Response surface optimization of biocatalytic biodiesel production with acid oil

Biodiesel production has received considerable attention in the recent years as a biodegradable and non polluting fuel. Utilizing soluble lipase biocatalyst presented an alternative approach to lipase-mediated biodiesel production besides the immobilized lipase and whole cell catalysts. The central composite design (CCD) of the response surface methodology (RSM) was employed to evaluate the effects of enzyme concentration, temperature, molar ratio of methanol to oil and stirring rate on the yield of fatty methyl ester in present work. Soluble lipase NS81006 and NS81020, produced by submerged fermentation of genetically modified Aspergillus oryzae/Aspergillus niger microorganism, were proposed here as the catalysts for biodiesel production with acid oil. The results indicated that enzyme concentration, temperature, molar ratio of methanol to oil and stirring rate were the significant factors on the yield of fatty methyl ester and a quadratic polynomial equation was obtained for methyl ester yield by multiple regression analysis. The predicted biodiesel yield was 0.915 (w/w) under the optimal conditions and the subsequent verification experiments with biodiesel yield of 0.887 ± 0.0161 (w/w) confirmed the validity of the predicted model.