Biolubricant production by Novozym 435-catalyzed methanolysis of castor oil was studied in a fluidized-bed reactor operating in the batch recirculation mode. With 1g of enzyme and a methanol-to-oil molar ratio of 6:1, the highest yield of methyl ester was obtained (99.6%) after 24h at 40°C and a 30mL/min flow rate. The ping-pong bi-bi mechanistic model was used to treat the experimental data. Using non-linear regression analysis, a model with substrate inhibition by both methanol and castor oil gave the best fit, with kinetics constants V max =7.97mmol/Lmin, K m,oil =90.07mM, K m,methanol =733.27mM, K i,oil =923.23mM, and K i,methanol =317.11mM. The K m,oil value was indicative of the higher affinity of the lipase toward the oily substrate, and the castor oil was less inhibitory than methanol (K i,methanol <K i,oil ). The reusability of Novozym 435 was also evaluated using repeated batch experiments, and no significant decreases in the methanolysis yields were observed after ten cycles.