Degradation behaviors of seven organophosphorus pesticides in skimmed milk inoculated with Streptococcus thermophilus or Lactobacillus helveticus

摘要

Streptococcus (S.) thermophilus or Lactobacillus (L) helveticus were inoculated into skimmed milk at 42-C to study their impacts on the degradation behaviors of seven selected organophosphorus pesticides (OPPs) including dimethoate, fenthion, malathion, methyl parathion, monocrotophos, phorate and trichlorphon. The residual OPPs in the spiked milk were extracted with an acetone-acetonitrile solvent in proportion of 1:4 (v/v), purified with dichloromethane and quantified in a gas chromatography. The analysis results showed that during an incubation of 24 h, the residual amount of the investigated OPPs in the milk decreased gradually about 23-49% as the occurrence of OPPs degradation. The applied strains exhibited accelerating effects mainly on the degradation of methyl parathion, monocrotophos, phorate and trichlorphon. Among the OPPs investigated, both phorate and trichlorphon were more susceptive to the strains with an enhanced degradation rate about 109-114% and 61-77%, while malathion exhibitedresistance to the strains with an unchanged degradation rate. The present study shows that some lactic acid bacteria might have the ability to degrade some OPPs and provide safety help to some fermented foods.