Isolation and characterization of a thermophilic lipase from Bacillus thermoleovorans ID-1

Abstract

thermophilic microorganism, Bacillus thermoleovorans ID-1, isolated from hot springs in Indonesia, showed extracellular lipase activity and high growth rates on lipid substrates at elevated temperatures. On olive oil (1.5%, w/v) as the sole carbon source, the isolate ID-1 grew very rapidly at 65³C with its specific growth rate (2.50 h31) and its lipase activity reached the maximum value of 520 U l31 during the late exponential phase and then decreased. In addition to this, isolate ID-1 could grow on a variety of lipid substrates such as oils (olive oil, soybean oil and mineral oil), triglycerides (triolein, tributyrin) and emulsifiers (Tween 20, 40). The excreted lipase of ID-1 was purified 223-fold to homogeneity by ammonium sulfate precipitation, DEAE-Sephacel ion-exchange chromatography and Sephacryl S-200 gel filtration chromatography. As a result, the relative molecular mass of the lipase was determined to be 34 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme showed optimal activity at 70^75³C and pH 7.5 and exhibited 50% of its original activity after 1 h incubation at 60³C and 30 min at 70³C and its catalytic function was activated in the presence of Ca2 or Zn2 . ß 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved. Keywords: Lipase; Thermophile; Bacillus thermoleovorans