Factors contributing to the enhanced production of protease and lipase in Bacillus pumilus SG2 mutant

Abstract

A random mutagenesis on a wild strain Bacillus pumilus SG2 using physical and chemical agents was performed previously and a mutant Bacillus pumilus SGMM8 which produced comparatively higher levels of protease and lipase was isolated. This study was attempted to analyse the causes underlying the enhanced enzyme production by the mutant. Substrate uptake, repression/de-repression studies and determination of Km and Vmax were done to understand if de-repression and enhanced affinity to substrate are the plausible reasons for enhanced enzyme activity. It was observed that the protease production was not repressed at high glucose concentrations in the mutant. The Km and Vmax of SG2 lipase were 2.265 mg/ml and 158 U/ml respectively and those of SGMM8 lipase were 1.619 mg/ml and 159 U/ml respectively and thus enhanced affinity may be the underlying cause for enhanced lipase activity. The genome sequence of the mutant enzymes were analysed and transversion mutations were identified in the coding regions. The mutations in the signal peptide of the protease and near the active site of the lipase may have caused increased enzyme production/activity.