Effect of enzyme molecules covering of oil–water interfacial area on the kinetic of oil hydrolysis

Lipase catalysed reactions take place at the interface between the aqueous phase containing the enzyme and the oil phase. The reaction starts with the adsorption of the enzyme at the oil–water interface. In a mechanically agitated reactor, the total free interfacial area is limited and hence, there would be a critical enzyme concentration at which the interfacial area is saturated with the adsorbed enzyme. In this paper, an unsteady-state dynamic model is developed from Ping Pong Bi Bi mechanism, modified to take into consideration the effect of available interfacial area. The model is validated against experimental results from the hydrolysis of palm oil using lipase from Candida rugusa in a mechanically agitated batch bioreactor. It is shown that the model presented the experimental data better than previous models found in literature. The fraction of the enzyme, available in the aqueous phase, which is contributing in the coverage of oil–water interface in a stirred batch bioreactor, is determined at different agitation speeds. This fraction is found to increase as agitation speed increases, which is assumed to be a result of the increase in desorption to adsorption ratio of the enzyme at the interface with agitation.