, respectively. It mainly consisted of fucose glucose and galactose, with molecular weight of 255.83 kDa. UV spectrum, FTIR, SEM and AFM results showed that SFP was a typical sulfate polysaccharide with relative smooth surface and regular shape. After in vitro fermentation for 24 h, the pH value of fermentation medium declined significantly (p < 0.05), utilization of carbohydrate was 53.17%. The contents of total SCFAs increased by 10.77 times. Moreover, SFP fermentation could change obviously the microbiota composition. It significantly increased the abundance of Faecalibacterium (increased by 49.07% compared with the Blank24 group), Phascolarctobacterium (increased by 88.06%), Bifidobacterium (increased by 139.13%), Ruminococcaceae_UCG-014 (increased by 177.78%), and Lactobacillus (increased by 400.00%), decreased the abundance of Prevotella_9 (decreased by 34.54%) and Blautia (decreased by 40.79%) at genus level. These results showed that SFP could be utilized by microbiota in human feces, and may have the potential to improve intestinal health.

Algae-Derived Bioactive Molecules for the Potential Treatment of SARS-CoV-2

The recently emerged COVID-19 disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has adversely affected the whole world. As a significant public health threat, it has spread worldwide. Scientists and global health experts are collaborating to find and execute speedy diagnostics, robust and highly effective vaccines, and therapeutic techniques to tackle COVID-19. The ocean is an immense source of biologically active molecules and/or compounds with antiviral-associated biopharmaceutical and immunostimulatory attributes. Some specific algae-derived molecules can be used to produce antibodies and vaccines to treat the COVID-19 disease. Algae have successfully synthesized several metabolites as natural defense compounds that enable them to survive under extreme environments. Several algae-derived bioactive molecules and/or compounds can be used against many diseases, including microbial and viral infections. Moreover, some algae species can also improve immunity and suppress human viral activity. Therefore, they may be recommended for use as a preventive remedy against COVID-19. Considering the above critiques and unique attributes, herein, we aimed to systematically assess algae-derived, biologically active molecules that could be used against this disease by looking at their natural sources, mechanisms of action, and prior pharmacological uses. This review also serves as a starting point for this research area to accelerate the establishment of anti-SARS-CoV-2 bioproducts.

Structural characteristics and anti-inflammatory activity of UV/H2O2-treated algal sulfated polysaccharide from Gracilaria lemaneiformis

The study aimed to study the effects on structural characteristics and anti-inflammatory activities of algal sulfated polysaccharides isolated from Gracilaria lemaneiformis (GLP) after a combined treatment of UV irradiation (average irradiance of 6500 mJ/cm²) and H₂O₂ (50 mmol/L) for various time periods up to 60 min. After a 30-min treatment, the molecular weight and particle size of GLP was decreased by 15 and 2.6 fold, respectively with small but significant decrease in the contents of total sugars, uronic acids and proteins. There seemed to have no starch and the presence of longer side chains of branches in the GLP samples before and after UV/H₂O₂ treatment based on the I₂-KI assay. Scanning electron microscope and atomic force microscope analysis confirmed that the UV/H₂O₂ treatment could modify the surface morphology of GLP. GLP treated for 5 min possessed the strongest in vitro anti-inflammatory activity by inhibiting the production of nitric oxide, tumor necrosis factor-α and interleukin-6 by 60.49%, 62.81% and 36.29%, respectively in IEC-6 cells when compared to the model. Therefore, UV/H₂O₂ treatment had the potential to enhance the anti-inflammatory activity of algal sulfated polysaccharides.

Clinical Efficacy of Brown Seaweeds Ascophyllum nodosum and Fucus vesiculosus in the Prevention or Delay Progression of the Metabolic Syndrome: A Review of Clinical Trials

Metabolic syndrome (MetS) is a global public health problem affecting nearly 25.9% of the world population characterised by a cluster of disorders dominated by abdominal obesity, high blood pressure, high fasting plasma glucose, hypertriacylglycerolaemia and low HDL-cholesterol. In recent years, marine organisms, especially seaweeds, have been highlighted as potential natural sources of bioactive compounds and useful metabolites, with many biological and physiological activities to be used in functional foods or in human nutraceuticals for the management of MetS and related disorders. Of the three groups of seaweeds, brown seaweeds are known to contain more bioactive components than either red and green seaweeds. Among the different brown seaweed species, Ascophyllum nodosum and Fucus vesiculosus have the highest antioxidant values and highest total phenolic content. However, the evidence base relies mainly on cell line and small animal models, with few studies to date involving humans. This review intends to provide an overview of the potential of brown seaweed extracts Ascophyllum nodosum and Fucus vesiculosus for the management and prevention of MetS and related conditions, based on the available evidence obtained from clinical trials.

Taxonomic Composition and Diversity of the Gut Microbiota in Relation to Habitual Dietary Intake in Korean Adults

We investigated associations of habitual dietary intake with the taxonomic composition and diversity of the human gut microbiota in 222 Koreans aged 18-58 years in a cross-sectional study. Gut microbiota data were obtained by 16S rRNA gene sequencing on DNA extracted from fecal samples. The habitual diet for the previous year was assessed by a food frequency questionnaire. After multivariable adjustment, intake of several food groups including vegetables, fermented legumes, legumes, dairy products, processed meat, and non-alcoholic beverages were associated with major phyla of the gut microbiota. A dietary pattern related to higher α-diversity (HiαDP) derived by reduced rank regression was characterized by higher intakes of fermented legumes, vegetables, seaweeds, and nuts/seeds and lower intakes of non-alcoholic beverages. The HiαDP was positively associated with several genera of Firmicutes such as Lactobacillus, Ruminococcus, and Eubacterium (all p < 0.05). Among enterotypes identified by principal coordinate analysis based on the β-diversity, the Ruminococcus enterotype had higher HiαDP scores and was strongly positively associated with intakes of vegetables, seaweeds, and nuts/seeds, compared to the two other enterotypes. We conclude that a plant- and fermented food-based diet was positively associated with some genera of Firmicutes (e.g., Lactobacillus, Ruminococcus, and Eubacterium) reflecting better gut microbial health.

Insoluble dietary fiber derived from brown seaweed Laminaria japonica ameliorate obesity-related features via modulating gut microbiota dysbiosis in high-fat diet-fed mice

Gut microbiota (GM) is considered to play an important role in obesity. Additionally, the impact of dietary fiber (DF) consumption on GM has been well established. Brown seaweeds are known to be a rich source of DF. However, the effect of insoluble DFs (IDFs) alone from brown seaweed on obesity and GM remains to be determined. This study investigated the effect of IDFs prepared from Laminaria japonica Aresch on high-fat diet (HFD)-induced obesity and GM dysbiosis in mice. Although HFD-induced body weight gain was not significantly attenuated by the IDF treatment, HFD-induced liver injury was ameliorated, and the HFD-elevated serum cholesterol concentration and glucose level of obese mice were significantly lowered. IDF treatment significantly modulated the GM composition disturbed by the HFD. It was found that 5% IDFs restored the GM to a very similar composition to that in the normal mice. The relative abundance of Akkermansia genus was decreased by >300-fold in HFD-fed mice, and it was fully restored by 5% IDF administration. Akkermansia muciniphila, a short-chain fatty acid producer, was identified as a marker species in both control and high-dose IDF groups. Furthermore, IDFs significantly restored the HFD-reduced acetate and propionate levels in the cecal content. In conclusion, the beneficial effect of IDFs derived from L. japonica on obesity was confirmed in mice, and the underlying mechanism may be associated with the modulation of GM composition, possibly through the enrichment of Akkermansia.

Regulation effects of indigestible dietary polysaccharides on intestinal microflora: An overview

The human intestinal contains rich and diverse microbiota that utilizes a variety of polysaccharides. The intestinal microflora extends the metabolic functions of the body, obtaining energy from indigestible dietary polysaccharides. It is not only a highly competitive environment but also a comprehensive collaboration for these polysaccharides, as the microbiota work to maximize the energy harvested from them through the intestine. Indigestible dietary polysaccharides help to manage colon health and host health by affecting the gut microbial population. These polysaccharides also influence the metabolic activity of the intestinal microbiota by stimulating the formation of SCFAs. Most of these metabolic activities affect host physiology because the epithelium absorbs secondary metabolites and end products or transports them to the liver, where they could exert other beneficial effects. This article reviews the carbohydrates existing in the human intestine, the regulating actions of indigestible polysaccharides on intestinal microflora, and the molecular basis of the degradation process of these polysaccharides. PRACTICAL APPLICATIONS: Large deals of researches have shown that indigestible polysaccharides possess an outstanding regulation effect on the intestinal microflora, which indicates that indigestible polysaccharides have the potential to be used as prebiotics in the functional food and pharmaceutical industries. However, it is not clear how gut microbiota metabolizes these dietary polysaccharides, and how the resulting gut metabolites may further affect the intestinal microflora population and metabolism. This paper reviews the indigestible dietary polysaccharides existing in the human intestine, the regulation of polysaccharides on gut microbiota, and the molecular basis of the degradation process of these polysaccharides. This review helps to better understand the relationship between indigestible dietary polysaccharides and intestinal microflora, which will provide powerful evidence for the potential use of these polysaccharides as functional foods.

Anti-cancer effects of Porphyra haitanensis polysaccharides on human colon cancer cells via cell cycle arrest and apoptosis without causing adverse effects in vitro

In this study, the anticancer effects of Porphyra haitanensis polysaccharides (PHPs) on human colon cancer cells and non-cancerous cells were evaluated. PHP was extracted by an ultrasonic/microwave-assisted method, and three fractions of polysaccharides (PHP-F1, PHP-F2 and PHP-F3) were obtained through a DEAE-52 cellulose ion-exchange column. The results of the cytotoxicity test showed that all of the PHP fractions had inhibitory effects on the growth of colon cancer cells HT-29, LoVo and SW-480, but no toxic effects on the normal human cells HaCaT. The fractions PHP-F2 and PHP-F3 had the most significant cytotoxicity on HT-29 cells. Studies on intracellular reactive oxygen species (ROS) levels, cell apoptosis, the apoptosis index (using Hoechst 33342 staining) and analysis of cell cycle arrest using flow cytometry revealed that the fractions PHP-F2 and PHP-F3 could apparently induce oxidative stress and apoptosis in HT-29 cells and cause cell G0-G1 phase arrest. These findings suggest that polysaccharides from P. haitanensis have anticancer effects on human colon cancer cells and therefore might be regarded as new candidates for the prevention and treatment of colon cancers.

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.