Characterization of thermostable serine protease from Bacillus altitudinis strain BR1

Abstract

This study is carried out for partially purified and characterized thermostable serine protease from alkaliphilic estuarine bacterium Bacillus altitudinis strain BR1 from Goa, India. The extracellular protease was stable at 50 degrees C and alkaline pH 9-11. Protease activity was maximum at pH 9 and 50 degrees C confirming it to be a thermostable, alkaline protease. Interestingly this bacterial strain possessed 5 distinct alkaline protease isozymes with approximate molecular mass of 17, 22, 43, 64 and 88 kDa which was clearly revealed by Zymogram. These isozymes are possibly encoded by five different genes. Phenyl methyl sulfonyl fluoride (PMSF) significantly inhibited protease suggesting it to be a serine protease. Interestingly protease production remained unaltered in presence of EDTA-Na2 and b-mercaptoethanol. Significant morphological change as cell size reduction and transformation of rod shaped cells to oval cells at 50 degrees C without any adverse effect on protease activity may prove a protective mechanism to temperature stress. These results clearly demonstrated stability and activity of these serine protease isozymes at high temperature and alkalinity which is advantageous for various industrial applications.