The specific use of alginate from Laminaria japonica by Bacteroides species determined its modulation of the Bacteroides community

Differences in utilization and metabolism of Ulva lactuca polysaccharide by human gut Bacteroides species in the in vitro fermentation

Ulva lactuca polysaccharide (ULP), a sulfated polysaccharide, has been widely used in Asia. However, its digestion process and utilization by gut microbiota remain poorly understood. In this study, the in vitro simulated digestion and fermentation were used to analyze the digestibility of ULP. The results showed that ULP was not degraded during simulated digestion, but was utilized by human fecal microbiota. 16S rRNA sequencing revealed that ULP significantly increased the abundance of Bacteroides. Further evaluation of seven Bacteroides species showed that only B. thetaiotaomicron and B. vulgatus could utilize ULP. Interestingly, these two species exhibited different utilization patterns. B. vulgatus preferentially utilized rhamnose of ULP over glucuronic acid to promote growth. Metabolite profiles of B. thetaiotaomicron and B. vulgatus during in vitro fermentation with ULP as the sole carbon source were different. Although both B. thetaiotaomicron and B. vulgatus utilized ULP to produce various metabolites such as acetic acid, propionic acid, cysteic acid and riboflavin, B. thetaiotaomicron accumulated metabolites, such as linoleic acid, that were not accumulated by B. vulgatus. The effects of ULP on the metabolic pathways of B. thetaiotaomicron and B. vulgatus differed. These findings provide a new perspective on the utilization of ULP by human gut microbiota.

Cadmium bioavailability in market nori and kelp: A comparison with rice and mechanisms underlying reduction in rice cadmium bioavailability with nori and kelp consumption

Seaweeds, despite being rich in beneficial substances, also contain toxic metals such as cadmium (Cd), leading to ongoing debates about their health impacts. This study assessed the risk of Cd exposure from consuming nori and kelp, as well as the potential benefits of these seaweeds in mitigating Cd exposure from rice, using mouse bioassays. The results indicated that all test nori samples (n = 35) had Cd concentration exceeding 1.2 μg g-1, while the majority of kelp samples (18 out of 24) contained <0.5 μg g-1. When mixed with Cd-free rice at a 5 % (w/w) ratio and administered to mice for 14 days, kelp samples with 0.36 and 0.50 μg g-1 Cd (Kelp-0.36 and Kelp-0.50) did not result in Cd accumulation in the liver or kidneys. Conversely, nori samples with 1.30 and 1.67 μg g-1 Cd (Nori-1.30 and Nori-1.67) led to significant Cd accumulation, highlighting the exposure risk associated with nori. This risk was further emphasized by a doubling of Cd accumulation in the tissues of mice fed sushi containing nori compared to those fed sushi without nori. However, the Cd accumulation from consuming Nori-1.30 and Nori-1.67 was comparable to that from rice with a lower Cd concentration (0.93 μg g-1), suggesting a lower bioavailability of Cd in nori than in rice. More promisingly, when consumed with Cd-containing rice at a 5 % (w/w) ratio, Kelp-0.36, Kelp-0.50, Nori-1.30, and Nori-1.67 reduced the accumulation of rice Cd in mouse tissues by 25.8 %-48.1 %, primarily by increasing the relative abundances of Bacteroides in the gut of mice and enhancing fecal output, which in turn increased the excretion of rice-derived Cd by 1.46-1.54 times. These findings suggest that kelp consumption may be relatively safe, while caution is advised for nori. Moreover, regular consumption of specific amounts of seaweeds, particularly kelp, could help to reduce Cd exposure from rice.

Modulation effect of sulfated polysaccharide from Sargassum fusiforme on gut microbiota and their metabolites in vitro fermentation

The present study demonstrated the digestion behavior and fermentation characteristics of a sulfated polysaccharide from Sargassum fusiforme (SFSP) in the simulated digestion tract environment. The results showed that the molecular weight of two components in SFSP could not be changed by simulated digestion, and no free monosaccharide was produced. This indicates that most of SFSP can reach the colon as prototypes. During the fermentation with human intestinal flora in vitro, the higher-molecular-weight component of SFSP was utilized, the total sugar content decreased by 16%, the reducing sugar content increased, and the galactose content in monosaccharide composition decreased relatively. This indicates that SFSP can be selectively utilized by human intestinal flora. At the same time, SFSP also changed the structure of intestinal flora. Compared with the blank group, SFSP significantly increased the abundance of Bacteroidetes and decreased the abundance of Firmicutes. At the genus level, the abundances of Bacteroides and Megamonas increased, while the abundances of Shigella, Klebsiella, and Collinsella decreased. Moreover, the concentrations of total short-chain fatty acids (SCFAs), acetic, propionic and n-butyric acids significantly increased compared to the blank group. SFSP could down-regulate the contents of trimethylamine, piperidone and secondary bile acid in fermentation broth. The contents of nicotinic acid, pantothenic acid and other organic acids were increased. Therefore, SFSP shows significant potential to regulate gut microbiota and promote human health.

Laminaria japonica Polysaccharides Improves the Growth Performance and Faecal Digestive Enzyme Activity of Weaned Piglets

The aim of this experiment was to investigate the effect of Laminaria japonica polysaccharide (LJP) supplementation at levels of 100, 200, or 400 mg/kg on the growth performance, faecal digestive enzyme activity, and serum biochemistry and amino acids of weaned piglets. One hundred and twenty weaned piglets (Barkshire × Licha Black, 21 days old, 6.13 ± 0.16 kg) were randomly divided into four groups with five replicates of six piglets in each group based on body weight. Piglets were fed with different levels (0, 100, 200, and 400 mg/kg) of LJP for a 21-day trial. On day 21, faecal and blood samples were collected from one piglet per pen. The results showed that the supplementation of the 200 and 400 mg/kg LJP significantly increased average daily gain (ADG) and average daily feed intake (ADFI) compared to the control group (p = 0.007; p = 0.002), and dietary LJP linearly increased ADG and ADFI (p = 0.002; p < 0.001). In addition, the supplementation of the 200 and 400 mg/kg LJP significantly increased faecal amylase activity (p < 0.001) compared to the control group, and dietary LJP linearly increased faecal amylase and lipase activities (p = 0.001; p = 0.037). Moreover, dietary LJP at 400 mg/kg increased serum histidine content compared to the other groups (p = 0.002), and dietary LJP linearly increased the contents of serum histidine and asparagine in piglets (p < 0.001; p = 0.046). In conclusion, supplementation of 200 and 400 mg/kg LJP could enhance growth performance and faecal digestive enzyme activity and modulate the serum amino acid content of weaned piglets, potentially contributing to the health of weaned piglets.

Modulating in vitro fecal fermentation behavior of sodium alginate by Ca2+ cross-linking

Slow fermentable dietary fibers can be utilized by human gut microbiota in the distal region of the colon and thus exert a sufficient short-chain fatty acids (SCFAs) supplement in the distal region of the human colon. Alginate (Alg) based microgels are widely fabricated and used to control their digestion by digestive enzymes releasing active substances site-specifically. Herein, sodium alginate microgels with gradient calcium-ion (Ca2+) cross-linking densities were developed, restricting their degradation by gut microbiota. Alg microgels were prepared using high-speed shearing after Alg was cross-linked with 10, 40, and 60 mmol/L Ca2+, respectively (named 10-Alg, 40-Alg, and 60-Alg). The fluorescence and atomic force microscopic results showed that the 40-Alg particle has the densest structure among the three cross-linked Alg. In vitro human fecal fermentation results revealed that the Ca2+ cross-linking exerted more restricting effects than delaying effects on the fermentation of Alg, and the 40-Alg exhibited the slowest fermentation rate and the least fermentation extent, by characterizing the residual total carbohydrate content, residual monosaccharide content, pH, and total short-chain fatty acids. The 16S rRNA gene sequencing results indicated that cross-linking structures shaped a high specifical Bacteroides-type microbial community and that OTU205 (Bacteroides_xylanisolvens) highly correlated to the cross-linking density (R = 0.65, p = 0.047). In sum, Ca2+ cross-linking generated a dense and compact structure of sodium alginate that facilitated a more restricted fermentation property and specificity-targeting microbial community structure in comparison to the original sodium alginate.

Effects of dietary sodium butyrate on growth performance, immune function, and intestinal microflora of Chinese soft-shelled turtle (Pelodiscus sinensis)

The Chinese soft-shelled turtle (Pelodiscus sinensis) has become increasingly susceptible to frequent diseases with the intensification of farming, which severely impacts the development of the aquaculture industry. Sodium butyrate (SB) is widely used as a feed additive due to its promotion of growth, enhancement of immune function, and antioxidative properties. This study aimed to investigate the effects of dietary SB on the growth performance, immune function, and intestinal microflora of Chinese soft-shelled turtles. A total of 300 Chinese soft-shelled turtles (mean weight: 11.36 ± 0.21g) were randomly divided into four groups with three parallel sets in each group. Each group was fed a diet supplemented with 0%, 0.005%, 0.01%, or 0.02% SB for 60 days. The results demonstrated an upward trend in weight gain rate (WGR) and specific growth rate (SGR) with increasing SB supplementation, and the experimental group fed with 0.02% SB showed a significant increase in WGR and SGR compared to other groups (P< 0.05). These levels of SB also decreased the levels of feed conversion ratio (FCR) and the total cholesterol (TC) content of Chinese soft-shelled turtles, and the 0.02% SB was significantly lower than that of other groups (P< 0.05). The activity of complement protein in vivo increased with increases in SB content, and the activities of complement C3 and C4 reached the highest level with 0.02% SB. The species abundance of the experimental group D fed with 0.02% SB was significantly higher than that of other groups (P< 0.05). Furthermore, the relative abundance of Clostridium sensu stricto 1 was significantly increased with 0.02% SB (P< 0.05). In conclusion, adding 0.02% SB to the diet improves the growth performance, feed digestion ability, and intestinal microbiota of Chinese soft-shelled turtles.

Interaction between Bacteroidetes species in the fermentation of Lycium barbarum arabinogalactan

The present study investigated the utilization of an arabinogalactan from Lycium barbarum (LBP-3) by intestinal Bacteroidetes species. The mixed-culture assay showed 58.4 % LBP-3 was utilized, and Bacteroides caccae and Phocaeicola vulgatus utilized more LBP-3 in single-culture compared to others. During in vitro fermentation of LBP-3, P. vulgatus favored arabinose while B. caccae preferred galactose. Moreover, 9 and 25 oligosaccharides were identified by HPLC-MSⁿ in conditioned media (CM) derived from B. caccae and P. vulgatus, respectively. All of 3 tested Parabacteroides species (P. distasonis, P. goldsteinii, and P. johnsonii) markedly proliferated in CM of B. caccae and P. vulgatus, and proliferations of B. uniformis, B. finegoldii, B. ovatus and B. thetaiotaomicron also increased significantly in CM of B. caccae. The study suggests that the ability of Bacteroidetes species to degrade LBP-3 and sheds light on cooperative interactions of Bacteroides, Phocaeicola, and Parabacteroides species in the presence of LBP-3.

Metabolites of sea cucumber sulfated polysaccharides fermented by Parabacteroides distasonis and their effects on cross-feeding

Sea cucumber sulfated polysaccharide (SCSPsj) is one of the dietary components which effectively modulates gut microbiota; however, the underlying mechanism remains unclear. In the present study, the interaction between SCSPsj and its utilizer (Parabacteroides distasonis) was investigated. Further study was carried out to explore the cross-feeding between intestinal Bacteroidales mediated by SCSPsj. The results revealed that SCSPsj can be fermented by P. distasonis to produce various microbial metabolites, including organic acids and derivatives, lipids and lipid-like molecules, organoheterocyclic compounds. SCSPsj can regulate the succinate pathway and acetyl-CoA pathway to influence the production of propanoic acid and acetic acid, respectively. Moreover, the SCSPsj-fermented supernatants of P. distasonis can only promote the growth of B. stercoris, B. vulgatus and P. johnsonii among 8 intestinal Bacteroidales strains through cross-feeding. The effect of cross-feeding was related to spatial distances and bacterial species. Moreover, the cross-feeding was correlated with compounds belonging to organic acids and derivatives, lipids and lipid-like molecules. These findings could provide new insights into the interaction between SCSPsj and gut microbiota.

Research Progress on the Protective Effect of Brown Algae-Derived Polysaccharides on Metabolic Diseases and Intestinal Barrier Injury

In the human body, the intestine is the largest digestive and immune organ, where nutrients are digested and absorbed, and this organ plays a key role in host immunity. In recent years, intestinal health issues have gained attention and many studies have shown that oxidative stress, inflammation, intestinal barrier damage, and an imbalance of intestinal microbiota may cause a range of intestinal diseases, as well as other problems. Brown algae polysaccharides, mainly including alginate, fucoidan, and laminaran, are food-derived natural products that have received wide attention from scholars owing to their good biological activity and low toxic side effects. It has been found that brown algae polysaccharides can repair intestinal physical, chemical, immune and biological barrier damage. Principally, this review describes the protective effects and mechanisms of brown algae-derived polysaccharides on intestinal health, as indicated by the ability of polysaccharides to maintain intestinal barrier integrity, inhibit lipid peroxidation-associated damage, and suppress inflammatory cytokines. Furthermore, our review aims to provide new ideas on the prevention and treatment of intestinal diseases and act as a reference for the development of fucoidan as a functional product for intestinal protection.

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.

A Randomized Placebo-Controlled Trial of Combination Therapy With Post-triple-antibiotic-therapy Fecal Microbiota Transplantation and Alginate for Ulcerative Colitis: Protocol

Background

Fecal microbiota transplantation (FMT) has been widely performed for ulcerative colitis (UC) treatment at the clinical trial stage. Previous reports have used multiple FMT methods to enhance the colonization of healthy donor microbiota in the recipient's intestines. FMT following triple antibiotic therapy with amoxicillin, fosfomycin, and metronidazole (A-FMT) is not only effective but also requires only one FMT, which improves dysbiosis caused by reduced Bacteroidetes diversity in patients with UC. Alginate and its derivatives have the potential to induce the growth of intestinal bacteria including Bacteroides members and produce short-chain fatty acids (SCFAs), which are beneficial in regulating overactive autoimmunity. Our trial aims to investigate whether post-intervention with alginate, which can improve the intestinal environment, will enhance the therapeutic effect of A-FMT in UC and increase the long-term remission rate.

Methods and Analysis

This trial is a double-blinded, randomized, placebo-controlled, parallel assignment trial. Patients with UC and fecal donation candidates will undergo strict screening before being involved in the trial. Eligible patients are randomly divided into two groups: one group will drink one bottle of alginate twice a day for 8 consecutive weeks after A-FMT, while the other group will take a placebo instead of the alginate drink. The primary endpoints are the changes in the Total Mayo Score at 8 weeks after study initiation and A-FMT from baseline. The secondary endpoint is the comparison of clinical features, microbiota, and metabolomic analysis before and after 8 weeks of study food intake. Changes at 6, 12, 18, and 24 months after A-FMT will be assessed. Finally, a subpopulation analysis of the relationship between patients and donors is an exploratory endpoint.

Discussion

The FMT post-treatment used in this study is an oral alginate drink that is easily accepted by patients. If the regimen achieves the desired results, it can further improve the A-FMT regimen and provide evidence for clinical practice guidelines for UC.

Clinical Trial Registration

https://jrct.niph.go.jp/latest-detail/jRCTs031200103, identifier: jRCTs031200103.

Fabrication of astaxanthin-enriched colon-targeted alginate microspheres and its beneficial effect on dextran sulfate sodium-induced ulcerative colitis in mice

Astaxanthin (Ax) with a strong antioxidant activity is beneficial to human health, but its application is limited by its highly unsaturated structure and poor water-solubility. Ax-enriched colon targeted alginate particles (Ax-Alg) was prepared by high-pressure spraying and ionic gelation, and most of particles was in the range of 0.5-3.2 μm in a diameter. The in vitro models showed that Ax-Alg can maintain the structural integrity in the different conditions (pH, heat and ion). In addition, Ax-Alg can well tolerate the conditions in the mouth, stomach and small intestine and reach the colon where Ax was released due to fermentation of gut microbiota. Mice experiment showed that Ax-Alg reduced dextran sulfate sodium-induced colitis, involving weight loss, disease activity index, colonic mucosal integrity and inflammation, and oxidative damage. On the other hand, Ax-Alg regulated the gut microbiota composition and reduced the abundances of Bacteroidetes members that had positive correlation with ulcerative colitis. Ax-Alg had better effect on the treatment of ulcerative colitis than oil-in-water emulsion, which can be attributed to the synergistic effect of Ax and alginate. This study can be helpful for the application of colon-targeted delivery system in the foods and treatment of colon diseases.

Effects of Bacteroides-Based Microecologics against Antibiotic-Associated Diarrhea in Mice

Antibiotic-associated diarrhea (AAD) is a self-limiting disease mediated by antibiotic therapy. In clinical practice, several types of probiotics are used in treating AAD, but minimal research has been done on Bacteroides-based microecologics. Our aim was to evaluate the therapeutic effects of Bacteroidetes uniformis FGDLZ48B1, B. intestinalis FJSWX61K18, Bifidobacterium adolescentis FHNFQ48M5, and B. bifidum FGZ30MM3 and their mixture on AAD in mice. The lincomycin hydrochloride-induced AAD models were gavaged with a single strain or a probiotic mixture for a short period to assess the changes in colonic histopathology and cytokine concentrations, intestinal epithelial permeability and integrity, short-chain fatty acids (SCFAs), and the diversity of intestinal microbiota. Our data indicated that both the sole use of Bacteroides and the combination of Bacteroides and Bifidobacterium beneficially weakened systemic inflammation, increased the recovery rate of tissue structures, increased the concentrations of SCFAs, and restored the gut microbiota. Moreover, the probiotic mixture was more effective than the single strain. Specifically, B. uniformis FGDLZ48B1 combined with the B. adolescentis FHNFQ48M5 group was more effective in alleviating the pathological features of the colon, downregulating the concentrations of interleukin (IL)-6, and upregulating the expression of occludin. In summary, our research suggests that administration of a mixture of B. uniformis FGDLZ48B1 and B. adolescentis FHNFQ48M5 is an effective approach for treating AAD.

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.

Gut microbiota response to sulfated sea cucumber polysaccharides in a differential manner using an in vitro fermentation model

Sea cucumber Stichopus japonicus has been consumed as high-valued seafood in Asian, and its sulfated polysaccharide (SCSPsj) has been inferred to benefit the host health via modulating gut microbiota composition. The present study compared the responses of gut microbiota communities from different donors to SCSPsj, and the key bacteria were identified by 16S rRNA gene sequencing analysis and in vitro fermentation with specific bacteria. Gut microbiota communities from 6 donors (A ~ F) utilized the polysaccharides to different degrees in vitro fermentation. Further comparison of Samples A and C demonstrated that Sample C with the relatively strong SCSPsj utilization capability possessed more Parabacteroides while Sample A contained more Bacteroides. Further in vitro fermentation of SCSPsj with 10 Parabacteroides and Bacteroides species suggests that Parabacteroides distasonis, enriched in Sample C, plays a critical role in the utilization of the polysaccharides. Moreover, short chain fatty acids and the metabolite profiles of Samples A and C were also compared, and the results showed that more beneficial metabolites were accumulated by the microbiota community consuming more sulfated sea cucumber polysaccharides. Our findings revealed that certain key members of gut microbiota, such as Parabacteroides distasonis, are critical for SCSPsj utilization in gut so as to influence the benefits of the polysaccharide supplement for host. Thus, to obtain better functional outcome for sulfated sea cucumber polysaccharides and sea cucumber, more attention needs to be paid to the effects of inter-individual differences in microbiota community structure.

Polysaccharides from Laminaria japonica: an insight into the current research on structural features and biological properties

Laminaria japonica, one of the most widespread seafood consumed in China and many other nations, has been traditionally utilized as an effective therapeutically active substance for treating weight loss, phlegm elimination, and detumescence for more than 2000 years. Numerous studies have found that the polysaccharides play an indispensable role in the nutritional and medicinal value of L. japonica. Water extraction and alcohol precipitation method is the most used method. Approximately 56 LJPs were successfully isolated and purified from L. japonica, whereas only few of them were well characterized. Modern pharmacological studies have shown that L. japonica polysaccharides (LJPs) have high-order structural features and multiple biological activities, including anti-tumor, anti-thrombotic, anti-atherosclerosis, hypolipidemic, hypoglycemic, antioxidant, anti-inflammatory, renoprotective, and immunomodulatory. In addition, the structural characteristics of LJPs are closely related to their biological activity. In this review, the extraction and purification methods, structural characteristics, biological activities, clinical settings, toxicities, and structure-activity relationships of LJPs are comprehensively summarized. The structural characteristics and biological activities as well as the underlying molecular mechanisms of LJPs were also outlined. Furthermore, the clinical settings and structure-activity functions of LJPs were highlighted. Some research perspectives and challenges in the study of LJPs were also proposed.

Sulfated polysaccharides from Undaria pinnatifida improved high fat diet-induced metabolic syndrome, gut microbiota dysbiosis and inflammation in BALB/c mice

Undaria pinnatifida was shown to reduce serum lipids and fat accumulation and produce beneficial effect on type 2 diabetes, but its effect on intestinal micro-ecology remains unclear. This study showed that sulfated polysaccharides from U. pinnatifida (UPSP) reduced weight gain, fat accumulation and metabolic disorders in mice fed with high fat diet (HFD). UPSP not only alleviated HFD-induced microbiota dysbiosis indicated as increased abundances of some Bacteroidales members that had positive correlations with the improvement of physiological indexes, but also maintained gut barrier integrity and reduced metabolic endotoxemia. A dose-effect relationship was observed between the dose of UPSP and its effect on some physiological indexes, gut microbiota community and nutrient utilization. The in vitro result showed that the use of Bacteroides species within Bacteroidales on UPSP was species-dependent, and the dose of UPSP affected the growth properties of some Bacteroides species. It implied that UPSP can be considered as prebiotic agent to prevent gut dysbiosis and obesity-related diseases in obese individuals.

Interaction of sulfated polysaccharides with intestinal Bacteroidales plays an important role in its biological activities

The bioactivities of sulfated polysaccharides have shown to be associated with the gut microbiota, but the underlying mechanisms remain unclear. In this study, the effect of sulfated polysaccharides from pacific abalone (AGSP) on the human gut microbiota was analyzed via an in vitro fermentation model. The results revealed that AGSP altered the overall structure of the gut microbiota and increased relative abundances of some Bacteroidales members, implying that intestinal Bacteroidales can play important roles in the bioactivities of AGSP. To elucidate the underlying mechanisms, some species from the Bacteroides and Parabacteroides within Bacteroidales were isolated, and their characteristics on AGSP utilization were analyzed. It showed that AGSP utilization by intestinal Bacteroidales was species-dependent, and some species that liberated AGSP breakdown products promoted the growth of others unable to live in AGSP, forming an AGSP utilization network. The in vitro cell model showed that AGSP oligosaccharides had better anti-inflammatory activity and weaker cytotoxicity, implying that microbial degradation of AGSP can influence its reaction with host cells. These results indicated that the interaction between polysaccharides and gut microbes can together determine the beneficial effects of polysaccharides on the host health.

The Pros and Cons of Using Algal Polysaccharides as Prebiotics

Macroalgae stand out for their high content of dietary fiber (30–75%) that include soluble, sulfated (fucoidan, agaran, carrageenan, and ulvan) and non-sulfated (laminaran and alginate) polysaccharides. Many studies indicate that these compounds exert varied biological activities and health-promoting effects and for this reason, there is a growing interest for using them in food products. The aim of this review was to critically evaluate prebiotic properties of algal polysaccharides, i.e., their ability to exert biological activities by modulating the composition and/or diversity of gut microbiota (GM). Pre-clinical studies show that the non-sulfated alginate and laminaran are well-fermented by GM, promoting the formation of short chain fatty acids (SCFAs) including butyrate, and preventing that of harmful putrefactive compounds (NH₃, phenol, p-cresol, indole and H₂S). Alginate increases Bacteroides, Bifidobacterium, and Lactobacillus species while laminaran mostly stimulates Bacteroides sp. Results with sulfated polysaccharides are more questionable. Agarans are poorly fermentable but agarose-oligosaccharides exhibit an interesting prebiotic potential, increasing butyrate-producing bacteria and SCFAs. Though carrageenan-oligosaccharides are also fermented, their use is currently limited due to safety concerns. Regarding fucoidan, only one study reports SCFAs production, suggesting that it is poorly fermented. Its effect on GM does not indicate a clear pattern, making difficult to conclude whether it is beneficial or not. Notably, fucoidan impact on H₂S production has not been evaluated, though some studies report it increases sulfate-reducing bacteria. Ulvan is badly fermented by GM and some studies show that part of its sulfate is dissimilated to H₂S, which could affect colonic mitochondrial function. Accordingly, these results support the use of laminaran, alginate and agaro-oligosaccharides as prebiotics while more studies are necessary regarding that of fucoidan, carrageenan and ulvan. However, the realization of clinical trials is necessary to confirm such prebiotic properties in humans.

A Review of the Varied Uses of Macroalgae as Dietary Supplements in Selected Poultry with Special Reference to Laying Hen and Broiler Chickens

Seaweeds comprise ca. 12,000 species. Global annual harvest is ca. 30.13 million metric tonnes, (valued ca. $11.7 billion USD in 2016) for various commercial applications. The growing scope of seaweed-based applications in food, agricultural fertilizers, animal feed additives, pharmaceuticals, cosmetics and personal care is expected to boost market demand. Agriculture and animal feed applications held the second largest seaweed market share in 2017, and the combined market is anticipated to reach much higher values by 2024 due to the impacts of current research and development targeting enhanced animal health and productivity. In general, seaweeds have been utilized in animal feed as a rich source of carbohydrates, protein, minerals, vitamins and dietary fibers with relatively well-balanced amino acid profiles and a unique blend of bioactive compounds. Worldwide, the animal nutrition market is largely driven by rising demand for poultry feeds, which represents ca. 47% of the total consumption for all animal nutrition. This review provides an overview of the utilization of specific seaweeds as sustainable feed sources for poultry production, including a detailed survey of seaweed-supplemented diets on growth, performance, gastrointestinal flora, disease, immunity and overall health of laying/broiler hens. Anti-microbial effects of seaweeds are also discussed.

Seaweed and seaweed-derived metabolites as prebiotics

Seaweeds and their bioactive compounds, particularly polysaccharides and phenolics can be regarded as great dietary supplements with gut health benefits and prebiotics. These components are resistant to digestion by enzymes present in the human gastrointestinal tract, also selectively stimulate the growth of beneficial gut bacteria and the production of fermentation products such as short chain fatty acids. Commonly, the health benefits of seaweed components are assessed by including them in an in vitro anaerobic fermentation system containing human fecal inocula that mimics the environment of the human large bowel. Regarding to the complex interactions between dietary components, gastrointestinal physiological processes, and gut microbiota are difficult to model in vitro. Consequently it is important to follow up the promising in vitro results with in vivo animal or human testing. The aim of this chapter is to have a comprehensive review on the application of seaweeds and seaweed-derived metabolites as prebiotics, and understand the trends, gaps and future directions of both scientific and industrial developments. This work contributes to develop and expand new platform of seaweed utilization for higher-value products, particularly to functional food and nutraceutical industries in order to serve the social demand for health awareness and support economic development.