Optimization of alkaline protease production from a locally isolated Bacillus sp. ZR-5: Potential application as a detergent additive

Abstract

The aim of this study was to optimize protease production using a novel Bacillus sp. ZR-5 strain<br />isolated from the soil, and evaluate its application in detergent industry. The proteolytic activity<br />of the strain was demonstrated using gelatin hydrolysis screening test. Protease production<br />optimization was carried out using a two-step approach: a conventional method in order to<br />identify the best carbon and nitrogen sources followed by the application of response surface<br />methodology (RSM) to optimize the factors, which include temperature, pH and incubation<br />time. Glucose or fructose (5 g/L), wheat bran (5 g/L), temperatures of 25 and 55°C, pH 10.0 and<br />an approximate incubation time of 44 h, were determined as the optimal conditions according to<br />optimization processes. Validation tests were carried out under these conditions and the results<br />were in good agreement with RSM predicted data. The in-gel activity (zymogram) test showed<br />two hydrolytic zones with 66.2 and 36.5 kDa molecular weight on the casein containing<br />polyacrylamide gel. The high compatibility in the presence of detergent powder and washing<br />performance test suggested that the crude enzyme could be an appropriate choice as a detergent<br />additive in detergent industries.