Multi-Enzymatic Biosynthesis of Chiral β-Hydroxy Nitriles through Co-Expression of Oxidoreductase and Halohydrin Dehalogenase

To establish a system for the efficient one bacterial multi-enzymatic biosynthesis of both (R)- and (S)--hydroxy nitriles, we co-expressed alcohol dehydrogenases with opposite stereoselectivities, cofactor regeneration enzymes, and a halohydrin dehalogenase in Escherichia coli. By researching cofactor recycling and various co-expression strategies and by selecting and engineering the halohydrin dehalogenase, we engineered two E. coli strains, which were subsequently used in a cascade of reactions to produce chiral -hydroxy nitriles with high enantiomeric excess directly from prochiral -halo ketones. Three valuable pharmaceutical intermediates were prepared by means of this catalytic system, and substrate conversion reached about >99%. More importantly, the system is of low cost because there is no need for expensive cofactors or for expression and purification of the component enzymes.