Optimization of enzymatic transesterification of rapeseed oil using response surface methodology

Enzymatic synthesis of methyl esters from crude rapeseed oil has been studied. The commercial immobilized lipases Novozym® 435, Lipozyme® TL IM and Lipozyme® RM IM have been tested as biocatalyst. At the same experimental conditions, Lipozyme® TL IM showed the best performance allowing a final product with an ester content within the biodiesel specifications (> 96.5%). This enzymatic process was then optimized through a central composite design of four variables - temperature, methanol-to-oil molar ratio, catalyst amount and water content. Based on the response surface methodology, the optimal values of the variables were as follow: reaction temperature of 37.5ºC, protein amount of 0.22 wt%, methanol-to-oil molar ratio of 6.2:5 and water content of 22.3 wt%, with 15 h reaction time. Different oil sources (rapeseed, soybean and used frying oils) were also tested in the enzymatic process using Lipozyme® TL IM. The experimental data obtained, at the same reaction conditions, showed that raw material properties have influence on the biocatalytic process.