Screening Of Benzene-degrading Bacteria And Their Degradation Characteristics

Toxic organic compounds such as phenol and aniline are discharged into the environment directly or indirectly with industrial waste water,through food,drinking water and other ways into the human and animal body,affect organ function,damage the body's health,and even life-threatening.In this study,three kinds of toxic organic compounds,phenol,resorcinol and aniline,were selected as the research object,to screen for microorganisms that can degrade these toxic contaminants.After the experiment,the final selected microbial strains that can be highly efficient degradation of phenol,aniline,resorcinol,respectively.In this experiment,the detection methods of phenol,resorcinol and aniline were4-aminoantipyrine method,N-(1-naphthyl)ethylenediamine azo spectrophotometry,respectively.The sludge samples were collected from a sewage ditch in the city of Qufu,Shandong province,after enrichment,screening,re-screening and other steps,six strains of phenol-degrading bacteria were screened out,after acclimation,the strain F-2 could completely degrade phenol with initial concentration of 900 mg/L,strains F-5,E-2,E-3,E-4 could completely degrade phenol with initial concentration of 1200 mg/L,and strain F-1 could completely degrade phenol with initial concentration of 1500 mg/L.Three strains of aniline-degrading bacteria were screened out,After acclimation,and the degradation rates of the strain BA-3 and BA-4 in the initial concentration of 350 mg/L aniline were up to 50.39%,100% respectively.Strain BA-2 could completely degrade aniline with initial concentration of 1000 mg/L.Re-screening out four resorcinol biodegradable bacteria,After acclimation,the degradation rates of the isolates JB-1 and JB-2 to resorcinol at the initial concentration of 300 mg/L were 24.88%,24.09% respectively.The degradation rates of the isolates JB-4 to resorcinol with the initial concentration of 400 mg/L and 700mg/L were 94.58% and 26.35% respectively.Strain JB-3 could completely degrade resorcinol with initial concentration of 1700 mg/L.The phenol degrading bacteria F-1,aniline degrading bacteria BA-2 and resorcinol degrading bacteria JB-3,capable of effectively degrading the degrading bacteria of higher concentration of organic matter,were selected as the follow-up study object.Identified by 16 S rDNA molecular biology,strain F-1 is Alcaligenes sp.,strain BA-2 is Rhodococcus sp.,and strain JB-3 is Paracoccus sp.The degrading bacteria were subjected to immobilization treatment.The effects of threeenvironmental factors including initial concentration of toxic organic matter,temperature and pH on the degradation of organic pollutants by free bacteria and their immobilized pellets,and the effect of the number of times of immobilization pellets on the degradation of organic compounds were studied.The results showed that the tolerances of the immobilized strains were not significantly changed compared with free bacteria.The culture temperature and the pH value of the culture medium had a great effect on the degradation of toxic organic compounds.The maximum initial concentration of the strain F-1 free bacteria and its immobilized pellets could completely degrade phenol was 1500 mg/L,could be effective degrade phenol in the range of 26~36?,pH5~9,the best degradation conditions were 30?,pH7,under this condition,immobilized pellets completely degraded phenol was only 54 h.After repeated use of 9 times,the immobilized pellets were damaged,and the degradation rate of phenol could reach to 51.97% after repeated use of 7 times.The degradation conditions of the strain BA-2 and its immobilized pellets were initial concentration of aniline with 1000 mg / L,could both at 26 ~ 38? and pH5 ~ 10 range effective degradation of aniline.The optimum degradation conditions were 30?,pH 7,under this condition the immobilized pellets cuold completely degrade aniline just in 48 h.Ater repeated use of 10 times,the immobilized pellets were damaged,and the degradation rate of aniline was still up to53.13% after repeated use of 8 times.When the maximum initial concentration of resorcinol was 1700 mg/L,the strain F-1 free bacteria and its immobilized pellets could effectively degrade resorcinol in the range of 22 ~ 38? and pH5 ~ 10.The optimum degradation conditions were 30? and pH7.Under this conditions,the immobilized beads could completely degraded resorcinol only in 42 h.After repeated use of 12 times,the immobilized pellets were damaged,the degradation rate of resorcinol could still reach 54.29% after repeated use of 10 times.