Purification and Physicochemical Properties of Lipase from Thermophilic Bacillus aerius

A thermophilic bacterial isolate producing lipase was isolated from soil of hot spring and identified as Bacillus aerius (MTCC 10978). Peak lipase activity was observed when 30 h old inoculum was used and incubated in shaking conditions for 48 h. The optimal temperature and pH for the bacterial growth and lipase production was found to be 55°C and 8.0 respectively with cottonseed oil as carbon source, yeast extract and beef extract as nitrogen source. The enzyme produced by thermophilic Bacillus aerius (MTCC 10978) was purified to 9-fold with 7.2% recovery by ammonium sulfate precipitation and DEAE-Cellulose Column Chromatography. The enzyme was found to be a protein having a molecular weight of 33 kDa on SDS-PAGE. The Km and Vmax value of lipase using p-nitrophenyl palmitate as calculated from Lineweaver-Burk plot was 2.13 mM and 0.66 µmol/ml/min respectively.