Kinetics of the dissipation of azoxystrobin, quizalofop-p-ethyl, fluazifop-p-butyl and clomazone in fermented legume seeds

Abstract

In this study, four plant matrices, including soybean, chickpea, pea, and lens, underwent fermentation by Bacillus subtilis var. natto. Then, the process influence on the content of four pesticides (clomazone, azoxystrobin, fluazifop-p-butyl, and quizalofop-p-ethyl) was evaluated, depending on the fermentation length. Fermentation was conducted for 312 h in controlled conditions of temperature and relative humidity (37 °C, 75%). The pesticide residue content in fermented seeds was assessed with the QuEChERS multiresidue method, combined with gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). The studies demonstrated that Bacillus subtilis can biodegrade pesticides in legume seeds, with those microorganisms having a greater potential to degrade herbicides, especially fluazifop-p-butyl, and quizalofop-p-ethyl, than azoxystrobin and clomazone. The highest pesticide degradation occurred during first hours of fermentation. The quizalofop-p-ethyl and fluazifop-p-butyl levels reached < 0.02 mg/kg in nearly all studied seeds already after 48 h. At the end of fermentation (after 312 h), the azoxystrobin and clomazone levels ranged from 0.0203 mg/kg (soybean) to 0.0475 mg/kg (lens) and from 0.001 mg/kg (chickpeas) to 0.0753 mg/kg (lens), respectively. In all studied plant matrices, levels of pesticide residues were below the established MRLs, with clomazone being the sole exception.