Thermostable alkaline protease from Bacillus brevis and its characterization as a laundry detergent additive

An alkaline protease from a facultatively thermophilic and alkalophilic str ain of Bacillus brevis has been studied. The enzyme from a shake flask cult ure displayed maximum activity at pH 10.5 and 37 degrees C. The extracellul ar production of the enzyme, its thermostable nature and compatibility with most commercial detergents are features which suggest its application in d etergent industry. The organism utilized several carbon sources for the pro duction of proteases, lactose was the best substrate followed by glucose an d sucrose. Among the various organic nitrogen sources, soyabean meal was fo und to be the best. The protease was stable at 25 degrees C for 288 h where as, at 50 and 60 degrees C, the half lives were 60 and 7 h, respectively. T he thermostability of the protease was enhanced by modifying its microenvir onment. Acetate salts of Ca2+ and Na+ increased thermostability and protect ed against autolysis. Addition of Ca2+ (10 mM) and glycine (1 M) individual ly and in combination was found to be effective in increasing the half life of protease by many folds. The enzyme retained more than 50% activity afte r 4 days at 60 degrees C in the presence of both Ca2+ (10 mM) and glycine ( 1 M). The enzyme showed compatibility at 60 degrees C with commercial deter gents such as Aerial Microshine(R), Surf excel(R), Surf Ultra(R) and Rin(R) in the presence of Ca2+ and glycine. This enzyme improved the cleaning pow er of various detergents. It could remove blood stains completely when used with detergents in the presence of Ca2+ and glycine. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.