AbstractA mathematical model was developed to describe the effect of external mass transfer for a packed‐bed enzyme reactor in which a reversible, one‐substrate, two‐intermediate enzyme reaction took place. The model equation was applied to the analysis of an immobilized glucose isomerase reactor system. A Colburn‐type mass transfer correlation was obtained from the Colburnj‐factor versus Reynolds number plot: i.e.,jD= 0.045NRe−0.48. The values of mass transfer coefficient for the system under study ranged from 0.01 to 0.1 cm h−1depending on the substrate flow rate. Very good agreements were observed between the computer simulation using a plug flow reactor model with the derived mass transfer correlation and the experimental results obtained from the packed‐bed re