Soybean oil hydrolysis catalyzed by castor bean (Ricinus communis L.) seeds lipase was investigated. The optimum operational temperature (in the range 25-50 degrees C) was 37 degrees C, and Na+ increased reaction velocities. When stirring at 300 rpm, gum arabic enhanced the rate of hydrolysis, but at 1000 rpm the emulsifier decreased long-term conversions. Experiments using different particle sizes indicated the presence of diffusion delays above 300 mu m. A parsimonious model for this complex system was proposed. Initial rates (V-0) experiments, spanning 0.01-0.5 w/w of oil, showed a decrease in V-0 for high substrate concentrations, depending on the stirring conditions, indicating coalescence of substrate droplets. This hypothesis was confirmed by experiments with more impeller paddles. A pseudo-homogeneous Michaelis-Menten model with substrate inhibition (to represent coalescence effects), fitted well to the initial rates. Product inhibition for high loads of substrate and enzyme deactivation were also considered. The kinetic model was validated by independent experiments, and thus may be useful for design and optimization of industrial enzymatic reactors. (C) 2019 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.