Antimicrobial activity of chitosan against vibrios from freshwater prawn Macrobrachium rosenbergii larval rearing systems

Effects of bovine lactoferrin and chitosan nanoparticles on serum biochemical indices, antioxidative enzymes, transcriptomic responses, and resistance of Nile tilapia against Aeromonas hydrophila

The present study was carried out to investigate the effects of dietary bovine lactoferrin (BLF) or chitosan nanoparticles (CHN) alone or in combinations on serum biochemical indices, antioxidative capacity, transcriptomic responses, non-specific immunity, and resistance of Nile tilapia (Oreochromis niloticus) against challenge with Aeromonas hydrophila. Fish were fed on the basal diet with no supplements and served as control (CTR), and six other experimental diets containing different levels of BLF (800 and 1200 mg per kg diet), CHN (500 and 1000 mg per kg diet), and their combinations (400 mg BLF plus 250 mg CHN per kg diet, and 600 mg BLF plus 500 mg CHN per kg diet) for 45 days. At the end of the experiment, serum, and tissue specimens (liver and kidney) were collected, fish in all groups were challenged with A. hydrophila and then observed for another ten days to calculate the RPS. Compared to the CTR group, no significant differences were recorded in TP, ALB, GLO, BUN, and CREAT values among all treatments. Serum LYZ, ALT, AST, and ALP enzyme activities were significantly increased in all experimental groups over the CTR (P < 0.05), and their highest values were recorded in the combined treatments. Moreover, dietary supplementation with CHN (1000 mg/kg) and combined treatments significantly increased the SOD, CAT, and GSH-Px enzyme activities compared to other groups (P < 0.05). The highest mRNA expression levels of IGF-1 gene in liver, and IL-1β, and IFN-γ genes in kidneys were found in CHN (1000 mg/kg) group and combined treatments more than other groups. Interestingly, no, or mild histopathological alterations were noticed in the hepatopancreas and posterior kidney of the treated groups. A significantly higher RPS was identified in the combined treatments challenged with A. hydrophila compared with the CTR group. This study exemplifies the positive impacts of dietary supplementation with BLF or CHN alone or combinations on the antioxidative status, immunity, and disease resistance of Nile tilapia.

Immunostimulatory effect of dietary chitosan nanoparticles on the performance of Nile tilapia, Oreochromis niloticus (L.)

Feed supplements to fish are generally used to overcome any expected diseases and stressors and to sustain eco-friendly fish farming. One of these feed supplements is chitosan, which stimulated growth and immune properties for many aquatic organisms. It is expected that the nano-sized materials may have stronger immune activation in fish than the ordinary size. Therefore, the current study was conducted to evaluate the effect of dietary chitosan nanoparticles (CNP) on growth performance, antioxidant activity, and innate immunity of Nile tilapia, Oreochromis niloticus (L.). Fish (19.8 ± 0.59 g) were fed on diets enriched with 0.0, 0.25, 0.5, 1.0, and 2.0 g CNP/kg diet for 45 days. Fish performance was significantly improved with increasing CNP levels over the control diet with optimum level of 1.0 g CNP/kg diet. Antioxidant-stimulated activity was observed due to dietary CNP supplementation over the control diet in a dose-dependent manner. However, malondialdehyde level decreased significantly, whereas activities of catalase, superoxide dismutase, lysozyme, and respiratory burst increased significantly due to CNP supplementation in a dose-dependent manner. The current study evoked that dietary CNP showed strong immune modulatory properties and enhanced significantly the performance and health of Nile tilapia with optimum level of 1.0 g CNP/kg diet.

Application of marine-derived polysaccharides as immunostimulants in aquaculture: A review of current knowledge and further perspectives

The use of antibiotics in the feeds of cultivable aquatic animals has been generally practised to reduce infectious diseases as well as to improve the survival and growth. In recent years, many countries ban to aquatic animals due to the use of large amount of antibiotics and chemotherapies, thus alternative novel strategies are need to promote the growth of aquatic animals and control the pathogens. Dietary supplementation of marine-derived polysaccharides (MDPs) is one of the potential substitutes for antibiotics in aquatic animal feeds. Recently, the use of dietary MDPs in the aquaculture animals has been focused with much interest. In aquaculture, MDPs are used as prebiotic substance which is mostly accepted as a nutritional component for improving the growth performance and health conditions. Hence, present review is a comprehensive and an updated collection of available research reports on different MDPs (alginate, fucoidan, carrageenan, laminarin, ulvan, galactan, agar, chitin and chitosan), route of administration, dosage and applications for improving aqua feeds with emphasis on its effects on growth, biochemical indices, immune response, gut microbiota and disease resistance of aquaculture animals. This review describes the sustainability of global aquaculture production by providing a best alternative to harmful antibiotics, thereby meeting the emerging consumer demand for antibiotic-free aquatic food products.

Crosslinked chitosan films with controllable properties for commercial applications

In this research, sustainable and green bioproducts with controlled sorption and good mechanical properties have been developed from chitosan for commercial applications. Addition of citric acid, a biocompatible crosslinker, and later treating with alkali imparts excellent tensile strength and aqueous stability to the chitosan films. Films were developed from chitosan and studied for their sorption capabilities, mechanical properties, oxygen/water vapour transmission rates and antimicrobial abilities. Moisture sorption of up to 1466% based on the dry weight of chitosan was seen when the films were untreated. However, treating the films with alkali decreased their water sorption to 100-250% and made the films resistant even to boiling water. Modified chitosan could be moulded into various forms and made into bioproducts that could replace plastic based materials. The chitosan bioproducts developed have the potential to replace plastic based products and will help to provide a greener alternative for the plastic based commodity products in current use.

Assessment of the immune-modulatory and antimicrobial effects of dietary chitosan on Nile tilapia (Oreochrmis niloticus) with special emphasis to its bio-remediating impacts

Fish, pathogen and environment are three counterparts who are sharing the same circle of life. To keep fish up to their optimal health, environment should be competently improved and pathogen count/virulence should be seized. Using of bioactive immunostimulants to achieve these objectives is the hypothesis under assessment. Thus, the present study was performed to evaluate the use of shrimp shells derived chitosan as an immunostimulant as well as preventive regime against Aeromonas hydrophila infection of Nile tilapia and to assess its antibacterial/aquatic bio-remediating effects. Results achieved by feeding 1% chitosan as preventive/therapeutic regimes have revealed a remarkably enhanced several innate immunological parameters (e.g., Phagocytic activity/index, NBT, Lysozyme activity and ACH50), increased resistance against A. hydrophila and strikingly improved water quality compared to the 0.5 and 2% chitosan containing diets. Conclusively, experimental results suggest the commercial usage of chitosan as an efficient immunostimulant and bio-remediating agent in aquaculture.

Antibacterial action of a novel functionalized chitosan-arginine against Gram-negative bacteria

The antimicrobial activity of chitosan and chitosan derivatives has been well established. However, although several mechanisms have been proposed, the exact mode of action is still unclear. Here we report on the investigation of antibacterial activity and the antibacterial mode of action of a novel water-soluble chitosan derivative, arginine-functionalized chitosan, on the Gram-negative bacteria Pseudomonas fluorescens and Escherichia coli. Two different arginine-functionalized chitosans (6% arginine-substituted and 30% arginine-substituted) each strongly inhibited P. fluorescens and E. coli growth. Time-dependent killing efficacy experiments showed that 5000 mg l(-1) of 6%- and 30%-substituted chitosan-arginine killed 2.7 logs and 4.5 logs of P. fluorescens, and 4.8 logs and 4.6 logs of E. coli in 4h, respectively. At low concentrations, the 6%-substituted chitosan-arginine was more effective in inhibiting cell growth even though the 30%-substituted chitosan-arginine appeared to be more effective in permeabilizing the cell membranes of both P. fluorescens and E. coli. Studies using fluorescent probes, 1-N-phenyl-naphthylamine (NPN), nile red (NR) and propidium iodide (PI), and field emission scanning electron microscopy (FESEM) suggest that chitosan-arginine's antibacterial activity is, at least in part, due to its interaction with the cell membrane, in which it increases membrane permeability.