A biocatalytic cascade reaction sensitive to the gas–liquid interface: Modeling and upscaling in a dynamic membrane aeration reactor

The oxidation of lactose to lactobionic acid by a bi-enzymatic system in a membrane-aerated reactor was scaled up 100-fold from a miniaturized membrane contactor to a 20-L dynamic membrane aeration reactor. The conversion was catalyzed by an enzyme cascade consisting of cellobiose dehydrogenase as synthesizing enzyme and laccase as regenerating enzyme coupled by a redox mediator. A model of the process, combining mass-transfer and enzyme kinetics, was developed to predict optimal conversion conditions. The dynamic membrane aeration reactor was successfully operated in discontinuous and CSTR mode to achieve maximum productivity at very low power input (27.7 W m−3) and also greatly reduced enzyme inactivation by eliminating the high gas/liquid interfacial area of conventionally aerated stirred reactors or bubble columns. The reaction product, lactobionic acid was obtained with a space–time yield of 74.4 g L−1 d−1 and a degree of conversion higher than 97%. The dynamic membrane aeration reactor is well suited for the bubbleless oxygenation of laccase-regenerated dehydrogenase reactions and other oxidase-catalyzed reactions on large scale to perform sustainable enzymatic oxidation reactions employing enzymes sensitive to shear or the gas/liquid interface.