Characterization and stability of proteases from Penicillium sp produced by solid-state fermentation

Investigations were carried out to characterize the protease produced by a wild strain of Penicillium sp. in solid-state fermentation (SSF). Defatted soybean cake was used as carbon and nitrogen source and solid matrix for SSF. The enzyme was produced at 28 degreesC using defatted soybean cake supplemented with 0.2 mol/l citrate-phosphate buffer and with an initial pH and substrate moisture of 5.0 and 55% (w/w), respectively. Optimum temperature for enzyme activity in the crude extract was 45 degreesC at a slightly acidic pH (6.5). The studies on pH stability showed that the enzyme was stable in a range of pH 6.0-9.0 and the effect of the inhibitors showed it to be possibly a serine protease. Stability studies revealed temperatures around 35-45 degreesC. The activity was reduced in the presence of Co2+, Mg2+ and Zn2+ ions, while the presence of Ca2+ and Na+ resulted in a discreet increase in proteolytic activity. The enzyme presented good stability towards oxidizing agent. The crude enzyme preparation was compatible with commercial detergents, retaining their 50-60% activities. The results demonstrated the importance of solid-state fermentation for the production of protease using defatted soybean cake as substrate, which offer significance benefit due to cheaper cost and abundant availability. (C) 2002 Elsevier Science Inc. All rights reserved.