11-19: Microwave assisted enzymatic synthesis of beef tallow biodiesel: Optimization by factorial design

Optimal conditions for the microwave assisted enzymatic synthesis of biodiesel have been developed by a full 2² factorial design leading to a set of 7 runs with different combinations of molar ratio and temperature. The main goal is to reduce the reaction time preliminarily established by a process of conventional heating. Reactions yielding biodiesel were catalyzed by lipase from Burkholderia cepacia immobilized on silica-PVA using beef tallow and ethanol as raw materials. Microwave irradiations within the range 8 to 15 W have been performed to attain the reaction temperature. Under optimized conditions (1:6 beef tallow  to ethanol molar ratio at 50°C) almost total conversion of the fatty acid presented in the original beef tallow has been converted into ethyl esters in a reaction that has been lasted 8 h, i.e. a productivity of about 92 mg ethyl esters/g.h. The microwave assistance yields a process outcome augmentation of about 6 times higher then that under conventional heating conditions. In general, the new process promises low energy demand and faster beef tallow conversion into biodiesel with several advantages, among them: (i) microwaves speed up the enzyme catalyzed reactions; (ii) there are destructive effects on the enzyme properties such as stability and substrate specificity, and (iii) the microwave assistance allows the entire reaction volume to be heated uniformly.