Preparation of chitooligosaccharides from Clanis bilineata larvae skin and their antibacterial activity

Clanis bilineata larvae are widely consumed in China. In this study, chitooligosaccharides were prepared from C. bilineata larvae skin by demineralisation, deproteination, washing, drying, deacetylation, hydrolysis using commercial α-amylase, filtration, setting the preparation at approximately 15% (w/v), precipitation with 6 volumes of ethanol, and drying at 60 °C for 2 h. The optimal hydrolysis conditions were determined as follows: pH 5.5; temperature, 55 °C; enzyme amount, 40 mg/(g chitosan); reaction time, 4 h. The Fourier transform infrared spectra revealed that chitooligosaccharides with a degree of polymerisation in the range of 2-8 were the main component of the resulting product, with the chitooligosaccharide content and yield being 95.8% and 96.2% (w/w), respectively. The resulting product showed high antibacterial activity compared with the original chitosan.