摘要:

Phenol, or hydroxybenzene, is both a synthetically and naturally produced aromatic compound. Microorganisms capable of degrading phenol are common and include both aerobes and anaerobes. Many aerobic phenol-degrading microorganisms have been isolated and the pathways for the aerobic degradation of phenol are now firmly established. The first steps include oxygenation of phenol by phenol hydroxylase enzymes to form catechol, followed by ring cleavage adjacent to or in between the two hydroxyl groups of catechol. Phenol hydroxylases ranging from simple flavoprotein monooxygenases to multicomponent hydroxylases, as well as the genes coding for these enzymes, have been described for a number of aerobic phenol-degrading microorganisms. Phenol can also be degraded in the absence of oxygen. Our knowledge of this process is less advanced than that of the aerobic process, and only a few anaerobic phenol-degrading bacteria have been isolated to date. Convincing evidence from both pure culture studies with the denitrifying organismThauera aromaticaK172 and with twoClostridiumspecies, as well as from mixed culture studies, indicates that the first step in anaerobic phenol degradation is carboxylation in thepara-position to form 4-hydroxybenzoate. Followingpara-carboxylation, thioesterification of 4-hydroxybenzoate to co-enzyme A allows subsequent ring reduction, hydration, and fission. Para-carboxylation appears to be involved in the anaerobic degradation of a number of aromatic compounds. Numerous practical applications exist for microbial phenol degradation. These include the exploitation of indigenous anaerobic phenol-degrading bacteria in the in situ bioremediation of creosote-contaminated subsurface environments, and the use of phenol as a co-substrate for indigenous aerobic phenol-degrading bacteria to enhance in situ biodegradation of chlorinated solvents.

ISSN:1088-9868    

DOI:10.1080/10588330008951128

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The effects of bioaugmentation with a pentachlorophenol (PCP)-adapted consortium and biostimulation with glucose as a carbon source on anaerobic bioremediation of PCP-contaminated soil were investigated in terms of the initial PCP removal rate and the extent of PCP dechlorination and mineralization. Samples from two PCP-contaminated sites were prepared, put into a series of Hungate tubes, inoculated, and fed under different conditions. Chlorophenols in the tubes were monitored over a 4-month period to measure PCP transformation in the soil. In less contaminated soil (10 mg PCP/kg soil), it was found that biostimulation with glucose at 1 g/kg soil or bioaugmentation at 0.14 g volatile suspended solids (VSS)/kg soil could greatly improve PCP degradation. The best PCP degradation was obtained when both bioaugmentation and biostimulation were applied, but higher levels of glucose (2 g/kg soil) or inoculum (0.56 g VSS/kg soil) had little additional effect. The highest initial PCP-removal rate reached 8.1 μmol/kg soil-d, which is almost 20 times greater than in the unamended controls. PCP was dechlorinated to lesser chlorinated phenols with 0.6 chlorine remaining on average, and the extent of mineralization approached 70% in 4 months. In highly PCP-contaminated soil (90 mg PCP/kg soil), PCP degradation was partially inhibited, but the relative effects of augmentation, stimulation, and combined treatments were the same as in the less contaminated soil.

ISSN:1088-9868    

DOI:10.1080/10588330008951129

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Native soil microbial populations and unadapted municipal anaerobic sludges were compared for nitramine explosive degradation in microcosm assays under various conditions. Microbial populations from an explosive-contaminated soil were only able to mineralize 12% hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) (at a concentration of 800 mg/kg slurry) or 4% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) (at a concentration of 267 mg/kg slurry). In contrast, municipal anaerobic sludges were able to mineralize them to carbon dioxide, with efficiencies of up to 65%. Reduction of RDX and HMX into their corresponding nitroso-derivatives was notably faster than their mineralization. The biodegradation of HMX was typically delayed by the presence of RDX in the microcosm, confirming RDX is used as an electron acceptor preferentially to HMX. The laboratory-scale bioslurry reactor reproduced the results of the microcosm assays, yet with much higher RDX and HMX degradation rates. A radiolabel-based mass balance in the soil slurry indicated that, besides a significant mineralization to carbon dioxide, 25% and 31% of RDX and HMX, respectively, appeared as acetonitrile-extractable metabolites, while the remaining part was incorporated into biomass and irreversibly bound to the soil matrix. About 10% of the HMX derivatives were estimated to be chemically bound to the soil matrix, while for RDX the estimation was nil.

ISSN:1088-9868    

DOI:10.1080/10588330008951130

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Substrate utilization tests with Biolog® plates were used to obtain information on shifts in community composition and on changes in the metabolic diversity and activity of microorganisms in soil polluted with hydrocarbons. and/or heavy metals. Differences between the patterns of substrate utilization of endogenous microorganisms of pristine and contaminated soils were investigated by multivariate analysis. Population changes and shifts in metabolic diversity were observed both after hydrocarbon pollution or heavy metal contamination. The overall activity on the 95 Biolog® Gram-negative (GN) substrates correlated well with the respiration rate of the soil. Soils contaminated with hydrocarbons showed higher metabolic potentials than the corresponding controls. In contrast, heavy metal pollution caused both lower metabolic activity and a loss in diversity. The Biolog® assay was found to be suitable to describe changes in functional diversity of soils caused by hydrocarbon contamination or heavy metal stress.

ISSN:1088-9868    

DOI:10.1080/10588330008951131

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Particulate, or chunk 2,4,6-trinitrotoluene (TNT), in soil was found to be recalcitrant to composting down to particle sizes of approximately 2 mm. Evidence for the colonization of TNT surfaces was obtained, but no pitting or otherwise preferential solid TNT solubilization was observed. Acetone pretreatments were used to make the chunk-TNT-contaminated soil more amenable to bioremediation. A pretreatment of acetone slurrying to dissolve and redisperse solid TNT in soil before applying remedial treatments was developed. The well-described treatment of composting was subsequently applied to native and acetone-pretreated contaminated soils. Acetone-pretreated soil responded to composting significantly better than untreated soil. After evaporating off the acetone used as pretreatment, composting microcosms held at 55°C showed sporadic removal from 3000 ppm to 300 ppm TNT in 24 days for untreated soil, while pretreated soil demonstrated conclusive removal from 3000 ppm to 18.1 ppm TNT in 6 days. Separate results indicated that residual acetone from pretreatment without subsequent evaporation was found to delay, but not otherwise inhibit, the compost's ability to degrade TNT. Community level physiological profile testing of 13-day-old composts, with pretreatment and residual acetone, suggests that three significantly different microbiological compost communities were equally adept at degrading the repartitioned TNT. The superior removal rates and efficiencies in the acetone-pretreated systems are likely to be due to the increased availability of TNT to the necessary microflora.

ISSN:1088-9868    

DOI:10.1080/10588330008951132

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A lysimeter facility at Oak Ridge National Laboratory, originally constructed to investigate leaching from low-level radioactive waste, was converted for use as an intermediate-scale facility for subsurface bioremediation research. The six experimental lysimeters are 2.5 m diameter by 4 m deep. The number and size of the lysimeters allow for replicate experiments and extensive sampling of the soil under controlled conditions. The facility provided containment of the contaminated soil, leachate, and microorganisms; positive control of the water table within the lysimeter; the ability to aerate the subsurface; multiple means of adding nutrients, electron acceptors, and electron donors to the subsurface; instrumentation for monitoring oxygen level, temperature, and moisture level; and means for obtaining samples of groundwater, soil, and liquid and gas samples from the soil pores. The flexibility of the facility allows for simulation of a wide range of subsurface bioremediation technologies. Startup and operational procedures and the advantages and disadvantages of the lysimeter facility are discussed. The facility is currently available to the bioremediation research community.

ISSN:1088-9868    

DOI:10.1080/10588330008951133

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Fibers are suggested for bacterial immobilization in trickle-bed bioreactors used for the removal of volatile organic compounds (VOCs) from air. Fiber-based bioreactors retain up to 200 to 300 mg of dry biomass per 1 g of support, which is a much larger value than that of traditional, granule-based bioreactors. Air pollutant removal efficiency for fiber-based bioreactors remains high with large inlet pollutant concentrations or space velocities (lower contact times). Efficient removal is achieved not only for a water-miscible substrate (ethanol), but also for some less water-soluble compounds, such as ethyl acetate and styrene. Specific pollutant elimination capacity per unit fiber-based biocatalyst volume (up to 4000 g/m3-h) exceeds those of biological air purification methods and is comparable to chemical methods. Unlike granule-based biocatalysts, oxygen limitation for pollutant biodegradation is not observed. Evidence obtained shows that the higher air purification efficiency is due to the greater surface-to-volume ratio of fibers when compared with granules, which results in a more efficient substrate mass transfer.

ISSN:1088-9868    

DOI:10.1080/10588330008951134

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor