Optimized transformation of animal fats to alkyl esters

The optimum conditions for the preparation of fatty acid ethyl ester (FAEE) were investigated in three experiments to assess the linear, quadratic, and bilinear effects of temperature, enzyme load, and oil:alcohol molar ratio on FAEE yield. In each experiment, second-order polynomial models fitted to the FAEE yield data provided response surfaces at various reaction times (8 h–48 h). These models were generally significant (p < 0.05) and produced reliable and stable predictions, especially at 24 h and 36 h. At these reaction times, optimum conditions were found to be close to the center point values of the reaction variables (50 °C, using an enzyme load of 39.06 U, and an oil:alcohol ratio of 1:2). Fuel testing of the transesterified oils revealed various proportions of total and bound glycerol, acid number (AN), triacylglycerol (TAG), diacylglycerol (DAG), monoacylglycerol (MAG), and moisture.