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

<p>Optically pure (<i>R</i>)-3-quinuclidinol [(<i>R</i>)-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 (<i>R</i>)-3-Qui. In this study, a biocatalyst for producing (<i>R</i>)-3-Qui was developed by using <i>Escherichia coli</i> that coexpressed <i>Kaistia granuli</i> (<i>Kg</i>QR) and mutant glucose dehydrogenase (GDH). <i>Kg</i>QR catalyses the synthesis of (<i>R</i>)-3-Qui through the efficient reduction of 3-quinuclidinone. The specific activity of recombinant <i>Kg</i>QR was 254 U/mg, and the Michaelis–Menten constant (K<sub>m</sub>) for 3-quinuclidinone was 0.51 mM. The thermal stability of <i>Kg</i>QR was relatively high compared with <i>ArQR</i>. 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 (<i>R</i>)-3-Qui in 3 h by coexpressing <i>Kg</i>QR and mutant GDH in <i>E. coli</i>. 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.</p>