| For recent years,oil which known as the "industrial blood",promoting the continuous development of industrialization,Meanwhile it also caused serious environmental pollution problems,such as widespread soil,water,sediment and air pollution.Different degrees of pollution was arose by the process during oil extraction,such as oil collection,transportation,refining,storage and so on.Oil pollution have posed huge threatens on the ecological environment and human health in the way of accumulating and taking part in the food chain in nature.Due to the wide distribution of microorganisms in the natural environment,they conducted the bioremediation in non-aqueous oil phase of the hydrophobic organic compound(hydrophobic organic compounds,HOCs).Based on the results obtained from early laboratory cooperation with China Northern Shaanxi Changqing Oilfield Company,after analysing the soil and water that surrounding by oil production area,we found that the area not only contaminated with polycyclic aromatic hydrocarbons but also accompanied by heavy metal ions,that's to say,both of them constitutes the combined pollution.Therefore,research on the biodegradation principles of polycyclic aromatic hydrocarbons(PAHs)by oil-degrading fungus under the pressure of heavy metal ions is of practical significance.In this study,a fungal strain,isolated from waste drilling samples in our laboratory,was characterized to produce biosurfactant.This strain was shown to be able to degrade crude oil efficiently.The variation of surface tense of the fungal culture was observed during crude oil degradation by this fungus.The surface tension of culture initially decreased at a very high rate,and reached the lowest level of 38 mN m-1 when degradation was terminated.The fungus was confirmed to produce biosurfactants/bioemulsifiers when challenged with crude oil as a sole carbon source.Infrared spectroscopy and thin layer chromatography suggested a lipopeptide structure for the obtained biosurfactant in this study.Combined with the results of morphological observation and ITS sequence,the strain was identified as Acremonium sp.The ITS sequence of the isolate strain had been submitted to GenBank in NCBI and an accession number KF803999 was obtained,at the same time the strain was deposited in the China Center for Type Culture Collection(CCTCC)with a depositing number of CCTCCM 2013569.The co-occurrence of polycyclic aromatic hydrocarbons(PAHs)and heavy metals(HMs)is very common in contaminated environments.It is of paramount importance and great challenge to exploit a bioremediation to remove PAHs in the systems with combined pollution.In order to simulate the actual environmental pollution,We approached this question by probing the influence of HMs coexisting with PAHs on the removal of PAHs by Acremonium sp.possessing metal resistance.The results showed that this strain was able to remove PAHs individually and in mixture efficiently and displayed high resistance to the individual HM ions(Mn2+,Fe2+,Zn2+,Cu2+,Al3+and Pb2+)in mineral culture.The removal of individual PAHs existing in mixture by this fungus was differently affected by the separate tested HMs.The presence of Cu2+enhanced the partition process of anthracene to dead or live mycelia and the contribution of the biosorption of this strain but imposed a little negative influence on the contribution of biodegradation to the total removal of anthracene existing individually in culture.However,Mn2+ had an inhibitory effect on the partition process of anthracene to dead or live mycelia and decreased the contributions of both biosorption and biodegradation of this strain to the total anthracene removal.This work showcased the value of fungi in bioremediation for the environments with combined pollution and the findings are significant for the establishment of bioremediation strategies in natural co-contaminated environments.The fungal-bacteria consortia was constructed to study the synergistic effect between fungus and bacteria,and explore the PAHs degradation pathways.The conclusion is as follows:(1)Elaborated Acremonium sp.on bioremediation of PAHs in aqueous solution including biological adsorption and biodegradation which viewed as two important process for the dead body of mycelia,the adsorption of biological is the only way to remove the solution of PAHs.For living mycelia,the biological effect of the adsorption and biodegradation removing solution PAHs efficiently.Biosorption is a prerequisite for biodegradation,and biodegradation is capable to use the accumulated PAHs on the cells and remove the PAHs by metabolic processes efficiently(2)After heavy metal tolerance experiments we found that the fungus can tolerate a certain concentration of heavy metals.Meanwhile the fungal microbial activity and lipase activity exhibited inhibition.(3)the presence of copper sulfate can accumulate the adsorption of anthracene by dead and living mycelia thus contributing to the occurrence of biological adsorption.While with the increase concentration of Cu2+,biological degradation decreased.Fungi microbial activity reduced,but the lipase activity in the copper reaches 400 mg/L does not changed any more.(4)the presence of manganese sulfate can decrease the adsorption of anthracene by dead and living mycelia,both biosorption and biodegradation are showing a decreasing trend.Fungal microbial activity and lipase activity are increased to a level as manganese sulfate concentration decreased.(5)The PAHs degradation experiment carried out by predominant fungal-bacterial consortia,fungus can assist bacertial transport and improve the PAHs removal efficiency.The degradation intermediates of anthracene are phthalic acid diisobutyl ester,1,2-benzenedicarboxylic acid and benzoic acid etc,which eventually converted into CO2 and H2O.Therefore,the bioremediation mechanisms consist two process which known as biosorption and biodegradation. |
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