Highly Efficient Deacidification of High-Acid Rice Bran Oil Using Methanol as a Novel Acyl Acceptor
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A highly efficient process for reducing the fatty acid (FA) content of high-acid rice bran oil (RBO) was developed by immobilized partial glycerides-selective lipase SMG1-F278N-catalyzed esterification/transesterification using methanol as a novel acyl acceptor. Molecular docking simulation indicated that methanol was much closer to the catalytic serine (Ser-171) compared with ethanol and glycerol, which might be one of the reasons for its high efficiency in the deacidification of high-acid RBO. Additionally, the reaction parameters were optimized to minimize the FA content of high-acid RBO. Under the optimal conditions (substrate molar ratio of methanol to FAs of 1.8:1, enzyme loading of 40 U/g, and at 30 °C), FA content decreased from 25.14 to 0.03% after 6 h of reaction. Immobilized SMG1-F278N exhibited excellent methanol tolerance and retained almost 100% of its initial activity after being used for ten batches. After purification by molecular distillation, the final product contained 97.86% triacylglycerol, 2.10% diacylglycerol, and 0.04% FA. The acid value of the final product was 0.09 mg KOH/g, which reached the grade one standard of edible oil. Overall, methanol was a superior acyl acceptor for the deacidification of high-acid RBO and the high reusability of immobilized SMG1-F278N indicates an economically attractive process.
KeywordsDeacidification High-acid rice bran oil Methanol Molecular docking Partial glycerides-selective lipase
This work was supported by the National Natural Science Foundation of China (21376098) and the Science and Technology Planning Project of Guangdong Province (2014B020204003, 2015B020231006, 2015TX01N207).
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Conflict of Interest
The authors declare that they have no conflict of interest.
- 4.Wilson, T. A., Nicolosi, R. J., Woolfery, B., & Kritchevsky, D. (2007). Rice bran oil and oryzanol reduce plasma lipid and lipoprotein cholesterol concentrations and aortic cholesterol ester accumulation to a greater extent than ferulic acid in hypercholesterolemic hamsters. The Journal of Nutritional Biochemistry, 18, 105–112.CrossRefGoogle Scholar
- 5.Chou, T. W., Ma, C. Y., Cheng, H. H., Chen, Y. Y., & Lai, M. H. (2009). A rice bran oil diet improves lipid abnormalities and suppress hyperinsulinemic responses in rats with streptozotocin/nicotinamide-induced type 2 diabetes. Journal of Clinical Biochemistry and Nutrition, 45, 29–36.CrossRefGoogle Scholar
- 17.Zheng, M. M., Zhu, J. X., Huang, F. H., Xiang, X., Shi, J., Deng, Q. C., Ma, F. L., & Feng, Y. Q. (2015). Enzymatic deacidification of the rice bran oil and simultaneous preparation of phytosterol esters-enriched functional oil catalyzed by immobilized lipase arrays. RSC Advances, 5, 70073–70079.CrossRefGoogle Scholar
- 18.Xu, T. T., Liu, L., Hou, S. L., Xu, J. X., Yang, B., Wang, Y. H., & Liu, J. S. (2012). Crystal structure of a mono- and diacylglycerol lipase from Malassezia globosa reveals a novel lid conformation and insights into the substrate specificity. Journal of Structural Biology, 178, 363–369.CrossRefGoogle Scholar
- 22.Trott, O., & Olson, A. J. (2010). AutoDock Vina: improving the speed and accuracy of docking with a new scoring function, efficient optimization, and multithreading. Journal of Computational Chemistry, 31, 455–461.Google Scholar