Application of Hydronium-Releasing Bioslurry Reactor for Pyrene Biodegradation in Acidic Soil

Autor: Chu-Chun Yu, 于筑君
Rok vydání: 2011
Druh dokumentu: 學位論文 ; thesis
Popis: 100
Polycyclic Aromatic Hydrcarbons (PAHs) are mainly produced due to oil leakage or incomplete fossil fuel generated by thermal cracking being distributed as a wide range of pollutants in the environment. The distribution of acidic red soil is very widespread in Taiwan, and up to 33 % can be polluted by oil pollution improving opportunity. Bioslurry reactor technology can effectively promote the decomposition of the pollutants during the process and reduce the cost of remediation without casuing secondary pollution. In this study, a novel hydronium-releasing bioslurry reactor (HRBR) was designed and successfully develpoed to degrade high-molecular-weight (HMW) PAHs (Pyrene) at high concentration in the acidic soil. The bacteria was cultured in the outer reactor tank, releasing hydrogen ions at a rate of 1.06 x 10-4 ([H+]/day), which is significantly higher than the inner reactor tank’s hydrogen ion releasing rate of 7.95x 10-5 ([H+]/day). A high hydrogen ion releasing rate is required in order to maintain the stable growth and thereby accelerating the degradation rate of the acidophilic Pyrene degrading bacteria. Acidophilic Pyrene was applied to the bacteria for the degradation, and within 18 days, the concentration of Pyrene decreased from 1,996 mg/L to below method detection limits. The proposed first-order model biodegradation rate is 0.0973 day-1 (r2 = 0.8567), which is faster than neutral Pyrene degrading bacteria, with a biodegradation rate of 0.0696 day-1 (r2 = 0.9504), which takes 42 days for the concentration to drop below method dectection limits. The reactor also produced a power density of 0.0146 ~ 0.0414 (mW/cm2) and coulombic efficiency was 40.51 %. The microbial community structures used Sulfobacillus sp., uncultured Geobacter sp., uncultured Desulfobacca sp., Rhodanobacter thiooxydans and Alicyclobacillus disulfidooxidans. As for acidophilic Pyrene degrading bacteria populations, the forms were free-living Mycobacterium sp., Rhodanobacter sp., Pseudomonas sp., Acinetobacter sp. and Sphingomonas sp.. Other bacteria in the composition of attached bacteria were uncultured Acidobacteria bacterium, uncultured Verrucomicrobium sp. and uncultured Planctomycetales bacterium. On the other hand, the community level physiological profile (CLPP) analysis shows that both acidiphilic Pyrene degrading bacteria and neutral Pyrene degrading bacteria have signicantly different physical performance group for free-living and attached bacteria. In the free state, the Pyrene concentration decreased with the changes in bacteria population. However, the attached bacteria were maintained regardless of Pyrene concentration. Presumably, the performance of microbial physiological differences in group is because the degradation process results in a higher variety of water-soluble metatboilites, and free-living bacteria lead to abundant diversity. Using a Biolog MT2 microplate, combined with HPLC/UV determination of the concentration of Pyrene degradation experiments, three bacteria were screened for the degradation of Pyrene and its metabolites by using a functional gene primer positive reaction testing. These strains are Pseudomonas putida strain 31920-1 (Ident. = 100 %), Deinococcus grandis strain DSM 3963 (Ident. = 98 %) and Brevibacterium frigoritolerans strain DSM 8801 (Ident. = 100 %). The diversity detection analysis was administerd to the dioxygenase gene of the acidophilic Pyrene degrading bacteria. The aromatic ring hydrolsing dioxygenase gene (RHDα) and the Rieske domain of the α subunit were both found. However the path segment of Protocatechuate metabolic 3,4-dioxygenase (P34O) and Catechol 2,3-dioxygenase (C23O) gene vaired with the decomposition process. Based on the degradation of acidophilic Pyrene degrading bacteria population structure, there is biological information exchange throughout the aromatic ring hydrolysing dioxygenase gene (ARHDα) functional gene primer (MSFR) design, and it was successfully used to detect oil contaminated sites. Compared to using 16S rDNA primers for detection, MSFR is better suited for detection dioxygenase of microbial metabolic potential targets. The results of this study will be applied to HRBR treatment of organic pollutants in Taiwan by the acidic soil of the site. In addition to reducing the cost of bioslurry reactor, it can enhance the effect of the degradation rate of biological and bioremediation technology to understand the key functional genes.
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