Depolymerization of chitosan by enzymes from the digestive tract of sea cucumber Stichopus japonicus

Abstract

A complex of enzymes was isolated in a preparation derived from the digestive tract of sea cucumber, Stichopus japonicus. Hydrolysis of chitosan using this enzyme preparation decreased its molecular weight (Mw), increased its water solubility and produced water-soluble chitosan (WSC). The conditions for hydrolysis were optimized to pH 6.0, temperature 45°C, 16 mg enzyme preparation (22.08 U of chitosanase activity) in a reaction solution (500 ml) containing 5 g chitosan and total reaction time of 3 h. The Mw of hydrolyzed chitosan was 1260 Da, and the WSC content in the resulting product and the yield were 96.7 and 95.4% (w/w), respectively. The structure of WSC was characterized using Fourier transform infrared (FTIR) spectroscopy.

Key words: Water-soluble chitosan, complex enzyme preparation, sea cucumber Stichopus japonicus, hydrolysis.