Screening Of Different Types Of Plastics Degradable Microbes And Its Potential Genetic Mechanism

With the progress and development of human society,plastic products came into human's daily life in order to improve food production and quality of human life,but at the same time,the large number of plastic products have also caused serious pollution to the environment.With the widespread use of disposable plastic products,the pressure of waste plastics on the environment has become more serious.In order to alleviate the environmental pollution caused by waste plastics,this study takes polyethylene and polyadipate / butylene terephthalate(PBAT)as the main research objects,to separate and screen plastic degrading bacteria from the environment where plastics have been existed for a long time,and use the weight loss rate to determine the degrading ability of potential plastic degrading bacteria.By observing the changes of micro-characteristics in the plastic surface before and after biodegradation,changes in the surface hydrophobicity,and whether new oxygen-containing functional groups are produced on the surface,etc.,to further verify the potential degradability of isolated plastic degrading bacteria.Finally,the whole genome sequencing analysis of the high-efficiency plastic degrading bacteria was carried out to explore the potential molecular mechanism of plastic degradation,in order to provide a theoretical basis for the microbial degradation of plastics.The main results of this study are as follows:(1)In this study,a total of 123 strains of bacteria that could grow in a medium with plastic as the sole carbon source were isolated and screened.These bacteria mainly belong to the genus Pseudomonas,Bacillus,Enterobacter,Paleobacillus,Microbacterium and Chrysobacterium.(2)The high-efficiency plastic-degrading strains Pseudomona knackmussii N1-2 and Pseudomonas aeruginosa RD1-3 caused a large number of gullies,pits and folds on the surface of the polyethylene and PBAT plastic mulches after degradation for 8 weeks,and significantly reduced the hydrophobicity of the plastic surface.At the same time,it can introduce oxygen into the stable and inert plastic chemical structure.The degradation rate of strain N1-2 to polyethylene was 5.95 ± 0.03%,the degradation rate to PBAT was 6.49 ± 0.01%;the degradation rate of strain RD1-3 to PBAT was as high as 6.88 ± 0.06%,and the degradation rate to polyethylene was 3.62 ± 0.32%.Strain N1-2 can lower the p H of the medium.(3)The full-length genomes of high-efficiency plastic-degrading strains P.knackmussii N1-2 and P.aeruginosa RD1-3 are 6,095,635 bp and 6,397,159 bp,respectively,with G + C% content of 65.65% and 66.42%,encoding 5,612 and 5,818 genes,the coding genes related to plastic metabolism-related pathways are 102 and 91 respectively,these pathways are mainly the degradation of chloroalkane and chloroalkene,the degradation of chlorocyclohexane and chlorobenzene,the degradation of polycyclic aromatic hydrocarbons,dioxins British degradation pathways,etc.Monooxygenase,dioxygenase,and hydroxylase have plastic degradation potential.The numbers genes encoding these enzymes in the genome of strain N1-2 are 6,14 and 6,respectively,and that in the genome of strain RD1-3 are 7,12 and 1respectively.In summary,the strains P.knackmussii N1-2 and P.aeruginosa RD1-3 have high efficiency of plastic degradation,and their genomes include genes encoding degradation plastic.The results of this study not only provide a theoretical basis for further study on the degradation mechanism of these two highly efficient plastic-degrading bacteria and the metabolism mechanism of plastic-degrading enzymes,but also provide potential bacterial resources for the biodegradation of waste plastics in the environment.