| This paper studied the process of degrading chitosan,the anti-bacterial property of chitosan oligosaccharide and the edible film prepared from chitosan oligosaccharide.Firstly,the chitosan was degraded by ultrasonic treatment.On the basis of single factor experiment,the optimum conditions: chlorhydric acid mass fraction of 2%,ultrasonic time of 2 h,ultrasonic frequency of 450 kHz and the reaction temperature of 45℃ were obtained by orthogonal experiment.The degradation of chitosan average molecular weight is 4370 at the optimal conditions.The order of main factors effecting chitosan degradation was ultrasonic time,ultrasonic frequency and ultrasonic reaction temperature.By the analysis of variance,ultrasonic time extremely remarkable influenced on the degradation of chitosan,and hydrochloric acid concentration and ultrasonic frequency remarkable influenced on the degradation of chitosan.The inhibitory action and the antibacterial mechanism of chitosan oligosaccharide were researched.For fungus Aspergillus niger,antibacterial ability decreased along with the increase of molecular weight of chitosan,antibacterial ability increased along with the increase of the concentration of chitosan,and antibacterial ability decreased along with the increase of pH and the antibacterial ability attained the maximum when pH value was 6.0.Meanwhile,the inhibitory ability disappeared when molecular weight was large and concentration was strong.For Saccharomyces cerevisiae,antibacterial ability increased along with the decrease of molecular weight of chitosan and the increase of concentration.For Penicillium notatum and Candida albicans,the inhibitory ability increased along with the the decrease of molecular weight of chitosan and the increase of concentration.The inhibitory action of chitosan oligosaccharide with the molecular weight of 4370 against Saccharomyces cerevisiae was stronger than Penicillium notatum,that of Penicillium notatum was stronger than Aspergillus niger,and that of Aspergillus niger was stronger than Candida albicans.For chitosan oligosaccharide with the molecular weight of 1000,the inhibitory ability declined after Aspergillus niger and Saccharomyces cerevisiae were cultivated for 72 h,and the inhibitory ability against Penicillium notatum and Candida albicans were not declined.Chitosan oligosaccharide with low molecular weight inhibited the growth of fungus by hindering the DNA duplication in cell.The edible film was prepared from chitosan oligosaccharide.The optimal composition of carboxymethyl cellulose 2 g,chitosan concentration 0.5 g,glycerol 1 ml and stearic acid 0.2 g was obtained by the single factor experiment and orthogonal experiment.Among the factors,carboxymethyl cellulose,chitosan and glycerol were the main influence factors,and stearic acid was the secondary influence factors. |
