Screening And Characterization Of Degrading-polyacrylamide Bacteria

Polyacrylamide is a linear macromolecular compound, and it has been widely used in oilexploration, medicine, water treatment, papermaking, printing and dyeing, agriculture and otherfields. Since the polyacrylamide persists in the environment, it will change both the physical andchemical properties of the soil and water, and affect the COD of water. Under special conditionsthe polyacrylamide will degrade slowly, its decomposition acrylamide monomer（AM） has a strongbiological toxicity, which can lead to damage to the mucous membrane and function of humanorgans, and even lead to central nervous system damage. So degradation of polyacrylamide in theenvironment will become an important concern and research topics of the users andenvironmentalist.Numerous studies indicated that the microbial degradation of polyacrylamide is an effectivemethod to eliminate the cause of environmental pollution and the potential toxicity. At present, theresearch on microbial degradation of polyacrylamide mainly focus on the bacteria due to growthfastly and adaptable. In this article, a method of tablet stressing preconcentration and separationhad been used, the polyacrylamide degrading bacteria were screened from the soil and muddywater of the Daqing City chemical plant which producted the polyacrylamide, and then taken theidentification of molecular biology. Simultaneously the author studied the growth and degradationcharacteristics of these bacteria, and examined degradation characteristics and cometabolism of thecomposite bacteria for further. This research purposes were to provide bacteria source fordegrading polyacrylamide and technical support for the biological treatment of thepolyacrylamide-contaminated water. The research results were as follows:1. Three polyacrylamide-degrading bacteria were screened out by the method of tabletstressing preconcentration and separation. The initial identification were as follow: PAMB3wasBacillus subtilis, PAMB7was Bacillus licheniformis and PAMB8was Bacillus amyloliquefaciens.The results showed that PAMB3could grow only by using the polyacrylamide as the sole nitrogensources. In addition, PAMB7and PAMB8could grow by using the polyacrylamide as the solecarbon source, the sole nitrogen source, or the sole carbon/nitrogen source.2. The study based on3degrading bacteria growing by polyacrylamide as the sole nitrogensources showed that PAMB3’s the appropriate temperature ranged from25～40°C, the initialpolyacrylamide concentration was from200to700mg·L^-1and the pH value was from6to11. Themost effective degradation happened at temperature30°C, the polyacrylamide concentration500mg·L^-1and pH9, resulting in the degradation rate45.1%. PAMB7’s appropriate initial polyacrylamide concentration ranged from50to700mg·L^-1, the temperature was from25～35°Cand the pH value was from6to11. The most effective degradation happened at temperature30°C,the polyacrylamide concentration500mg·L^-1and pH8.0, resulting in the degradation rate39.9%.PAMB8’s appropriate initial polyacrylamide concentration ranged from100to700mg·L^-1, thetemperature was from25～35°C and the pH value was from7to10. The most effectivedegradation happened at temperature35°C, the polyacrylamide concentration500mg·L^-1and pH9.0, resulting in the degradation rate36.2%.3. PB378and PB37could degrade more polyacrylamide in combination of3degradingbacteria. PB378’s and PB37’s appropriate initial polyacrylamide concentration ranged from50to1000mg·L^-1, the appropriate temperature ranged from20⁴0°C, the optimum pH value rangedfrom5to12and from5to11respectively. The most effective degradation occurred at temperature30°C, the polyacrylamide concentration700mg·L^-1, pH9.0and8.0respectively, resulting in thePB378’s and PB37’s degradation rate58.2%and57.1%.4. The study on cometabolism showed NH4Cl and NH4NO3could promote the degradationrate of PB378and PB37. And the degradation rate was60.9%and60.4%,58.8%and59.5%.There were no significant effects on growing and metabolizing by petroleum. But the carbamide,beef extract and peptone caused a competitive metabolism of the degrading polyacrylamide of thePB378’s and PB37’s, and degradation rate was very low.The oil extraction wastewater containing polyacrylamide is always alkaline, and contains oil.The PB378and PB37are suitable for the polyacrylamide degradation of the oil extractionwastewater. The degradation ability of the two kinds obtains a small difference, and the authorsuggests PB378in practice.