Effects of dietary inulin and mannan oligosaccharide on immune related genes expression and disease resistance of Pacific white shrimp, Litopenaeus vannamei

Impact of THIONIL® on reducing water and soil micro-pollutant and enhancement of growth, survival, anti-vibrio, immunity and health indices of Litopenaeus vannamei in pond trial

There is an urgent requirement for the improvement of the white leg shrimp, Litopenaeus vannamei; health-related indices; and immunity due to emerging diseases. Recently, probiotics have been playing an important role in L. vannamei health management. Therefore, the current pond trial was to evaluate the probiotic proficiency of commercial probiotic products of THIONIL (THIO) on the enhancement of the water, soil, growth, digestibility, survival, immune-related indices, and susceptibility of L. vannamei to infection. The study was carried out in the major shrimp culturing regions of Kavali, Nellore (Andhra Pradesh), and Ponneri (Tamil Nadu), India. Six groups (lacks/ha) of the experimental L. vannamei were allocated, including a control group (THIO 0%-untreated) and groups containing 2%, 4%, 6%, 8%, and 10% of THIO that were encapsulated with commercial feed (CP Aqua). Bioassays were performed on PLs/ shrimp at various days interval of 0, 5, 25, 50, 100, and 123th to assess productivity, anti-vibrio activity, and digestive enzyme for digestibility, histological and immunological indices, and cytotoxicity in Artemia nauplii. Significant differences were observed in the increased growth (35.71 ± 3.24 g/shrimp) and digestive parameters in 10% THIO-fed shrimp. Although in contrast to the control group, the other THIO-fed prawn groups also displayed appreciable development. The findings showed that, in comparison to the control, the gill, hepatopancreas, and stomach had reduced tissue damage with 10% THIO. Furthermore, Vibrio parahaemolyticus (0.008 × 104 cfu/g) and Vibrio harveyi (0.051 × 105 cfu/g) (vibriosis) were potentially resistant to the 10% THIO-fed group. In addition, THIO-fed prawns (10%) showed significant improvements in immune-related expresses (proPO, SOD, and SOA) in comparison to the control. In conclusion, the findings showed that the THIO treatment prawns significantly improved the quality of their water (pH, ammonia, nitrogen dioxide, hydrogen sulfide, and DO) and soil (Pb, Cr, Hg, Mg, Cu, Fe, and Ni), increased and demonstrated protection against vibrio infections.

Effects of Dietary β-Glucan Feeding Strategy on the Growth, Physiological Response, and Gut Microbiota of Pacific White Shrimp, Litopenaeus vannamei, under Low Salinity

An eight-week feeding trial was conducted to investigate the effects of a dietary β-glucan application strategy on the growth performance, physiological response, and gut microbiota of Pacific white shrimp (Litopenaeus vannamei) (0.49 ± 0.17 g) under low salinity. Six feeding strategies were established, including a continuous β-glucan-free diet group (control), a continuously fed group with a 0.1% β-glucan diet (T1), and groups with the following intermittent feeding patterns: 1 day of β-glucan diet and 6 days of β-glucan-free diet (T2), 2 days of β-glucan diet and 5 days of β-glucan-free diet (T3), 3 days of β-glucan diet and 4 days of β-glucan-free diet (T4), and 4 days of β-glucan diet and 3 days of β-glucan-free diet (T5) each week. No significant differences in growth performance among all the groups were found, although the condition factor was significantly higher in the T3 group than in the T1 and T5 groups (p < 0.05). The T-AOC and GPX activities were significantly lower in the T3 group than in the control group (p < 0.05). The MDA content was also significantly lower in the T2 group than in the T3 and T4 groups (p < 0.05). Additionally, the mRNA expression of the Pen3a gene was significantly upregulated in the hepatopancreas of the T4 group compared to the control and T5 groups (p < 0.05), and the Toll gene was also significantly upregulated in the T3 group compared to the T1 and T2 groups (p < 0.05). Dietary β-glucan induced changes in the alpha diversity and composition of the gut microbiota in different feeding strategies. The beta diversity of the gut microbiota in the T2 group was significantly different from that in the control group. The results of a KEGG analysis showed that gut function in the carbohydrate metabolism, immune system, and environmental adaptation pathways was significantly enhanced in the T3 group. These findings provide evidence that the intermittent feeding strategy of β-glucan could alleviate immune fatigue, impact antioxidant ability, and change gut microbiota composition of L. vannamei under low salinity.

Epigenetic Modulations for Prevention of Infectious Diseases in Shrimp Aquaculture

Aquaculture assumes a pivotal role in meeting the escalating global food demand, and shrimp farming, in particular, holds a significant role in the global economy and food security, providing a rich source of nutrients for human consumption. Nonetheless, the industry faces formidable challenges, primarily attributed to disease outbreaks and the diminishing efficacy of conventional disease management approaches, such as antibiotic usage. Consequently, there is an urgent imperative to explore alternative strategies to ensure the sustainability of the industry. In this context, the field of epigenetics emerges as a promising avenue for combating infectious diseases in shrimp aquaculture. Epigenetic modulations entail chemical alterations in DNA and proteins, orchestrating gene expression patterns without modifying the underlying DNA sequence through DNA methylation, histone modifications, and non-coding RNA molecules. Utilizing epigenetic mechanisms presents an opportunity to enhance immune gene expression and bolster disease resistance in shrimp, thereby contributing to disease management strategies and optimizing shrimp health and productivity. Additionally, the concept of epigenetic inheritability in marine animals holds immense potential for the future of the shrimp farming industry. To this end, this comprehensive review thoroughly explores the dynamics of epigenetic modulations in shrimp aquaculture, with a particular emphasis on its pivotal role in disease management. It conveys the significance of harnessing advantageous epigenetic changes to ensure the long-term viability of shrimp farming while deliberating on the potential consequences of these interventions. Overall, this appraisal highlights the promising trajectory of epigenetic applications, propelling the field toward strengthening sustainability in shrimp aquaculture.

Dietary supplementation of Pseudoalteromonas piscicida 1UB and fructooligosaccharide enhance growth performance and protect the whiteleg shrimp (Litopenaeus vannamei) against WSSV and Vibrio harveyi coinfection

P. piscicida 1Ub and FOS were evaluated for their potential synbiotic effects on growth, immunological responses, and disease resistance against white spot syndrome virus and V. harveyi coinfection, the major pathogen in whiteleg shrimp aquaculture. Four different supplemented diets were used to feed the experimental shrimp for 40 days: control (control, no probiotic, and prebiotic), probiotic (PRO, P. piscisida 1UB 10⁸ CFU mL^-1), prebiotic (PRE, FOS 0.5% w/w), and the synbiotic (SYN, PRO + PRE). Shrimp's body weight, weight gain, specific growth rate, feed conversion ratio, survival, digestive enzyme activity, and metabolism-related gene expression were all evaluated on day 40. After 40 days, shrimp were infected with WSSV as the primary infection and V. harveyi as the secondary infection 24 h later. Shrimp were then grown for seven days and fed with a control diet. Survival, total hemocyte count (THC), differential hemocyte, phenol-oxidase (PO), respiratory burst activity (RB), and immune-gene expression were all analyzed at 0, 3, and 7 days after infection. The results showed that the PRO, PRE, and SYN supplementation improves whiteleg shrimp growth performance, immune responses, and protection against WSSV and V. harveyi coinfection. The increased activity of digestive enzymes and metabolism-related genes correlates with higher growth performance. The increase in THC, PO, RB, and immune-related gene expression after coinfection was associated with a significant reduction in shrimp mortality. Our findings also suggest that supplementing with synbiotics improves the overall performance of whiteleg shrimp significantly more than probiotics or prebiotics only.

Nutrigenomics in crustaceans: Current status and future prospects

In aquaculture, nutrigenomics or "nutritional genomics" is concerned with studying the impacts of nutrients and food ingredients on gene expressions and understanding the interactions that may occur between nutrients and dietary bioactive ingredients with the genome and cellular molecules of the treated aquatic animals at the molecular levels that will, in turn, mediate gene expression. This concept will throw light on or provide important information to recognize better how specific nutrients may influence the overall health status of aquatic organisms. In crustaceans, it is well known that the nutritional requirements vary among different species. Thus, studying the nutrigenomics in different crustacean species is of significant importance. Of interest, recognition of the actual mechanisms that may be associated with the effects of the nutrients on the immune responses of crustaceans will provide clear outstanding protection, build a solid immune system, and also decrease the possibilities of the emergence of infectious diseases in the culture systems. Similarly, the growth, molting, lipid metabolism, antioxidant capacity, and reproduction could be effectively enhanced by using specific nutrients. In the area of crustacean research, nutrigenomics has been rapidly grown for addressing several aspects related to the influences of nutrients on crustacean development. Several researchers have studied the relationships between several functional genes and their expression profile with several physiological functions of crustaceans. They found a close association between the effects of optimal feeding with efficient production, growth, reproduction development, and health status of several crustacean species. Moreover, they illustrated that regulation of the gene expression in individual cells by different nutrients and formulated feeds could improve the growth development and immunity-boosting of several crustacean species. The present review will spotlight on such relationships between the dietary nutrients and expression of genes linked with growth, metabolism, molting, antioxidant, reproduction, and immunity of several crustacean species. The literature included in this review article will provide references and future outlooks for the upcoming research plans. This will contribute positively for maintaining the sustainability of the sector of the crustacean industry.

Isolation and Characterization of Mannanase-Producing Bacteria for Potential Synbiotic Application in Shrimp Farming

Prebiotics such as mannan-oligosaccharides (MOS) are a promising approach to improve performance and disease resistance in shrimp. To improve prebiotic utilization, we investigated the potential probiotics and their feasibility of synbiotic use in vitro. Two bacterial isolates, Man26 and Man122, were isolated from shrimp intestines and screened for mannanase, the enzyme for mannan digestion. The crude mannanase from both isolates showed optimal activities at pH 8 with optimum temperatures at 60 °C and 50 °C, respectively. The enzymes remained stable at pH 8−10 for 3 h (>70% relative activity). The thermostability range of Man26 was 20−40 °C for 20 min (>50%), while that of Man122 was 20−60 °C for 30 min (>50%). The Vmax of Man122 against locust bean gum substrate was 41.15 ± 12.33 U·mg−1, six times higher than that of Man26. The Km of Man26 and Man122 were 18.92 ± 4.36 mg·mL−1 and 34.53 ± 14.46 mg·mL−1, respectively. With the addition of crude enzymes, reducing sugars of copra meal, palm kernel cake, and soybean meal were significantly increased (p < 0.05), as well as protein release. The results suggest that Man26 and Man122 could potentially be used in animal feeds and synbiotically with copra meal to improve absorption and utilization of feedstuffs.

Potential synbiotic effects of a Bacillus mixture and chitosan on growth, immune responses and VP(AHPND) resistance in Pacific white shrimp (Litopenaeus vannamei, Boone, 1931)

The potential synbiotic effects of a Bacillus mixture and chitosan on growth, immune responses and disease resistance against Vibrio parahaemolyticus, the causative agent of acute hepatopancreatic necrosis disease (AHPND) in Pacific white shrimp, were intensively investigated. Three effective strains of Bacillus amyloliquefaciens (A), Bacillus pumilus (P) and Bacillus subtilis (S) were mixed in pairs at a ratio of 5 × 10⁸:5 × 10⁸ CFU/kg diet and coated with the prebiotic chitosan (C) at a concentration of 20 mL/kg diet. Five different feed treatments were used to feed experimental shrimp for 5 weeks: control (control, no synbiotics), chitosan (coat, C) and the synbiotic treatments PAC, PSC and ASC. At week 5, the final length, final weight gain, weight gain, length, average daily gain, specific growth rate and feed conversion ratio, measured as growth parameters, were significantly upregulated in the PSC and ASC groups compared with the control and coat groups (P < 0.05). This result was consistent with the expression analysis of two growth-related genes (Rap-2a and GF-II) in the hepatopancreas and intestines of treated shrimp, as determined using qRT-PCR. The prebiotic chitosan and synbiotics PAC, PSC and ASC strongly induced significant differences in the expression of the Rap-2a and GF-II genes in the target organs compared with the expression in the control group at various time points (P < 0.05). Additionally, application of the synbiotic treatments also significantly enhanced the hepatopancreas characteristics and epithelial and intestinal wall thicknesses of the shrimp compared with the control. Interestingly, all the synbiotic treatments elevated phagocytic activity significantly at weeks 3 and 5 compared with that in the other groups. qRT-PCR analysis of immune-related genes also indicated that the prebiotic group and all synbiotic groups showed strong expression of anti-lipopolysaccharide (ALF) and prophenoloxidase (proPO) genes in the intestine. Finally, the synbiotic groups PAC, PSC and ASC exhibited stronger VP_AHPND resistance at 120 h after exposure than the chitosan coat and control groups, with survival rates of 41.7 ± 11.55, 41.7 ± 0.00, 52.8 ± 5.77, 30.6 ± 15.28 and 22.2 ± 5.77%, respectively (P < 0.05). Based on the obtained information, all synbiotics were recommended for improved growth and immune responses, while ASC was the best for disease resistance against VP_AHPND in Pacific white shrimp.

Dietary Mannan Oligosaccharides Enhance the Non-Specific Immunity, Intestinal Health, and Resistance Capacity of Juvenile Blunt Snout Bream (Megalobrama amblycephala) Against Aeromonas hydrophila

Mannan oligosaccharides (MOS) have been studied and applied as a feed additive, whereas their regulation on the growth performance and immunity of aquatic animals lacks consensus. Furthermore, their immunoprotective effects on the freshwater fish Megalobrama amblycephala have not been sufficiently studied. Thus, we investigated the effects of dietary MOS of 0, 200, and 400 mg/kg on the growth performance, non-specific immunity, intestinal health, and resistance to Aeromonas hydrophila infection in juvenile M. amblycephala. The results showed that the weight gain rate of juvenile M. amblycephala was not significantly different after 8 weeks of feeding, whereas the feed conversion ratio decreased in the MOS group of 400 mg/kg. Moreover, dietary MOS increased the survival rate of juvenile M. amblycephala upon infection, which may be attributed to enhanced host immunity. For instance, dietary MOS increase host bactericidal and antioxidative abilities by regulating the activities of hepatic antimicrobial and antioxidant enzymes. In addition, MOS supplementation increased the number of intestinal goblet cells, and the intestine was protected from necrosis of the intestinal folds and disruption of the microvilli and junctional complexes, thus maintaining the stability of the intestinal epithelial barrier. The expression levels of M. amblycephala immune and tight junction-related genes increased after feeding dietary MOS for 8 weeks. However, the upregulated expression of immune and tight junction-related genes in the MOS supplemental groups was not as notable as that in the control group postinfection. Therefore, MOS supplementation might suppress the damage caused by excessive intestinal inflammation. Furthermore, dietary MOS affected the richness and composition of the gut microbiota, which improved the gut health of juvenile M. amblycephala by increasing the relative abundance of beneficial gut microbiota. Briefly, dietary MOS exhibited significant immune protective effects to juvenile M. amblycephala, which is a functional feed additive and immunostimulant.

Effects of Intestinal Flora on Irritable Bowel Syndrome and Therapeutic Significance of Polysaccharides

In recent years, the relevant research on intestinal flora has been in full swing, and it has become an extremely important research direction in clinical medicine and life science. Irritable bowel syndrome (IBS) is a common disease characterized by changes in intestinal function and accompanied by comorbid anxiety. At present, the pathogenic mechanism of IBS is not yet clear. The gut-brain axis (GBA), as a two-way information exchange system between the gut and the brain, has an important influence on the prevention of IBS. Present studies have shown that polysaccharides are important for maintaining the steady status of intestinal micro-environment. This review summarized the relationship between intestinal flora, GBA and immune activation, and provided a new idea for the preventive treatment of IBS from the perspective of polysaccharides.

Evaluation of immune stimulatory products for whiteleg shrimp (Penaeus vannamei) by a metabolomics approach

The use of probiotics, prebiotics and dietary fiber has become a common practice in shrimp aquaculture as alternatives to antibiotic treatment. However, not much is known about the metabolic mechanisms underlying the effects of probiotics and immunostimulant used in shrimp aquaculture. In this study, a gas chromatography-mass spectrometry (GC-MS) based metabolomics approach was used to characterize metabolite profiles of haemolymph and gills of whiteleg shrimp (Penaeus vannamei) exposed to four treatments (cellulose fiber, probiotics with Vibrio alginolyticus, a combination of cellulose fiber and V. alginolyticus and a control treatment). The cellulose fiber was administrated as a feed additive (100 mg⋅Kg^-1 feed), while the probiotics was applied in the water (10⁵ UFC⋅mL^-1 culture water). The results showed significant differences in haemolymph metabolite profiles of immune stimulated treatments compared to the control and among treatments. The combination of cellulose fiber and probiotics resulted in greater differences in metabolic profiles, suggesting a better immune stimulation with this approach. The changes in haemolymph metabolome of treated shrimp reflected several biochemical pathway modifications, including changes in amino acid and fatty acid metabolism, disturbances in energy metabolism and antimicrobial activity and stress responses. For gill tissues, significant differences were only found in lactic acid between the probiotic group and the control. Among the altered metabolites, the increases of itaconic acid in haemolymph, and lactic acid in both haemolymph and gill tissues of immune-stimulated suggest the potential use of these metabolites as biomarkers for health assessment in aquaculture.

Enhanced immunity and hemocytes proliferation by three immunostimulants in tri-spine horseshoe crab Tachypleus tridentatus

Tachypleus amebocyte lysate (TAL) is crucial in medical testing, but its industry in China has been restricted due to the decline of horseshoe crab population in recent years. Exploring methods of enhancing immunity and rapid hemocytes proliferation is urgent for the industrial horseshoe crab culture. In this study, β-glucan (G), peptidoglycan (P), and squalene (S) were injected to horseshoe crabs at two concentrations (5 and 10 mg/kg), in order to compare their effects on total hemocyte count (THC), reactive oxygen species (ROS), and non-specific immune enzyme activities. Results showed that the THC, superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC) were significantly increased by three immunostimulants at different points of time; ROS was significantly increased except at two squalene groups; lysozyme (LZM) and alkaline phosphatase (AKP) activity were increased except at low dose (5 mg/kg) squalene group; malondialdehyde (MDA) activity was decreased in all treatments; and hemocyanin concentration (HC) changed little during the experiment. At the 48th hour, THC, ROS, SOD, CAT, T-AOC, LZM, and AKP activities were significantly higher in the two peptidoglycan groups than those in the control group; the low dose β-glucan and squalene groups showed significantly higher SOD and CAT, but their THC and AKP were not significantly different from those of the control group. In general, all three immunostimulants stimulated the hemolymph parameters of horseshoe crabs, notably, peptidoglycan could significantly increase the THC and enzyme activities, suggesting that peptidoglycan can be developed as an efficient immunostimulant for horseshoe crabs.

Inulin alleviates adverse metabolic syndrome and regulates intestinal microbiota composition in Nile tilapia (Oreochromis niloticus) fed with high-carbohydrate diet

A high-carbohydrate diet could achieve a protein-sparing effect, but it may cause negative impacts on the growth condition of fish due to their poor utilisation ability of carbohydrate. How to reduce the adverse effects caused by a high-carbohydrate diet is important for the development of aquaculture. In the present study, we aimed to identify whether inulin could attenuate the metabolic syndrome caused by a high-carbohydrate diet in fish. Nile tilapia (Oreochromis niloticus) (1·19 (sd 0·01) g) were supplied with 35 % carbohydrate (CON), 45 % carbohydrate (HC) and 45 % carbohydrate + 5 g/kg inulin (HCI) diets for 10 weeks. The results showed that addition of inulin improved the survival rate when fish were challenged with Aeromonas hydrophila, indicating that inulin had an immunostimulatory effect. Compared with the HC group, the HCI group had lower lipid accumulation in liver and the gene expression analyses indicated that addition of inulin down-regulated genes related to lipogenesis and up-regulated genes relevant to β-oxidation significantly (P < 0·05). Higher liver glycogen and glucose tolerance were found in the HCI group compared with the HC group (P < 0·05). These results indicated that inulin could alleviate the metabolic syndrome induced by a high-carbohydrate diet. Furthermore, addition of inulin to a high-carbohydrate diet changed the intestinal bacterial composition and significantly increased the concentration of acetic acid and propionic acid in fish gut which have the potential to increase pathogen resistance and regulate metabolic characteristics in fish. Collectively, our results demonstrated a possible causal role for the gut microbiome in metabolic improvements induced by inulin in fish.

Enhanced antitumor activity of inulin-capped Se nanoparticles synthesized using Jerusalem artichoke tubers

An inulin polysaccharide with a molecular weight of ~ 2600 Da was derived from Jerusalem artichoke tubers and referred to as "JAP". Previous studies have shown that inulin can improve glucose tolerance and the liver lipid profile; however, its antitumor activity remains to be examined in detail. Therefore, to investigate the possible improvement of the antitumor activity of JAP, a novel nanostructured biomaterial was constructed by capping Se nanoparticles with JAP using sodium selenite, via a redox reaction with ascorbic acid, and referred to as "JAP-SeNPs". Transmission electron microscopy revealed that the average diameter of JAP-SeNPs is ~ 50 nm, and the C:Se mass ratio in JAP-SeNPs was found to be 15.4:1 by energy-dispersive X-ray spectroscopy. The well-dispersed JAP-SeNPs exhibited a significant in vitro antiproliferative effect on mouse forestomach carcinoma cells at a concentration of 400 μg/mL when incubated for 48 h, with an inhibition rate of 41.5%. Moreover, 38.9% of later apoptotic cells were observed. These results reveal that a combination of Se and JAP can effectively enhance the antitumor activity of polysaccharides obtained from Jerusalem artichoke tubers.

Overview of the latest developments in the role of probiotics, prebiotics and synbiotics in shrimp aquaculture

With the growing world population, the demand for food has increased, leading to excessive and intensive breeding and cultivation of fisheries, simultaneously exacerbating the risk of disease. Recently, shrimp producers have faced major losses of stocks due to the prevalence of periodical diseases and inappropriate use of antibiotics for disease prevention and treatment, leading to bacterial resistance in shrimp, along with imposing health hazards on human consumers. Strict regulations have been placed to ban or reduce the use of prophylactic antibiotics to lessen their detrimental effects on aquatic life. Dietary and water supplements have been used as substitutes, among which probiotics, prebiotics, and synbiotics have been the most beneficial for controlling or treating bacterial, viral, and parasitic diseases in shrimp. The present analysis addresses the issues and current progress in the administration of pro-, pre-, and synbiotics as disease controlling agents in the field of shrimp farming. Furthermore, the benefits of pro-, pre-, and synbiotics and their mechanism of action have been identified such as; strengthening of immune responses, growth of antibacterial agents, alteration in gut microflora, competition for nutrients and binding sites, and enzymes related activities. Overall, this study aims to depict the antagonistic action of these supplements against a variety of pathogens and their mode of action to counter diseases and benefit shrimp species.

Modulation of growth performance, gut microflora, non-specific immunity and gene expression of proinflammatory cytokines in shabout (Tor grypus) upon dietary prebiotic supplementation

In this study, the effect of dietary supplementation of mannan oligosaccharide (MOS) + β-glucan (Immunogen®) was investigated on growth performance, body composition, gut microflora, innate immune responses and gene expression of some proinflammatory cytokines in shabout (Tor grypus). Shabout fingerlings (35 ± 1.2 g) were fed with basal diet (control) or basal diet supplemented with Immunogen® at 0.5, 1 and 1.5% of feed for 90 days. According to the results, growth parameters were significantly improved in fish fed with prebiotic (1 and 1.5%) for 90 days (p < 0.05). The carcass protein content was significantly higher in fish nourished by prebiotic at 1.5% of feed for 90 days compared to fish received the basal diet (p < 0.05). Feeding with various levels of Immunogen® resulted in the significant promotion of the population of intestinal Lactobacillus spp. in the prebiotic-treated groups relative to the control group (p < 0.05). Serum total globulin was significantly higher in all prebiotic groups relative to the control group at day 60. Serum bactericidal and lysozyme activities were significantly (p < 0.05) elevated after feeding with dietary prebiotic at all intervals (days 30, 60 and 90). However, the highest serum bactericidal activities were recorded in fish fed with Immunogen® at 1.5% of diet (p < 0.05). The transcription levels of interleukin 1 beta (IL-1β), interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-α) were significantly increased in the head kidney of fish treated with dietary prebiotic at all intervals. The results show that dietary supplementation with Immunogen®, particularly at the level of 1.5%, can positively alter growth parameters, carcass protein, intestinal microflora and immune responses of shabout.

A gelatinized lipopeptide diet effectively modulates immune response, disease resistance and gut microbiome in Penaeus vannamei challenged with Vibrio parahaemolyticus

Penaeus vannamei is one of the most economically vital shrimp globally, but infectious diseases have hampered its proper production and supply. As antibiotics pose a huge threat to the environment and humankind, it is essential to seek an alternative strategy to overcome infection and ensure proper culture and production. The present study investigates the effect of an anti-infective biosurfactant derivative lipopeptide MSA31 produced by a marine bacterium on the growth performance, disease resistance, and the gut microbiome of P. vannamei when challenged with pathogenic Vibrio parahaemolyticus SF14. The shrimp were fed with a commercial and lipopeptide formulated diet for 60 days and the growth performance was analyzed. The lipopeptide fed shrimp group showed enhanced growth performance and specific growth rate with improved weight gain than the control group. The challenge experiment showed that the survival rate was significant in the lipopeptide fed group compared to the control group. The results revealed 100% mortality in the control group at the end of 12 h of challenge, while 50% of the lipopeptide diet-fed group survived 24 h, which indicates the enhanced disease resistance in shrimp fed with a lipopeptide diet. The test group also showed higher levels of digestive and immune enzymes, which suggests that the lipopeptide diet could positively modulate the digestive and immune activity of the shrimp. The gut microbiome profiling by Illumina high-throughput sequencing revealed that the most abundant genera in the lipopeptide diet-fed group were Adhaeribacter, Acidothermus, Brevibacillus, Candidatus, Mycobacterium, Rodopila, and Streptomyces, while opportunistic pathogens such as Streptococcus, Escherichia, Klebsiella, Neisseria, Rhizobium, and Salmonella were abundant in the control diet-fed shrimp. Also, lipopeptide diet-fed shrimp were found to have a high abundance of ammonia and nitrogen oxidizing bacteria, which are essential pollutant degraders. Therefore, the study reveals that the dietary supplementation of lipopeptide in shrimp aquaculture could positively modulate the gut microbiome and enhance the shrimp's overall health and immunity in an eco-friendly manner.

Vibrio and major commercially important vibriosis diseases in decapod crustaceans

Bacteria fromthe Vibriogenus are autochthonous to aquatic environments and ubiquitous in aquaculture production systems. Many Vibrio species are non-pathogenic and can be commonly found in healthy farmed aquatic animals. However, some Vibrio species and strains are pathogenic leading to a variety of 'vibriosis' diseases. These diseases can have a significant negative impact on animal production, including farmed crustaceans such as shrimps, lobsters, and crabs. As such, vibriosis can pose a threat to meeting growing food demand and global food security. Preventive management is essential to avoid the onset of vibriosis. This includes a robust health management plan, the use of prophylaxis and treatment measures, and enhancing animal health through nutrition. Furthermore, the use of probiotics, prebiotics, synbiotics, quorum sensing disruption, green water, biofloc, bacteriophages, and immune priming could also play a role in preventing and controlling a vibriosis outbreak. This review aims to inform and update the reader about the current state of knowledge about Vibrio and associated vibriosis in farmed crustaceans (i.e. shrimp, lobster, and crabs). Furthermore, the review will identify potential knowledge gaps in the literature, which serves as a basis for future research priorities.

The regulation of immune responses against white spot syndrome virus or Vibrio alginolyticus in toll-like receptors silenced giant freshwater prawn (Macrobrachium rosenbergii)

Toll-like receptors, which are a class of cell-surface proteins, have been regarded as the most important pattern recognition receptors in the innate immunity and play a vital role in multiple innate immune responses against pathogen invasion. The full-length cDNA of a novel Toll-like receptor (MrToll3) was identified from Macrobrachium rosenbergii in the current research. The nucleotide sequence of MrToll3 is 4481 bp long and contains a 3726-bp open reading frame encoding a putative protein of 1241 amino acids. MrToll3 was constitutively expressed in all the examined tissues, and high expression of MrToll3 was detected in gill, heart, and ganglion. The result of RNA interference assay revealed that silencing of MrToll1 remarkably suppressed the prophenoloxidase (proPO) expression and phenoloxidase (PO) activities while enhancing MrToll2 expression in the prawns. Furthermore, the expression of myeloid differentiation factor 88 (MyD88), anti-lipopolysaccharide factor (ALF) and crustin was remarkably down-regulated in the MrToll1-silenced prawns after white spot syndrome virus (WSSV) or Vibrio alginolyticus challenge. MrToll2-silenced prawns exhibited the significant decline of ALF and crustin expression post the pathogen challenges, and silencing of MrToll3 obviously improved the immune deficiency (IMD) expression during the whole RNA interference assay. Additionally, higher mortality was observed in MrToll1-or MrToll2-silenced prawns after V. alginolyticus challenge, and the MrToll1-silenced prawns also showed the obviously enhanced susceptibility to WSSV. These results suggested that MrToll1, 2, and 3 were involved in the innate immune responses against WSSV and V. alginolyticus in M. rosenbergii.

Prebiotic mannooligosaccharides: Synthesis, characterization and bioactive properties

Functional oligosaccharides are non-digestible food ingredients that confer numerous health benefits. Among these, mannooligosaccharides (MOS) are emerging prebiotics that have characteristic potential bio-active properties. Microbial mannanases can be used to break down mannan rich agro-residues to yield MOS. Various applications of MOS as health promoting functional food ingredient may open up newer opportunities in food and feed industry. Enzymatic hydrolysis is the widely preferred method over chemical hydrolysis for MOS production. Presently, commercial MOS is being derived from yeast cell wall mannan and is widely used as prebiotic in feed supplements for poultry and aquaculture. Apart from stimulating the growth of probiotic microflora, MOS impart anticancer and immunomodulatory effects by inducing different gene markers in colon cells. This review summarizes recent developments and future prospects of enzymatic synthesis of MOS from various mannans, their structural characteristics and their potential health benefits.

The physiological functions and pharmaceutical applications of inulin: A review

Inulin (IN), a fructan-type plant polysaccharide, is widely found in nature. The major plant sources of IN include chicory, Jerusalem artichoke, dahlia etc. Studies have found that IN possessed a wide array of biological activities, e.g. as a prebiotic to improve the intestinal microbe environment, regulating blood sugar, regulating blood lipids, antioxidant, anticancer, immune regulation and so on. Currently, IN is widely used in the food and pharmaceutical industries. IN can be used as thickener, fat replacer, sweetener and water retaining agent in the food industry. IN also can be applied in the pharmaceutics as stabilizer, drug carrier, and auxiliary therapeutic agent for certain diseases such as constipation and diabetes. This paper reviews the physiological functions of IN and its applications in the field of pharmaceutics, analyzes its present research status and future research direction. This review will serve as a one-in-all resource for the researchers who are interested to work on IN.

Effects of Yu-Ping-Feng polysaccharides (YPS) on the immune response, intestinal microbiota, disease resistance and growth performance of Litopenaeus vannamei

A 28-day feeding trial was conducted to investigate the effects of Yu-Ping-Feng polysaccharides (YPS) containing Astragalus polysaccharides (APS), Atractylodes macrocephala polysaccharides (AMP) and Saposhnikoviae polysaccharides (SPS) on the immune response, intestinal microbiota, disease resistance and growth performance of Litopenaeus vannamei. Seven hundred and twenty shrimp (3.04 ± 0.33 g) were fed the following diets: Control, YPS1 (0.13% APS + 0.0325% AMP + 0.0325% SPS), YPS2 (0.13% APS + 0.0325% AMP + 0.065% SPS) and YPS3 (0.13% APS + 0.0325% AMP+0.0975% SPS). After 14 and 28 days of feeding, the immune responses of hemocytes and intestine were measured. Intestinal microbiota and growth performance were measured after 28 days of feeding, after that, a 7-day challenge test against Vibrio harveyi was conducted. A significant (P < 0.05) increase of the total haemocyte count (THC), phagocytic activity, antibacterial activity and phenoloxidase (PO) activity was observed in shrimp fed YPS diets compared to the control. Also, dietary YPS supplementation particularly YPS3 group significantly increased the expressions of immune-related genes in the hemocytes and intestine. Regarding the intestinal microbiota, the microbial diversity and richness decreased and functional genes associated with short-chain fatty acids metabolism increased in YPS groups. After Vibrio harveyi challenge, the cumulative mortality in YPS groups was significantly lower than that of the control. Besides, dietary YPS had no significant effect on growth performance of shrimp (P > 0.05). The present results suggested that YPS could be considered as potential prebiotics for aquaculture farmed shrimp.

Oligosaccharides derived from dragon fruit modulate gut microbiota, reduce oxidative stress and stimulate toll-pathway related gene expression in freshwater crustacean Daphnia magna

Dragon fruit oligosaccharide (DFO) is an indigestible prebiotic. In this study, we aimed to investigate the effects of DFO on gut microbiota, oxidative stress and immune-related gene expression in Daphnia magna. The 10-day-old D. magna were treated with 0, 9, and 27 mg l^-1 DFO for 85 h. The gut bacterial communities, superoxide dismutase (SOD) activity, lipid peroxidation and the expressions of genes in Toll signaling pathway were observed. The results showed that D. magna treated with 9 and 27 mg l^-1 DFO altered gut microbiota composition by increasing Limnohabitans and Lactobacillus, and significantly increased SOD activity and reduced lipid peroxidation. Moreover, the expressions of Toll2, Toll3, Toll5, Toll7 and Pelle genes were significantly increased in D. magna treated with 9 and 27 mg l^-1 DFO. Our results suggested that DFO changed the composition of the gut microbiota of D. magna by increasing the beneficial bacteria. DFO also had the ability to stimulate innate immunity in D. magna by increasing SOD activity, reducing lipid peroxidation, and increasing the expression of immune-related genes.

Modulation of transcriptomic profile in aquatic animals: Probiotics, prebiotics and synbiotics scenarios

Aquaculture and fisheries have provided protein sources for human consumption for a long time, but diseases have induced declines in product benefits and raised concerns, resulting in great losses to these industries in many countries. The overuse of antibiotics for the treatment of diseases has increased the chemical concentrations in culture systems and weakened the natural immunity of aquatic organisms. Concerns regarding the detrimental effects of antibiotics on the environment and human health due to residual antibiotic-related issues encourage the development of reliable, environmental and health safety methods, such as vaccines, probiotics, prebiotics, synbiotics and phytobiotics, for protection against disease and for reducing and possibly eliminating disease occurrence. Immunity has been effectively enhanced by pro-, pre-, and synbiotics, which confer strong protection and reduce the risks associated with stressors and disease outbreaks in culture systems. These agents confer several benefits, including enhancing both host growth and immune responses against pathogens, while sustaining health and environmental stability, and their use is thus widely accepted. Alterations in gene expression in individual cells could serve as an indicator of the immunity and growth rate of aquatic animals after pro-, pre- and synbiotic feeding. This review addresses the potential use of pro, pre- and synbiotics as immunostimulants for improved aquaculture management and environmental health and chronicles the recent insights regarding the application of pro-, pre- and synbiotics with special emphasis on their immunomodulatory and antioxidative responses based on gene expression changes. Furthermore, the current review describes the research gaps and other issues that merit further investigation.

Mannan oligosaccharide increases the growth performance, immunity and resistance capability against Vibro Parahemolyticus in juvenile abalone Haliotis discus hannai Ino

This trial was conducted to investigate the effect of mannose oligosaccharides (MOS) on the growth performance, antioxidation, immunity and disease resistance of Vibro Parahemolyticus in juvenile abalone Haliotis discus hannai Ino. Four formulated diets were produced to contain 0.00 g/kg, 0.40 g/kg, 0.80 g/kg and 1.60 g/kg Actigen®, with functional ingredients of MOS, respectively. Accordingly, the experimental diets were named as A0, A4, A8 and A16. After 120-days feeding trial, the best growth performance was observed in A8 group (P < 0.05) and there was no significant difference in A0, A4 and A16 groups. With the increase of dietary MOS, the activity of the total antioxidant capacity in hepatopancreas is increasingly elevated (P < 0.05) while no significant difference was observed on activity of glutathione S-transferase (P > 0.05). The activities of superoxide dismutase and glutathione peroxidase were firstly increased and then decreased, with the highest values in A8 group (P < 0.05). Immune-related parameters were significantly affected by dietary MOS inclusion. Specifically, the activities of alkaline phosphatase and acid phosphatase in hepatopancreas and serum of abalone fed diets containing MOS were significantly higher than those of control A0 group (P < 0.05). Moreover, the highest values of both enzymes were observed in hepatopancreas of A8 group but in serum of A16 group, respectively. The lysozyme activities in hepatopancreas and serum of A4 group were significantly higher than those of other groups (P < 0.05) and there was no significant difference in A0, A8 and A16 groups (P > 0.05). The activities of cytophagy and respiratory burst in serum of abalone were not significantly affected by dietary MOS content (P > 0.05). The mRNA levels of focal adhesion kinase and integrin-linked kinase were gradually elevated with the increase of dietary MOS, with the highest value recorded in A16 group (P < 0.05). The gene expression of caspse-3 in A8 group was dramatically higher than those of other groups (P < 0.05) and there was no significant difference in A0, A4 and A16 groups (P > 0.05). The mRNA level of nuclear factor-κB was not significantly affected by dietary MOS (P > 0.05). During 56 h of V. Parahemolyticus challenge period, the accumulated mortality rate of abalone fed diets containing MOS were significantly lower than that of control A0 group in each time point (P < 0.05). Overall, the lowest rate was happened in A8 group (P < 0.05). In conclusion, MOS inclusion in diet has obviously positive effect on growth, immunity and disease resistance capability of abalone, with the optimal level of Actigen® at 0.80 g/kg in diet.

Diet-microbiome-disease: Investigating diet's influence on infectious disease resistance through alteration of the gut microbiome

Abiotic and biotic factors can affect host resistance to parasites. Host diet and host gut microbiomes are two increasingly recognized factors influencing disease resistance. In particular, recent studies demonstrate that (1) particular diets can reduce parasitism; (2) diets can alter the gut microbiome; and (3) the gut microbiome can decrease parasitism. These three separate relationships suggest the existence of indirect links through which diets reduce parasitism through an alteration of the gut microbiome. However, such links are rarely considered and even more rarely experimentally validated. This is surprising because there is increasing discussion of the therapeutic potential of diets and gut microbiomes to control infectious disease. To elucidate these potential indirect links, we review and examine studies on a wide range of animal systems commonly used in diet, microbiome, and disease research. We also examine the relative benefits and disadvantages of particular systems for the study of these indirect links and conclude that mice and insects are currently the best animal systems to test for the effect of diet-altered protective gut microbiomes on infectious disease. Focusing on these systems, we provide experimental guidelines and highlight challenges that must be overcome. Although previous studies have recommended these systems for microbiome research, here we specifically recommend these systems because of their proven relationships between diet and parasitism, between diet and the microbiome, and between the microbiome and parasite resistance. Thus, they provide a sound foundation to explore the three-way interaction between diet, the microbiome, and infectious disease.

Effect of single and combined immunostimulants on growth, anti-oxidation activity, non-specific immunity and resistance to Aeromonas hydrophila in Chinese mitten crab (Eriocheir sinensis)

This study evaluates the effect of dietary supplementation of immunostimulants on the Chinese mitten crab (Eriocheir sinensis) with a single administration of mannan oligosaccharide (MOS), or its combination with either β-glucan or with inulin for 8 weeks. Four diets included an untreated control diet (C), MOS alone (3 g kg^-1, M), MOS with β-glucan (3 g kg ^-1 MOS + 1.5 g kg ^-1 β-glucan, MB), and MOS with inulin (3 g kg ^-1 MOS + 10 g kg ^-1 inulin, MI). The weight gain and specific growth rate of the crabs fed M, MB, and MI diets were improved by lowing feed conversion ratio. The growth and feed utilization of the crabs fed the MB diet were improved compared with the other three groups. The crabs fed the M, MB and MI diets showed a higher intestinal trypsin activity than that in the M and control groups. The highest trypsin activity in the hepatopancreas was observed in the MB group. Crabs fed M, MB and MI diets increased antioxidant system-related enzyme activities, but reduced malondialdehyde. The highest activities of alkaline phosphatase, acid phosphatase, lysozyme and phenol oxidase in the gut and the respiratory burst of the crabs were found in the MB group. The MB diet promoted the mRNA expression of E. sinensis immune genes (ES-PT, ES-Relish, ES-LITAF, p38MAPK and Crustin) compared with the control. After 3 days of infection with Aeromonas hydrophila, the highest survival of crabs was also found in the MB group. This study indicates that the combination of MOS with β-glucan or with inulin can improve growth, antioxidant capacity, non-specific immunity and disease resistance in E. sinensis.

Effects of prebiotic mixtures on growth performance, intestinal microbiota and immune response in juvenile chu's croaker, Nibea coibor

Prebiotics has been known to be growth promoter and immunostimulant in aquatic animals. In this study, we investigated the effects of prebiotics on growth performance, intestinal microbiota, short-chain fatty acids (SCFAs) production and immune response of the marine fish, juvenile chu's croaker (Nibea coibor). The fish were fed IG (including 0.5% inulin and 0.5% GOS), GS (0.5% GOS and 0.5% D-sorbitol), IGS (0.33% inulin, 0.33% GOS and 0.33% D-sorbitol) or control diets for 8 weeks. The results showed that the growth performance of the fish was promoted by IG and GS, but not by IGS. The intestinal microbiota in NDC (non-digestible carbohydrates, NDC)-supplemented groups was clearly separated from that of the control, and the highest Shannon and Simpson diversity indices were observed in the IGS group. In the intestine of the croaker, Proteobacteria, Firmicutes, and Bacteroidetes were dominant; among them, 24 taxa revealed a significant difference among groups. Most of these bacteria are able to produce SCFAs, which were significantly increased in all NDC-supplemented groups. Moreover, NDCs were found to activate the immune system of the fish by modulating the serum complements, cytokine levels, lysozyme activities and antioxidant capacity. Furthermore, the results of this study revealed correlations among intestinal microbiota, SCFAs production, innate immunity, antioxidant capacity and digestive enzymes in the croaker fed NDCs. Taken together, our results demonstrated that NDC mixtures might promote growth performance, antioxidant capacity and immune responses of the croaker through modulating the composition of intestinal microbiota and the subsequent SCFAs production, which suggest that NDCs were efficient feed additives for marine fish.