Degradation of glyphosate and other pesticides by ligninolytic enzymes

The ability of pure manganese peroxidase (MnP), laccase, lignin peroxidase (LiP) and horseradish peroxidase (HRP) to degrade the widely used herbicide glyphosate and other pesticides was studied in separate in vitro assays with addition of different mediators. Complete degradation of glyphosate was obtained with MnP, MnSO₄ and Tween 80, with or without H₂O₂. In the presence of MnSO₄, with or without H₂O₂, MnP also transformed the herbicide, but to a lower rate. Laccase degraded glyphosate in the presence of (a) 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), (b) MnSO₄ and Tween 80 and (c) ABTS, MnSO₄ and Tween 80. The metabolite AMPA was detected in all cases where degradation of glyphosate occurred and was not degraded. The LiP was tested alone or with MnSO₄, Tween 80, veratryl alcohol or H₂O₂ and in the HRP assay the enzyme was added alone or with H₂O₂ in the reaction mixture. However, these enzymes did not degrade glyphosate. Further experiments using MnP together with MnSO₄ and Tween 80 showed that the enzyme was also able to degrade glyphosate in its commercial formulation Roundup^® Bio. The same enzyme mixture was tested for degradation of 22 other pesticides and degradation products present in a mixture and all the compounds were transformed, with degradation percentages ranging between 20 and 100%. Our results highlight the potential of ligninolytic enzymes to degrade pesticides. Moreover, they suggest that the formation of AMPA, the main metabolite of glyphosate degradation found in soils, can be a result of the activity of lignin-degrading enzymes.