Enumeration of aromatic oxygenase genes to evaluate biodegradation during multi-phase extraction at a gasoline-contaminated site

• Published in: Journal of hazardous materials Vol. 163; no. 2; pp. 524 - 530
• Main Authors: Baldwin, Brett R., Nakatsu, Cindy H., Nebe, Jennifer, Wickham, Gene S., Parks, Christopher, Nies, Loring
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 30-04-2009; Elsevier
• Subjects: Applied sciences; Benzene - metabolism; Benzene Derivatives; Biodegradation, Environmental; Bioremediation; BTEX; Chemical engineering; Dioxygenases; Exact sciences and technology; Gasoline - microbiology; Groundwaters; Hydrocarbons - metabolism; Industrial Waste; Multi-phase extraction; Multienzyme Complexes; Natural water pollution; Oxygenase; Oxygenases - metabolism; Petroleum; Pollution; Quantitative PCR; Reactors; Toluene - metabolism; Water Pollutants, Chemical - metabolism; Water treatment and pollution; Xylenes - metabolism; Oxygenase; BTEX; Bioremediation; Quantitative PCR; Petroleum; Multi-phase extraction; Metabolite; Activation; Aquifers; Pollution; Decontamination; Xylene; Bacteria; Aromatic compound; Oxidation; Microbial community; Organic compounds; Ground water; Biodegradation; Community structure; Hydrocarbon; Pollutant behavior; Toluene; Denaturing gradient gel electrophoresis; Aerobe; Real time; Real time system; Polymerase chain reaction; Air flow; Phenols; Degradation product
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2008.07.002

Multi-phase extraction (MPE) is commonly used at petroleum-contaminated sites to volatilize and recover hydrocarbons from the vadose and saturated zones in contaminant source areas. Although primarily a physical treatment technology, the induced subsurface air flow can potentially increase oxygen supply and promote aerobic biodegradation of benzene, toluene, ethylbenzene, and xylenes (BTEX), the contaminants of concern at gasoline-contaminated sites. In this study, real-time PCR enumeration of aromatic oxygenase genes and PCR-DGGE profiles were used to elucidate the impact of MPE operation on the aquifer microbial community structure and function at a gasoline-contaminated site. Prior to system activation, ring-hydroxylating toluene monooxygenase (RMO) and naphthalene dioxygenase (NAH) gene copies were on the order of 10
6 to 10
10
copies
L
−1 in groundwater samples obtained from BTEX-impacted wells. Aromatic oxygenase genes were not detected in groundwater samples obtained during continuous MPE indicating decreased populations of BTEX-utilizing bacteria. During periods of pulsed MPE, total aromatic oxygenase gene copies were not significantly different than prior to system activation, however, shifts in aromatic catabolic genotypes were noted. The consistent detection of RMO, NAH, and phenol hydroxylase (PHE), which catabolizes further oxidation of hydroxylated BTEX metabolites indicated the potential for aerobic biodegradation of dissolved BTEX during pulsed MPE.