One-pot heterogeneous catalysis using co-immobilized enzymes is simulated, both in batch and continuous stirred bioreactors to produce fructose from lactose. Results show that operational temperature has a stronger impact than the ratio between enzymes activity load on volumetric productivity. Furthermore, volumetric productivity is higher in batch reactor, while fructose yield is higher in continuous reactor.

Abstract

Multi-enzyme reaction systems have become an interesting option to avoid transformation and purification steps in productive reactor-based systems; when carried out in a single vessel, they are termed one-pot systems. This novel work aims to model and simulate the behavior of a one-pot heterogeneous catalysis system in a batch-stirred bioreactor and in a continuous stirred bioreactor with co-immobilized enzymes to determine the compromise operation temperature that maximizes the volumetric productivity, considering thermal decay of the biocatalyst. The production of fructose from lactose is considered a case study, using co-immobilized -galactosidase ( -gal) and glucose-isomerase (GI) in a spherical particle. A diffusion and reaction mathematical model was used to calculate the effectiveness factor for every reaction species considering the thermal decay of both enzymes. Simulations in both batch and continuous operation were done at temperatures ranging from 40 to 60 °C, for initial enzyme activity load ratios ranging from 0.1 to 0.9 IU_GI IU . Resulting effectiveness factors were close to one, indicating no significant limitations on reaction rates due to internal diffusional constraints. In both cases, temperature exerted a more substantial effect than the initial enzyme activity load ratio, showing different scenarios of high volumetric productivity (batch) or amount of produced fructose (continuous).