A novel surfactant- and oxidation-stable alkaline protease from Vibrio metschnikovii DL 33-51 was purified using acetone precipitation, Q-sepharose ion exchange and Sephacryl S-100 gel filtration chromatographic techniques. The enzyme had a relative molecular weight of 29.5 kDa by SDS polyacrylamide gel electrophoresis. The optimal temperature and pH were found to be 60 degrees C and 12.0, respectively. The protease was stable in a pH range of 9.0-11.0. The half-lives of protease recorded at 50 and 60 degrees C were 7.5 h and 30 min, respectively. The enzyme activity could be strongly activated by several commercially available laboratory surfactants (Triton X-100, Tween-80) and bleaches (H2O2, sodium hypochlorite), and showed a valuable stability towards them when their concentrations ranged up to 1.0%. Enzyme activity was increased up to 19 and 18% by Mn2+ and Ba2+, respectively. (c) 2004 Elsevier Ltd. All rights reserved.