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 750 mM 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.