Cold-active extracellular alkaline protease from an alkaliphilic Stenotrophomonas maltophilia: production of enzyme and its industrial applications.

A novel psychro-tolerant bacterium Stenotrophomonas maltophilia (MTCC 7528) with an ability to produce extracellular, cold-active, alkaline, and detergent-stable protease was isolated from soil samples obtained from Gangotri glacier, Western Himalaya, India. The culture conditions for higher protease production were optimized with respect to incubation time, agitation, substrate, pH, and temperature. Maximum protease production of 56.2 U x mL(-1) was achieved in the medium at 20 degrees C and pH 9.0 after 120 h incubation. The protease was partially purified by ion-exchange chromatography and approximately 55-fold purification was achieved. The purified enzyme was a 75 kDa protease with maximum activity and stability at pH 10 and 20 degrees C. The activity of enzyme is stimulated by Mn2+ and inhibited completely by metalloprotease inhibitors, indicating that it is a metalloprotease. The protease showed excellent stability and compatibility with commercial detergents and exhibited high efficiency for the removal of different types of protein-containing stains at low temperature. The wash performance analysis of blood and grass stains on cotton fabric showed an increase in reflectance by 26% and 23%, respectively, after treatment with enzyme in comparison to detergent only. These results indicate that it may be a potential component to use as a detergent additive for cold washing and in environmental bioremediation in cold regions.