Asymmetric reduction of β-carbonyl ester with respiratory-deficient mutants of baker's yeast

Asymmetric synthesis of ethyl ( S)-4-choloro-3-hydroxybutanoate was studied using ethyl 4-chloro-3-oxobutanoate as the model substrate and glucose as the carbon source. Six respiratory deficient (RD) mutants of natural baker's yeast were induced by ultraviolet radiation at 254 nm and were identified by 2,3,5-triphenyltetrazolium chloride plate and carbon sources without sugar. The characteristics of catalytic asymmetric reduction and the activity of four mitochondria complexes, I, I + III, II + III, and IV, in the electron transfer chain of RD mutants were detected. The results showed that the substrate conversions catalyzed by RD mutants were 49%-75%, and the yields were 31%-68%, which were lower than that of natural baker's yeast. The enantiomeric excess (ee) of RD mutants increased to 72%, being 18 % higher than that of natural baker's yeast. The activities of I-IV mitochondrial complexes in RD mutants were all lower than that in natural baker's yeast to various degrees.