Study on mutation breeding of Bacillus amyloliquefaciens producing milk- clotting enzyme

To obtain an industrial strain with high milk- clotting activity,Bacillus amyloliquefaciens producing milkclotting enzyme was mutagenized with ultraviolet and diethyl sulfate. On the basis of multiple mutation,mutant DES-6 was screened.The milk- clotting activity of L-6 reached 1419.7 SU / m L,which was 40.2% higher than that of the parent strain,while the proteolytic activity was reduced by 22.39%. The ratio of milk- clotting activity to proteolytic activity reached 125.64,which was 81.32% higher than that of the parent strain.The pass- generation test indicated that DES-6 had good genetic stability.