RESUMO
Among 97 fungal strains isolated from soil collected in the arctic tundra (Spitsbergen), Penicillium chrysogenum 9' was found to be the best lipase producer. The maximum lipase activity was 68 units mL(-1) culture medium on the fifth day of incubation at pH 6.0 and 20 degrees C. Therefore, P. chrysogenum 9' was classified as a psychrotrophic microorganism. The non-specific extracellular lipase showed a maximum activity at 30 degrees C and pH 5.0 for natural oils or at pH 7.0 for synthetic substrates. Tributyrin was found to be the best substrate for lipase, among those tested. The Km and Vmax were calculated to be 2.33 mM and 22.1 units mL(-1), respectively, with tributyrin as substrate. The enzyme was inhibited more by EDTA than by phenylmethylsulfonyl fluoride and was reactivated by Ca2+. The P. chrysogenum 9' lipase was very stable in the presence of hexane and 1,4-dioxane at a concentration of 50%, whereas it was unstable in presence of xylene.
Assuntos
Microbiologia Industrial , Lipase/metabolismo , Penicillium chrysogenum/enzimologia , Regiões Árticas , Detergentes , Inibidores Enzimáticos/farmacologia , Concentração de Íons de Hidrogênio , Cinética , Lipase/antagonistas & inibidores , Lipase/isolamento & purificação , Metais/metabolismo , Microbiologia do Solo , Solventes , Especificidade por Substrato , TemperaturaRESUMO
Growth and production of lipase by a new Geotrichum-like strain, R59, were studied. Production of extracellular lipase was substantially enhanced when the initial pH of the culture medium, types of carbon and nitrogen sources, substances probably stimulating the lipase biosynthesis, the temperature, and time of growth were optimized. Sucrose and triolein were the most effective carbon sources for lipase production. Maximum lipase activity (146 U/ml(-1)) was obtained with urea as the nitrogen source. Growth at 30 degrees C, an initial pH of 6.0 and incubation time of 48 h were found as optimum conditions for cell growth and production of lipase by Geotrichum-like strain R59. The enzyme was thermostable and exhibited very high activity after 1 h incubation at 60 degrees C.