An extracellular alkaline serine protease was produced by Aspergillus parasiticus by solid state fermentation. The protease was purified and characterized. A 200-fold purified protease was obtained by acetone precipitation, ion exchange and gel filtration chromatography (FPLC). The molecular weight of the protease was 23 kDa as estimated by SDS-PAGE. This enzyme was stable over a wide range of pH (6-10) and temperature (4-40degreesC) and showed maximum activity at pH 8.0 and 40 degreesC. The enzyme remained active in the presence of oxidizing, reducing agents and also stable in various derergents. Several heavy metals such as Hg+2, Co+2 and Sn+2 had no effect on protease activity. According to the inhibition profiles obtained with the serine protease inhibitor, PMSF, it was confirmed that purified protease belongs to the serine protease family. (C) 2003 Elsevier Science Ltd. All rights reserved.