摘要：An NAD-dependent d -lactate dehydrogenase ( d -nLDH) of Lactobacillus bulgaricus ATCC 11842 was rationally re-designed for asymmetric reduction of a homologous series of α-keto carboxylic acids such as phenylpyruvic acid (PPA), α-ketobutyric acid, α-ketovaleric acid, β-hydroxypyruvate. Compared with wild-type d -nLDH, the Y52L mutant d -nLDH showed elevated activities toward unnatural substrates especially with large substitutes at C-3. By the biocatalysis combined with a formate dehydrogenase for in situ generation of NADH, the corresponding ( R )-α-hydroxy carboxylic acids could be produced at high yields and highly optical purities. Taking the production of chiral ( R )-phenyllactic acid (PLA) from PPA for example, 50 mM PPA was completely reduced to ( R )-PLA in 90 min with a high yield of 99.0% and a highly optical purity (>99.9% e.e.) by the coupling system. The results presented in this work suggest a promising alternative for the production of chiral α-hydroxy carboxylic acids.
