The Study Of Screening Identification And Degradation Characteristics Of Polyurethane Plastic Degrading Strain

In recent years,there are endless reports about plastic pollution.Due to the stable chemical properties of plastic products,plastic waste has caused serious environmental pollution problems.As one of the large plastic family of plastics,the pollution of the waste to the environment can not be underestimated.At present,there are incineration and landfill methods for the treatment of polyurethanes,but both methods are not the best methods for solving polyurethane pollution.The method of treating polyurethane waste by microorganism is considered as the most environmentally friendly method,and is also one of the hotspots in the research of polyurethane waste at present.Finding microorganisms that can efficiently degrade polyurethanes is a major difficulty in this research.In this study,8 downward bacteria isolated from the water treatment system of Shenzhou IX and X were used as screening strains.It indicated that S10-2 strain has the ability to degrade polyurethane.In order to verify the degradation ability of S10-2 strain,the degradation experiment of S10-2 strain on polyether polyurethane foam and polyester polyurethane film under lean nutrient environment was designed and the degradation behavior was characterized accordingly.The main conclusions are as follows:(1)Gram stain identification results show that strain H2?H6 and S10-2 belong to gram-positive bacterium,the strain S10-2 belonged to Bacillus sp.Strain H1?H3? H4?H5and S10-1 belong to gram-negative bacterium.(2)The preliminary screening results showed that the S10-2 strain can degrade the Impranil DLN emulsion and make the LBD plate produce a transparent circle,which also can improve the transparency of the LBD liquid medium.(3)In the experiment of degradation of polyether polyurethane foam by S10-2 strain,the number of bacteria in the degradation process shows that the strain can survive and thrive in the environment of nitrogen-containing inorganic salt medium;the mass loss results shows that the S10-2 strain has a certain degradation effect on the polyether polyurethane foam;however,the surface morphology(SEM)of the polyether polyurethane foam indicated the structure of the foam is not too much change,it can be explained that the S10-2 strain has low degradation efficiency for polyether polyurethane and the experimental scheme needs to be improved.S10-2 was analyzed for its ability to utilize solid polyester PU as a sole carbon source in shaking culture for 9 weeks.The degradation was analyzed through measurement of weight loss,scanning electron microscopy(SEM),gel permeation chromatography(GPC).SEM revealed the appearance of widespread cracks on the surface of PU film.Increase in polydispersity index was observed in GPC,which indicates chain scission as a result of microbial treatment.We have identified an extracellular esterase activity which might be responsible for the polyurethanolytic activity.(4)The first complete sequencing of polyurethane degradation bacteria was completed using the third generation high throughput sequencing technology.The results shows that: S10-2 genome consists of a circular chromosome(3609810bp),the number of genes is 4224,the average longth of genes is 854.6 bp,the density of genes is 1.04,GC content of the S10-2 chromosome was 44.49%.S10-2 strain consists a plasmid(73041bp),the number of genes is 102,the average longth of genes is 716 bp,the density of genes is 1.226,GC content of the S10-2 chromosome was 35.6%.