Cyanide-free synthesis of an aromatic nitrile from a biorenewable-based aldoxime: Development and application of a recombinant aldoxime dehydratase as a biocatalyst

Abstract

An Escherichia coli host microorganism was used for the production of the aldoxime dehydratase from Rhodococcus sp. YH3-3 (OxdYH3-3), which showed good activity toward aromatic aldoximes. Biotransformation of aromatic aldoximes to nitriles was studied using this recombinant biocatalyst OxdYH3-3, exemplified in particular for the synthesis of biorenewable-based 2-furonitrile. The gene encoding for the enzyme OxdYH3-3 was cloned to a histidine tag-containing overexpression vector pET15b, pET22b and pET28b and transformed to E. coli BL21 (DE3) and BL21-Codonplus (DE3). The preferred overexpression was achieved when utilizing the strain BL21 (DE3)/pET28b. Apart from this expression system, however, an overexpression was not observed. The bioconversion transforming E-pyridine-3-aldoxime into 3-cyanopyridine was dependent on the overexpression level of OxdYH3-3. The initial activity for 3 h of BL21 (DE3)/pET28b-OxdYH3-3 toward E-2-furfurylaldoxime (75%) was 13% lower compared to the initial activity toward E-pyridine-3-aldoxime (88%). Even though the initial conversion was lower, BL21 (DE3)/pET28b-OxdYH3-3 showed full conversion of E-2-furfurylaldoxime under formation of 2-furonitrile after 9 h of reaction time. The new recombinant enzyme OxdYH3-3 was successfully overexpressed and used for the biocatalytic synthesis of the pharmaceutical intermediate 2-furonitrile. The enzyme OxdYH3-3 showed a high catalytic activity for aromatic aldoximes, which enables a perspective for an efficient production of aromatic nitriles.

Keywords:

• Aldoxime dehydratase
• aromatic nitriles
• E-2-furfurylaldoxime
• 2-furonitrile
• Rhodococcus sp. YH3-3

Acknowledgements

We gratefully acknowledge generous support from the German Academic Exchange Service (DAAD) and Japan Society for the Promotion of Science (JSPS) under the joint Japan-Germany Research Cooperative Programme [DAAD grant number: 57345566]. This work was supported in part by a grant-in-aid for Scientific Research (S) from the Japan Society for Promotion of Sciences [Grant No. 17H06169].

Disclosure statement

No potential conflict of interest was reported by the authors.