Biodegradation And Biosorption Mechanisms Of Phenanthrene By Massilia Sp.WF1 And Phanerochaete Chrysosporium

Polycyclic aromatic hydrocarbons(PAHs)are typical persistent organic compounds(POPs)that widespreadly distributed in environments.PAHs have aroused considerable public concerns with respect to their high bioaccumulation,mutagenic,carcinogenic,teratogenic properties and adverse impacts on ecosystems and human health.Many studies indicated that microbial degradation is one of the primary methods for the removal of PAHs from environment.Thus,thoroughly understanding the mechanisms of PAHs bioremediation is valuable to the removal of PAHs in the polluted environment.In the present study,phenanthrene(PHE),a PAH with three benzene rings,was selected as the target pollutant because it is widespread in environment.A PHE-degrading strain Massilia sp.WF1,isolated from an aged PAHs-contaminated soil and an intensively researched model fungus for the degradation of PAHs and other OPs,Phanerochaete chrysosporium(P.chrysosporium),were chosen as our research strains.Here,we investigated(1)the biodegradation,biosorption,and the trans-membrane transport mechanism of PHE by these two strains,(2)the characteristics of PHE biosorption by natural and chemically modified P.chrysosporium,(3)the synergistic effect of WF1-P.chrysosporium co-culture on PHE degradation in soil,and(4)the mechanism of bacterial mobilization by P.chrysosporium mycelia.The main results were as follows:(1)Compared with WF1,more PHE was biosorbed and less was degraded slowly by active P.chrysosporium.Regression analysis showed that the transport rate constant of PHE from the outside solution into the cells(KinS/Vout)for WF1 was greater than the efflux rate constant of PHE from the cells to the outside solution(KoutS/Vin),while the opposite phenomena were observed for spores and mycelial pellets of P.chrysosporium.In addition,the intracellular(Kdin)and extracellular(Kdout)dissipation rate constants of PHE by WF1 were greater than those by spores and mycelial pellets.Besides,the inhibition treatments of 4?,and the presence of sodium azide,colchicine,and cytochalasin B did not prevent PHE from entering into WF1 and P.chrysosporium by the passive trans-membrane transport mechanism.(2)The results of elemental analysis,fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy spectra indicated that the natural(S0)and modified P.chrysosporium(methylation of amino groups(S1),acetylation of hydroxyl groups(S2),lipid removal(S3),esterification of carboxyl groups(S4),and base hydrolysis(S5))contain abundant functional groups and aromatic components.Moreover,the sorption isotherm of PHE on natural biomasses was linear,while it was nonlinear for the modified ones.The PHE adsorption fitted well to the pseudo-second-order kinetic model,and the sorption capacity was in the order of S5>S0>S2>S1>S3>S4.Besides,the?-?and electron donor-acceptor interactions might govern PHE sorption which processed spontaneously and exothermally.(3)The WF1 and soil indigenous microorganisms have played roles in PHE biodegradation in the non-autoclaved soil.Moreover,the relative abundances of PAHs-degrading function genes(RHDa-GP and nidA)were increased during PHE biodegradation in soil.While in the autoclaved soil,the added WF1 contributed more to PHE biodegradation than that of P.chrysosporium,the PHE degraded fastest in the co-culture system of WF1-P.chrysosporium.Meanwhile,the synergistic biodegradation effect of the co-culture system was further proved by the PHE bioremediation experiments after WF1 migrated by P.chrysosporium mycelia.(4)Both the hydrophilic WF1 and the hydrophobic WY10 can be migrated by the hydrophobic P.chrysosporium mycelia in the agar disk simulated experiment.Compared with WY10,the interaction energy change between WF1 and P.chrysosporium was lower but the interactive forces(capillary force,van der waals forces and cross-linking interaction)were stronger because WF1 possessed flagellum and the type?secretion system(TTSS).Thus,the adhesive attraction between WF1 and P.chrysosporium mycelia was stronger and more WF1 can be migrated by P.chrysosporium mycelia.