Abstract: In order to obtain a novel and clean preparation process for food-grade oligo-chitosan without monosaccharide, an endo-chitosanase (eCSN) that can degrade chitosan was purified from fermentation broth of Aspergillus JXSD-01 and its properties were also explored. The specific activity of the eCSN was above 50 U/mg, and its molecular mass was approximately 25 kD. The optimal reaction temperature and pH of the enzyme were 63 ℃ and 6.5, respectively. The sequence of N-terminal in the enzyme was YNLPNNLKQ. The eCSN could used for the degradation of chitosan as a natural large molecule to produce oligosaccharides with molecular weights in the range of 1000－3500 D. The obtained oligosaccharides did not contain monosaccharides and could reach the international quality standard for food-grade oligo-chitosan.

Key words: fermentation broth of Aspergillus, endo-chitosanase (eCSN), chitosan, oligo-chitosan