Enhanced Electroreduction of Acetophenone Using Lipase Stabilization: Improved Conversion to 1-Phenylethanol

Few works present effective or viable alternatives to the problem of the electroreduction of acetophenone which usually leads to the pinacol dimer as a primary product in addition to 1-phenylethanol. Here, various lipases were applied in acetophenone electroreduction. The optimized reaction conditions are tin/lead (63 : 37) combined working electrode coated with Nafion film modified with lipase from Thermomyces lanuginosus, a platinum counter electrode, applied potential of -2.0 V vs. Ag/AgCl (KCl 3.0 mol L-1), acetate buffer (0.1 mol L-1) pH 5.0 in 4 hours, and led to the formation of 87.8 % of 1-phenylethanol. The same working electrode was used five times over five days, and the conversion remained constant. A voltammetric study indicates an alteration of the electroreduction mechanism in the presence of the cited lipase. Adding lipase from Thermomyces lanuginosus directly in the medium immobilized in a clay mineral or in silica gel (Lipolase 100T) resulted in even higher conversions (93.2-93.9 %). The modified electrode improved the methodology regarding enzyme stability, process reproducibility, and material reusability.