Continuous retention of native NADP(H) in an enzyme membrane reactor for gluconate and glutamate production

Abstract

A new concept of membrane reactor for continuous retention of NADP(H) with non-charged ultrafiltration membranes is proposed. The presence of the high molecular weight polymer polyethyleneimine (PEI) in the reaction medium allow to achieve high retainment ratios for the native coenzyme when the molar ratio PEI/NADP(H) in the reactor is > 1. Nad concentrations > 0.3 M decrease significantly the retainment ratio of NADP + in the reactor. Therefore, this system is applicable for enzyme reactions requiring low ionic strength media. This reactor configuration has been applied to obtain simultaneously gluconate and glutamate by coupling two enzymes for coenzyme regeneration, glucose dehydrogenase and glutamate dehydrogenase. Sorbitol stabilization of the halophilic enzymes allows to compensate the reduced NaCl concentration required for coenzyme retention. Experimental performance of the reaction is compared successfully with a theoretical model that considers the kinetic mechanisms of the enzymes involved.