A two-step enzymatic strategy to produce ethyl esters using frying oil as substrate

This work reports a strategy for enzymatic esters production through hydroesterification using soybean and frying oils by ultrasound bath-assisted, comprising two steps, enzymatic hydrolysis in batch mode followed by esterification in continuous mode. The hydrolysis reaction was conducted using 1:20 molar ratio (oil/water), ultrasound power 132 W, 40 °C, 300 rpm, 2 h of reaction time, and 10 wt% Lipozyme TL IM. For esterification reactions, fatty acids obtained in the previous hydrolysis step was employed at a molar ratio of 1:6 (fatty acid/ethanol), 132 W, 65 °C, substrate feed rate 2.5 mL/min, and 1 wt% Novozym 435. The experimental apparatus used for the esterification step consisted in a packed glass reactor, submerged in an ultrasound bath. Results showed a conversion to ethyl esters as high as 94% after 28 min for soybean oil and 79% in 9 min using frying oil in the esterification step. Finally, and based on our results, the procedure suggested here, enzymatic hydroesterification, is a good alternative to the continuous production of ethyl esters from low cost raw materials.