The bacteria that could grow on media containing olive mill wastewater (OMW) were isolated and their lipase production capacities were investigated. The strain possessing the highest lipase activity among 17 strains grown on tributyrin agar medium was identified as Bacillus sp. The effect of initial pH on the lipase activity was investigated in tributyrin medium and pH 6 was found to be the optimal. The liquid medium composition was improved by replacing tributyrin with various carbon sources. Among the media containing different compositions of triolein, trimyristim, trilaurin, tricaprin, tricaprylin, tributyrin, triacetin, Tween 80, OMW, glucose, and whey; the medium contained 20% whey +1% triolein was found to give the highest lipase activity. Cultivation of Bacillus sp. in the optimal medium at pH 6 and 30 degrees C for 64 h resulted in the extracellular and intracellular lipase activities of 15 and 168 U/ml, respectively. (c) 2007 Elsevier B.V. All rights reserved.