Abstract
A mini-scale external loop airlift bubble column (MELBC) of 20 ml in volume was utilized for evaluating the performance of a novel type biocatalyst consisting of glucose oxidase (GO), phospholipid vesicle, i.e., liposome and gel beads for immobilization. It was found that the glucose oxidase-containing liposomes (GOL) as well as the immobilized glucose oxidase-containing liposomes (IGOL) in the MELBC were extraordinarily stable and reusable at 40°C in the glucose oxidation under the initial glucose concentration of 10 mM and the superficial gas velocity UG of 0.94 cm/s for the GOL or 1.4 cm/s for the IGOL. The simultaneous reaction and mass transfer model for the glucose oxidation catalyzed by the liposomal glucose oxidase above was proposed to determine the gas–liquid oxygen transfer coefficient, kLa, the permeability coefficient of glucose through liposome membrane, PG, and the apparent effectiveness factor of the liposomal GO, α. It was shown that the values of kLa, PG and α could be obtained based on the model with the observed steady-state oxygen concentration as well as the glucose consumption rate. The model proposed was applied to calculate the time courses of glucose concentrations in both inner and outer aqueous phases of the liposomes during the liposomal GO-catalyzed glucose oxidation. It was found that the model was useful to predict the earlier stage of the prolonged reaction since the deactivation of GO leaked from liposomes was considered to be negligible initially. The time course of the glucose concentration inside liposomes, which could not be measured, was reasonably predicted with the model proposed.
