Screening And Immobilization Mechanism Of Phenanthrene Efficient Degrading Bacteria

In this study,PHE was used as the target pollutant,and a new group of aerobic microbial degradation bacteria LFH-1 was isolated from polluted river surface sediments,and its microbial community structure was identified and its degradation characteristics were studied.Through further screening to degrading bacteria group,a new type of efficient strains were YM-6 PHE degradation bacterium,using 16 S r RNA technology of YM-6 strains were identified,and YM-6 strains was determined by the single factor experiment and the best conditions for growth and degradation using gas chromatography-mass spectrometry(GC-MS)to identify strain degradation products,preliminary judgment YM-6 degradation pathway of PHE degradation.Finally,selects the polyvinyl alcohol(PVA)and sodium alginate(SA)as immobilized carrier,by embedding-crosslinked immobilized methods will select PHE YM-6 fixed high efficiency degradation bacterium,degradation by simulation experiment to explore the immobilized microorganisms technology practical application value,provide data basis for PAHs in situ bioremediation and practical experience.The results show that:LFH-1 bacteria mainly include Diaphorobacter 83.35%,Pseudomonas 7.46%,Castellaniella 1.67%,Aquamicrobium 1.65%,Achromobacter0.68%,Stenotrophomonas 0.39%.Thermomonas 0.34%,Acinetobacter 0.16%,Azorhizophilus 0.13%.The degradation rate of PHE(100 mg/L)by bacteria reached95.78% within 60 h,with a wide p H range(ph5-ph11),better adapted to low temperature stress(20-35 ?),and able to tolerate high salinity(2%)and high concentration of pollutants(PHE 400 mg/L).Strain YM-6 was preliminarily identified as Diaphorobacter sp.the strain removed 96% of PHE(100 mg/L)within 52 h.The optimal growth temperature of strain ym-6 was 30 ?,and it was suitable for high temperature stress(30-40 ?).The optimal p H of growth is 7,which can withstand 400 mg/L of PHE.The addition of phthalic acid can promote the degradation ability of the strain,while the addition of salicylic acid and 2-naphthol can inhibit the growth of the strain.The PHE metabolites of ym-6 strain showed that the degradation of PHE by YM-6 mainly went through the phthalic acid pathway,but there were differences in details.Under the action of YM-6strain,PHE was converted into 1,2-dihydro-acenaphthylenee by opening the ring,on the one hand,it entered the phthalic acid pathway,on the other hand,it was directly decomposed into 2-isopropyl-5-methylphenol,and then converted into ?-resorcylic acid and entered the TCA cycle.Experiments with different ratios of PVA and SA showed that 10% PVA+0.5%SA was the optimal mixture ratio,and the immobilized pellets were made with uniform appearance and texture,showing that the surface of the pellets was uneven and porous,which could provide more sites for microbial adsorption and growth and provide an appropriate microenvironment for microbial growth.When the initial pollutant concentration was low(10 mg/Kg),the degradation rates of immobilized microorganisms and free bacteria were little different,and the removal rates of PHE on the 14 th day were 88.65% and 91.52%,respectively.When the initial concentration was high(50 mg/Kg or 100 mg/Kg),the free bacteria could not grow normally,the natural digestion rate of PHE reached 83.51% within 35 days,and the removal rate of PHE by immobilized microorganisms reached 97.89% at 35 days.