A new approach for describing and solving the reversible Briggs-Haldane mechanism using immobilized enzyme

Abstract

Recently immobilized enzymes have been widely used in industrial processes due to their outstanding advantages, such as high stability and recyclability; however, their kinetic behaviour is generally controlled by mass diffusion effects. Thus, in order to improve these enzymatic processes, a clear discernment between the kinetic and diffusion mechanisms that control the production of the metabolite require investigation. In practice, it is typical to establish apparent kinetics for immobilized enzyme operations, and the validity of the apparent kinetics is restricted to the studied cases. In this work, a new approach for mathematically describing the kinetic and diffusion mechanics in an immobilized biocatalyst bead is established, in which the fraction of residual enzymatic activity is included, and is defined as a measure of the active and available enzymes in the bead porous network. In addition, the diffusion and kinetic mechanisms are described by the effective diffusion coefficient and the free enzyme kinetics, since the porous network of the bead is assumed as the bioreaction volume. Therefore, free enzyme kinetics were determined from glucose to fructose bioconversion using a stirred tank reactor with free glucose-isomerase, in which substrate and enzyme concentrations and temperature were varied. The fraction of residual enzymatic activity ((Formula presented.)) and the effective diffusion coefficient ((Formula presented.)) were obtained from the isomerization of glucose to fructose using a stirred tank reactor with immobilized glucose-isomerase in calcium alginate beads at different substrate and enzyme concentrations. Finally, simulations were carried out to establish the bioreaction solid-phase characteristics that most significantly influence productivity.