In situ Generation of Aldehydes for Subsequent Biocatalytic Cascade Reactions in Whole Cells

Abstract

Aldehydes represent valuable precursors for chemical compounds. However, the incorporation of aldehydes in whole-cell-based synthetic enzyme cascades is problematic. Due to their toxicity, they are metabolized to the corresponding alcohols or carboxylic acids by the host enzymatic background. Previous research has shown that these endogenous side reactions can be reversed by alcohol dehydrogenase (AlkJ, Pseudomonas putida) and carboxylic acid reductase (CARNi, Nocardia iowensis) in Escherichia coli. Thereby, the aldehyde is available for further enzymatic conversion to a product of choice. Three different enzymes were incorporated into the concept for the transformation of the aldehyde intermediate: A pyruvate decarboxylase (PDCApE469Q, Acetobacter pasteurianus), ω-transaminase (ω-TAVf, Vibrio fluvialis) and imine reductase (IREDCf, Cystobacter ferrugineus). (R)-Phenylacetylcarbinol and a range of primary and secondary amines were obtained as final products. Either the alcohol, the carboxylic acid or a 50 : 50 mixture could be employed as starting material.