Kinetic modeling of ethyl ester production by Burkholderia cepacia lipase in semi batch reactor

The production of biodiesel esters by the enzymatic route has been shown to be promising compared to inorganic catalysts, from an environmental point of view. However, the mechanism of enzymatic reactions is not sufficiently well modeled and that makes the determination of optimal process conditions more difficult.

The objective of this work is the development of phenomenological models for production of ethyl esters by transesterification of vegetable oil in batch and semi batch reactor systems, considering or not enzymatic inactivation by temperature and irreversible inhibition by ethanol.

Burkholderia cepacia lipase catalyzed the transesterification reaction between canola oil and ethanol. Experiments were carried out at different temperatures (40, 50 and 60 °C), with enzyme load of 5, 7.5 and 10% of the oil mass and alcohol-to-oil molar ratio of 6:1, 9:1 and 12:1, for 72 h of reaction time. Ethanol was added to the reaction medium at the times of 0, 24 and 48 h in equal amounts. Samples were analyzed using HPLC. Kinetic parameters were evaluated using MATLAB.

The results showed that both models considered had a satisfactory fit to the data at the beginning of the reaction. However, disregarding lipase inactivation showed an increase in data deviation after 12 h with errors reaching 25%, while considering inactivation a lower maximum error of 9% was obtained. Thus, the lipase inactivation by temperature and irreversible inhibition by ethanol are important phenomena that must be taken into account, and the resultant model is appropriated for simulation and optimization of the biodiesel process.