Optimization of whole cell-catalyzed methanolysis of soybean oil for biodiesel production using response surface methodology

Utilizing whole cell biocatalyst instead of free or immobilized enzyme is a potential way to reduce the cost of catalyst in lipase-catalyzed biodiesel production. Rhizopus oryzae (R. oryzae) IFO4697 whole cell immobilized within biomass support particles (BSPs) was used for the methanolysis of soybean oil for biodiesel production in this paper. tert-Butanol was demonstrated to be an ideal reaction medium, in which the negative effects caused by substrate methanol could be eliminated effectively. A central composite design was adopted to study the effect of tert-butanol quantity, methanol quantity, water content and dry biomass of the immobilized cell on biodiesel (methyl ester) yield. Each factor was studied in five levels. Using response surface methodology, a quadratic polynomial equation was obtained for methyl ester yield by multiple regression analysis. Biodiesel yield of 72% could be obtained under the optimal conditions and further verification experiments confirmed the validity of the predicted model.