Preparation of Diacylglycerol-enriched Rice Bran Oil by Lipase-catalyzed Deacidification in Packed-bed Reactors by Continuous Dehydration.

Diacylglycerol-enriched rice bran oil (RBO-DAG) was produced by deacidification of high-acid rice bran oil (RBO) with glycerol (Gly) using Lipozyme RM IM by continuous dehydration by combination of two enzyme columns (column 1 and 3, used for deacidification) with one molecular sieves column (column 2, used for dehydration). The conditions for three columns were respectively optimized. Response surface methodology (RSM) was used to optimize the conditions of column 1. The content of DAG and conversion of free fatty acid (FFA) were used as indicators and the effects of the enzyme load (8-12 g), flow rate (0.3-0.6 mL/min), substrate molar ratio (4-6) and reaction temperature (55-75°C) were investigated. The content of DAG and conversion of FFA were significantly correlated to the flow rate and substrate molar ratio. Most desirable conditions of the reaction with respect to the maximal DAG content and FFA conversion was attained under the residence time of 40 min, substrate molar ratio of 5.52 (Gly: RBO) and temperature of 66°C. The conditions for column 2 were investigated by varying molecular sieves load and flow rate, and the maximal dehydration rate of 85.22% was obtained under the optimal conditions. For column 3, the optimum conditions were obtained as: flow rate, 0.2mL/min; temperature, 65°C, and the content of DAG and FFA were 38.99% and 3.04%, respectively under these conditions. The catalytic activity of the lipase was stable in twelve continuous operations with 83.22% of its original ability, demonstrating its potential in the continuous packed-bed reactors (PBRs) system. These results showed that packed-bed reactors combined with continuous deacidification and dehydration in one system had great value in industrial production for high-acid RBO with the improved conversion rate.