title: Selective Enzymatic Transformation to Aldehydesin vivoby Fungal Carboxylate Reductase fromNeurospora crassa.
abstract: 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 fromNeurospora crassaOR74A (NcCAR).NcCAR was efficiently expressed inE. coliusing an autoinduction protocol at low temperature. It was purified and characterizedin vitro, revealing a broad substrate acceptance, a pH optimum at pH 5.5-6.0, aTmof 45 °C and inhibition by the co-product pyrophosphate which can be alleviated by the addition of pyrophosphatase. The synthetic utility ofNcCAR was demonstrated in a whole-cell biotransformation using theEscherichia coliK-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.
authors.affiliation: acib GmbH Petersgasse 14 8010 Graz Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schwendenwein
authors.affiliation: Institute of Molecular Biotechnology Graz University of Technology NAWI Graz Petersgasse 14 8010 Graz Austria.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Fiume
authors.affiliation: Institute of Organic Chemistry Graz University of Technology NAWI Graz Stremayrgasse 9 8010 Graz Austria.
authors.forename: Hansjörg
authors.initials: H
authors.lastname: Weber
authors.affiliation: Institute of Applied Synthetic Chemistry TU Wien Getreidemarkt 9/OC-163 1060 Vienna Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Rudroff
authors.affiliation: acib GmbH Petersgasse 14 8010 Graz Austria; Institute of Molecular Biotechnology Graz University of Technology NAWI Graz Petersgasse 14 8010 Graz Austria.
authors.forename: Margit
authors.initials: M
authors.lastname: Winkler
keywords: aldehydes; biocatalysis; carboxylate reductase; carboxylic acids; flavours and fragrances