Preparation and Characterization of Chitinase from Marine Bacteria Aeromonas sp. YS-54

To achieve efficient degradation of crustacean raw materials and eco-preparation of N-acetyl-oligosaccharides, YS-54 strain screened from offshore soil in Qingdao was used for chitinase preparation in the present study. Chitinase was prepared through 60% ammonium sulfate precipitation and Sephadex G-100 gel filtration chromatography. Enzymatic properties such as optimal temperature, optimal pH, and substrate specificity were characterized. Mass spectrometry was used to determine the polymerization degree of enzymatic products. The 16S rRNA identification result showed that YS-54 strain belonged to the Aeromonas species. Chitinase from Aeromonas sp. YS-54 showed a specific activity of 23.44 U/mg. The molecular weights of chitinase were 63 and 75 kDa as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Chitinase was stable under the condition of 40 ℃ and pH5.0. The enzymatic activity was significantly activated by Ba²⁺, Co²⁺, Mg²⁺ and TritonX-100 (P<0.05), while inhibited by Fe³⁺, Cu²⁺ and SDS. The specific activity of chitinase toward α-chitin was 7.99 U/mg, 34.09% of that toward colloidal chitin. The polymerization degree of enzymatic hydrolysis products from colloidal chitin and α-chitin were 1~4 and 1~3, respectively. Chitinase from Aeromonas sp. YS-54 was stable in broad range of temperature and pH, meanwhile showed high catalytic efficiency toward α-chitin. The hydrolysis characteristics of chitinase from Aeromonas sp. YS-54 would provide technical support for the comprehensive utilization of crustacean waste.