Continuous enzymatic conversion of glucose-fructose mixtures into gluconic acid and sorbitol or mannitol within a hollow fiber membrane reactor

A membrane reactor for the continuous enzymatic transformation of glucose-fructose mixtures into gluconic acid and mannitol/sorbitol has been developed. The process consists of two steps: 1. Oxidation of glucose to gluconic acid by glucose dehydrogenase (GDH), 2. Reduction of fructose to mannitol by mannitol dehydrogenase (MDH) or to sorbitol by sorbitol dehydrogenase (SDH). The combination of these two reactions allows continuous regeneration of the polymer bound coenzyme NAD (H). The experimental conditions (pH, temperature, buffer system etc.) have been optimized for the coupled system GDH/MDH. Based on a kinetic model the performance of 3 different reactor types was investigated.- Ion exchange, crystallization and membrane techniques have been considered for downstream processing.