Study On The Synergistic Mechanism Of Fungi On The Degradation Of PAHs By Bacteria Under Compound Pollution (polycyclic Aromatic Hydrocarbons PAHs-heavy Metals)

In modern society,crude oil has become the important "strategic energy" and be widely used as "chemical raw materials".However,the process during the petroleum exploration,extraction,transport,refining and storage also results in different degrees of pollution.Oil pollution accidents occurs frequently,it not only causes significant and negative environmental impacts such as biodiversity decrease,environmental ecological damage and haze weather,but also presents substantial hazards to human health.Heavy metals(HMs)are one of the ingredients of petroleum and often generated by various industrial activities such as mining and smelting of metalliferous ores,wastewater irrigation and so on.As a result,HMs always accompanied by crude oil.The combined pollution of HMs and polycyclic aromatic hydrocarbons(PAHs)has became a major environmental concern on a world scale due to its high harmfulness and difficult administer.Microbial remediation,which relies on microbial remediation,has the advantage of both low cost and high efficiency without further pollution and played an important role in the treatment of petroleum contaminant compared with conventional methods.Therefore,the series of experiment and research of biodegradation principles on bioaugmentation and bioremediation of PAHs by fungi-bacteria consortia in the presence of HMs hereby is of great significance on ecological restoration and environment purification of oil polluted soil.In this study,we used oil contaminated soil in North Shaanxi as samples,to screen oil-degrading strains through enrichment,separation and purification.Through morphology observation,some physiological and biochemical methods,molecular biology technique identified oil degradation strains.Their degradation ability of crude oil,aromatic hydrocarbon and the actual pollution mediation ability were also analyzed.In order to obtain a more effective bioaugmentation strategy and explore the synergistic degradation mechanism of fungi and bacteria,we simulated actual soil heavily contaminated with crude oil,through reinoculation of filamentous fungal Acremonium sp.(YC-ZJ-1)in bacteria Bacillus subbilis(Bal)inoculated bioaugmentation process.and probing the existence of fungi in soil influence on oil degradation rate,microorganism quantity and enzyme activity.To explore the synergistic degradation mechanismsin by fungal-bacterial consortia in the typical compound pollution of PAHs and heavy metals,we inquired the influence of HMs coexisting with PAHs on the removal of PAHs by fungal-bacterial consortia with metal resistance.Moreover,we designed laboratory model systems mimicking bacteria transport by fungal hyphae from the water-unsaturated phase to saturated phase and biodegradation experiments to individual aromatic hydrocarbon.The presence of two kinds of heavy metal copper sulfate and manganese sulfate had effect on the capacity of fungi to serve as vectors for the dispersion of bacteria and the synergistic degradation between fungi and bacteria was analyzed at the same time.The results were as follows:(1)Thirteen strains were isolated from oil-contaminated soil,and t-8 with oil degradation rate of 74%was screened for later use.Through morphology observation,some physiological and biochemical methods,molecular biology technique,this strain was preliminarily identified as Bacillus subtilis,with an abbreviation name of Bal and a depositing number of CCTCC AB 2014248 in the China Center for Type Culture Collection(CCTCC).This strain was shown to be able to degrade crude oil and low molecular weight aromatic hydrocarbons efficiently after further investigated by GC-MS and HPLC method.(2)The reinoculation treatments of fungus alone and fungal-bacterial consortium improved biodegradation efficiency of PAHs and heavy petroleum hydrocarbon fractions and increased the Dehydrogenase activity(DHA),a degradation enzyme indicator.However,the fungus reinoculation alone showed low capacity to transform accumulated refractory co-oxidation product C22,as its degradation process was suppressed.In this case,fungus-bacterium consortium was more effective than fungal alone because the fungus in consortia effectively utilize metabolites from bacteria,thus showed the highest degradation rate for PAHs and heavy petroleum hydrocarbon fractions.(3)The bacterium could grow in the presence of high concentrations of metals and the order of toxicity of the metals to the bacterium was Fe2+>Ni2+>Al3+>Cu2+>Mn2+>Zn2+.(4)Although the presence of Mn2+ can not increase the bacteria swimming along the fungal hyphae obviously,but the vectors capacity of fungi for the dispersion of bacteria and the degradation of fluoranthene by fungal-bacterial consortium were significantly promoted.(5)The degradation of fluoranthene by fungal-bacterial consortium,the bacteria spread along the fungal hyphae and the vectors capacity of fungi for bacteria transport were all inhibited significantly when Cu2+ was present.Conclusion:fungi-bacteria flora have the advantage in degradation of high toxic pollutants.Moreover,bioaugmentation with fungi-bacteria flora is given priority to become one of the important strategy used in soil heavily contaminated with crude oil and polycyclic aromatic hydrocarbons.