Improvement of synthetic activity and stability of a commercial lipase in a low-water system via immobilization of hydrated lipase aggregates

Abstract

Abstract Activation and immobilization of a commercial lipase from Candida cylindracea were investigated to improve its catalytic performance for esterification reaction between 1-octanol and three butyric acid derivatives in low-water solvent-free systems. Lipase powder was suspended in 1-octanol, which is the alcohol substrate of the esterification reaction, and then an appropriate amount of water (10% to 1-octanol in volume) was added to form hydrated lipase aggregates. Lipase exhibited high activity in this aggregated state, in contrast with the very low activity of nonhydrated lipase powder. We believe that activation using this hydration-aggregation pretreatment was based on interfacial activation at the 1-octanol-water interface. The hydrated lipase aggregates had paste-like morphology and could be immobilized on nonwoven fabrics by physical compression. Polypropylene exhibited the best specific activity among the tested nonwoven fabric materials. A stirred tank batch bioreactor was developed using lipase-immobilizing polypropylene nonwoven fabric sheets. This bioreactor stably maintained its reaction performance in repetitive-batch (maximum 30 times, for a total of 2000 h) esterification with three different acid substrates. The ester yields were over 90% throughout the all repetitive batches. During repeated reaction, the immobilized lipase maintained its water content at a constant level, thus exhibiting catalytic activity in nonaqueous reaction systems.