The potency of Saccharomyces cerevisiae and Lactobacillus plantarum to dissipate organophosphorus pesticides in wheat during fermentation.

Abstract

The degradation behaviour of pirimiphos methyl with Saccharomyces cerevisiae and chlorpyrifos methyl with Lactobacillus plantarum in wheat during fermentation was studied. Yeast fermentation was especially effective for reduction of pirimiphos methyl applied at 5mgkg-1 (maximum residue limit-MRL) causing dissipation for max 48.8%. Pesticide reduction rate decreased with an increase of fortification rate. Thus in samples fortified with 25 and 75mgkg-1 a reduction up to 27.1%, and 23.7% respectively, was observed. Activity of L. plantarum was especially effective for reduction of chlorpyrifos methyl applied at 3mgkg-1 (MRL) causing dissipation for max 56.7%. This reduction rate decreased with an increase of fortification rate. In samples contaminated with 15 and 45mgkg-1 dissipation reached up to 38.6% and 34.7% respectively. For both experiments, initial inoculums sizes had no statistically significant effect on pesticides dissipation level, while concerning fermentation temperatures at all fortification levels the highest degradations occurred at 30°C. Overall, regardless fermentation parameters, the degradation rate constants of pirimiphos methyl fermented with yeast were increased comparing with control samples by 255-573, 56-116 and 119-594% in samples contaminated at MRL, 5MRL and 15MRL of pesticide, while the degradation rate constants of chlorpyrifos methyl fermented with lactobacilli were increased by 74-769, 59-237 and 46-469% respectively. These results evidenced that yeast and lactobacilli played an important role in promoting pirimiphos methyl i.e. chlorpyrifos methyl dissipation in wheat.