Screening And Biodegradation Characteristics Of Carbendazim-Degrading Strains

Soil is the basic elements of the human environment, and one of mankind's survival and the material basis for productive activities, so it is link to human health closely. The application of chemical fertilizers, pesticides and other chemical substances is large and their possible application rate will be in a very long time to maintain a relatively high level. These chemicals continue to accumulate in the soil, so ecosystems have been seriously damaged and the interference caused soil deterioration of the environment, declining soil fertility and soil production declined, but also so that the contaminated soil area increase further. Therefore, pesticide-contaminated soil remediation technology research is significance.The experiment took the vegetable sheds soil contanminated by pesticides as experiment object and the effects of bactericide carbendazim on soil microorganism and soil enzymes were researched systematically. The research isolated and screened carbendizm -degrading bacterial strain and fungi strain by enrichment culture. And through their physiological , biochemical and cell morphology, features of the colony, we determined their species. The conditions of carbendazim-degrading were studied. The main results of the experiment are as follows:1. During the experiment phase, soil bacteria were significantly inhibited, but the population of bacteria restored to the control level gradually later. And the population of Actinomycosis was shown that inhibited at first and inspired by the changes later. And fungi were inhibited and eventually the population returned to the control level failed. The effect of carbendazim on soil enzyme activities was shown that carbendazim could promot the activity of hydrogen peroxidase, and the activity of urease was inhibited at first and promoted gradually. The activity of sucrase was inhibited weakly.2. Through enrichment culture method, we isolated and screened a carbendizm -degrading bacterial strain DJ-1and fungi strain T8.2, respectly. And through their physiological and biochemical and cell morphology, features of the colony, we determine the bacterial strain DJ-1 was Pseudomonas and the fungi strain T8.2 was Trichoderma. 3. The influence of culture conditions on the growth of carbendizm -degrading stains and the degradation of carbendazim was great. And only in appropriate circumstances and conditions, the strains can give full play to their degradate abilities. The optimum degradation conditions of carbendazim and the optimum growth conditions of stains was consistent. And the additions of carbon and nitrogen sources could greatly facilitate stains growth and the degradation of carbendazim. pH7.0, the culture temperature was 30℃, inoculum size was 10%, adding 0.5% peptone, was the optimum degradation conditions of the strain DJ-1 degradaing carbendizm, and the degradation of carbendazim up to 90%. But the optimum degradation conditions of the strain T_8.2 degradaing carbendizm was pH6.0, the culture temperature was 25℃, inoculum size was 10%, adding 0.5% yeast powder. These two strains could degradate some commonly-used pesticides.4. The results of fermentation were shown that: the number of viable bacteria DJ-1 could up to maxium in pH 7.0 and 30℃, installed capacity 50/250mL liquid cultured and cultivated 36 hours. Through orthogonal experiments, we obtained the best group of fermentation medium, was A₂B₃C₁D₂(beef extract 0.6%, peptone 2%, glucose 1% and NaCl 0.8%). T8.2 was fermentated by using fluid - solid two-phase fermentation method, and the optimum fermentation conditions were 25℃, pH 5.5, and solid-phase fermentation time for 7 days. When we control the ratio of straw and bran was 7:3, the number of strain spores was largest, up to 1010 cfu/g. The most important is that straw is cheap and easy to get to as the main fermentation raw material.5. The results of the degradation of carbendazim in soil were showed that: inoculum size of cabendazim-degrading strains impacted on the carbendazim degradation directly. When the inoculum size of strains was 10%, carbendazim was degradated 86.1% and 75.2% in original soil respectly, and were followed in air-dry soil and drying soil. The reason of this result may be due to the existence of microorganism in original soil. When the mixed ratio of Trichoderma and bacteria was 1:1, the degradation of carbendazim was superior to adding a single strain. It is probably due to the enteraction of Trichoderma and bacteria.