In situ 1H NMR study of the biodegradation of xenobiotics: application to heterocyclic compounds

In vivo or in situ nuclear magnetic resonance (NMR) offers a powerful tool to study the degradation of xenobiotics by microorganisms. Most studies reported are based on the use of heteronuclei, and experiments with xenobiotics have been limited because specifically labeled xenobiotics are not commercially available, with the exception of ¹⁹F and ³¹P. ¹H NMR is, thus, of great interest in this area. To avoid problems caused by the presence of water and intrinsic metabolite signals, some studies were performed using a deuterated medium or specific detection of protons linked to the ¹³C–¹⁵N enriched pattern. We report here the application of in situ ¹H NMR, performed directly on culture media, to study the metabolism of heterocyclic compounds. In this review, we show that a common pathway is involved in the biodegradation of morpholine, piperidine, and thiomorpholine by Mycobacterium aurum MO1 and Mycobacterium sp. RP1. In all cases, the first step is the cleavage of the C–N bond, which results in an amino acid. Thiomorpholine is first oxidized to sulfoxide before the opening of the ring. The second step is the deamination of the intermediate amino acid, which leads to the formation of a diacid. We have shown that the cleavage of the C–N bond and the oxidation of thiomorpholine are initiated by reactions involving a cytochrome P450. Journal of Industrial Microbiology & Biotechnology (2001) 26, 2–8. Received 27 December 1999/ Accepted in revised form 08 May 2000