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Production of a thermostable lipase by Aeromonas sp. EBB-1 isolated from marine sludge in Angsila, Thailand

Jittima Charoenpanich^a,b,*, Sureeporn Suktanarag^a,c, Naruemon Toobbucha^a

 
ABSTRACT:     Aeromonas sp. EBB-1 isolated from marine sludge in Angsila, Thailand produced an extracellular thermophilic lipase. Maximum lipase activity of the culture medium was obtained after 15 h at 25 °C and pH 8.0 with 0.5% (v/v) olive oil as a carbon source. The enzyme was successfully purified 30-fold to homogeneity by successive ammonium sulphate precipitation, gel-permeation column chromatography, and ultrafiltration. The purified bacterial lipase possessed a relative molecular mass of 45 kDa. Highest lipase activity was determined at pH 8.0 and 37 °C with p-nitrophenyl palmitate as a substrate. The enzyme was stable at pH 6.0–8.0 and at temperatures of 30–80 °C. Enzyme activity decreased slightly in 50% (v/v) isoamyl alcohol, decane, or heptane. Lipase activity decreased to a half in the presence of butanol and benzene, and by more than 60% in DMSO, methanol, ethanol, and hexadecane. Lipase activity was inhibited by most of the salt ions (except Ca²⁺ ions) as well as by Tween 80, DTT, PMSF, SDS, and EDTA. Although lipase showed variable specificity/hydrolytic activity towards a number of p-nitrophenyl esters, it was preferentially active towards long-carbon chain acyl esters (C₁₂–C₁₆). The high temperature stability and ability to hydrolyse long length esters support the potential of this lipase enzyme as a vigorous biocatalyst for industrial applications.

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* Corresponding author, E-mail: jittima@buu.ac.th

Received 29 Nov 2010, Accepted 25 Apr 2011