EXPERIMENTAL INVESTIGATION OF CONTINUOUS NAD RECYCLING BY CONJUGATED ENZYMES IMMOBILIZED IN ULTRAFILTRATION HOLLOW FIBER

Abstract

Dynamic NAD recycling, in which native NAD, without immobilization, was dynamically recycled in continuous operation by immobilized conjugated enzymes (alcohol dehydrogenase and lactate dehydrogenase), was investigated experimentally. The results were compared with the theoretical model calculations in the preceding paper. Although there were some quantitative differences, the theoretical model could explain the experimental results at various operating conditions. Under a properly selected operating condition, a high NAD recycle number (6180) as well as a satisfactory conversion (34.6 %) of the limiting substrate was obtained experimentally. The operational stability of the present system was fairly good, retaining 70 % of its original activity after one month''s continuous operation. Compared with the immobilized-NAD method, the dynamic NAD recycling method is simple and is free from the problem of coenzyme inactivation during continuous operation. The experimental results obtained here showed the practicability of dynamic NAD recycling.