Continuous enzymatic transformation in an enzyme membrane reactor with simultaneous NAD(H) regeneration

Abstract

Abstract Multienzyme reaction systems with simultaneous coenzyme regeneration have been investigated in a continuously operated membrane reactor at bench scale. NAD(H) covalently bound to polyethylene glycol with a molecular weight of 10 4 [PEG‐10,000‐NAD(H)] was used as coenzyme. It could be retained in the membrane reactor together with the enzymes. L ‐leucine dehydrogenase (LEUDH) was used as catalyze for the reductive amination of α‐ketoisocaproate (2‐oxo‐4‐methylpentanoic acid) to L ‐leucine. Format dehydrogenease (FDH) was used for the regeneration of NADH. Kinetic experiments were carried out to obtain data which could be used in a kinetic model in order to predict the performance of an enzyme membrane reactor for the continuous production of L ‐leucine. The kinetic constants V max and K m of enzymes are all in the same range regardless of whether native NAD(H) or PEG‐10,000‐NAD(H) is used as coenzyme. L ‐leucine was produced continuously out of α‐ketoisocaproate for 48 days; a maximal conversion of 99.7% was reached. The space‐time yield was 324 mmol/L day (or 42.5 g/L day).