Improved production of (R)-1-phenyl-1,2-ethanediol using Candida parapsilosis (R)-carbonyl reductase expressed in Pichia pastoris

(R)-Specific carbonyl reductase (RCR), a member of the Zn-dependent medium-chain dehydrogenase/reductase family, catalyzes the reduction of 2-hydroxyacetophenone to (R)-1-phenyl-1,2-ethanediol (PED). In this work, we cloned a 6× histidine-tagged RCR from Candida parapsilosis and expressed it in Pichia pastoris GS115 under the methanol-inducible promoter, AOX1. The RCR enzyme was efficiently secreted into the culture media. Western blotting showed that the recombinant RCR was bound specifically by a mouse anti-His× tag monoclonal antibody. Under optimized culture parameters (pH 7.0, initial A600 of 2.0, daily addition of methanol at a concentration of 1% and an induction duration of 3.5-4.0 days), RCR was produced at 185.0 mg/L. The enzyme was purified through one-step Ni2+ affinity chromatography and had a specific activity of 1.35 U/mg, which was nearly 3-fold that of Escherichia coli RCR. The addition of Zn2+ improved the transformation efficiency considerably. The (R)-PED product had the desired optical purity of 95.4% and a yield of 87.2%. Compared to E. coli RCR, the optical purity and yield were increased by 17.8% and 43.4%, respectively. This effective expression system will facilitate further biochemical studies of RCR and its use in chiral alcohol preparation in industry.