화학공학소재연구정보센터
Journal of Applied Polymer Science, Vol.102, No.4, 3986-3993, 2006
Thermostability and esterification of a polyethylene-immobilized lipase from Bacillus coagulans BTS-3
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 37 degrees C. The pH and temperature optima for AS- and NS-bound lipase were 9.0 and 55 degrees C and 8.5 and 55 degrees C respectively. At 55 degrees C 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 55 degrees C, 60 degrees C, 65 degrees C, and 70 degrees C 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 55 degrees C. With free or NS-bound lipase in similar conditions, the conversion of reactants into ester was relatively low (40%). (c) 2006 Wiley Periodicals, Inc.