Isolation and characterization of the cotinine-degrading bacterium Nocardioides sp. Strain JQ2195

Cotinine, the primary nicotine metabolite, not only more stable and more difficult to degrade in the environment but is a potential health risk to human. To date, little is known about the biodegradation process of cotinine. In this study, a bacterial strain JQ2195 was isolated from municipal wastewater and was identified as Nocardioides sp. based on morphological, physiological characteristics, and 16 S rRNA gene phylogenetic analysis. This strain utilized cotinine as a sole carbon source and degraded 0.5 g L^-1 cotinine completely within 32 h. Optimum degradation of cotinine by JQ2195 was at 30 °C and pH 7.0. Two cotinine degradation intermediates were identified as 6-hydroxy-cotinine and 6-hydroxy-3-succinoylpyridine by UV/VIS spectroscopy and liquid chromatography coupled with time-of-flight mass spectrometry. In addition, about half of cotinine was transformed to 6-hydroxy-3-succinoylpyridine which was a value-added compound for biocatalysis. When 2,6-dichlorophenolindophenol was used as an electron acceptor, the cell-free extract containing the inducible cotinine dehydrogenase could convert cotinine into 6-hydroxy-cotinine with the activity 40 ± 6 mUnmg^-1.