Abstract

We partially purified extracellular metalloprotease of a halotolerant alkaliphilic bacterium isolated from coastal sediment of Goa, India, which was identified asBacillus cereus strain CS1 based on biochemical characteristics and 16S rDNA sequence. Zymogram of partially purified enzyme clearly revealed two prominent protease isozymes of 210 and 215 kDa. Although, protease showed activity over a wide range of pH (pH 8 to 12) and temperature (30, 37, 45 and 50°C), optimum pH and temperature were 9 and 37°C, respectively. Protease exhibited extreme halotolerance upto 8% NaCl making it one of the industrially valuable enzyme. Among different carbon sources, glucose (1%) enhanced maximum enzyme activity (71U/ml), whereas, among the nitrogen sources, tryptone (0.2%) proved best to enhance enzyme activity (158U/ml). Ca⁺⁺ ions enhanced protease activity by 7%, whereas, Cu⁺⁺, Mg⁺⁺, Pb⁺⁺ and Hg⁺⁺ ions inhibited activity by 91, 79, 87 and 77%, respectively. Among inhibitors tested, protease activity was significantly inhibited by Na₂–EDTA as residual enzyme activity was only 21%, which clearly confirmed it to be a metalloprotease. The partially purified protease mixed separately with two detergents Rin and Wheel clearly demonstrated significant stain removing capability. Thus, protease produced by Bacillus is a potential candidate as an additive in detergent industry.

Key words: Halo-tolerant, isozymes, zymogram, metalloprotease.

Abbreviation

 Na₂ –EDTA, Disodium ethylene diamine tetra acetic acid; PMSF,phenyl methyl sulphonyl fluoride; DTT, dithiothreitol; SDS, sodium dodecyl sulphate;kDa, kilodalton.