Dietary fiber from Indian edible seaweeds and its in-vitro prebiotic effect on the gut microbiota

Scope and challenges of seaweed utilization in food and nutraceutical industry in India: a review

Seaweeds are an excellent source of unique antioxidant phytochemicals, dietary fibres, essential amino acids, vitamins, polyunsaturated fatty acids and minerals. The presence of such structurally diverse and high value bioactive compounds has led to popularization of seaweed as functional food ingredient in global health supplement market. India, with a long coastline of 8100 km and exclusive economic zone of 2.17 million km2, is rich in diverse seaweed resources belonging to almost 700 species. However, food and nutraceutical application of Indian seaweed is highly constrained. Apart from Kappaphycus alvarezii, there is no systematic commercial cultivation of seaweed in India. The regulatory framework for use of seaweed as food is still developing and consumer acceptance is still low. However, there is a timely and renewed interest from different government agencies and research organisations to develop a thriving food and nutraceutical industry using India's vast seaweed resources. The review briefly describes the nutritional and functional food potential of the seaweed and goes on to discuss the scope of seaweed utilization in food and nutraceutical industry in India. Further, the review has identified the regulatory challenges and quality control requirements for use of seaweeds in food and nutraceuticals.

Effects of glycation with chitooligosaccharide on digestion and fermentation processes of lactoferrin in vitro

This study aimed to investigate the digestion and fermentation processes of lactoferrin (LF) glycated with chitooligosaccharide (COS) under a controlled Maillard reaction, utilizing the in vitro digestion and fermentation model, and to compare the results of these processes to LF undertaken without glycation. After gastrointestinal digestion, the products of the LF-COS conjugate were found to have more fragments with lower molecular weight than LF, and the antioxidant capabilities (via ABTS and ORAC assay) of the LF-COS conjugate digesta also increased. In addition, the undigested fractions could be further fermented by the intestinal microbiota. Compared with LF, more short-chain fatty acids (SCFAs) were generated (from 2397.40 to 2623.10 μg/g), and more species of microbiota (from 451.78 to 568.10) were observed in LF-COS conjugate treatment. Furthermore, the relative abundance of Bacteroides and Faecalibacterium that could utilize carbohydrates and metabolic intermediates to produce SCFAs also increased in LF-COS conjugate than that of LF. Our results demonstrated that glycation with COS under the controlled wet-heat treatment Maillard reaction could modify the digestion of LF and have a potentially positive influence on the intestinal microbiota community.

Characterization and identification of inulin from Pachyrhizus erosus and evaluation of its antioxidant and in-vitro prebiotic efficacy

Inulin is the polysaccharide obtained from different plant sources i.e. Wheat, Chicory, Jerusalem artichoke and Dahlia. In this study, Jicama (Pachyrhizus erosus) is used to isolate inulin using the microwave heating. The 1H NMR study reveals the presence of fructose and glucose unit which is the backbone of inulin. Further FT-IR and Raman confirmed the functional groups present in inulin. The UV-Vis spectroscopy analysis depicts the purity of the isolated inulin. The shape and size of the extracted inulin was determined from scanning electron microscopy and dynamic light scattering appeared as flat-flakes and 135 nm respectively. X-ray diffractogram showed semi-crystalline nature suggesting the stability of the extracted inulin. The isolated inulin has phenolic and flavonoid content of 8.1804 ± 6.26 mg gallic acid equivalent/g and 14.387 ± 4.192 mg rutin equivalent/g of dried polysaccharide respectively. The inhibition percentage of DPPH and FRAP of isolated inulin were found to be 75.74 ± 4.5% and 0.11 ± 0.007 respectively. The isolated inulin promotes the growth of probiotics like Enterococcus faecium (MZ540315) and Lactiplantibacillus plantarum (MZ540317). All the analysis suggest the isolated inulin has good prebiotic potential as the commercially available one. The current study proposes that isolated inulin can be used as a prebiotic in the future.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05619-6.

An effective universal protocol for the extraction of fructooligosaccharide from the different agricultural byproducts

Alternative bio-refinery technologies are required to promote the commercial utilization of plant biomass components. The fructooligosaccharide (FOS) obtained after hydrolysis of the hemicellulose fractions was mainly applied in the pharmaceutical and food industries. Agricultural bi-product is a rich constituent in dietary fibres, which have prebiotic effects on the intestinal microbiota and the host. Herein we explored the impact of FOS on microbiota modulation and the gut homeostasis effect. High fructooligosaccharide recovery was obtained using alkaline extraction techniques. The enzymatic method produced fructooligosaccharides with minor contamination from fructan and glucan components, although it had a low yield. But combining the alkaline and enzymatic process provides a higher yield ratio and purity of fructooligosaccharides. The structure of the fructooligosaccharide was confirmed, according to FTIR, ¹³C NMR, ¹H NMR and 2D-NMR data. Our results could be applied to the development of efficient extraction of valuable products from agricultural materials using enzyme-mediated methods, which were found to be a cost-effective way to boost bio-refining value. Fructooligosaccharides with varying yields, purity, and structure can be obtained.

The prebiotic properties of polysaccharides obtained by differentiated deproteinization methods from Flos Sophorae Immaturus on Lactobacillus fermentum

The polysaccharides derived from various deproteinization methods were prepared from Flos Sophorae Immaturus (FSI) to investigate the prebiotic efficacy of Lactobacillus fermentum (L.f ). The implications of polysaccharides from FSI (PFSI) gained after purification performed by non-deproteinization and different deproteinization processes (Savage method, papain method, and TCA method) via one-factor optimization were firstly investigated for the influences on the growth of L.f. The utilization of carbohydrate sources and the synthesis of protein and lactate during its growth were analyzed, as well as the variations of LDH, SOD, and GSH- Px enzyme dynamics. The results showed that the one-factor optimization of the deproteinization process with the protein removal rate and polysaccharide retention rate as the indexes led to the optimal methods of the Sevage method with 5 elution times, papain method with 80 U/mL concentration, and TCA method with 2.5 ratio, respectively. In addition, the PFSI obtained with or without deproteinization purification had a certain effect on promoting L.f proliferation. Moreover, the PFSI gained by the third deproteinization purification, at a concentration of 10 g/L, significantly elevated L.f biomass and growth rate compared with the blank control, and the utilization of reducing sugars and the synthesis of protein and lactic acid were higher than the control (P < 0.05); improved LDH, SOD, and GSH-Px activity in L.f (P < 0.05), and the TCA method could be effectively applied to eliminate the proteins affecting FSI in probiotics, and PFSI may be a potentially beneficial prebiotic and intestinal reinforcer.

Antimicrobial, anti-biofilm, antioxidant and cytotoxic effects of bacteriocin by Lactococcus lactis strain CH3 isolated from fermented dairy products-An in vitro and in silico approach

The current study aimed to screen bacteriocin producing LAB from different dairy products and evaluation of their biological properties. Initially, 12 (4-chess, 4-curd, and 4-yohurt) LAB species were isolated and only 4 isolates alone were selected based on their clear yellow halo zone around the colonies in the selective medium. The selected 4 isolates were identified based on their morphological and biochemical characteristics. Among them, the strain CH3 have showed better antimicrobial effects on selected human pathogens. The isolated strain CH3 were further identified as Lactococcus lactis strain CH3 (MZ636710) by SEM imaging and 16 s rRNA molecular sequencing. Bacteriocin was extracted from L. lactis strain CH3 and partially purified using 60 % ammonium sulphate and then completely purified by G-50 column chromatography. The purified bacteriocin showed a specific activity of 5859.37 AU/mg in 24.7 % of recovery and 10.9-fold purification. The molecular weight of bacteriocin was 3.5 kDa as observed in SDS-PAGE. The bacteriocin showed sensitivity to proteolytic enzymes and resistance to high temperature, wide range of pH, organic solvents and detergents. FT-IR spectral studies of bacteriocin detected the existence of OH/NH-stretching, CH, and COC and CO bonds. NMR spectrum showed one doublet and 4 various singlet peaks at different ppm, indicating the occurrence of six amino acids in the structure of purified bacteriocin. The purified bacteriocin have shown stronger antimicrobial and anti-biofilm activity against selected human pathogens at 100 μg/mL. SEM showed the evidence of structural deformation and loss of membrane integrity of bacterial cells treated with bacteriocin. Bacteriocin exhibited greater DPPH radical scavenging potential with an EC₅₀ value of 12.5 μg/mL. Bacteriocin have not shown significant toxicity on normal human dermal fibroblast (NHDF) cells (83.2 % at 100 μg/ mL). Furthermore, in silico studies using molecular modeling and docking were performed to know the proteins involved in antimicrobial action. The results suggests that bacteriocin could be an alternative to combat AMR pathogens and more suitable for food and dairy industries to preserve food without contamination.

Treating the Onset of Diabetes Using Probiotics Along with Prebiotic from Pachyrhizus erosus in High-Fat Diet Fed Drosophila melanogaster

The increasing mortality due to hypertension and hypercholesterolemia is directly linked with type-2 diabetes. This shows the lethality of the disease. Reports suggest that the prebiotics along with probiotics help in lowering the effects of type-2 diabetes. Prebiotic like inulin is best known for its anti-diabetic effect. The current study utilizes jicama extract as prebiotic source of inulin along with the bacterial strains with probiotic properties (Lactiplantibacillus plantarum and Enterococcus faecium) for treating type-2 diabetes in high-fat diet-induced Drosophila melanogaster model. The high-fat diet-induced Drosophila showed deposition of lipid droplets and formation of micronuclei in the gut. The larva and adult treated with probiotics and synbiotic (probiotic + prebiotic- inulin) comparatively reduced the lipid deposition and micronuclei number in the gut. The increased amount of triglyceride in the whole body of the fatty larva and adult indicated the onset of diabetes. The overexpression of insulin-like genes (Dilp 2) and (Dilp 5) confirmed the insulin resistance, whereas the expression was reduced in the larva and adult supplemented with probiotics and synbiotic. The reactive oxygen species level was reduced with the supplementation of probiotics. The weight, larva size, crawling speed and climbing were also altered in high-fat diet-induced Drosophila melanogaster. The study confirmed the effects of probiotics and synbiotic in successfully lowering diabetes in Drosophila. The study also proved the anti-diabetic potential of the probiotics. Further, it was also confirmed that the probiotics work better in the presence of prebiotic.

A Retrospective Review of Global Commercial Seaweed Production-Current Challenges, Biosecurity and Mitigation Measures and Prospects

Commercial seaweed cultivation has undergone drastic changes to keep up with the increasing demand in terms of the quantity and quality of the algal biomass needed to meet the requirements of constant innovation in industrial applications. Diseases caused by both biotic and abiotic factors have been identified as contributing to the economic loss of precious biomass. Biosecurity risk will eventually affect seaweed production as a whole and could cripple the seaweed industry. The current review sheds light on the biosecurity measures that address issues in the seaweed industry pushing towards increasing the quantity and quality of algal biomass, research on algal diseases, and tackling existing challenges as well as discussions on future directions of seaweed research. The review is presented to provide a clear understanding of the latest biosecurity developments from several segments in the seaweed research, especially from upstream cultivation encompassing the farming stages from seeding, harvesting, drying, and packing, which may lead to better management of this precious natural resource, conserving ecological balance while thriving on the economic momentum that seaweed can potentially provide in the future. Recommended breeding strategies and seedling stock selection are discussed that aim to address the importance of sustainable seaweed farming and facilitate informed decision-making. Sustainable seaweed cultivation also holds the key to reducing our carbon footprint, thereby fighting the existential crisis of climate change plaguing our generation.

Effect of Polysaccharides From Enteromorpha intestinalis on Intestinal Function in Sprague Dawley Rats

This study aims to determine the effect of polysaccharides extracted from Enteromorpha intestinalis (EI) on the intestinal function of Sprague Dawley (SD) rats. The polysaccharides were extracted from the green alga using water and alkaline solution, where these extracts were named WPEI and APEI, respectively. The dried powder of EI was labeled as DPEI. Proximate compositions, minerals, and amino acids of the DPEI, WPEI, and APEI were determined. The growth-promoting effect of the polysaccharides on selected intestinal microflora was determined based on the plate count method. In contrast, the in vivo effect of DPEI and its polysaccharides on the intestinal function of the SD rats was determined. These rats were fed with 1% WPEI, APEI, and DPEI. The result showed that APEI had lower total sugars and total proteins content than the WPEI. WPEI did not contain arabinose. The WPEI and APEI also had a better ability to promote microbial growth than the DPEI. The in vivo study showed that WPEI improved intestinal peristalsis and other intestinal functions compared with the other rat groups. The average final body weight of the experimental rats treated with DPEI was also lower than the other groups. The pH value of the feces of all treated rats was lower than the control rats, and the moisture content of the fecal samples of these experimental groups was higher than the control group. Also, the intestinal activated carbon propulsion of the WPEI, APEI, and DPEI fed rats increased. Among the short-chain fatty acids content determined in the fecal samples, the propionic acid content of the WPEI group was significantly highest. Therefore, WPEI had the best effect in improving intestinal digestion.

Bioactive polysaccharides from red seaweed as potent food supplements: a systematic review of their extraction, purification, and biological activities

Most marine macroalgae such as red seaweeds are potential alternative sources of useful bioactive compounds. Beside serving as food source, recent studies have shown that red seaweeds are rich sources of bioactive polysaccharides. Red seaweed polysaccharides (RSPs) have various physiological and biological activities, which allow them to be used as immunomodulators, anti-obesity agents, and prebiotic ingredients. Lack of summary information and human clinical trials on the various polysaccharides from red seaweeds, however limits industrial-scale utilization of RSPs in functional foods. This review summarizes recent information on the approaches used for RSPs extraction and purification, mechanistic investigations of their biological activities, and related molecular principles behind their purported ability to prevent diseases. The information here also provides a theoretical foundation for further research into the structure and mechanism of action of RSPs and their potential applications in functional foods.

Potential of Persimmon Dietary Fiber Obtained from Byproducts as Antioxidant, Prebiotic and Modulating Agent of the Intestinal Epithelial Barrier Function

Appropriate nutrition targets decrease the risk of incidence of preventable diseases in addition to providing physiological benefits. Dietary fiber, despite being available and necessary in balanced nutrition, are consumed at below daily requirements. Food byproducts high in dietary fiber and free and bonded bioactive compounds are often discarded. Herein, persimmon byproducts are presented as an interesting source of fiber and bioactive compounds. The solvent extraction effects of dietary fiber from persimmon byproducts on its techno- and physio-functional properties, and on the Caco-2 cell model after being subjected to in vitro gastrointestinal digestion and probiotic bacterial fermentation, were evaluated. The total, soluble, and insoluble dietary fiber, total phenolic, carotenoid, flavonoid contents, and antioxidant activity were determined. After in vitro digestion, low quantities of bonded phenolic compounds were detected in all fiber fractions. Moreover, total phenolic and carotenoid contents, as well as antioxidant activity, decreased depending on the extraction solvent, whereas short chain fatty acids production increased. Covalently bonded compounds in persimmon fiber mainly consisted of hydroxycinnamic acids and flavanols. After probiotic bacterial fermentation, few phenolic compounds were determined in all fiber fractions. Results suggest that persimmon's dietary fiber functional properties are dependent on the extraction process used, which may promote a strong probiotic response and modulate the epithelial barrier function.

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.

The Impacts of Urbanization and Dietary Knowledge on Seaweed Consumption in China

Edible seaweed, a nutrient-rich and sustainable food, has a long dietary history in China. To get a better understanding of the seaweed consumption of consumers in China, this study investigates the quantity and trend of seaweed consumption of Chinese residents and employs a Tobit model to examine the effects of urbanization and dietary knowledge on seaweed consumption among residents. The results show an increasing trend of household seaweed consumption in China, including both seaweeds consumed at home (SAH) and seaweeds consumed away from home (SAFH). Households in urban areas consumed more seaweeds on average than those in rural areas. Urbanization promotes total household seaweed consumption, including SAH and SAFH, whilst dietary knowledge has a significantly positive impact on total household seaweed consumption and SAH. The findings supplement empirical evidence on the seaweed consumption behavior of Chinese residents and have important policy implications for further promoting Chinese seaweeds consumption in the context of urbanization and increasing dietary knowledge.

In vitro fermentation of hyaluronan by human gut microbiota: Changes in microbiota community and potential degradation mechanism

Hyaluronan (HA) has been widely used as a dietary supplement which can be degraded by gut microbiota. However, the interactions between HA and gut microbiota have not been fully characterized. Here, using an in vitro system, we found that HA is readily fermented by human gut microbiota but with differing fermentative activities among individuals. HA-fermentation boosted Bacteroides spp., Bifidobacterium spp., Dialister spp., Faecalibacterium spp. and produced a significant amount of acetate, propionate and butyrate. Fermentation products profiling indicated that HA could be degraded into unsaturated even-numbered and saturated odd-numbered oligosaccharides. Further, polysaccharide lyases (PLs) and glycoside hydrolases (GHs) including GH88, PL8, PL29, PL35 and PL33 were identified from B. ovatus E3, which can help to explain the structure of the fermentation products. Collectively, our study sheds new light into the metabolism of HA and forms the basis for understanding the bioavailability of HA from a gut microbiota perspective.

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.

Comparative analysis of the morphological property and chemical composition of soluble and insoluble dietary fiber with bound phenolic compounds from different algae

The morphological, physicochemical, and biochemical properties of soluble and insoluble dietary fiber from seven types of algae were investigated. The soluble dietary fiber (SDF) contents (6.48 to 60.90% of the total fiber) in most of the investigated algae were significantly lower than the insoluble dietary fiber (IDF) contents (39.10 to 93.52% of the total fiber). It can be inferred from the infrared and UV-Vis spectra that the SDF and IDF of algae may contain cellulose, hemicellulose, various monosaccharides, phenolic compounds, and quinone pigments. The bound phenolic in the seven algae varied widely in contents (3.76 to 14.08 mg GAE/g in IDF and 1.94 to 8.61 mg GAE/g in SDF), whose antioxidant activities in the IDF were stronger than those in SDF because of different phenolic compositions. The HPLC-mass spectrometry (MS)/MS results showed that the IDF may contain methyl-8α-hydroxy-grindelate-7β-O-7'β-ether hydrate, hydroxydecanoic acid, and malyngic acid. PRACTICAL APPLICATION: Polysaccharides of high content in algae cannot be digested by humans, hence regarded as dietary fibers. A large amount of bound phenolic compounds in dietary fibers can add to the biological activities of dietary fibers. These topics are important to the development of seaweed-based functional foods.

Comparison of physicochemical properties and antidiabetic effects of polysaccharides extracted from three seaweed species

Three algae polysaccharides (APs) extracted from Ascophyllum nodosum (ANP), Fucus vesiculosus (FVP) and Undaria Pinnatifida (USP) significantly differed in the zeta potential, water and oil holding capacity, monosaccharide composition, organic element composition, molecular weight distribution, microstructure and rheological properties. Antidiabetic effects of APs were compared by oral intervention at the dose of 400 mg/kg·body weight/day in high sugar and fat diets and streptozotocin injection induced type 2 diabetic rats. The analysis of body weight, water intake, fasting blood glucose, insulin, oral glucose tolerance, blood lipid indicators (including total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C) and free fatty acid (FFA)), liver function indexes (involving alanine aminotransferase (ALT) and aspartate aminotransferase (AST)) and renal function profiles (comprising uric acid (UA) and urea nitrogen (BUN)) showed that APs possessed obvious antidiabetic activities, and FVP showed better effects in controlling the levels of FFA, AST, ALT, UA and BUN. Intervention of FVP reduced the total bile acid (TBA) level and elevated high density lipoprotein cholesterol (HDL-C) level of diabetic rats. Histomorphological observation further demonstrated that APs, especially FVP, could attenuate liver and kidney damage caused by diabetes. This study concluded that the antidiabetic effects of ANP, FVP and USP were distinctly different, which might be attributed to their different chemical structures. Therefore, the structure-activity relationship and antidiabetic mechanism of APs will be our future research direction.

Cytotoxic and pharmacokinetic studies of Indian seaweed polysaccharides for formulating raindrop synbiotic candy

Gut microbiome evidenced as the assembling mode of action facilitates the relationship of environmental factors (such as diet and lifestyle) with colorectal cancer. The cytotoxic and anticancer studies of the enzymatically extracted polysaccharides from selected Indian seaweeds (such as S. wightii, E. compressa, and A. spicifera) on Raw 264.7 macrophage and HT-29 human colon cancer cell line were investigated. E. compressa showed nitric oxide production up to a concentration of 6.99 ± 0.05 μM. The polysaccharide extract of seaweed (PES), A. spicifera (100 μg/ml) had shown the highest in-vitro cytotoxicity effect on HT-29 cells up to 52.13 ± 1.4%. Absorption, distribution, metabolism and excretion (ADME) predictions were performed for exploring the possibility of anti-cancer drug development. The formulated synbiotic candy exhibited post storage survivability of probiotic species L. plantarum NCIM 2083 up to 10⁷ CFU/ml until three weeks and it could be an aesthetic functional food for treating colon cancer.

Trends in Seaweed Extract Based Biostimulants: Manufacturing Process and Beneficial Effect on Soil-Plant Systems

The time when plant biostimulants were considered as "snake oil" is erstwhile and the skepticism regarding their agricultural benefits has significantly faded, as solid scientific evidences of their positive effects are continuously provided. Currently plant biostimulants are considered as a full-fledged class of agri-inputs and highly attractive business opportunity for major actors of the agroindustry. As the dominant category of the biostimulant segment, seaweed extracts were key in this growing renown. They are widely known as substances with the function of mitigating abiotic stress and enhancing plant productivity. Seaweed extracts are derived from the extraction of several macroalgae species, which depending on the extraction methodology lead to the production of complex mixtures of biologically active compounds. Consequently, plant responses are often inconsistent, and precisely deciphering the involved mechanism of action remains highly intricate. Recently, scientists all over the world have been interested to exploring hidden mechanism of action of these resources through the employment of multidisciplinary and high-throughput approaches, combining plant physiology, molecular biology, agronomy, and multi-omics techniques. The aim of this review is to provide fresh insights into the concept of seaweed extract (SE), through addressing the subject in newfangled standpoints based on current scientific knowledge, and taking into consideration both academic and industrial claims in concomitance with market's requirements. The crucial extraction process as well as the effect of such products on nutrient uptake and their role in abiotic and biotic stress tolerance are scrutinized with emphasizing the involved mechanisms at the metabolic and genetic level. Additionally, some often overlooked and indirect effects of seaweed extracts, such as their influence on plant microbiome are discussed. Finally, the plausible impact of the recently approved plant biostimulant regulation on seaweed extract industry is addressed.

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.

The Antioxidant Activity of Polysaccharides Derived from Marine Organisms: An Overview

Marine-derived antioxidant polysaccharides have aroused extensive attention because of their potential nutritional and therapeutic benefits. However, the comprehensive comparison of identified marine-derived antioxidant polysaccharides is still inaccessible, which would facilitate the discovery of more efficient antioxidants from marine organisms. Thus, this review summarizes the sources, chemical composition, structural characteristics, and antioxidant capacity of marine antioxidant polysaccharides, as well as their protective in vivo effects mediated by antioxidative stress reported in the last few years (2013-2019), and especially highlights the dominant role of marine algae as antioxidant polysaccharide source. In addition, the relationships between the chemical composition and structural characteristics of marine antioxidant polysaccharides with their antioxidant capacity were also discussed. The antioxidant activity was found to be determined by multiple factors, including molecular weight, monosaccharide composition, sulfate position and its degree.