Bioremediation Of Petroleum-contaminated Soil Enhanced By Biosurfactants

In recent years,the oil industry has developed rapidly,and the problem of environmental pollution along with oil has become more and more serious.Microbial remediation is an important method to degrade petroleum hydrocarbon contaminants in the environment.However,the poor solubility and refractory nature of petroleum hydrocarbons are the main factors limiting their biodegradation.The introduction of surfactants is an effective method to improve their bioavailability.In the environment of repairing petroleum hydrocarbon pollution,some microorganisms can both degrade pollutants and metabolize and secrete surfactants,thereby improving the bioavailability of petroleum hydrocarbons.In this paper,the activated sludge from the sludge concentrate tank of the Coking Plant of Huanyu Coking Co.,Ltd.is taken as the source of the bacteria.The petroleum is the sole carbon source,and the stable mixed bacteria are domesticated by liquid phase acclimation,and the effect of the surfactant is separated and screened.Good strains,optimize their environmental factors,and explore the effect of inoculating high-producing surfactant strains and adding rhamnolipidenhanced mixed bacteria to repair oil-contaminated soil.The main findings are as follows:(1)A group of petroleum-degraded mixed bacteria were domesticated from the activated sludge in the sludge concentration tank of the coking plant of Xuzhou Huanyu Coking Co.,Ltd.High throughput sequencing results show flora,predominantly Community of:(.Paenibacillus sp)(.Acinetobacter sp)(.Pseudomonas sp)class Bacillus,Acinetobacter,Pseudomonas,Chryseobacterium(Chryseobacterium sp.),Bacillus chrysogenum(Rhodanobacter sp.),Rhizobium(Rhizobiales sp.),Rhodospirillum(Rhodospirillaceae sp.),and the like.A biosurfactant-producing strain FDM1 was screened and cultured in an inorganic medium with sodium citrate as the sole carbon source for five days,the surface tension of the fermentation broth was reduced to 37.1 mN/m,and the oil drain diameter was It is 6.5 cm.The 16 S rDNA gene sequence analysis showed that the strain FDM1 was Pseudomonas aeruginosa.The infrared result of the surfactant produced by the strain FDM1 showed that the functional groups contained in the molecular structure of the surfactant produced by the strain FDM1 mainly include a hydroxyl group,a C-H bond,a C-O-C bond,and a C=O bond.(2)The growth curve of the strain FDM1 in the fermentation medium was determined.The results showed that the strain was in the logarithmic growth phase 4 to 16 hours after inoculation,and entered the stable phase after 16 hours of inoculation.The effects of sodium citrate,glucose,beef extract and paraffin as carbon sources on the fermentation of the strain were studied.The results showed that the best carbon source of the strain was sodium citrate.The results were as follows: peptone,urea,NaNO3,(NH4)2SO4 as nitrogen.The effect of the source on the fermentation of the strain showed that the optimal nitrogen source of the strain was NaNO3.Experiments on temperature and pH fermentation of the strain showed that the optimal environmental factors for the strain were: temperature of 35 oC and initial pH of 7.The orthogonal test results showed that the optimum conditions for the fermentation of the strain were: pH=7,with 5 g/L NaNO3 as the nitrogen source and 30 g/L sodium citrate as the carbon source,and the fermentation temperature was 35 °C.(3)The results of biological surfactant-enhanced mixed bacteria to degrade petroleum hydrocarbons show that in the system with water-soil ratio of 10:1 and petroleum hydrocarbons and mixed bacteria,inoculating biosurfactant-producing bacteria can strengthen mixed bacteria to petroleum hydrocarbons.The degradation rate of petroleum hydrocarbons increases with the increase of the amount of bacteria in the strain FDM1.When the inoculum of the mixed flora was 10% and the inoculum of the strain FDM1 was 8%,the degradation rate of petroleum hydrocarbons reached a maximum of 26.5% when the culture time was 60 h.In the system,the addition of rhamnolipids below the critical micelle concentration inhibits the degradation of petroleum hydrocarbons by mixed bacteria.The addition of rhamnolipids at or above the critical micelle concentration can enhance the degradation of petroleum hydrocarbons by mixed bacteria..When the concentration of rhamnolipid was 5 CMC and the culture time reached 72 h,the highest degradation rate of petroleum hydrocarbons was 29.8%.