Abstract: In order to reduce the content of starch in tobacco leaves and improve the usability of tobacco leaves,A high performance amylase-producing strain was isolated from tobacco leaf samples C3F from Malong which is in Yunnan province,China.It was identified as Bacillus koreensis by 16s RNA analysis.The culture medium of Bacillus koreensis was optimized by response surface methodology,remarkable elevated the expression of amylase.First,single parameter experiments show that the optimal carbon,nitrogen,metal ion, initial pH,temperature and inoculums size were starch,peptone,Ca²⁺ ,8.0,37 ℃,3% respectively.Then,a three factors-three levels experiment was carried out based on the Box-Behnken central composite design.The highest amylase activity was 959.39±22.34 U/mL in the validation experiment under the optimized conditions of 18.74 g/L soluble starch,21.56 g/L peptone,0.52 g/L CaCl2.The amylase activity of Bacillus koreensis was elevated 69.76% than before,which was similar to the predicted value of the model.This study was based on Bacillus koreensis from natural tobacco leaves,providing a basis for industrial application of improving tobacco quality.

Key words: Bacillus koreensis, amylase, medium culture optimization, response surface methodology, tobacco