Effect of crude oil composition and process parameters on the catalytic performance of immobilized lipase during enzymatic deacidification of high-acid soy sauce by-product oil and its bioprocess scale-up

Abstract

Heterogeneities and impurities in high-acid soy sauce by-product oil (SSBO) and the complex process of enzymatic deacidification led to the low stability of immobilized lipase. This study aimed to investigate the effects of non-acylglycerol components and process parameters (glycerol amount and vacuum) on improving catalytic performance of immobilized lipase during deacidification. The non-acylglycerol components significantly affected the performance of immobilized lipase. Fatty acid salts remarkably activated enzyme to catalyze deacidification, in which 0.8 and 1.6 g/100 g sodium oleate obtained the highest deacidification efficiency (97%). High-acid substrate oil with various acid values could be used to deacidify and showed a high deacidification efficiency (over 83%). The excessive addition of glycerol resulted in activity loss, which was associated with the marked changes in the secondary structure of lipase induced by excessive remaining glycerol with low water content. Thus, reaction process should be controlled at a low remaining glycerol content (under 0.9 g/100 g) with proper water content against the deactivation of lipase. Finally, enzymatic deacidification of high-acid SSBO was successfully scaled up to an industrial scale, in which immobilized lipase was recycled for 30 consecutive batches, suggesting that enzymatic deacidification of high-acid SSBO is feasible for industrial implementation.