Dissipation of pirimiphos-methyl during wheat fermentation by Lactobacillus plantarum

In this study, the dissipation of pirimiphos-methyl during wheat fermentation by Lactobacillus plantarum was investigated. Sample preparation for GC/MS detection of pirimiphos-methyl residues from fermented wheat substrate was carried out by two steps: extraction with 25mL of methanol:acetone=1:1 solvent mix for 30min, followed by clean-up procedure through a glass column with florisil coupled with elution by 25mL of ethyl acetate:acetone=4:1. To obtain the highest pesticide degradation level, the fermentation conditions were optimized according to response surface methodology. Our results showed that L.plantarum was able to reduce the level of pirimiphos-methyl in wheat. Although pirimiphos-methyl was partially labile during sterilization prior inoculation (similar to 37-50%), and there was also spontaneous chemical degradation of pesticide (similar to 6-11%), overall L.plantarum enhanced degradation from 15 to 34%, that is, to nearly 81%. Additionally, the effect of pirimiphos-methyl on the lactobacilli growth, and efficiency of fermentation, was studied where pirimiphos-methyl inhibit the growth of bacteria in concentrations higher than 5mgkg(-1), while the presence of pirimiphos-methyl did not overall affect the lactic acid fermentation.