Process of enzymatically converting glucose to fructose wherein a glucose-containing solution is passed, under specific conditions, through a bed composed of an immobilized glucose isomerase in a fine, particulate form and non-porous beads or granular inert material such as polystyrene beads. The porous beads and granular inert material comprise between 40% and about 75% of the bed by volume. The bead's presence exerts a buoyant effect which prevents bed packing and promotes desirable flow patterns with no observable channelling. This helps to minimize the formation of undesired or undesirable carbohydrates such as psicose.