Enantioselective Degradation of the Chiral Fungicides Metalaxyl and Furalaxyl by Brevibacillus brevis

For almost four decades, the chiral fungicides metalaxyl and furalaxyl have been in use in plant protection on a global scale. Both substances are distributed as racemic mixtures, yet the desirable interference in nucleic acid synthesis of harmful fungi only occurs by the (‐)‐ R ‐enantiomer. As enantioselective degradation in Scheyern (Germany) and Yaoundé (Cameroon) soils has been documented, the influence of 50 isolated microorganisms on the R/S ratio was investigated. A high‐pressure liquid chromatography method with a chiral column to separate enantiomers of metalaxyl and furalaxyl, and subsequent detection by tandem mass spectrometry, was employed. Only one of these microorganisms, a strain of Brevibacillus brevis , showed an enantioselective degradation pattern in liquid culture; the respective (‐)‐ R ‐enantiomers were preferably degraded. Moreover, (‐)‐ R ‐furalaxyl was degraded faster in cultures supplemented simultaneously with both fungicides of the same concentration. Chirality 25 : 336–340 , 2013 . © 2013 Wiley‐Liss Inc. Chirality 00:000‐000:, 2013. © 2013 Wiley Periodicals, Inc.