초록
<P><B>Abstract</B></P><P>The enzymatic reduction of carboxylic acids is in its infancy with only a handful of biocatalysts available to this end. We have increased the spectrum of carboxylate‐reducing enzymes (CARs) with the sequence of a fungal CAR from <I>Neurospora crassa</I> OR74A (<I>Nc</I>CAR). <I>Nc</I>CAR was efficiently expressed in <I>E. coli</I> using an autoinduction protocol at low temperature. It was purified and characterized <I>in vitro</I>, revealing a broad substrate acceptance, a pH optimum at pH 5.5–6.0, a <I>T</I><SUB>m</SUB> of 45 °C and inhibition by the co‐product pyrophosphate which can be alleviated by the addition of pyrophosphatase. The synthetic utility of <I>Nc</I>CAR was demonstrated in a whole‐cell biotransformation using the <I>Escherichia coli</I> K‐12 MG1655 RARE strain in order to suppress overreduction to undesired alcohol. The fragrance compound piperonal was prepared from piperonylic acid (30 mM) on gram scale in 92 % isolated yield in >98% purity. This corresponds to a productivity of 1.5 g/L/h.</P><P/>