Discovery of a New Thermostable Chitinase from Streptomyces No. 6

Chitinases are a class of hydrolases that hydrolyze the β-1, 4-glycosidic bonds between N-acetyl-D-glucosamine (GlcNAc) in chitin. Among chitinases, thermophilic chitinases and thermostable chitinases have received extensive attention in recent years due to their ability to tolerate higher temperatures and maintain enzyme stability for a longer period of time. However, it has previously been observed that not all chitinases are thermostable and there are few studies about chitinases isolated from Streptomyces No. 6. Hence, the properties of the chitinase of Streptomyces No. 6 were investigated in this study. In this experiment, the enzyme activity was explored by a single-factor experiment, and the enzymatic properties were detected by a 3,5-Dinitrosalicylic acid (DNS) assay. At the same time, the fermentation conditions of Streptomyces No. 6 producing chitinase were optimized to improve the yield by a single-factor experiment and a response surface experiment. The results showed that the chitinase of Streptomyces No.6 can remain active at high temperatures (65°C). The optimal activity of the enzyme is obtained at a temperature of 65°C, a pH value of 5.0, and the substrate of colloidal chitin. Moreover, in this study, a Box-Behnken Design (BBD) was applied to increase the yield of chitinase. The optimization process showed that the enzyme activity reached 6.3756 U/mL at an inoculum size of 2%, fermentation time of 144 h, and pH of 5.5 (as optimum conditions). These results provided theoretical support for the production of chitinase for biotechnological and industrial applications.