Optimized expression of (S)-carbonyl reductase in Pichia pastoris for efficient production of (S)-1-phenyl-1, 2-ethanediol.

The recombinant (S)-carbonyl reductase (SCR) in Escherichia coli catalyzed the reduction of 2-hydroxyacetophenone to (S)-1-phenyl-1,2-ethanediol (PED) with low efficiency. In this work, its 6× histidine fusion gene his6 -scr was cloned in Pichia pastoris under the control of the AOX1 methanol inducible promoter. The heterologous protein SCR was expressed through a Mut(s) phenotype. Under the optimal conditions: pH 7.0, initial OD600 2.5, methanol daily addition concentration 1.0% and induction duration 4-5 days, the recombinant protein SCR was produced at the highest level. The enzyme activity in the cell-free exacts of P. pastoris was 0.38, which was over twofold than that of the recombinant E. coli-SCR. The enzyme was purified to homogeneity with a specific activity of 3.41 U mg(-1) , and it catalyzed the biotransformation of (S)-PED with a high optical purity of 96.9% in a high yield of 89.7% at optimum pH of 7.0. The developed effective system of P. pastoris-SCR will facilitate the preparation of pure chiral alcohol in industry.