Production of (R)-3-quinuclidinol by a whole-cell biocatalyst with high efficiency

Optically pure (R)-3-quinuclidinol [(R)-3-Qui] is widely used as a chiral building block for producing various antimuscarinic agents. An asymmetric bioreduction approach using 3-quinuclidinone reductases is an effective way to produce (R)-3-Qui. In this study, a biocatalyst for producing (R)-3-Qui was developed by using Escherichia coli that coexpressed Kaistia granuli (KgQR) and mutant glucose dehydrogenase (GDH). KgQR catalyses the synthesis of (R)-3-Qui through the efficient reduction of 3-quinuclidinone. The specific activity of recombinant KgQR was 254 U/mg, and the Michaelis–Menten constant (K_m) for 3-quinuclidinone was 0.51 mM. The thermal stability of KgQR was relatively high compared with ArQR. Approximately 73% of the residual activity remained after incubation in 0.2 M potassium phosphate buffer (KPB) (pH 7.0) for 8 h at 30 °C. In addition, 80% residual activity remained for the double-mutant GDH (Q252L and E170K) after incubation in a buffer (pH 7.0) for 8 h at 30 and 40 °C. 3-Quinuclidinone (242 g/L) can be reduced to (R)-3-Qui in 3 h by coexpressing KgQR and mutant GDH in E. coli. The conversion rate reached 80.6 g/L/h, which is the highest reported to date. The results demonstrates that this whole-cell biocatalyst will have a great potential in industrial manufacturing.