Biosafety and Fermentation Optimization of Acinetobacter sp. WML1 for Chitinase Production
1. Hunan Provincial Key Laboratory for Health Aquaculture and Product Processing in Dongting Lake Area, Changde Research Center for Agricultural Biomacromolecule, College of Life and Environmental Sciences, Hunan University of Arts and Science, Changde 415000, Hunan, China; 2. School of Life Sciences, Central South University, Changsha 410013, Hunan, China
Abstract：Acinetobacter sp. WML1 was isolated from the fishery sediments of freshwater lakes and proved to have application value due to its ability to degrade chitin. Herein, the biosafety of the chitinase-producing strain WML1 was first evaluated for application. The drug resistance of the strain was detected with the disk diffusion method, haemolytic activity was analyzed by streaking the blood agar plate, amino acid decarboxy-lase and nitrate reductase activities were measured by the chromogenic assay with bromocresol purple and nitrate reductase activity assay kit, respectively. On the basis of biosafety analysis, the fermentation condi-tions of the strain were then optimized by single-factor and orthogonal tests for chitinase production. The re-sults showed that the strain WML1 was sensitive to most antibiotics, and had no haemolytic activity or ni-trate reductase activity, had arginine decarboxylase activity and weak lysine and ornithine decarboxylase ac-tivities. The optimal enzyme production conditions of strain WML1 were as follows: 25 mL medium containing 0.4% soybean powder, 0.20% galactose, 0.03% KH2PO4, 0.07% K2HPO4, 0.002% FeSO4, 0.05% MgSO4·7H2O, 0.001% ZnSO4, 0.60% colloidal chitin in a 250 mL flask, with the initial pH of 9.5, 5.0% inoculum size and culture temperature of 37 ℃. Under the optimized conditions, the chitinase activity reached (2.72±0.09) U/mL. In conclusion, Acinetobacter sp. WML1 is generally safe in application, with only low toxicity that is preven-table and controllable, and the enzyme activity could be about 4.61 times higher than that before optimiza-tion. The study provides a theoretical foundation for the industrial application of chitinase-producing bacteria.
