An alkaline lipase from organic solvent tolerant Acinetobacter sp. EH28: Application for ethyl caprylate synthesis

A mesophilic bacterium producing a thermostable alkaline lipase was isolated from oil rich soil sample and identified as Acinetobacter sp. EH28. The lipase was partially purified by ammonium sulphate precipitation followed by hydrophobic interaction chromatography with 24.2-fold purification and 57.1 U/ml specific activity. The partially purified enzyme exhibited maximum activity at pH 10.0 and at 50 °C and was highly stable at 50 °C retaining 100% of its activity up to 90 min. It was highly stable and retained more than 80% of its initial activity upon exposure to various organic solvents. The EH28 lipase was used for synthesis of the flavor ester ethyl caprylate in organic solvents, thus providing a concept of application of Acinetobacter sp. lipase in non-aqueous catalysis. Reaction parameters best suited for this esterification reaction were 40 °C reaction temperature, 1.3:1 ratio of caprylic acid to ethanol and cyclohexane as the medium.