Biodegradation\nof Cyromazine by <i>Mycobacterium</i> sp. M15: Performance,\nDegradation Pathways, and Key Enzymes

Cyromazine,\na triazine insecticide, raises food safety concerns\ndue to residues in vegetables like cowpeas. Microbial metabolism is\nkey for pesticide elimination, but bacteria efficient in cyromazine\ndegradation are limited, with uncharacterized enzymes. This study\nisolated a highly efficient cyromazine-degrading bacterium, <i>Mycobacterium</i> sp. M15, from a cowpea field. M15 utilized\ncyromazine as the sole carbon source for its growth and completely\ndegraded 0.5 mM cyromazine within 24 h. The degradation pathway involved\nhydrolyzing cyromazine to <i>N</i>-cyclopropylammeline and\nfurther to <i>N</i>-cyclopropylammelide, with amino groups\nremoved sequentially. The cyclopropylamine group in N-cyclopropionamide\ncontinued to hydrolyze to cyanuric acid. A protein, CriA, identified\nas an aminohydrolase in M15, degraded cyromazine to <i>N</i>-cyclopropylammeline. Using CriA reduced cyromazine residues on cowpea\nsurfaces and completely degraded them in immersion solutions. These\nfindings offer insights into cyromazine’s microbial degradation\nmechanism and highlight the potential of cyromazine-degrading enzymes\nin enhancing food safety.