A review on the impact of seaweed polysaccharide on the growth of probiotic bacteria and its application in aquaculture

Extraction, Characterisation and Evaluation of Antioxidant and Probiotic Growth Potential of Water-Soluble Polysaccharides from Ulva rigida Macroalgae

Ulva rigida green macroalgae contain a variety of polysaccharides. A recent study investigated the optimum concentration and yield of polysaccharide extraction from oven-dried U. rigida biomass using a water-soluble polysaccharide extraction method that adhered to safety standards. This study utilised complete factorial experiments to examine the effects of varying factors on polysaccharide extraction. Results showed a positive correlation between increased levels of all factors and higher polysaccharide extraction yield. This study also found that the main factors and their interaction had a significant impact on the extracted polysaccharides from U. rigida. The highest polysaccharide content and yield were 9.5 mg/mL and 189 mg/g, respectively. Water-soluble polysaccharides demonstrated the presence of reducing sugar (8 mg/g), phenolics (0.69 mg/g) and flavonoids (1.42 mg/g) and exhibited antioxidant properties. Results revealed that freeze-dried polysaccharide powders were primarily composed of the monosaccharide rhamnose. Preliminary results on the effect of these powders on probiotics demonstrated that supplementation of polysaccharides from U. rigida promoted viable Lactobacillus rhamnosus ATCC 53103 growth during cultivation. This discovery has the potential to revolutionise the human food industry and promote the development of functional ingredients for novel and future food products, with numerous applications in the nutraceutical and pharmaceutical industries.

Unveiling the Probiotic Potential of the Anaerobic Bacterium Cetobacterium sp. nov. C33 for Enhancing Nile Tilapia (Oreochromis niloticus) Cultures

The bacterium strain Cetobacterium sp. C33 was isolated from the intestinal microbial content of Nile tilapia (O. niloticus) under anaerobic conditions. Given that Cetobacterium species are recognized as primary constituents of the intestinal microbiota in cultured Nile tilapia by culture-independent techniques, the adaptability of the C33 strain to the host gastrointestinal conditions, its antibacterial activity against aquaculture bacterial and its antibiotic susceptibility were assessed. The genome of C33 was sequenced, assembled, annotated, and subjected to functional inference, particularly regarding pinpointed probiotic activities. Furthermore, phylogenomic comparative analyses were performed including closely reported strains/species relatives. Comparative genomics with closely related species disclosed that the isolate is not phylogenetically identical to other Cetobacterium species, displaying an approximately 5% sequence divergence from C. somerae and a 13% sequence divergence from Cetobacterium ceti. It can be distinguished from other species through physiological and biochemical criteria. Whole-genome annotation highlighted that Cetobacterium sp. nov. C33 possesses a set of genes that may contribute to antagonism against competing bacteria and has specific symbiotic adaptations in fish. Additional in vivo experiments should be carried out to verify favorable features, reinforcing its potential as a probiotic bacterium.

Impact of Dietary Administration of Seaweed Polysaccharide on Growth, Microbial Abundance, and Growth and Immune-Related Genes Expression of The Pacific Whiteleg Shrimp (Litopenaeus vannamei)

This work aims to determine the impact of dietary supplementation of polysaccharide, extracted from brown seaweeds Sargassum dentifolium on growth indices, feed utilization, biochemical compositions, microbial abundance, expressions of growth and immunity-related genes, and stress genes of the Pacific Whiteleg shrimp Litopenaeus vannamei. A total of 360 post-larvae of L. vannamei were randomly distributed into a 12-glass aquarium (40 L of each) at a stocking density of 30 shrimp with an initial weight of (0.0017 ± 0.001 g). During the 90-day experiment trial, all shrimp larvae were fed their respective diets at 10% of total body weight, three times a day. Three experimental diets were prepared with different seaweed polysaccharide (SWP) levels. The basal control diet had no polysaccharide level (SWP₀), while SWP₁, SWP₂, and SWP₃ contained polysaccharides at concentrations of 1, 2, and 3 g kg^-1 diet, respectively. Diets supplemented with polysaccharide levels showed significant improvements in weight gain and survival rate, compared to the control diet. Whole-body biochemical composition and the microbial abundance (the total count of heterotrophic bacteria and Vibrio spp.) of L. vannamei showed significant differences among polysaccharide-treated diets compared to the control. At the end of the feeding experiment, the dietary supplementation of polysaccharide levels enhanced the expression of growth-related genes (Insulin-like growth factors (IGF-I, IGF-II), immune-related genes (β -Glucan-binding protein (β-Bgp), Prophenoloxidase (ProPO), Lysozyme (Lys), and Crustin), and stress genes (Superoxide dismutase (SOD) and Glutathione peroxidase (GPx) in the muscle tissue of L. vannamei. However, the current study concluded that the inclusion rate of 2 g kg^-1 of polysaccharide as a dietary additive administration enhanced both weight gain and survival rate of L. vannamei, while the incorporation level of 3 g kg^-1 reduces the abundance of pathogenic microbes and enhances the growth-, immunity- and stress-related gene expressions of L. vannamei.

The Roles of Polysaccharides in Carp Farming: A Review

Carp is an important aquaculture species globally, and the production is expected to increase with the growing market demands. Despite that, disease outbreaks remain a major challenge, impeding the development of sustainable carp farming. Moreover, the application of antibiotics, a common prophylactic agent, can adversely impact public health and the environment. Therefore, polysaccharide has been recognized as a novel prophylactic agent in the health management of carp farming, as well as gaining consumers' confidence in carp farming products. In this review, the definition, sources, and main roles of polysaccharides in improving growth performance, stimulating the immune system, enhancing disease resistance, and alleviating abiotic stresses in carp farming are discussed and summarized. In addition, the use of polysaccharides in combination with other prophylactic agents to improve carp farming production is also highlighted. This review aims to highlight the roles of polysaccharides and provide valuable information on the benefits of polysaccharides in carp farming.

Competitive Exclusion Bacterial Culture Derived from the Gut Microbiome of Nile Tilapia (Oreochromis niloticus) as a Resource to Efficiently Recover Probiotic Strains: Taxonomic, Genomic, and Functional Proof of Concept

This study aims to mine a previously developed continuous-flow competitive exclusion culture (CFCEC) originating from the Tilapia gut microbiome as a rational and efficient autochthonous probiotic strain recovery source. Three isolated strains were tested on their adaptability to host gastrointestinal conditions, their antibacterial activities against aquaculture bacterial pathogens, and their antibiotic susceptibility patterns. Their genomes were fully sequenced, assembled, annotated, and relevant functions inferred, such as those related to pinpointed probiotic activities and phylogenomic comparative analyses to the closer reported strains/species relatives. The strains are possible candidates of novel genus/species taxa inside Lactococcus spp. and Priestia spp. (previously known as Bacillus spp.) These results were consistent with reports on strains inside these phyla exhibiting probiotic features, and the strains we found are expanding their known diversity. Furthermore, their pangenomes showed that these bacteria have indeed a set of so far uncharacterized genes that may play a role in the antagonism to competing strains or specific symbiotic adaptations to the fish host. In conclusion, CFCEC proved to effectively allow the enrichment and further pure culture isolation of strains with probiotic potential.

Dietary supplementation with Gracilaria gracilis by-products modulates the immune status and oxidative stress response of gilthead seabream (Sparus aurata) stimulated with Photobacterium damselae subsp. piscicida

This study evaluated the effects of agar waste (AW) dietary supplementation, obtained from the seaweed Gracilaria gracilis cultivated under two different spectral lights, neutral (NT) and blue (BL), on haematological parameters, inflammatory response, and antioxidant biomarkers of gilthead seabream (Sparus aurata). Three diets were prepared: i) a basal diet (CTR), ii) a diet supplemented with 2.5% NT, and iii) a diet supplemented with 2.5% BL. After 15 days of feeding, fish were injected with PBS (placebo) or inactivated Photobacterium damselae subsp. piscicida (stimulated) and sampled at 4 h and 24 h post-stimulus. Results indicated that fish fed NT and BL supplemented diets had lower Ht value and mean corpuscular volume (MCV) than fish fed the CTR diet, regardless of the stimulus and the sampling time. No differences in mean corpuscular haemoglobin (MCH) were found between fish fed the different diets, while the mean corpuscular haemoglobin concentration (MCHC) increased in fish fed AW supplemented diets compared to fish fed the CTR diet, regardless of the stimulus and the sampling time. In response to inflammation, fish fed the NT diet displayed higher neutrophils count in blood when compared to the CTR group, regardless of the stimulus and sampling time. Thrombocyte count was higher in fish fed NT and BL diets than in the CTR group, especially in the stimulated fish (Diet*injection (D*I), P = 0.004). An increase in plasma protease activity was detected in fish fed NT or BL diets in both placebo and stimulated fish regardless of the sampling time. Hepatic catalase activity was higher in fish fed the NT and BL than in the CTR group, particularly in the stimulated fish (D*I, P < 0.001). In addition, both stimulated and placebo fish that received the BL diet showed an increase in hepatic GR activity compared to the CTR group, regardless of the sampling time. Dietary supplementation with AW by-products obtained from G. gracilis cultured under NT and BL conditions showed to improve the inflammatory and antioxidant mechanisms in gilthead seabream in response to a UV-killed bacterial stimulus, having valuable applications for the sustainable use of seaweed toward improving the health and welfare of cultured fish.

Stretchable and fatigue resistant hydrogels constructed by natural galactomannan for flexible sensing application

Exploration of sustainable and functional materials from biomolecules has received much interest, while the limited mechanical property and possible bacterial contamination were proved to be their major shortages. Here, we proposed novel double network (DN) hydrogels based on galactomannan (GM) polysaccharide as backbone. Folic acid (FA) and polyacrylamide (PAM) were introduced to form hydrogen bond linkages and covalent bond networks respectively. The three-dimensional hydrogel networks showed greatly improved mechanical strength. Impressive compressive fatigue resistance was present for 100 cycles' compression forming only 0.7 % shape deformation. The phenomenon was mainly attributed to promoted stress-bearing and energy dissipation from the DN cross-linking. The GM hydrogels also exhibited good electronic conductivity and excellent anti-bacterial capabilities with inhibition against more than 80 % of E. coli., attributing to the tunable attachments of FA. Thus, we provided multi-functional hydrogels of high potential serving as anti-fatigue/bacterial and conductive strain sensors on the fields of wearable devices.

Effects of dietary Gracilaria persica on the intestinal microflora, thyroid hormones, and resistance against Aeromonas hydrophila in Persian sturgeon (Acipenser persicus)

Red seaweeds have several biomedical derivatives making them healthy additives for the aquaculture industry. Previously we reported enhanced growth performance, feed utilization, and immunity of Persian sturgeon treated with Gracilaria gracilis. Herein, we investigated the effects of G. gracilis on the intestinal microflora, thyroid hormones, and resistance against Aeromonas hydrophila in Persian sturgeon. Fish fed G. gracilis at 0, 2.5, 5, and 10 g/kg for eight weeks, then challenged with A. hydrophila for ten days. The results showed that the total bacterial count in the fish intestines had no meaningful differences among the groups of fish fed varying levels of G. persica (P˃0.05). Fish fed 10 g/kg of G. persica had a higher lactic acid bacteria (LAB) count than fish fed 0, 2.5, and 5 g/kg (P<0.05). Serum thyroid-stimulating hormone (TSH) showed higher levels in fish treated with 2.5 and 5 g/kg of G. persica than the other groups (P<0.05). Besides, fish fed 2.5 g/kg G. persica had higher thyroxine (T4) and triiodothyronine (T3) levels than the other groups (P<0.05). At the end of the challenge test, the highest mortality was seen in the fish fed the G. persica free diet. In summary, Persian sturgeon treated G. gracilis had improved intestinal microflora, thyroid hormones, and resistance against A. hydrophila.

Prebiotic Agrocybe cylindracea crude polysaccharides combined with Lactobacillus rhamnosus GG postpone aging-related oxidative stress in mice

This study aimed to investigate the potential anti-aging mechanisms of Agrocybe cylindracea crude polysaccharides (APS), when used synergistically with Lactobacillus rhamnosus GG (APS + LGG) in a D-galactose-induced aging mouse model. In the Morris water maze test, APS + LGG showed a significantly higher memory and learning capacity compared to untreated, APS only treated and LGG treated mice. This was thought to be mediated by increased levels of brain-derived neurotrophic factor, which decreased escape latency. In addition to this, in the aging mouse model, APS + LGG co-treatment markedly alleviated liver oxidation and metabolism by enhancing the antioxidant activity of enzymes; this decreased the lipid metabolism and peroxidation levels. Furthermore, high throughput sequencing analysis revealed that an APS + LGG supplemented feed increased the relative abundance of positive bacteria in the gut microbiota such as Alloprevotella and Parvibacter. Importantly, Alloprevotella and Parvibacter showed a negative relationship with low density lipoprotein-cholesterol in the Spearman correlation analysis. These results illustrate that APS, in combination with LGG, postponed aging related oxidative stress when used as a prebiotic. The proposed mechanism for this is the reduction in liver oxidation and lipid metabolism, as well as the regulation of gut microbiota.

Dietary Guduchi (Tinospora cordifolia) enhanced the growth performance, antioxidative capacity, immune response and ameliorated stress-related markers induced by hypoxia stress in Nile tilapia (Oreochromis niloticus)

Nile tilapia can tolerate a wide range of farming conditions; however, fluctuations in the environmental conditions may impair their health status. The incorporation of medicinal herbs in aquafeed is suggested to overcome stressful conditions. In this study, dietary Guduchi (Tinospora cordifolia) was evaluated on the growth performance, antioxidative capacity, immune response, and resistance of Nile tilapia against hypoxia stress. Fish fed five diets incorporated with Guduchi at 0, 2, 4, 6, and 8 g/kg for 56 days then exposed with hypoxia stress for 72 h. The growth performance, feed intake, and feed efficiency ratio were significantly (P < 0.05) increased by including Guduchi in tilapia diets regardless of the inclusion level. Similarly, the lipase and protease activities were markedly (P < 0.05) increased in tilapia fed dietary Guduchi. The activities of lysozyme and bactericidal activities in serum and mucus, nitro-blue tetrazolium (NBT), and alternative complement activity (ACH50) were markedly (P < 0.05) enhanced in tilapia treated with Guduchi supplements regardless of the dose. Additionally, the activities of liver and intestinal superoxide dismutase, catalase, and glutathione peroxidase were markedly enhanced (P < 0.05) by including Guduchi in tilapia diets compared with the control. Before and after hypoxia stress, tilapia-fed dietary Guduchi had lower glucose and cortisol levels than fish-fed Guduchi-free diets (P < 0.05). In all groups, glucose and cortisol levels were markedly higher after hypoxia compared before hypoxia stress (P < 0.05). In conclusion, dietary Guduchi can be included at 5.17-5.49 g/kg to enhance the growth performance, digestive enzyme activity, immune and antioxidative responses, and the resistance of Nile tilapia against hypoxia stress.

Effect of dietary Ficus carica polysaccharides on the growth performance, innate immune response and survival of crucian carp against Aeromonas hydrophila infection

Ficus carica polysaccharides (FCPS), one of the most effective and important compo-nents in Ficus carica L., had been considered to be a beneficial immunostimulant and may be used in immunotherapy for animals and human. However, studies were little about the effect of FCPS used as immunomodulatory and the suitable dosage in fish. The present study investigated the effect of four different dietary levels of FCPS (0.1%, 0.2%, 0.4%, 0.8%) on the growth performance, innate immune responses and survival of crucian carp against Aeromonas hydrophila infection. The results showed that compared with control group, dietary FCPS had positive effects the growth performance (final weight, feed conversion ratio and survival rate) of crucian carp. FCPS induced significant higher (p < 0.05) leukocyte phagocytosis activity, serum bactericidal activity, lysozyme activity, com-plement C3, SOD activity and total protein level in the serum of crucian carp. Moreover, innate immune response of fish in FCPS groups increased first and then decreased with increasing dietary FCPS from 0.1% to 0.8%, and reached up to the peak in 0.4% dietary FCPS groups. Besides, the cumulative mortalities in FCPS groups were remarkably lower than that of control group when challenged with A. hydrophila, the relative percent survivals were 22.67%, 55.56%, 62.22% and 17.78% in 0.1% group, 0.2% group, 0.4% group and 0.8% group, respectively. These results suggested that dietary FCPS could improve the growth performance, innate immune response and disease resistance against A. hydrophila in fish, and the suitable dietary dose of FCPS was 0.4% in crucian carp.

Potential use of macroalgae Gracilaria gracilis in diets for European seabass (Dicentrarchus labrax): Health benefits from a sustainable source

Seaweeds still possess a large undisclosed potential, mainly due to their constituent's richness, which may have several uses for society. In aquaculture, they may play a role as an ecological sustainable aquafeed supplement to increase overall health and fight pathogenic outbreaks. This study aimed to evaluate the general health modulation that the inclusion of Gracilaria gracilis could accomplish in the diet of Dicentrarchus labrax. Dried algae at 2.5% and 5% and algal extract at 0.35% inclusion levels were supplemented to seabass diet to evaluate possible growth, haematological, immunological, antioxidant, metabolic, and intestinal morphological modulations. The supplementations did not impact growth or feed utilization, and barely affected the haematological profile and some metabolic parameters. Nevertheless, it caused a marked outcome on lysozyme, some oxidative stress biomarkers, and intestine morphology, suggesting beneficial consequences from the algal inclusion. Dried algae powder, with a 2.5% inclusion, boosted immune response, with higher plasmatic lysozyme and intestinal acid goblet cells and protected against oxidative damages by improved enzymatic and non-enzymatic responses. Thus, we provide evidence that dietary seaweed application may be a path towards a more sustainable aquaculture industry.

Seaweeds as a Fermentation Substrate: A Challenge for the Food Processing Industry

Seaweeds are gaining momentum as novel and functional food and feed products. From whole consumption to small bioactive compounds, seaweeds have remarkable flexibility in their applicability, ranging from food production to fertilizers or usages in chemical industries. Regarding food production, there is an increasing interest in the development of novel foods that, at the same time, present high nutritious content and are sustainably developed. Seaweeds, because they require no arable land, no usage of fresh water, and they have high nutritious and bioactive content, can be further explored for the development of newer and functional food products. Fermentation, especially performed by lactic acid bacteria, is a method used to produce functional foods. However, fermentation of seaweed biomass remains an underdeveloped topic that nevertheless demonstrates high potential for the production of new alimentary products that hold and further improve the organoleptic and beneficial properties that these organisms are characterized for. Although further research has to be deployed in this field, the prebiotic and probiotic potential demonstrated by fermented seaweed can boost the development of new functional foods.

Saccharomyces cerevisiae Enhanced the Growth, Immune and Antioxidative Responses of European Seabass (Dicentrarchus labrax)

The concept of probiotics is widely applied in the field of aquaculture for their beneficial and friendly influences. In this sense, the role of Saccharomyces cerevisiae on the growth, immune and antioxidative responses of European seabass was tested in this study. Fish were distributed in 3 groups (triplicates) with ten fish in each replicate and fed 0, 1, and 2 g/kg of S. cerevisiae (15×109 CFU/g) for 90 days. Fish fed S. cerevisiae showed higher final body, weight gain, and specific growth rate as well as lower FCR than fish fed the basal diet (P<0.05). The RBCs, WBCs, Hb, and PCV values were increased in fish fed dietary S. cerevisiae when compared to the control (P<0.05). The blood total protein, albumin, and globulin were higher in fish fed S. cerevisiae than the control (P<0.05). Fish fed dietary S. cerevisiae had enhanced phagocytic index, phagocytic, and lysozyme activity comparing the control. In a similar sense, the antioxidative enzymes (SOD, GPx, and CAT) were higher in fish fed S. cerevisiae than the control (P<0.05). However, the level of MDA was lowered (P<0.05) by S. cerevisiae in European seabass. Gene expression of IL-8, IL-1β, GH, and IGF-1 was upregulated and HSP70 was downregulated by S. cerevisiae (P<0.05). It can be concluded that European seabass fed S. cerevisiae at 1–2 g/kg (15×109 CFU/g) diet had markedly enhanced growth, haemato-biochemical, and immune performances.

The Effects of Oral Rehmannia glutinosa Polysaccharide Administration on Immune Responses, Antioxidant Activity and Resistance Against Aeromonas hydrophila in the Common Carp, Cyprinus carpio L

The effects of the oral administration of Rehmannia glutinosa polysaccharide (RGP-1) on the immunoregulatory properties, antioxidant activity, and resistance against Aeromonas hydrophila in Cyprinus carpio L. were investigated. The purified RGP-1 (250, 500, and 1,000 μg/mL) was co-cultured with the head kidney cells of the common carp. The proliferation and phagocytosis activities of the head kidney cells, and the concentration of nitric oxide (NO) and cytokines in the culture medium were determined. Next, 300 common carps (47.66 ± 0.43 g) were randomly divided into five groups; the two control groups (negative and positive) were administered sterile PBS and the three treatment groups were administered different concentrations of RGP-1 (250, 500, and 1,000 μg/mL) for seven days. Subsequently, the positive and treatment groups were infected with A. hydrophila, and the negative group was administered sterile PBS for 24 h. The concentration of NO, cytokines, lysozyme (LZM), and alkaline phosphatase (AKP) in serum, the total antioxidant capacity (T-AOC), the levels of malonaldehyde (MDA) and glutathione (GSH), and the total activities of superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in the hepatopancreas of the common carp were tested. We observed that RGP-1 could significantly enhance the proliferation and phagocytosis activities (P < 0.05), besides inducing the production of NO, pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-12) and anti-inflammatory cytokines (IL-10, TGF-β) (P < 0.05) in vitro. The in vivo experimental results revealed that RGP-1 significantly enhanced NO production, protein levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-12), LZM and AKP activities, and the antioxidant content (T-AOC, SOD, CAT, GSH, GSH-Px, and MDA) compared to that observed in the negative group prior to A. hydrophila infection (P < 0.05). NO, pro-inflammatory cytokines, LZM and AKP activities were significantly lower than that in the positive group after infection (P < 0.05). However, whether infected or not, the expression of anti-inflammatory cytokines (IL-10, TGF-β) increased significantly in the RGP-1-treated groups (P < 0.05). Therefore, the results suggested that RGP-1 could enhance the non-specific immunity, antioxidant activity and anti-A. hydrophila activity of the common carp, and could be used as a safe and effective feed additive in aquaculture.

Antibacterial and Antiviral Activities of Local Thai Green Macroalgae Crude Extracts in Pacific white Shrimp (Litopenaeus vannamei)

Macroalgae are potentially excellent sources of bioactive secondary metabolites useful for the development of new functional ingredients. This study was conducted to determine the antimicrobial efficacy of the hot water crude extracts (HWCEs) of three species of local Thai green macroalgae Ulva intestinalis (Ui), U. rigida (Ur), and Caulopa lentillifera (Cl) and a commercial ulvan from U. armoricana (Ua). Chemical analysis indicated that the HWCE of Ur showed the highest sulfate content (13.9% ± 0.4%), while that of Ua contained the highest uronic acid and carbohydrate contents (41.47% ± 4.98% and 64.03% ± 2.75%, respectively), which were higher than those of Ur (32.75% ± 1.53% and 51.02% ± 3.72%). Structural analysis of these extracts by Fourier-transform infrared (FTIR) spectroscopy revealed that these HWCEs are complex with a signal at 1250 cm-1 corresponding to S=O stretching vibrations, while the signals at 850 cm-1 were attributed to the C-O-S bending vibration of the sulfate ester in the axial position. These HWCEs showed the growth suppression against some pathogenic Vibrio spp. Interestingly, the HWCEs from Ui at concentrations of 5 and 10 mg/mL completely inhibited white spot syndrome virus (WSSV) in shrimp injected with HWCE-WSSV preincubated solutions. This inhibitory effect was further confirmed by the reduction in viral loads and histopathology of surviving and moribund shrimp.