Dissipation of chlorpyrifos-methyl by Saccharomyces cerevisiae during wheat fermentation

Abstract The dissipation of chlorpyrifos-methyl during wheat fermentation by Saccharomyces cerevisiae was investigated. The effect of pesticide on the yeast growth, and on the efficiency of wheat fermentation, was studied. Obtained results indicate that growth of yeast in medium was significantly inhibited by chlorpyrifos-methyl applied in higher than 5MRL concentration (growth inhibition 53%), reaching inhibition of 88.3 and 90.1% at the two highest doses (15MRL, 20MRL). The presence of chlorpyrifos-methyl in wheat, overall negatively affected the yeast fermentation expressed through pH alteration, number of yeast cells mg −1 and CO 2 production. Further in order to evaluate chlorpyrifos-methyl dissipation during preparation of wheat substrate, the effect of sterilization on reduction of pesticide in wheat was determinate. Dissipation of pesticide was extremely high at all fortification levels (MRL, 5MRL and 15MRL), reaching 79.4, 79.2 ad 78.8% respectively. During the incubation period in samples without yeast there was no further reduction of the chlorpyrifos-methyl with time on different temperatures. Finally, activity of yeast itself caused pesticide reduction for approx. 14.8, 18.8 and 19% respectively, without significant differences regarding fortification levels, or variations of incubation parameters. Overall, maximum reduction of approximately 94.2, 98.0 and 97.8% at three fortification levels respectively was reached during fermentation.