Enhanced Thermostability of Silica-immobilized Lipase fromBacillus coagulansBTS-3 and Synthesis of Ethyl Propionate

Abstract

A lipase from the thermophilic isolate Bacillus coagulans BTS-3 was produced and purified. The enzyme was purified 40-fold to homogeneity by ammonium sulfate precipitation and DEAE-Sepharose column chromatography. Its molecular weight was 31 kDa on SDS-PAGE. The purified lipase was immobilized on silica and its binding efficiency was found to be 60%. The enzyme took 60 min to bind maximally onto the support. The pH and temperature optima of immobilized lipase were same as those of the free enzyme, i.e. 8.5 and 55 degrees C, respectively. The immobilized enzyme had shown marked thermostability on the elevated temperatures of 55, 60, 65 and 70 degrees C. The immobilized enzyme was reused for eigth cycles as it retained almost 80% of its activity. The catalytic activity of immobilized enzyme was enhanced in n-hexane and ethanol. The immobilized enzyme when used for esterification of ethanol and propionic acid showed 96% conversion in n-hexane in 12 h at 55 degrees C.

Purification and Physicochemical Properties of Lipase from Thermophilic Bacillus aerius

“…Moreover the activity of enzyme is stabilized by various immobilized techniques with inert supports, also its thermostability and usability can be enhanced by immobili-zation onto hydrophobic support like nylon 6, molecular sieve etc. 10,11 . Most of the microbial lipases are active at alkaline pH pH 7.0-11.0 .…”

Immobilization of Lipase from <i>Geobacillus</i> sp. and Its Application in Synthesis of Methyl Salicylate

“…Thus in the subsequent esterification reactions, a reaction time of 12 h was considered optimum for the synthesis of ester Table 1 . The optimum incubation time of 12 h for the synthesis of ethyl propionate using silica bound lipase from Bacillus coagulans BTS-3 has been reported earlier 30 . A reaction time of 3 h for immobilized lipase from Bacillus coagulans BTS-3 was considered optimum for synthesis of p-Nitrophenyl acetate 32 .…”

“…ethanol for the synthesis of ethyl propionate in hexane using silica immobilized lipase from Bacillus coagulans has been reported earlier 30 . It was reported that optimal synthesis of butyl acetate by lipase from Bacillus coagulans, immobilized on nylon-6 was achieved when acid and alcohol were used in equimolar ratio 100 mM in the reaction mixture 27 .…”

“…Further increase in incubation time led to decrease in the activity of both free and immobilized lipase. Previously, maximum lipase activity of Bacillus coagulans BTS-3 was obtained after 10 min of incubation at 55 30 .…”

“…Increase or decrease in temperature of reaction mixture might interfere with the porosity, hydrophobic character and diffusion of the reactants and/or products at the catalytic site of the enzyme 36 . In an earlier study, a reaction temperature of 55 was found to be optimum for the synthesis of ethyl propionate using silica bound lipase from Bacillus coagulans BTS-3 30 . A reaction temperature of 65 for immobilized lipase of Bacillus coagulans was considered optimum for synthesis of p-nitrophenyl acetate 26 .…”