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.

Extracellular lipase from Bacillus coagulans BTS-3 was immobilized on activated (alkylated, 2.5% glutaraldehyde) and native (nonactivated) polyethylene powder, and its thermostability and esterification efficiency were studied. Immobilization on activated support was found to enhance thermostability as well as esterification efficiency. The optimum time for immobilization on activated (AS) and nonactivated (NS) polyethylene support was found to be 10 min, and the binding of the lipase was markedly higher on AS. Lipase was more efficiently bound to AS (64%) than to NS (30%) at an optimum temperature of 378C. The pH and temperature optima for AS-and NS-bound lipase were 9.0 and 558C and 8.5 and 558C respectively. At 558C the free lipase, which had a half-life of 2 h, lost most of its activity at elevated temperatures. In contrast, AS-bound lipase retained 60%-80% of its original activity at 558C, 608C, 658C, and 708C for 2 h. Exposure to organic solvents resulted in enhanced lipase activity in n-hexane (45%) and ethanol (30%). Both AS-and NS-bound biocatalysts were recyclable and retained more than 85% of their initial activity up to the fourth cycle of hydrolysis of p-nitrophenyl palmitate. The AS-bound lipase efficiently performed maximum esterification (98%) of ethanol and propionic acid (300 mM each, 1 : 1) in n-hexane at 558C. With free or NS-bound lipase in similar conditions, the conversion of reactants into ester was relatively low (40%).