Regeneration of NAD(P)H by immobilized whole cells of Clostridium butyricum under hydrogen high pressure

Immobilized whole cells of Clostridium butyricum reduced both NAD⁺ and NADP⁺ in the presence of hydrogen at a pressure of 100 atm. The NAD⁺ and NADP⁺ reduction activities were 4.45 and 4.30 U/g dry cells, respectively [U = NAD(P)H regenerated, μ mol/min]. The amount of NADH regenerated by immobilized cells increased with increasing hydrogen pressure above 10 atm. Immobilized cells (6 mg dry cells) of Cl. butyricum completely converted NAD⁺ (6.4 μmole) to NADH for 5 h, whereas only 60% of NAD⁺ were reduced by free cells. Immobilized cells retained 89% activity after the 5‐h reactions were repeated 4 times. L‐Alanine was continuously produced at the rate of 12.8 μmol/min g dry cells from hydrogen, ammonium, and pyruvate with immobilized Cl. butyricum‐alanine dehydrogenase.