Improving the soluble lipase-catalyzed biodiesel production through a two-step hydroesterification reaction system

摘要

The application of lipases in liquid formulation instead of immobilized forms in the enzymatic biodiesel synthesis can make the process cost-efficient, more competitive, and sustainable. However, despite the benefits, the long reaction times required to achieve satisfactory yields is still a drawback of this biotechnological process. In this sense, employing the novel low-cost soluble NS40116 lipase, this paper proposes an innovative two-step hydroesterification reaction (TSHR) system as a technique of improving the reaction rate of an enzymatic biodiesel production. With the employment of two central composite statistical design to optimize the parameters of each of the reactions involved, the influence of the parameters "water concentration added to the reaction," "methanol-to-oil molar ratio," and "lipase load" on the process yield, besides the acid value of the samples, was investigated. After only 8 h of reaction, the highest fatty acid methyl ester yield reached was 97.1% with an acid value of 4.62 mg KOH g(-1) utilizing a total of 8 wt% water, methanol-to-oil molar ratio of 6.3:1, and 0.70 wt% of lipase. Furthermore, the statistical models for both reactions indicated to be significant with 95% of reliability. Considering that the papers published using soluble lipases in a one-step batch process normally reach similar yields to those obtained in this research after 16 h to 24 h of reaction, the proposed system demonstrated to be a promising option of process configuration for the enzymatic production of biodiesel.