Efficient Biosynthesis of (R)- or (S)-2-Hydroxybutyrate from l-Threonine through a Synthetic Biology Approach

An efficient multi-enzyme cascade reaction for the synthesis of (R)- or (S)-2-hydroxybutyric acid [(R)- or (S)-2-HB] from l-threonine was developed by using recombinant Escherichia coli cells expressing separately or co-expressing l-threonine deaminase from Escherichia coli K-12 (ilvA), formate dehydrogenase (FDH) from Candida boidinii and l-lactate dehydrogenase (l-LDH) from Oryctolagus cuniculus or d-lactate dehydrogenase (d-LDH) from Staphylococcus epidermidis ATCC 12228. Up to 750mM of l-threonine were completely transformed to (R)- or (S)-2-HB in optically pure form (>99% ee) with high isolated yields. This one-pot multi-enzyme transformation provides a new practical method for the synthesis of these important optically pure compounds.