Design of recombinant whole-cell catalysts for double reduction of CC and CO bonds in enals and application in the synthesis of Guerbet alcohols as industrial bulk chemicals for lubricants†
Whole-cell catalysts overexpressing two enzymes for a double reduction cascade in which aliphatic α-branched α,β-unsaturated aldehydes are converted into Guerbet alcohols as a highly demanded class of lubricants were constructed and characterized. The reaction conditions were optimized to suppress by-product formation, achieving high conversion and selectivity. Application of methanol as a co-solvent on a 500 mL scale enabled a substrate concentration of 18.5 g L−1 obtaining 97% yield and 88% purity without further distillation. Addressing the needs of industrial processes, substrate loading was increased up to 94 g L−1 and the E-factor (environmental factor) was significantly improved compared to the original process with isolated enzymes.