Construction of the highly secreted endochitinase Pichia pastoris strain and the optimization of chitin-degrading conditions

The endochitinase has a very important application in the preparation of bioactive chitooligosaccharides by chitin degradation. In this paper, the mature endochitinase cDNA from Trichoderma sp. was overexpressed in Pichia pastoris GS115 in order to enhance its activity. The screened recombinant strain could secrete the endochitinase into the culture broth highly on induction with methanol of 0.5%. The activity of the endochitinase was up to 89.3 U/mL, corresponding to its concentration of 365 mg/L, at 72 h after induction. The optimal chitin-degrading conditions with it were as follows: powder chitin concentration 4%, pH 7.0 and temperature 30 °C. Under above conditions, the content of the reducing sugar obtained was up to 398.4 μg/mL at 10 h. These results indicated that the expressed endochitinase exhibited an exceptionally excellent chitin-degrading ability, and could be used for the preparation of bioactive chitooligosaccharides in future.