Screening And Characters Of Carbendazim-Degrading Strains

China is a power country in a pesticide production and usage. China has been ranked the world’s top in pesticide usage, and pesticide production in China has been ranking second in the world, only after the United States. There are two sides in pesticide usage.On the one hand it can prevent and control the plant diseases and insect pests, and also can improve the production of crop production. On the other hand it can pollute the environment, causing harm to human and animals’ safety. Therefore, soil remediation,especially microbial remediation, has been attracting more and more attention.In this experiment, a high efficient, low toxic, broad-spectrum systemic fungicide carbendazim will be as the research object, the main research contents include: isolation and screening of carbendazim-degrading bacterium, and identification of the species by mor PHological observation, PHysiological and biochemical characteristics and 16 S rDNA;the growth characteristics, and gra PHing the growth curve; researching the optimum growth environment; understanding of the degradation characteristics of degrading-bacteria through the research of the culture temperature, the PH value, initial concentration, inoculation amount, different carbon sources, different nitrogen sources,and other factors; effect of the thermal stability of carbendazim-degrading enzyme, PH stability, and temperature on enzyme activity; the degradation characteristics of carbendazim in soil; the effect of carbendazim usage on soil enzymes activity.The carbendazim-degrading enzyme, concentrated, separated and purified from the suburbs of Hefei where have fertilized the carbendazim for a long-term, was named DY-1.The bacterial colony was circular, 1 ~ 2mm diameter, pale yellow, protrusive surface, neat edge, smooth surface and opaque. Observed under the microscope, the bacteria was rod-shaped, non spore producing. Gram staining experiments were negative. DY-1 was initially identified as pseudomonas genus(Pseudomonas sp.) through mor PHological observation, PHysiological and biochemical tests and 16 S rDNA identification.Through the culture, the strain DY-1 was found entering into the logarithmic PHase after a short delay period, and o to the stable stage after around 36hs’ culture, and the stable stage could last for a long period. Through the research of the growth environment of strain DY-1, it can be known that the optimum growth temperature is 30℃, the optimum PH is 7,and the external carbon sources can be put to good use, among which the glucose is the best carbon source for promoting the growth of the strain DY-1, which was shown most obviously. External nitrogen source can promote the growth of strains, among which theyeast extract was the best. The study of strain degradation showed that: the best temperature for degradation of strain DY-1was 30℃; The best PH value for degradation of strain DY-1was PH7; the initial concentration of carbendazim was higher, the degradation rate would be lower; the best inoculation amount was 5%; under the optimum temperature,PH value, inoculation concentration, glucose was the best carbon source, and peptone was the best nitrogen source.From the view of stability, temperature within10℃-45℃could inhibit the activity of carbendazim-degrading enzyme; the stability of degrading enzyme can be effected by acid-base, which will be relatively stable in neutral weak alkaline environment. From the effect of enzymatic degradation, temperature within25℃-35℃,the effects of the carbendazim-degrading enzyme can not be affected obviously, and the effect would be best at 30℃; degrading enzymes had the best effect in neutral environment, which in accordance with the best degrading PH value of degrading enzymes.Adding the degrading bacteria, the degrading rate of non sterilized soil is much higher than that of sterilized soil; the increase of water content in soil can promote the degradation of carbendazim. Bioremediation of carbendazim contaminated soil was provided scientific basis through the research of degradation characteristics of carbendazim in soilSoil catalase activity was in activated state after being applied with carbendazim with low concentration; while soil catalase activity was in the state of first inhibition and then activation after applied being applied with carbendazim with high concentration. The negative correlation was shown in the relationship between the carbendazim concentration and the activation degree of catalase. Soil sucrase activity was mainly shown as inhibition after being applied with carbendazim, and carbendazim concentration and the inhibition rate were in positive correlation. The inhibition degree of soil sucrase would reduced gradually with time extended, and even a slight activation would present; soil urease would in the state of first inhibition and then promotion after being applied with carbendazim, and carbendazim concentration and enzyme activity were in negative correlation.The degree of activity been activated is increased slowly during the late stage of the culture.The effects of carbendazim on the growth of different microbes in soil are not same: c arbendazim can inhibit the growth of bacteria in the soil samples, and the degree of inhibiti on increased with the enhancement of the concentration; carbendazim could inhibit the gro wth of the fungi in the soil with different concentrations, and similar to the bacteria, the inh ibition degree of fungal growth was in connection with carbendazim concentrations, the hi gher the concentration, the more obvious the inhibition; carbendazim promoted basically the growth of actinomycetes in the soil sample, the higher the concentration, the more obvious the of the promotion.