Antibacterial Activity against Escherichia coli and Cytotoxicity of Maillard Reaction Product of Chitosan and Glucosamine Prepared by Gamma Co-60 Ray Irradiation.

In this study, the gamma ray-induced Maillard reaction method was carried out for chitosan (CTS) and glucosamine (GA) to improve the water solubility and antibacterial activity. The mixture solution of CTS and GA was exposed to gamma rays at a dose of 25 kGy and freeze-dried to obtain a Maillard reaction product (MRP) powder. The physicochemical and biological properties of the CTS-GA MRP powder were investigated. The CTS-GA MRP powder expressed good solubility at a concentration of 0.05 g/mL. In addition, the result of the antibacterial activity test against Escherichia coli revealed that the CTS-GA MRP powder exhibited highly antibacterial activity at pH 7; in particular, bacterial density was reduced by over 4 logs. Furthermore, the cytotoxicity test of the CTS-GA MRP powder on mouse fibroblast cells (L929) showed non-cytotoxicity with high cell viability (>90%) at concentrations of 0.1-1 mg/mL. Owing to the high antibacterial activity and low cytotoxicity, the water-soluble CTS-GA MRP powder can be used as a favorable natural preservative for food and cosmetics.

Effect of oligochitosan and oligo-ß-glucan supplementation on growth, innate immunity, and disease resistance of striped catfish (Pangasianodon hypophthalmus).

Oligochitosan (COS) and oligo-ß-glucan (ßOG) were prepared by gamma Co-60 irradiation of chitosan/H2 O2 and ß-glucan/H2 O2 solutions. The striped catfish (Pangasianodon hypophthalmus) was fed diets containing 0-200 mg COS, ßOG, and a mixture of COS/ßOG per kg feed for 45 days, and then challenged with Edwardsiella ictaluri bacterium. The effects of supplemented COS, ßOG, and a mixture of COS/ßOG on immune stimulation and growth performance in striped catfish were investigated. The results indicated that when striped catfish fed with 100-200 mg COS or ßOG/kg feed the growth performance was significantly improved and the mortality was considerably decreased. Furthermore, striped catfish fed with supplementation of 50 mg COS + 50 mg ßOG/kg feed was the best for increasing weight gain (∼26%) and for decreasing mortality (∼38%) compared with the control group. Moreover, phagocytic activity and lysozyme activity of fish were enhanced by feeding diet-supplemented COS and/or ßOG. Thus, COS and/or ßOG can be potentially utilized as the immunostimulants and growth promoters for aquaculture.