Exploring the synthetic applicability of a new carboxylic acid reductase from Segniliparus rotundus DSM 44985

Abstract A new carboxylic acid reductase (CAR) gene from Segniliparus rotundus DSM 44985 was overexpressed in Escherichia coli . The recombinant enzyme exhibited high activity toward a variety of aromatic and aliphatic carboxylic acids. Especially, it effectively reduced 4-hydroxybenzoic acid ( 8a ) and 4-nitrobenzoic acid ( 19a ), toward which the known Nocardia CAR exhibited no or little activity. The recombinant E. coli cells co-expressing the Segniliparus CAR and Nocardia PPTase genes catalyzed the reductions of vanillic acid ( 20a ) and 3,4-dihydroxyphenylacetic acid ( 25a ) to give vanillyl alcohol ( 20c ) and 3-hydroxytyrosol ( 25c ) with high yield, respectively. The endogenous aldehyde reductases of E. coli should be responsible for the further reduction of the produced aldehydes. These results demonstrated that Segniliparus CAR was a useful addition to the biocatalyst tool-box for the reduction of carboxylic acids and might find applications in the synthesis of valuable bio-based chemicals from renewable resources.