Organic-Solvent and Surfactant Tolerant Thermostable Lipase, Isolated from a Thermophilic Bacterium, Geobacillus thermodenitrificans IBRL-nra

Lipases (triacylglycerol acylhydrolase, EC 3.1.1.3), catalyze the hydrolysis of long-chain triglycerides with the formation of diacylglyceride, monoglyceride, glycerol and fatty acids. Lipases are actively used in various industries which include food and diary, pharmaceuticals, organic synthesis and detergent and cosmetics. Thermostable lipases are commercially significant for their potential use in industries as it is stable and active in organic solvents and resistance to high temperature and chemical denaturation. The production of thermostable lipase from Geobacillus thermodenitrificans IBRL-nra was carried out in a shake-flasks system at 65 oC in cultivation medium containing (%; w/v or v/v): glucose 1.0; yeast extract 1.25; NaCl 0.45 and olive oil 0.1 with agitation of 200 rpm for 24 hours. The extracted extracellular crude thermostable lipase was purified to homogeneity by using ultrafiltration, Heparin-affinity chromatography and Sephadex G-100 gel-filtration chromatography by 34 folds with a final yield of 9%. The molecular weight of the purified enzyme was estimated to be 30 kDa after SDS-PAGE analysis. Purified thermostable lipase exhibited highest stability in the presence of acetone, ethanol and acetonitrile after 1h and 24h of incubation periods. Thermostable lipase showed elevated activity (220%) when pre-treated with Triton X-100 and could withstand 100% of its activity in the presence of protease up to 4 hours and could retain 70% of its initial activity after 24 hours of incubation.