BACKGROUND: Purification and characterization of an intracellular lipase produced by Rhizopus chinenesis cultured in solid-state fermentation was investigated. The potential application in concentrating eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil by the pure enzyme was also studied. RESULTS: Through four successive purification steps, the enzyme was purified to homogeneity with an apparent molecular mass of 36 kDa. The lipase was active for pH between 7.0 and 9.0 and temperatures 20-45 degrees C. Lipase activity was slightly increased in the presence of Ca2+ and Mg2+, but strongly inhibited by Hg2+ and SDS. The pure enzyme was most active on medium chain p-nitrophenol esters, with the highest activity towards pNP-caprylate (C8). The enzyme is a non-specific lipase, because it cleaved not only the 1,3-positioned ester bonds but also the 2-positioned bond in triolein. High EPA (17.6%) and DHA (32.9%) contents were achieved using the pure lipase (100 U) within 10 h. CONCLUSION: The enzymatic activity of the lipase on a wide variety of substrates and its stability in the presence of some organic solvents suggest that the lipase should be investigated for a range of commercial applications. The pure lipase was proved to possess potential ability for the production and concentration of EPA and DHA from fish oil. (C) 2008 Society of Chemical Industry