Isolation Of Polyacrylamide Degradation Bacteria And Study Of Its Cooperation With Earthworm

Polyacrylamide(PAM) as an important kind of water-soluble organic polymer, because of its unique excellent properties, it is applied in various areas, such as water treatment, agriculture, oil and so on.But with the increasing of application scope and scale, a lot of polyacrylamide was released to environment, and then accumulated, migrated and transformed. It is certainly harm to ecological environment. In addition, the polyacrylamide could produce a strong toxicity amide monomer(AM), which can produce direct or indirect harm to the human, and damage the environment at the same time. So we should pay more attention to deal with environment polyacrylamide problems, seek effective methods to degrade polyacrylamide. In this study, from the perspective of biodegradation, we screened two polyacrylamide degradation bacteria PAM1 and PAM5 from sludge of Harbin wenchang sewage treatment plantusing plate stress domestication method. Identifying the strains; investigating the utilization of polyacrylamide by the microorganisms as different nutrient source, suitable conditions for the growth and degradation of degrading-polyacrylamide bacteria and compound bacteria; Compound bacteria were inoculated to soil which contained polyacrylamide, and research the effect of polyacrylamide degraded by earthworms and microorganisms.This research purposes were to provide source of bacteria for polyacrylamide degradation, explore the feasibility of polyacrylamide contaminated soil repaired by earthworms and microorganisms. The research results were as follows:By observing the colony and strain morphology, physiological-biochemical test, biochemical test and molecular biology identification. The initial identification were as follows: PAM1 is Comamonas kerstersii, PAM5 is Comamonas terrigena.Both PAM1 and PAM5 strains could grow using polyacrylamide as the only nitrogen source,the only carbon source, and the only carbon-nitrogen source. When polyacrylamide was used as the only nitrogen source, the effect of degradation is the best. By the method of single factor variable, the results showed that the suitable polyacrylamide initial concentration range for PAM1 growth and degradation was 300-1100 mg/L, the temperature range was 25-35 ℃, the initial pH range was 6.0-9.0. Among them, PAM1’s optimal polyacrylamide initial concentration was 700mg/L, the optimal temperature was 30 ℃, the optimal initial pH value was 7.0, the optimum inoculation rate was 5%. Under the optimal condition, PAM1’s degradation rate was 36.26%. The suitable polyacrylamide initial concentration range for PAM5 growth and degradation was300-1100 mg/L, the temperature range was 25-40 ℃, the initial pH range was 5.0-10.0. Amongthem, PAM5’s optimal polyacrylamide initial concentration was 900 mg/L, the optimal temperature was 30℃, the optimal initial pH value was 7.0, the optimum inoculation rate was 5%.Under the optimal condition, PAM1’s degradation rate was 40.34%.The effect of polyacrylamide degraded by compound bacteria was better than single strain.Compound bacteria’s optimal polyacrylamide initial concentration is 900 mg/L, the suitable polyacrylamide initial concentration for degradation range was 300-1300 mg/L, optimal temperature is 30 ℃, the suitable temperature range for growth and degradation was 20-40 ℃,The optimal initial pH value was 7.0, the suitable pH range for growth and degradation was5.0-10.0.Under the optimal condition,compound bacteria’s degradation rate was 50.54%.Influence of earthworms on soil polyacrylamide degraded by bacteria was researched.four treatments were set: the control without inoculation(CK),inoculation of bacteria(B), puting in earthworms(E)and inoculation of bacteria and earthworms(BE)at the same time.The results showed that each treatment had significant difference after 24 d in the same initial concentration of polyacrylamide. It was in the sequence of BE > B > E > CK,. In different initial concentration of polyacrylamide cases, the degradation of polyacrylamide in the same treatment(B, BE, CK)decreased with the increasing initial concentration of pollution.The degradation rate of polyacrylamide in E treatment only fluctuate with the increasing initial concentration of polyacrylamide.