Characterization of Lipases from Geobacillus Stearothermophilus and Anoxybacillus Flavithermuscell Lysates

The aim of this study was to characterize lipases from two thermophilic bacteria, Geobacillus stearothermophilus (GS) and Anoxybacillus flavithermus (AF) in heat treated cell lysates. The pH optimum, pH stability, temperature stability and substrate kinetics and specificity of the lipases were determined. Optimum activity of the lipase from GS (LGS) was observed at pH 7.5, and the optimum activity of the lipase from AF (LAF) was at pH 8.0. LGS was stable up to 70˚C after 12 hrs while LAF was stable up to 90˚C after 12 hrs. Both enzymes were stable at a pH range of 6 to 8 over 12 h at 4˚C. LGS had a highest V max value of 22 mM·min −1 ·mg −1 with p-nitrophenyl acetate while the lowest K m was 0.8 mM with p-nitrophenyl laurate. The highest V max of LAF was 2.5 mM·min −1 ·mg −1 with p-nitrophenyl myristate, and the lowest K m was 0.4 mM with p-nitrophenyl octanoate. LGS preferentially hydrolyzed p-nitrophenyl acetate and p-nitrophenyl octanoate while LAF preferentially hydrolyzed p-nitrophenyl myristate and p-nitrophenyldodecanoate. Lipases from both GS and AF showed characteristics that would be beneficial in food processing.