An oxidant, detergent and salt stable alkaline protease from Bacillus cereus SIU1

Abstract

A novel soil bacterium, Bacillus cereus SIU1 was earlier isolated from non-saline, slightly alkaline soil of Eastern Uttar Pradesh, India. The isolate B. cereus SIU1 was grown in modified glucose yeast extract (modified GYE) medium at pH 9.0 and 45°C. It produced maximum protease at 20 h incubation. The enzyme was stable at pH 9.0 and 55°C. It was fully stable at 0.0 to 3.0% and moderately stable at 4.0 to 10.0% (w/v) NaCl concentrations. Whereas PMSF, EDTA and ascorbic acid were inhibitory, cysteine and β-mercaptoethanol enhanced protease activity. Calcium, magnesium, manganese and copper at 1 mM concentration increased the enzyme activity. Hydrogen peroxide, sodium perborate, sodium lauryl sulphate, Triton X100 and Tween 80 significantly increased the activity, while protease remained fairly stable (52 to 98%) at 0.1 and 1.0% concentrations of commercial detergents. The halotolerant thermoalkaline protease of B. cereus SIU1 was highly active and stable in the presence of several modulators, oxidants and detergents, revealing its possible use in several commercial and biological applications.

Key words: Bacillus cereus SIU1, thermoalkaline protease, PMSF, EDTA, Hydrogen peroxide, Triton X100, Tween 80.