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/FADH2) as redox mediator. The high specific surface area of the cathode (250 cm−1) provides favorable conditions to increase the FADH2/FAD concentration ratio and shifts the nonspontaneous reaction FADH2/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 cm3/min. © 2008 American Institute of Chemical Engineers AIChE J, 2008