Continuous Production of L-Alanine with NADH Regeneration by a Nanofiltration Membrane Reactor

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A conjugated enzyme system, alanine dehydrogenase (AlDH) for stereospecific reduction of pyruvate to L-alanine and glucose dehydrogenase (GDH) for regeneration of NADH, were coimmobilized in a nanofiltration membrane bioreactor (NFMBR) for the continuous production of L-alanine from pyruvate with NADH regeneration. Since pyruvate was proved to be unstable at neutral pH, it was kept under acidic conditions and supplied to NFMBR separately from the other substrates. As 0.2 M pyruvate in HCl solution (pH 4), 10 mM NAD, 0.2 M glucose, and 0.2 M NH_4Cl in 0.5 M Tris buffer (pH 8) were continuously supplied to NFMBR with immobilized AlDH (100 U/ml) and GDH (140 U/ml) at the retention time of 80 min, the maximum conversion, reactor productivity, and NAD regeneration number were 100%, 320 g/liter/d, and 20,000, respectively. To avoid the effect of pyruvate instability, a consecutive reaction system, lactate dehydrogenase (L-LDH) and AlDH, was also used. In this system, the L-LDH provides pyruvate, the substrate for the AlDH reaction, from L-lactate regenerating NADH simultaneously, so the pyruvate could be consumed as soon as it was produced. As 0.2 M L-lactate, 10 mM NAD, 0.2 M NH_4Cl in 0.5 M Tris buffer (pH 8) were continuously supplied to. NFMBR with immobilized L-LDH (100 U/ml) and AlDH (100 U/ml) at the retention time of 160 min, the maximum conversion, reactor productivity, and the NAD regeneration number were 100%, 160 g/liter/d, and 20,000, respectively.
社団法人日本農芸化学会の論文
1997-12-23

Continuous Production of L-Alanine with NADH Regeneration by a Nanofiltration Membrane Reactor

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