Enzymatic esterification of ethanol by an immobilised Rhizomucor miehei lipase in a perforated rotating disc bioreactor

A perforated rotating disc bioreactor was developed to perform the esterification of ethanol with oleic acid, catalyzed by a lipase from Rhizomucor miehei immobilized by adsorption on to a hydrophobic support—Accurel EP700. The bioreactor with total recirculation operated at an optimum agitation rate of 400 rev./min. The experimental results, in this condition, were predict by a kinetic model using the constants obtained in the batch (Erlenmeyer flasks) assays: a catalytic constant, kcat = 5.78 mmol/h · mg protein; a Michaelis constant for ethanol, Km(Et) = 1.20 M; a Michaelis constant for oleic acid, Km(Ol) = 1.16 × 10−8 M, and a dissociation constant of the ethanol-lipase complex, K(Et) = 9.46 × 107 M. The efficiency of conversion gradually decreased during continuous operation of the reactor. The enzymatic activity decayed according to a first order deactivation model and the integrated equations of a continuous stirred tank reactor (CSTR) and a plug flow reactor (PFR). A half-life time of the lipase of about 10 days and a deactivation constant of 0.003 h−1 were obtained in the present system.