Bacterial-Degradation of Pesticides Residue in Vegetables During Fermentation

An application of large quantity of agricultural pesticides in rural area is a common practice in order to increase the productivity and yield, to protect the agricultural crop from pests and prevent products lost due to insect and bacterial contamination is a common practice. Resistance and mutation of some pests to chemicals are the causes of using larger quantity of pesticide in the developing countries. According to the rate of degradation of chemicals, pesticides can be categorized as sensitive or tolerant to decomposition. Their destruction might be occurred under exposing to the normal atmospheric conditions or by biological activity of the soil microorganisms such as Pseudomonas, Flavobacterium, Alcaligenes, Rhadococcus, Gliocladium, Trichoderma and Penicillium. These microorganisms use the pesticides as their carbon and energy sources (Aislabie & Lloyd-Jones, 1995). Because agricultural pesticides are mostly artificial synthetic compounds without any identical in the nature, they are substantially tolerant towards degradation in natural conditions. In many cases, stability of these pesticides to the biological destruction arises from their insolubility in water, as the microorganisms are incapable of decaying such materials. Malathion, carbamate, pyrethriod, diazinon, dichloropicolinic acid and phenylalkanbic are sensitive pesticides to the hydrolytic activity of microorganism enzymes. Extracellular enzymes of the bacteria are capable of cleavage broad range of chemical pesticides. Apart from the natural structure of the pesticides, their volatility and adsorption ability to the soil compounds are also important factors affect sensitivity to the biological cleavage. These factors themselves are dependent on temperature, light, soil moisture and pH. The more fugacity of the pesticides, the more transfer of them to the atmosphere. Higher moisture of the soil ease degradation rate of the water soluble pesticides by the microorganisms, while reduce their volatility. Some of the pesticides such as diazinon are very sensitive to the low pH range and their degradation at this range dramatically occur (Muller & Korte, 1975; Freed et al., 1979). Because organophosphorous compounds are decomposed faster and easier compared to the organochlorine compounds, their application have been increasing day by day. Consumption of fruits and vegetables containing organochlorine components residue causes undesirable health disorders especially on the nerve system (Racke & Frank, 1997; Pehkonen & Zhang, 2002; Lal & Saxena, 1982). This danger is more acute in Iran because of the improper attitude that excessive application of the pesticides leads to the more efficient deterioration of the pests.