A continuous process for the enzymatic synthesis of biodiesel, fatty acid methyl esters (FAMEs) from soybean oil, catalyzed by immobilized lipase from Candida antarctica (Novozym 435) was investigated. Novozym 435 was packed in a packed-bed reactor and used to catalyze the alcoholysis of methanol and soybean oil to produce FAMEs in a cosolvent system. Response surface methodology (RSM) and 3-factor-3-level fractional factorial design were employed to evaluate the effects of synthesis parameters, such as reaction temperature (45-65 degrees C), flow rate (0.1-0.5 mL/min), and substrate molar ratio of methanol to soybean oil (3:1-5:1) on percentage molar conversion of FAMEs by alcoholysis. Reaction temperature and flow rate had significant effects on the percent molar conversion. On the basis of ridge mix analysis, the optimum conditions for synthesis were as follows: reaction temperature 52 degrees C, flow rate 0.1 mL/min, and substrate molar ratio 4.3:1. The predicted value was 74.2%, and the actual experimental value was 75.2% molar conversion.