Characterization of Bacillus cereus BM1 with Protease Activity

Abstract

Microbial alkaline proteases dominate the world enzyme market, accounting for nearly two-thirds shares of the detergent industry. To date, Bacillus species have been known to produce a substantial amount of extracellular proteases which gain application in commercial industry. A protease producing bacterium was isolated from the eye of sea bass, for the first time, in an attempt to search for microbial biocatalyst that is detergent compatible. The isolate was characterized based on 16S rRNA gene sequence homology and Biolog Gen III microplate system. The results for identification indicate that the isolate has 97% sequence identity to Bacillus cereus with regard to 16S rRNA gene sequence homology which ultimately tally with the result of Biolog system, and hence designated as Bacillus cereus BM1. Moreover, protease produced by the isolate BM1 was assayed according to an established method. Subsequently the protease was partially characterized on the basis of temperature and pH requirements. Further characterization evaluated the effects of different metal ions (5mM), EDTA (5mM), NaCl (Up to 15%w/v) and commercial detergent (up to 10%w/v) on protease activity and/or stability. The results indicate that the Bacillus cereus BM1 produced a protease that is stable in alkaline pH range of 8-12, with optimum at pH 8 when incubated at 60^oC for 1 hr. The protease was also stable at temperature ranges from 40-70^oC, with optimum at 60^oC when incubated for 1 hr. It shows activity in the presence of EDTA, as metal chelator suggesting that it is not a metalloprotease. Furthermore, none of the metal ions tested enhances protease activity above 100% from the control. The protease was also found to be stable in the presence of NaCl and commercial detergent. The results of partial characterization of the enzyme indicate that it is an alkaline, thermostable, halotolerant and detergent compatible non metalloprotease. This suggests that it will find application in detergent industry.