An extracellular alkaline protease producing strain was isolated from the sediment sample collected from a mangrove station in Cochin estuary and was identified as Vibrio fluvialis. The protease produced was purified to apparent homogeneity by ammonium sulphate precipitation and was determined to be a 33.5-kDa protease as shown by SDS-PAGE and its activity detected by casein zymography. This protease had optimum activity at pH 8 and temperature 55 degrees C. This was stable at alkaline pH range and up to a temperature of 50 degrees C, after incubation for 1 h. Hg2+ and Cu2+ showed complete inhibition of the enzyme activity, while Co2+, Ca2+ and Fe3+ were enhancing the activity. This protease was inhibited by the serine protease inhibitor PMSF and the metal chelator EDTA but not by the classic metalloprotease inhibitor 1,10 phenanthroline. The protease was found to be stable in presence of compounds like H2O2, SDS, and Triton-X-100 and also in some commonly used commercial detergents tested. The extracellular production of the enzyme, the pH and thermal stability, and the stability in presence of oxidants, surfactants and commercial detergents, suggest its possible use as a laundry additive. (c) 2006 Elsevier Ltd. All rights reserved.