STEPWISE ENHANCEMENT OF PRODUCTIVITY OF THERMOSTABLE AMYLASE IN BACILLUS LICHENIFORMIS BY A SERIES OF MUTATIONS1

Abstract

Methods for increasing the productivity of thermostable amylase of Bacillus licheniformis were investigated. Cells of B. licheniformis NYK 74 were treated with N-methyl-N′-nitro-N-nitrosoguanidine resulting in mutants which were resistant to D-cycloserine. These were selected first and among them amylase hyper producers were selected. By a series of the same treatments, except that the concentration of D-cycloserine was increased step by step, a strain was developed which produced 2, 000 times more amylase than the original one.