Partial characterization of a crude cold-active lipase from Rhodococcus cercidiphylli BZ22

Cold-active lipase production by the psychrophilic strain Rhodococcus cercidiphylli BZ22 isolated from hydrocarbon-contaminated alpine soil was investigated. Depending on the medium composition, high cell densities were observed at a temperature range of 1-10 A degrees C in Luria-Bertani (LB) broth or 1-30 A degrees C in Reasoner's 2A (R2A). Maximum enzyme production was achieved at a cultivation temperature of 1-10 A degrees C in LB medium. About 70-80 % of the secreted enzyme was bound to the cell and was highly active as a cell-immobilized lipase which exhibited good reusability; more than 60 % of the initial lipase activity was retained after five-fold reuse. The properties of the lipase produced by the investigated strain were compared with those of a mesophilic porcine pancreatic lipase (PPL). The thermal stability of the cell-immobilized bacterial lipase was higher than that of the extracellular enzyme. Highest activity was detected at 30 A degrees C for the cell-immobilized enzyme and for PPL, while the extracellular enzyme displayed highest activity at 10-20 A degrees C. The bacterial lipase hydrolyzed p-nitrophenyl (p-NP) esters with different acyl chain lengths (C-2-C-18). The highest hydrolytic activity was obtained with p-NP-butyrate (C-4) as substrate, while the highest substrate affinity was obtained with p-NP-dodecanoate (C-12) as substrate, indicating a clear preference of the enzyme for medium acyl chain lengths.