Kinetics of Continuous Hydrolysis of Olive Oil by Lipase in Microporous Hydrophobic Membrane Bioreactor

Abstract

Kinetics of the continuous hydrolysis of olive oil by Candida cylindracea lipase in a microporous hydrophobic membrane bioreactor (flat membrane or hollow fiber module) was studied. A general equation for outlet conversion was derived on the assumption that flow of oil is of plug-flow type when the reversible Michaelis-Menten equation was applied in “surface phase”. The cases of first-and zero-order kinetics and the diffusion-controlled case through micropores were also analyzed as limiting cases. The theoretical considerations indicate that the flow rate of oil divided by the total membrane area, F/A, is an important operating parameter which governs the performance of the microporous hydrophobic membrane bioreactor. Analyses of batch lipolysis data reported by three research groups showed that the hydrolysis reaction of oil obeyed the first-orded reversible kinetics. Experimental data for the flat membrane bioreactor (countercurrent operation) obtained by the authors agreed with the reversible first-order kinetics in a wide range of F/A, while the data for the hollow fiber module (countercurrent operation) agreed with the reversible first-order kinetics only at higher F/A. Lower rates of hydrolysis at lower F/A seemed to be due to non-uniform flow of oil through the hollow fibers. The new concept of “equivalent droplet size” is proposed to compare the performance of the membrane bioreactor system with that of the emulsion system.