Electrochemical microreactor for chiral syntheses using the cofactor NADH

An electrochemical filter‐press microreactor has been designed by electroerosion to perform chiral enzymatic syntheses. Semicylindrical channels are created in the electrodes, only separated by a Nafion membrane. Electrochemical and hydrodynamic characterization of the microreactor allows operating conditions to be optimized. Continuous enzymatic regeneration of NADH was achieved using flavin adenine dinucleotide (FAD/FADH 2 ) as redox mediator. The high specific surface area of the cathode (250 cm −1 ) provides favorable conditions to increase the FADH 2 /FAD concentration ratio and shifts the nonspontaneous reaction FADH 2 /NAD + toward regeneration of NADH. Synthesis of chiral L ‐lactate from pyruvate, in the presence of L ‐LDH, is the model reaction used to check the ability of the microreactor to regenerate NADH; the optimized device allows quantitative yields to be reached in NAD + conversion and in L ‐lactate production. The simulation (FemLab software) results are in good agreement with the experimental mass balances for flow in the range 0.1–0.2 cm 3 /min. © 2008 American Institute of Chemical Engineers AIChE J, 2008