Preparation of chitooligosaccharides from cicada slough and their antibacterial activity.

In this study, chitooligosaccharides were prepared from cicada slough of Cryptotympana atrata Fabricius by hydrolysis using hydrogen peroxide (H2O2). Factors affecting the hydrolysis of chitosan were investigated and the optimum hydrolysis conditions were as follows: time, 4 h; temperature, 65 °C; amount of H2O2, 2% (v/v); and pH, 5. Under these conditions, the average degree of polymerisation decreased to ~4.5. The Fourier transform infrared spectra and product sugar composition indicate that there were no significant chemical changes in the backbones of the chitosan treated with H2O2.The chitooligosaccharides had high antibacterial activity against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli at the concentration of 100mg/mL.