Reaction kinetics and mass transfer in glucose isomerisation with collagen‐immobilised whole microbial cells

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Abstract
Stable and active derivatives of collagen‐immobilised whole microbial cells containing glucose isomerase have been successfully prepared. The degree of crosslinking, swelling behaviour, and hydrophile/hydrophobe ratio of the complex was examined, since these factors could have a strong influence on the diffusional characteristics of the membrane. The studies on efficiency of glutaraldehyde tanning and its effect on the activity of the immobilised cells provided the connecting link between the network properties and the mass transfer effects. The catalytic pathway for the reversible enzymatic conversion of glucose to fructose has been elucidated by developing a kinetic model capable of describing the observed data over the entire range of substrate concentrations. In arriving at this model, we have also found that the bulk phase mass transfer limitations are negligible. Regarding the internal transport resistance, it has been determined that the effectiveness factor is between 0.95 and 1. A reactor design equation incorporating activity, packing density, and contact efficiency correction factors has been developed. Based on this equation, computer simulations of continuous reactor operation were performed to generate concentration–space time profiles. The model was verified experimentally and a close agreement between the predicted and observed values corroborated the correctness of the proposed bioreaction mechanism, the rate expression, and the design equation. The kinetics of a competing side reaction were found to be too slow to influence significantly the overall results.