Chitin, chitosan and chitooligosaccharides as potential growth promoters and immunostimulants in aquaculture: A comprehensive review

Optimizing chitosan nanoparticles for oral delivery of double-stranded RNA in treating white spot disease in shrimp: Key insights and practical implications

Delivering double-stranded RNA (dsRNA) in shrimp is challenging due to the lack of an effective carrier system. This study optimized chitosan nanoparticles (CNs) from two sources-α-chitosan from shrimp and β-chitosan from squid-to encapsulate antiviral dsRNA for oral administration via shrimp feed. Using response surface methodology (RSM), formulations were refined for encapsulation efficiency, particle size, polydispersity index, and zeta potential. Both types of CNs demonstrated high encapsulation efficiency (>95 %), small sizes (<300 nm), and stable zeta potential (>20 mV). Shrimp-derived CNs provided superior RNase protection and controlled release, while squid-derived CNs showed a burst release. Incorporated into feed, both types of CNs remained stable for over a month. Shrimp-derived CNs offered greater dsRNA protection (>70 %) and improved efficacy against white spot syndrome virus (WSSV), significantly reducing mortality. These results position shrimp-derived CNs as promising dsRNA carriers for combating WSSV in shrimp aquaculture.

Chitosan and its derivatives: A novel approach to gut microbiota modulation and immune system enhancement

Chitosan, a biopolymer derived from the deacetylation of chitin found in crustacean shells and certain fungi, has attracted considerable attention for its promising health benefits, particularly in gut microbiota maintenance and immune system modulation. This review critically examines chitosan's multifaceted role in supporting gut health and enhancing immunity, beginning with a comprehensive overview of its sources, chemical structure, and its dual function as a dietary supplement and biomaterial. Chitosan's prebiotic effects are highlighted, with a focus on its ability to selectively stimulate beneficial gut bacteria, such as Bifidobacteria and Lactobacillus, while enhancing gut barrier integrity and inhibiting the growth of pathogenic microorganisms. The review delves deeply into chitosan's immunomodulatory mechanisms, including its impact on antigen-presenting cells, cytokine profiles, and systemic immune responses. A detailed comparative analysis assesses chitosan's efficacy relative to other prebiotics and immunomodulatory agents, examining challenges related to bioavailability and metabolic activity. Beyond its role in gut health, this review explores chitosan's potential as a dual-action agent that not only supports gut microbiota but also fortifies immune resilience. It introduces emerging research on novel chitosan derivatives, such as chitooligosaccharides, and evaluates their enhanced bioactivity for functional food applications. Special attention is given to sustainability, with an exploration of alternative, plant-based sources of chitosan and their implications for both health and environmental stewardship. Also, the review identifies new research avenues, such as the growing interest in chitosan's role in the gut-brain axis and its potential mental health benefits through microbial interactions. By addressing these innovative areas, the review aims to shift the focus from basic health effects to chitosan's broader impact on public health. The findings encourage further exploration, particularly through human trials, and emphasize chitosan's untapped potential in revolutionizing health and disease management.

Chitosan oligosaccharide alleviates DON-induced liver injury via suppressing ferroptosis in mice

Chitosan oligosaccharide (COS), a water-soluble derivative of chitin, has been recognized for its diverse biological properties. Deoxynivalenol (DON) is a prevalent mycotoxin, causing extreme liver damage. However, the mechanism whereby COS alleviates DON-induced liver injury remains unclear. In the present study, C57BL/6 mice were randomly divided into four groups: control (CON), DON (1.0 mg/d/kg BW DON), COS (200 mg/d/kg BW COS), and COS+DON (200 mg/d/kg BW COS + 1.0 mg/d/kg BW DON), with a period of 28 days. The results indicated that COS effectively reversed DON-induced weight loss, elevated liver index, and liver hemorrhage and swelling in mice. Moreover, COS significantly reduced liver reactive oxygen species (ROS) levels, malondialdehyde (MDA) content, and lactate dehydrogenase (LDH) release in DON-exposed mice, while restoring the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and total antioxidant capacity (T-AOC). Further investigations revealed that COS modulated the expressions of pro-inflammatory cytokines and anti-apoptotic proteins through stimulation of the Nrf2/HO-1 signaling pathway and suppression of the NF-κB signaling pathway. Additionally, COS inhibited ferroptosis by modulating the SLC7A11/GSH/GPX4 pathway and the expression of FTH1 and FLC proteins, thereby reducing lipid peroxidation accumulation and iron overload. In summary, this research showed that COS mitigated DON-induced liver injury in mice by alleviating DON-induced oxidative stress, inflammation, apoptosis, and ferroptosis via modulating the Nrf2/HO-1/NF-κB and GPX4 signaling pathways. These results offer a theoretical basis for the development and application of COS as a novel liver protectant and propose innovative therapeutic strategies for combating DON-induced liver damage.

A review on the biological activities and the nutraceutical potential of chitooligosaccharides

Chitooligosaccharides (CHOS) or chitosan oligosaccharides (COS) are oligomers mainly composed of d-glucosamine (GlcN) units and structured in a positively charged, basic, amino molecule obtained from the degradation of chitin/chitosan through physical, chemical, or enzymatic methods. CHOS display physicochemical properties attractive to applications from the food to the biomedical field, such as non-toxicity to humans, high water solubility, low viscosity, biocompatibility, and biodegradability. These properties also allow CHOS to exert important biological activities, for example, antioxidant, antimicrobial, anti-inflammatory, immunomodulatory, antitumor, and hypocholesterolemic ones, besides to exhibit applications in food systems, technological, and nutraceutical potential. Therefore, this study summarized the synthesis and chemical structure, biological functions, and mechanisms of action of CHOS; with this, we aimed to contribute to the knowledge about the application of CHOS from the food to the biomedical industries.

Eukaryotic expression of chitinase from dark sleeper (Odontobutis potamophila) and its effects on growth and immunity

Chitinase, an enzyme that hydrolyzes β-1,4-glycosidic bonds to degrade chitin, is essential for the digestion of chitin in fish. In this study, the chitinase OpCht from Odontobutis potamophila was expressed in Pichia pastoris, and its enzymatic properties and functional effects were evaluated. The findings revealed that OpCht exhibited optimal activity at pH 6.0 and 50 °C, with stability in the pH range of 4-8 and temperatures from 4 to 40 °C. K+, Na+, Ca2+, Mg2+, Mn2+, Hg2+, and Al3+ showed varying degrees of activation on the enzyme. At the end of the 8-week trial, the addition of OpCht significantly increased the height of intestinal villi and the thickness of the muscular layer, leading to significantly weight in the treated groups. The alleviation of intestinal inflammation also resulted in an increased survival rate (SR) of O. potamophila. High concentration treatment groups (2, 4 μg/g) showed significantly elevated digestive enzyme activities, as well as increased antioxidant enzyme activities and immune parameters. These results demonstrate that the P. pastoris expression system has successfully produced the chitinase OpCht from O. potamophila, and the addition of a certain concentration of OpCht can promote fish growth and enhance immune functions, offering a promising enzyme preparation for the aquaculture industry.

Unraveling the web of defense: the crucial role of polysaccharides in immunity

The great potential of polysaccharides in immunological regulation has recently been highlighted in pharmacological and clinical studies. Polysaccharides can trigger immunostimulatory responses through molecular identification, intra- and intercellular communication via direct or indirect interactions with the immune system. Various immunostimulatory polysaccharides or their derivative compounds interacts at cellular level to boost the immune system, including arabinogalactans, fucoidans, mannans, xylans, galactans, hyaluronans, fructans, pectin and arabinogalactans, etc. These natural polysaccharides are derived from various plants, animals and microbes. A unique structural diversity has been identified in polysaccharides, while monosaccharides and glucosidic bonds mainly confer diverse biological activities. These natural polysaccharides improve antioxidant capacity, reduce the production of pro-inflammatory mediators, strengthen the intestinal barrier, influence the composition of intestinal microbial populations and promote the synthesis of short-chain fatty acids. These natural polysaccharides are also known to reduce excessive inflammatory responses. It is crucial to develop polysaccharide-based immunomodulators that could be used to prevent or treat certain diseases. This review highlights the structural features, immunomodulatory properties, underlying immunomodulatory mechanisms of naturally occurring polysaccharides, and activities related to immune effects by elucidating a complex relationship between polysaccharides and immunity. In addition, the future of these molecules as potential immunomodulatory components that could transform pharmaceutical applications at clinical level will also be highlighted.

Safety Assessment of Camelid-Derived Single-Domain Antibody as Feed Additive for Juvenile Whiteleg Shrimp (Litopenaeus vannamei) Against White Spot Syndrome Virus

A six-week feeding trial was conducted to assess the safety of single-domain antibodies (sdAbs) derived from camelids against the white spot syndrome virus (WSSV) (WSSVvp28 was used as the antigen), focusing on the whole-organism responses and molecular-level changes in juvenile whiteleg shrimp (Litopenaeus vannamei). Five experimental diets with varying levels of sdAbs were formulated: CON (no sdAb supplementation); SDA8.2 (8.20% of sdAbs); SDA16.4 (16.40% of sdAbs); SDA24.6 (24.60% of sdAbs); and SDA32.8 (32.80% of sdAbs). In the CON diet, 450 mL of water per kg of diet (45%) was used to form a feed dough, while sdAbs were used to replace the water in the treatment diets. A total of 450 shrimp, with an initial body weight of 3.27 ± 0.02 g (mean ± SEM), were randomly distributed in 15 tanks (30 shrimp per tank; three tanks per treatment). Each tank was filled with 30 L of seawater (77 L capacity) in an indoor semi-recirculating system with a constant water flow rate of 1.2 L min-1. The photoperiod was maintained at 12 h of light and 12 h of dark. The water temperature, pH, salinity, and dissolved oxygen were 27.3 ± 0.1 °C, 7.61 ± 0.01, 34 ± 1 ppt, and 5.94 ± 0.04 mg L-1, respectively. During the feeding trial, the shrimp were fed the experimental diet (40% protein and 11% lipid) three times a day for six weeks. Following the feeding trial, an acute cold-water-temperature stress test was conducted by abruptly exposing the shrimp from each treatment to 15 °C for 4 h, down from 27 °C. The results showed no significant differences in the growth performance (weight gain, feed utilization efficiency, survival, etc.), plasma metabolites (aspartate aminotransferase activity, alanine aminotransferase activity, total protein, and glucose), or antioxidant enzymes (superoxide dismutase and glutathione peroxidase) among all the experimental diets (p > 0.05). In the acute cold-temperature stress test, there was no significant interaction between sdAb supplementation and temperature stress, nor any main effect from either factor, except for the main effect of temperature stress on the glucose levels, which was significantly higher in shrimp exposed to cold-temperature stress (p < 0.05). The next-generation sequencing of differentially expressed genes (DEGs) in the hepatopancreases of shrimp fed the CON, SDA16.4, and SDA32.8 diets, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, indicated that DEGs were significantly enriched in signaling pathways associated with growth, cold stress, and antioxidant systems. Overall, the results from conventional measurements suggest that the use of sdAbs against the WSSV may be safe for juvenile whiteleg shrimp. However, findings from the sophisticated analysis indicate that further research is needed to understand the molecular mechanisms underlying the observed changes, and to evaluate the long-term effects of sdAb supplementation in shrimp diets.

Effect of Diets Supplemented With Yeast, Chitin, and Chitosan on the Growth, Immune, and Antioxidant Responses of the Freshwater Prawn Cryphiops (Cryphiops) caementarius

The purpose of the present research was to evaluate the effect of diets supplemented with activated yeast, crude chitin, and chitosan on the growth, immune, and antioxidant response of freshwater prawn Cryphiops (Cryphiops) caementarius. Adult male prawns were kept in individual culture vessels installed in aquarium tanks. The basal diet (control) was supplemented with activated Saccharomyces cerevisiae yeast (60 g/kg), crude chitin (20 g/kg), and chitosan (1 g/kg). Each dietary treatment consisted of three replicates. The diet supplemented with activated yeast causes greater growth, as well as a greater number of total hemocytes (82.54 × 105 cells/mL), semigranular (59 × 105 cells/mL), and granular (18.67 × 105 cells/mL) hemocytes and without atypical hemocytes. Furthermore, a higher number of hemocytes positive for prophenoloxidase (98%), a shorter hemolymph clotting time (42.87 s), a higher activity of acid phosphatase (12.50 U/mL) and glutathione-S-transferase (GST) (0.186 U/mL) were also observed in dietary yeast group. On the contrary, there were no differences in the activity of superoxide dismutase (SOD) enzyme in prawns from any dietary treatment. Results from this research demonstrate for the first time that the diet containing activated yeast increases the growth and immune response of the freshwater prawn through a significant increase in hemocyte and acid phosphatase levels, a decrease in hemolymph clotting time, and a greater number of proPO-positive hemocytes. However, activated yeast is not effective in increasing the activity of antioxidant enzymes SOD and GST. Therefore, the activated yeast diet can be useful to improve the aquaculture production of C. (C.) caementarius and possibly of other commercially important crustaceans.

Effects of Dietary Chitosan on Growth Performance, Serum Biochemical Indices, Antioxidant Capacity, and Immune Response of Juvenile Tilapia (Oreochromis niloticus) under Cadmium Stress

The objective of this study was to examine the effects of varying levels of dietary chitosan supplementation on mitigating cadmium stress and its influence on growth performance, serum biochemical indices, antioxidant capacity, immune response, inflammatory response, and the expression of related genes in juvenile Genetically Improved Farmed Tilapia (GIFT, Oreochromis niloticus). Five groups of juvenile tilapias (initial body weight 21.21 ± 0.24 g) were fed five diets with different levels (0%, 0.5%, 1.0%, 1.5%, and 2.0%) of chitosan supplementation for 60 days under cadmium stress (0.2 mg/L Cd2+). The findings indicated that, compared with the 0% chitosan group, dietary chitosan could significantly increase (p < 0.05) the final weight (Wf), weight gain rate (WGR), specific growth rate (SGR), daily growth index (DGI), and condition factor (CF), while the feed conversion ratio (FCR) expressed the opposite trend in juvenile GIFT. Dietary chitosan could significantly increase (p < 0.05) the activities (contents) of cholinesterase (CHE), albumin (ALB), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), acid phosphatase (ACP), and lysozyme (LZM), while glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), and complement 3 (C3) in the serum of juvenile GIFT expressed the opposite trend. Dietary chitosan could significantly increase (p < 0.05) the activities of superoxide dismutase (SOD) and catalase (CAT) and significantly decrease (p < 0.05) the activities (contents) of glutathione S-transferase (GST), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) in the serum of juvenile GIFT. Dietary chitosan could significantly increase (p < 0.05) the activities (contents) of CAT, GST, GSH-Px, and total antioxidant capacity (T-AOC) and significantly decrease (p < 0.05) the contents of MDA in the liver of juvenile GIFT. Dietary chitosan could significantly increase (p < 0.05) the activities (contents) of SOD, GSH-Px, T-AOC, Na+-K+-ATPase, and Ca2+-ATPase and significantly decrease (p < 0.05) the activities (contents) of CAT, GST, and MDA in the gills of juvenile GIFT. Dietary chitosan could significantly up-regulate (p < 0.05) the gene expression of cat, sod, gst, and gsh-px in the liver of juvenile GIFT. Dietary chitosan could significantly up-regulate (p < 0.05) the gene expression of interferon-γ (inf-γ) in the gills and spleen and significantly down-regulate (p < 0.05) the gene expression of inf-γ in the liver and head kidney of juvenile GIFT. Dietary chitosan could significantly down-regulate (p < 0.05) the gene expression of interleukin-6 (il-6), il-8, and tumor necrosis factor-α (tnf-α) in the liver, gills, head kidney, and spleen of juvenile GIFT. Dietary chitosan could significantly up-regulate (p < 0.05) the gene expression of il-10 in the liver, gills, head kidney, and spleen of juvenile GIFT. Dietary chitosan could significantly up-regulate (p < 0.05) the gene expression of transforming growth factor-β (tgf-β) in the liver and significantly down-regulate (p < 0.05) the gene expression of tgf-β in the head kidney and spleen of juvenile GIFT. In conclusion, dietary chitosan could mitigate the impact of cadmium stress on growth performance, serum biochemical indices, antioxidant capacity, immune response, inflammatory response, and related gene expression in juvenile GIFT. According to the analysis of second-order polynomial regression, it was found that the optimal dietary chitosan levels in juvenile GIFT was approximately 1.42% to 1.45%, based on its impact on Wf, WGR, SGR, and DGI.

Impact of O-acetylation on chitin oligosaccharides modulating inflammatory responses in LPS-induced RAW264.7 cells and mice

Chitin oligosaccharides have garnered significant attention due to their biological activities, particularly their immunomodulatory properties. However, O-acetylation in chemically preparing chitin oligosaccharides seems inevitable and leads to some uncertainty on the bioactivity of chitin oligosaccharides. In this study, an O-acetyl-free chitin oligosaccharides and three different O-acetylated chitin oligosaccharides with degree of polymerization ranging from 2 to 6 were prepared using ammonia hydrolysis, and their structures and detailed components were further characterized with FTIR, NMR and MS. Subsequently, the effects of O-acetylation on the immunomodulatory activity of chitin oligosaccharides were investigated in vitro and in vivo. The results suggested that the chitin oligosaccharides with O-acetylation exhibited better inflammatory inhibition than pure chitin oligosaccharides, significantly reducing the expression of inflammatory factors, such as IL-6 and iNOS, in the LPS-induced RAW264.7 macrophage. The chitin oligosaccharides with a degree of O-acetylation of 93 % was found to effectively alleviate LPS-induced endotoxemia in mice, including serum inflammation indices reduction and damage repairment of the intestinal liver, and kidney tissues.

Biomedical potency and mechanisms of marine polysaccharides and oligosaccharides: A review

Derived from bountiful marine organisms (predominantly algae, fauna, and microorganisms), marine polysaccharides and marine oligosaccharides are intricate macromolecules that play a significant role in the growth and development of marine life. Recently, considerable attention has been paid to marine polysaccharides and marine oligosaccharides as auspicious natural products due to their promising biological attributes. Herein, we provide an overview of recent advances in the miscellaneous biological activities of marine polysaccharides and marine oligosaccharides that encompasses their anti-cancer, anti-inflammatory, antibacterial, antiviral, antioxidant, anti-diabetes mellitus, and anticoagulant properties. Furthermore, we furnish a concise summary of the underlying mechanisms governing the behavior of these biological macromolecules. We hope that this review inspires research on marine polysaccharides and marine oligosaccharides in medicinal applications while offering fresh perspectives on their broader facets.

Improving Yellow Mealworm (Tenebrio molitor) Utilization with Sodium Butyrate in Nile Tilapia Diets: Effects on Growth Performance, Intestinal Histology, Antioxidative Response, and Blood Biomarkers

Yellow mealworm (Tenebrio molitor) meal was introduced to aquafeed as a suitable protein source to replace fish meal (FM) and soybean meal and, thereby, consistent aquaculture production. However, mealworms should be added at adequate levels due to the presence of antinutritional factors such as chitin. Consequently, sodium butyrate (SB) is suggested to improve feed quality and ensure aquatic animals' productivity and welfare. In this study, parallel with the protein source (T. molitor meal or FM), dietary supplementation of SB (1 g/kg) is involved as a factor in the 2 × 2 factorial study. The first and the second diets were formulated using FM as a protein source with or without SB, while the third and fourth diets were prepared by replacing FM with T. molitor meal with or without SB supplementation. After 60 days, fish fed with FM or T. molitor and SB showed improved final body weight and weight gain, while those fed with T. molitor without SB had a reduced protein efficiency ratio. Histological analysis revealed that dietary SB improved intestinal histological features by increasing the height and branching of intestinal villi and immune cell infiltration near intestinal crypts in Nile tilapia-fed FM or T. molitor. Furthermore, fish-fed FM or T. molitor and SB had higher Hb, red blood cells, PCV, total protein, and globulin levels than fish-fed respective test diets without SB supplementation. Dietary SB addition to FM or T. molitor-based diets also significantly enhanced blood lysozyme and phagocytic activities, catalase, superoxide dismutase, glutathione peroxidase, and reduced MDA levels. Our results demonstrate that T. molitor meal can replace FM without compromising Nile tilapia's growth performance and health status. Additionally, SB supplementation improved T. molitor meal utilization by Nile tilapia, thereby significantly enhancing the growth, digestion capacity, intestinal histological features, and antioxidative and immune responses. Consequently, dietary T. molitor meal reduces the reliance on FM and improves the sustainability and efficiency of Nile tilapia production.

Nanochitosan from crustacean and mollusk byproduct: Extraction, characterization, and applications in the food industry

Crustaceans and mollusks are widely consumed around the world due to their delicacy and nutritious value. During the processing, only 30-40 % of these shellfish are considered edible, while 70-60 % of portions are thrown away as waste or byproduct. These byproducts harbor valuable constituents, notably chitin. This chitin can be extracted from shellfish byproducts through chemical, microbial, enzymatic, and green technologies. However, chitin is insoluble in water and most of the organic solvents, hampering its wide application. Hence, chitin is de-acetylated into chitosan, which possesses various functional applications. Recently, nanotechnology has proven to improve the surface area and numerous functional properties of metals and molecules. Further, the nanotechnology principle can be extended to nanochitosan formation. Therefore, this review article centers on crustaceans and mollusks byproduct utilization for chitosan, its nano-formation, and their food industry applications. The extensive discussion has been focused on nanochitosan formation, characterization, and active site modification. Lastly, nanochitosan applications in various food industries, including biodegradable food packaging, fat replacer, bioactive compound carrier, and antimicrobial agent have been reported.

Effects of Dietary Supplementation with Chitosan on the Muscle Composition, Digestion, Lipid Metabolism, and Stress Resistance of Juvenile Tilapia (Oreochromis niloticus) Exposed to Cadmium-Induced Stress

The aim of this study was to investigate the effects of dietary chitosan supplementation on the muscle composition, digestion, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia (Oreochromis niloticus) subjected to cadmium (Cd2+) stress. Juvenile tilapia with an initial body weight of 21.21 ± 0.24 g were fed with a formulated feed containing five different levels (0%, 0.5%, 1.0%, 1.5%, and 2.0%) of chitosan for 60 days, while the water in all experimental groups contained a Cd2+ concentration of 0.2 mg/L. The results showed that, compared with the control group (0% chitosan), the contents of crude fat and crude protein in the muscle, the activities of lipase, trypsin, and amylase in the intestine, as well as the relative expression levels of metallothionein (mt), cytochrome P450 1A (cyp1a), carnitine palmitoyltransferase-1 (cpt-1), peroxisome proliferator-activated receptor alpha (pparα), peroxisome proliferator-activated receptor gamma (pparγ), hormone-sensitive lipase (hsl), lipoprotein lipase (lpl), malate dehydrogenase (mdh), leptin (lep), fatty acid synthase (fas), sterol regulatory element-binding protein 1 (srebp1), and stearoyl-CoA desaturase (scd) genes in the liver of juveniles were significantly increased (p < 0.05). In conclusion, dietary chitosan supplementation could alleviate the effects of Cd2+ stress on the muscle composition, digestive enzymes, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia, and to some extent reduce the toxic effect of Cd2+ stress on tilapia.