Screening And Identification Of Strains Degrading Polyethylene (PE) And Researches On Degradation Characteristics Of LBX-2Strian

Because of its high molecular weight, too strong hydrophobicity in thesurface, too low surface energy and lack of functional groups recognized by microbialenzymatic systems and so on, polyethylene plastics are degraded very slowly in anatural environment. So a large amount of accumulation resulted in "White pollution"for a long time, which is very harmful to our ecological environment. In order todegrade polyethylene wastes thoroughly by the way of the biodegradation, It becomes atopic of this study to researches on screening and cultivating strains degradingpolyethylene plastics from soils.Isolation of seven strains degrading low molecular weight polyethylene （LMWPE）The loams where the PE films were buried were made into10-1-10-6of soilsuspensions.10-4,10-5and10-6of the suspensions were respectively added to Medium A（a piece of3*3cm film，10g peptone，0.1mL paraffin oil，0.7g K₂HPO₄，0.7gKH₂PO₄，0.7g MgSO₄·7H₂O，1.0g NH₄NO₃，0.005g NaCl，0.002g FeSO₄·7H₂O，0.002gZnSO₄·7H₂O，0.001g MnSO₄·H₂O，1000mL aqua destillata、pH7.2）and Medium B（a piece of3*3cm film，3g beef extract，10g peptone，0.1mL paraffin oil，0.7gK₂HPO₄，0.7g KH₂PO₄，0.7g MgSO₄·7H₂O，1.0g NH₄NO₃，0.005g NaCl，0.002gFeSO₄·7H₂O，0.002g ZnSO₄·7H₂O，0.001g MnSO₄·H₂O，1000mL aqua destillata、pH7.2）.Then the cultures were added to basic mediums without carbon source but purePE powders（molecular weight is2,000） for further isolation and purification. Atlast,seven strains were isolated from the loams, and they were named LBX-1、LBX-2、LBX-3、LBX-4、LBX-5、LBX-6and LBX-7,of which LBX-1、LBX-2、LBX-5andLBX-7strains were of actinobacteria; LBX-3、LBX-4and LBX-6strains were ofeumycota. Seven strains were put into basic mediums without carbon source but purePE powders （molecular weight is5,000） for second purification. Screening and identification of strains degrading high molecular weight polyethylene（HMWPE）All of seven strains were respectively incubated in basic liquid mediums withoutcarbon source but pure PE powders （molecular weights are100,000and400,000）. After40days&60days, compared with the CK, the cultures of LBX-1, LBX-2and LBX-5strain all became muddy, of which the cultures of LBX-1and LBX-2were moremuddy. This suggested that these three strains could utilize PE powders （molecularweights are100,000and400,000）, thus they are of high molecular weight polyethylene（HMWPE） degradable ones. According to the phenotypic, physiological andbiochemical characteristics, and16SrDNA gene cloned sequence, LBX-1strain wasfinally identified as Amycolatopsis orientalis; LBX-2strain was finally identified asStreptomyces albogriseolus.Screening of strain with the ability to adhere to the surface of PE filmSeven activated strains were spreaded onto the surface of PE film modified withphotosensitizers for the cultivation at30℃.After14days, only LBX-6strain couldgrow out in the surface of PE film. It suggested that the strain could overcome stronghydrophobicity and low surface energy in the surface, meanwhile it could alsoovercome the inhibition of photosensitizers. Thus, LBX-6strain had the ability toadhere to the surface of PE film modified with photosensitizers. According to thephenotypic characteristics, LBX-6strain was initially identified as Eurotiaceae.Researches on degradation characteristics of LBX-2strainAccording to the curves of absorbances and growth, the result suggested that theabsorbance of PE powders（molecular weights is400,000） was best in600nm, and theexponential phase of LBX-2strain was between5days and14days during theincubation. According to the variance analysis of data of L2554orthogonal experimentdesigned by SSPS18.0, the optimization design of environmental factors onbiodegradation of PE powders（molecular weights is400,000） for LBX-2strain was32℃of growth temperature,7.3of pH, three rings of strain and33days of cultivationperiod. Meanwhile, the conclusion of researches on cometabolism was that CH3COONacould better promote the biodegradation of the powders for LBX-2strain.