Isolation And Identification Of Efficient PAH-degrading Fungi And Their Applications In Bioremediation

Polycyclic aromatic hydrocarbons(PAHs) are a group of molecular organic compounds containing two or more benzene ring. These chemically stable compounds have toxic side effects on human body, involving teratogenicity, carcinogenicity and mutagenicity. Deposition of PAHs in the environment comes mainly from the burning of coal and oil, while industrial production, waste incineration, and vehicle emissions exacerbate the significant increase of PAHs in global environment. Widespread and scattered distribution of PAHs in the environment make it difficult to perform centralized processing; physical and chemical remediation methods cannot eliminate them completely, and can cause secondary pollution to the environment. On the contrary, bioremediation technology can solve the problem very well.By domesticating Taxus mairei rhizosphere fungi, three strains were selected with pyrene as sole carbon source. Domestication method: 2 ml 100 g/L activated soil sample were added to 48 ml 25 mg/L pyrene solution, shaking culture 5 d at 28 °C, from which 2 ml concentration liquid were taken and added to 48 ml 50mg/L pyrene solution, shaking culture 5 d at 28 °C. Finally the pyrene concentration was increased to 0.2 g/L. By morphological observation and rDNA-ITS sequence analysis three PAH-degrading fungi were identified, i.e., Abortiporus biennis, Talaromyces verruculosus and Fusarium oxysporum. Abortiporus biennis and Talaromyces verruculosus can tolerate 0.2 g/L pyrene. The two strains were grown at 30 °C in 50 mL culture medium of 250 mL flask, shaking in 150 r/min for 3 d. Flocculating rate of fermented liquid was measured. By continuous passage culture, 90% flocculating rate was achieved in two strains. In the single factor experiment, when the initial concentration of pyrene, phenanthrene, naphthalene, and acenaphthene was 50 mg/L, the degradation rate of above 95% was obtained within 7 d for the single strain. Three factors optimized in Uniform design include pH, concentration of carbon source, the concentration of the surfactant concentration, while five levels of experimental design were adopted. Solid phase microextraction(SPME)- UV method was used to determine the content of PAH substrate and degradation product. Results: when mixed fungi and 95 mg/L of pyrene, 150 mg/L of Philippine, 200 mg/L of naphthalene and 200 mg/L of acenaphthene were used, the degradation rate within 7 d were 83.76%,89.65%, 96.58%, 90.18%, respectively. The results show that bioremediation technology is currently the most promising remediation technology, which not only is of low cost and no secondary pollution, but also can be applied in large scale to delete PAHs in the environment.