Biosorption And Biodegradation Of Polycyclic Aromatic Hydrocarbons In Aqueous Solution And Soil Slurry Systems By A Consortium Of White Rot Fungi And Their Bioremediation Implication

Persistent organic pollutants (POPs) have aroused widespread concerns because of their ubiquity, toxicity, persistent and long-range transport. The transport, transformation, bioavailability, and control method of POPs have been widely studied. As an ubiquitous medium in the environment, microorganisms play a critical role in environmental interfacial behavior, transport processes, and bioremediation practices of POPs. Microorganisms can be viewed as a bio-sorbent that accommodates POPs (biosorption). and simultaneously as a bioreactor that degrades them (biodegradation). Both biosorption and biodegradation of microorganisms are important processes in sewage treatment and sludge disposal, organic contaminated soil remediation, as well as the environmental behaviors of organic pollutants. So far, however, a few studies applied biological materials as sorbents to abate organic pollutants, and most of them focused on the biosorption of dead microorganisms with common organic pollutants (such as dye and pigment, phenols) rather than POPs in solution. The biosorption by live microorganisms and the relationship of biosorption and biodegradation are not elucidated. Thus, the fate of POPs in wastewater was unveiled. Meanwhile, the biosorption and biodegradation of POPs by live microorganisms in complex soil system have not been studied, which are vital to accurately understand the environmental behavior and bioavailability of POPs. The studies on regulating methods and bioaugmentation approaches of biosorption and biodegradation are necessary to provide a theoretical gist for the effective bioremediation of POPs contaminated soil. In this dissertation, the advances on biosorption and biodegradation of organic pollutants, and their bioremediation implication were reviewed. With polycyclic aromatic hydrocarbons (PAHs) as model POPs and white rot fungi as model microorganisms, the mechanism and influential factors of biosorption by heat-killed white rot fungi in solution were investigated. The biosorption and biodegradation of Phanerochaete chrysosporium (Pc, a model white rot fungi) in a continuous batch process were studied. A novel soil-slurry system containing allochthonous mycelial pellets of as a separable biophase was set up, and then used to distinguish biosorption and biodegradation contributions to bio-dissipation of dissolved-and sorbed-PAHs. The effects of allochthonous fungi on indigenous microbes were studied in sterilized and unsterilized soil slurry systems. Finally, a long-term sewage irrigated soil from Shengyang. China was selected to study the biosorption and biodegradation of PAHs in field polluted soil. The main original conclusions and innovations of this work are drawn as follows:(1) The mechanism and influential factors of the biosorption of PAHs on dead fungal biomass were studied, and relationship of sorption properties with structural characterization was discussed. The biosorption of white rot fungi was dominated by partition, and the partition medium was attributed to the extractable lipids and polymeric lipids. The carbon-normalized partition coefficient (Koc) was negatively correlated with the polarity index [(O+N)/C, atomic ratio]. The Koc values of PAHs to fungal biomass were comparable to those of soil. Sorption and desorption on fungal biomass was reversible, while for soil as a sorbent. obvious desorption hysteresis was observed. The biosorption of phenanthrene was enhanced by co-exsited Cu2+. Binding of Cu2+ neutralized the negative charge of the fungi surface, making it less hydrophilic and enhancing hydrophobic partitioning of phenanthrene. A specific interaction mechanism. i.e., cation-πbonding between phenanthrene and complexed Cu2+, contributed to the total biosorption enhancement. The cation-πinteraction was negatively correlated with the polarity index.(2) The biosorption and biodegradation of PAHs by Phanerochaete chrysosporium in solution and its regulating method were illustrated. Biosorption was the only contribution to the removal of PAHs by dead fungal biomass, therefore, which was not capable to remove PAHs continuously. After 40 d incubation,60.62% of phenanthrene and 49.21% pyrene were degraded by live fungi, which were viewed as a bio-sorbent and a bioreactor,. With the biodegradation of sorbed-PAHs, the removal percentage of live fungi was obviously higher than that of dead fungi. Carbon source and nitrogen source were critical factors to regulate biosorption and biodegradation. Biosorption was enhanced by rich carbon source, while biodegradation was stimulated by limited nitrogen source. With the augmentation of rich-carbon and limited nitrogen source, the biodegradation percentage of phenanthrene by live Pc were larger than 90% in a continuous batch process. The co-exsited Cu2+ can stimulate both biosorption and biodegradation, but in the continuous batch process, the increasing toxicity with the accumulation of Cu2+ limited biodegradation.(3) A novel soil-slurry system containing mycelial pellets of Phanerochaete chrysosporium as a separable biophase was firstly set up to identify contributions of biosorption and biodegradation to bio-dissipation of dissolved- and sorbed-PAHs, especially the coupling effect of biosorption and biodegradation. The fresh PAHs bonded to the soil particles gradually became less bioavailable. while the biosorbed-PAHs in Pc body as an interim pool exhibited reversibly desorption and were almost exhausted via biodegradation. The field aged PAHs in soil can be extracted by live fungal body and degraded subsequently. The efficiency of fungal extraction was negatively correlated with the Kow values of PAHs. The biodegradation kinetics of PAHs by allochthonous Pc and soil indigenous microorganisms were higher than those predicted by a coupled desorption-biodegradation model, suggesting both allochthonous and indigenous microorganisms could access sorbed-PAHs. After 90-day incubation, the respective biodegradation percentages for phenanthrene and pyrene sharply increased to 94.9% and 90.6% when amended with live Pc, indicating allochthonous fungi and indigenous microbes can synergistically attack sorbed-PAHs. The biodegradation of aged PAHs can be promoted by inoculating allochthonous Pc and addition of non-ionic surfactant such as Tween 80.