Strain improvement by UV mutagenesis for protease overproduction from bacillus subtilis E6-5 and nutritional optimization

Abstract

The purpose of the present study was to enhance the protease production of the parental type Bacillus subtilis E6-5 by UV irradiation. The parental type was subjected to UV irradiation at different distances (5-15 cm) for different time intervals ( 1-120 min). After each treatment, total 400 mutants were obtained. The mutants were screened on skim milk agar plates for the selection of best proteolytic mutant. Among mutants, the mutant MET39, which obtained at 15 cm distance and irradiation time 5 min of exposure, was selected as best mutant produced 1.5 fold more enzyme over the parent strain. The effects of nutritional factors (various carbon, nitrogen sources and metal ions) on the protease production from MET39 mutant strain were studied. The best carbon source was found as glycerol. Among the inorganic nitrogen sources, the highest enzyme production was obtained in the presence of tryptone. The metal ions did not indicate significant effect on enzyme production. In order to enhance the yield, new modified medium was obtained by combining the best carbon and nitrogen sources. In this medium, enzyme yield was enhanced 88% compared to basal medium. MET39 mutant strain might have a great potential for protease production at industrial scale.