Aliphatic halogenated hydrocarbons produce volatile Salmonella mutagens

Production of volatile mutagenic metabolites from 5 halogenated promutagens was examined by a simple modification of the conventional Salmonella/microsome mutagenicity assay. This method incorporates the taping together of 2 agar plates face to face during the initial portion of their incubation at 37 degrees C. By varying the contents of the soft agar in each of the two plates with respect to promutagen, S9 and tester strain cells, mutagenesis due to volatile promutagens and their metabolites could be quantitated separately. Using the taped plate assay, volatile mutagenic metabolites were detected from the promutagens 3-(2-chloroethoxy)-1,2-dichloropropene, the herbicides diallate, triallate and sulfallate, and the flame-retardant tris-(2,3-dibromopropyl) phosphate (Tris-BP). All compounds except Tris-BP were also found to be volatile promutagens. The mutagenic metabolites accounted for 50-80% of the activity of these compounds observed in the standard assay. Morever, our studies suggest that a small, but appreciable percentage of the mutagenic metabolites from all 5 compounds escaped detection in the conventional, untaped assay. Mutagenic activity of the volatile mutagenic metabolites from diallate was quenched by various Salmonella tester strains independent of their responsiveness to diallate mutagenesis. Detection of volatile mutagen formation from diallate was also prevented by cysteine and glutathione, but not by DNA or metyrapone. This taped plate method for the Salmonella assay should facilitate future investigations of the detection, isolation and identification of volatile mutagenic metabolites from other promutagenic compounds or mixtures.     

In Situ emulsification and mobilization of gasoline range hydrocarbons using surfactants

In this article the conditions that govern surfactant‐enhanced emulsification and mobilization of petroleum hydrocarbons in soil are reviewed. The effect of soil properties, groundwater constituents, and differing surfactant solutions on the emulsification process is discussed. A constant head soil flushing apparatus used to characterize surfactant‐enhanced mobilization of m‐xylene is described. Data showing the effect of surfactant‐enhanced mobilization on m‐xylene removal efficiency in washed sand is presented. Flushing solutions were used at concentrations from below to well above the critical micelle concentration (CMC) of the surfactants used. Removal efficiencies are shown to vary with surfactant concentration and with surfactant type. Flushing solutions of anionic, nonionic, and anionic/nonionic surfactant mixtures were evaluated.     

A Mycobacterium strain with extended capacities for degradation of gasoline hydrocarbons

A bacterial strain (strain IFP 2173) was selected from a gasoline-polluted aquifer on the basis of its capacity to use 2,2, 4-trimethylpentane (isooctane) as a sole carbon and energy source. This isolate, the first isolate with this capacity to be characterized, was identified by 16S ribosomal DNA analysis, and 100% sequence identity with a reference strain of Mycobacterium austroafricanum was found. Mycobacterium sp. strain IFP 2173 used an unusually wide spectrum of hydrocarbons as growth substrates, including n-alkanes and multimethyl-substituted isoalkanes with chains ranging from 5 to 16 carbon atoms long, as well as substituted monoaromatic hydrocarbons. It also attacked ethers, such as methyl t-butyl ether. During growth on gasoline, it degraded 86% of the substrate. Our results indicated that strain IFP 2173 was capable of degrading 3-methyl groups, possibly by a carboxylation and deacetylation mechanism. Evidence that it attacked the quaternary carbon atom structure by an as-yet-undefined mechanism during growth on 2,2,4-trimethylpentane and 2,2-dimethylpentane was also obtained.     

Metabolism of volatile chlorinated aliphatic hydrocarbons by Pseudomonas fluorescens

A Pseudomonas fluorescens strain designated PFL12 was isolated from soil and water that were contaminated with various chloroaliphatic hydrocarbons. The isolate was able to metabolize 1,2-dichloroethane, 1,1,2-trichloroethane, 1,2-dichloropropane, 2,2-dichloropropane, and trichloroethylene.     

Degradation of gasoline aromatic hydrocarbons by two N2-fixing soil bacteria

Two bacterial strains, 3A and 5A, isolated from soil, were selected for their ability to degrade gasoline aromatic compounds and to fix N₂. Strains 3A and 5A have been ascribed to the genera Agrobacterium and Alcaligenes, respectively. Using gasoline as the sole carbon source these strains were as effective at degrading benzene, toluene and xylene as Pseudomonas putida ATCC12236, a reference biodegrading strain.     

Biotransformation of monoaromatic and chlorinated hydrocarbons at an aviation gasoline spill site

A shallow water table aquifer under the U.S. Coast Guard Air Station at Traverse City, MI, has acclimated to the aerobic and anaerobic transformation of monoaromatic hydrocarbons (BTX) released from an aviation gasoline spill. The aquifer also exhibits reductive dechlorination of a chlorinated solvent spill adjacent to the aviation gasoline spill. The groundwater is buffered near neutrality. The aviation gasoline plume is methanogenic and the aquifer contains enough iron minerals to support significant iron solubilization. Field evidence of both aerobic and anaerobic biotransformation of monoaromatics was confirmed by laboratory studies of aquifer material obtained from the site. In the laboratory studies, the removal of the monoaromatics in the anaerobic material was rapid and compared favorably with removal in aerobic material. The kinetics of anaerobic removal of monoaromatics in the laboratory were similar to the kinetics at field scale in the aquifer. Biotransformation of the chlorinated solvents was not observed until late in the study, when daughter products from reductive dechlorination of the chlorinated solvents were identified by GC/MS.     

Metabolism of volatile chlorinated aliphatic hydrocarbons by Pseudomonas fluorescens.

A Pseudomonas fluorescens strain designated PFL12 was isolated from soil and water that were contaminated with various chloroaliphatic hydrocarbons. The isolate was able to metabolize 1,2-dichloroethane, 1,1,2-trichloroethane, 1,2-dichloropropane, 2,2-dichloropropane, and trichloroethylene.     

Biodegradation of gasoline: kinetics, mass balance and fate of individual hydrocarbons

The degradation of gasoline by a microflora from an urban waste water activated sludge was investigated in detail. Degradation kinetics were studied in liquid cultures at 30 degrees C by determination of overall O2 consumption and CO2 production and by chromatographic analysis of all 83 identifiable compounds. In a first fast phase (2 d) of biodegradation, 74% of gasoline, involving mostly aromatic hydrocarbons, was consumed. A further 20%, involving other hydrocarbons, was consumed in a second slow phase (23 d). Undegraded compounds (6% of gasoline) were essentially some branched alkanes with a quaternary carbon or/and alkyl chains on consecutive carbons but cycloalkanes, alkenes and C10- and C11-alkylated benzenes were degraded. The degradation kinetics of individual hydrocarbons, determined in separate incubations, followed patterns similar to those observed in cultures on gasoline. Carbon balance experiments of gasoline degradation were performed. The carbon of degraded gasoline was mainly (61.7%) mineralized into CO2, the remaining carbon being essentially converted into biomass.     

Selection of microbial populations degrading recalcitrant hydrocarbons of gasoline by monitoring of culture-headspace composition

A methodology was devised and was found useful for the selection of populations degrading recalcitrant hydrocarbons. The work was part of a programme aiming at developing knowledge of the intrinsic capacities of autochtonous microflorae of the environment for gasoline biodegradation. The methodology involved monitoring the progress of degradation in enrichment liquid cultures on the selected hydrocarbon by gas chromatographic analysis of CO2 production and O2 consumption. Populations degrading in particular o-xylene, 1,2,4-trimethylbenzene, cyclohexane were obtained. Concerning 2,2,4-trimethylpentane (isooctane), one microflora (and a pure strain derived from it) growing on this hydrocarbon were obtained from gasoline-polluted water.     

Biodegradability of diesel oil

In batch culture diesel oil was degraded rapidly, with a maximum growth rate (for a consortium of microorganisms) of 0.55 h^-1. The corresponding yield Y _SX was 0.1 Cmol/Cmol. In a continuous stirred tank reactor the maximum dilution rate was about 0.25 h^-1, with a yield of 0.3 Cmol/Cmol. With a residence time of 1 day 82% of the influent oil was degraded. In the batch reactor, of the mixture of linear and branched alkanes the linear alkanes were degraded fastest and with the highest yield. Only after most of the linear alkanes had disappeared were the branched alkanes consumed. In a CSTR a large part of the branched alkanes was not degraded.     

Biodegradability of bacterial surfactants

This work aimed at evaluating the biodegradability of different bacterial surfactants in liquid medium and in soil microcosms. The biodegradability of biosurfactants by pure and mixed bacterial cultures was evaluated through CO₂ evolution. Three bacterial strains, Acinetobacter baumanni LBBMA ES11, Acinetobacter haemolyticus LBBMA 53 and Pseudomonas sp. LBBMA 101B, used the biosurfactants produced by Bacillus sp. LBBMA 111A (mixed lipopeptide), Bacillus subtilis LBBMA 155 (lipopeptide), Flavobacterium sp. LBBMA 168 (mixture of flavolipids), Dietzia Maris LBBMA 191(glycolipid) and Arthrobacter oxydans LBBMA 201(lipopeptide) as carbon sources in minimal medium. The synthetic surfactant sodium dodecyl sulfate (SDS) was also mineralized by these microorganisms, but at a lower rate. CO₂ emitted by a mixed bacterial culture in soil microcosms with biosurfactants was higher than in the microcosm containing SDS. Biosurfactant mineralization in soil was confirmed by the increase in surface tension of the soil aqueous extracts after incubation with the mixed bacterial culture. It can be concluded that, in terms of biodegradability and environmental security, these compounds are more suitable for applications in remediation technologies in comparison to synthetic surfactants. However, more information is needed on structure of biosurfactants, their interaction with soil and contaminants and scale up and cost for biosurfactant production.     

Degradation of volatile hydrocarbons from steam-classified solid waste by a mixture of aromatic hydrocarbon-degrading bacteria

Steam classification is a process for treatment of solid waste that allows recovery of volatile organic compounds from the waste via steam condensate and off-gases. A mixed culture of aromatic hydrocarbon-degrading bacteria was used to degrade the contaminants in the condensate, which contained approx. 60 hydrocarbons, of which 38 were degraded within 4 d. Many of the hydrocarbons, including styrene, 1,2,4-trimethylbenzene, naphthalene, ethylbenzene, m-/p-xylene, chloroform, 1,3-dichloropropene, were completely or nearly completely degraded within one day, while trichloroethylene and 1,2,3-trichloropropane were degraded more slowly.     

A rapid column technique for trapping and collecting of volatile fungal hydrocarbons and hydrocarbon derivatives

A custom-made stainless steel column was designed to contain various materials that would trap the hydrocarbons and hydrocarbon derivatives during the processes of fungal fermentation ultimately yielding preparative amounts of volatile organic substances (VOCs). Trapping materials tested in the column were Carbotrap materials A and B (Supelco) as well as bentonite-shale from the oil bearing areas of Eastern Montana, the former allowed for the effective and efficient trapping of VOCs from purged cultures of Hypoxylon sp. Trapping efficiencies of various materials were measured by both gravimetric as well as proton transfer reaction mass spectroscopy with the Carbotraps A and B being 99% efficient when tested with known amounts of 1,8-cineole. Trapped fungal VOCs could effectively be removed and recovered via controlled heating of the stainless steel column followed by passage of the gases through a liquid nitrogen trap at a recovery rate of ca 65–70%. This method provides for the recovery of mg quantities of compounds normally present in the gas phase that may be needed for spectroscopy, bioassays and further separation and analysis and may have wide applicability for many other biological systems involving VOCs. Other available Carbotraps could be used for other applications.     

Biodegradability of Food-Associated Extracellular Polysaccharides

Exopolysaccharides (EPSs) produced by lactic acid bacteria, which are common in fermented foods, are claimed to have various beneficial physiological effects on humans. Although the biodegradability of EPSs is important in relation to the bioactive properties, knowledge on this topic is limited. Therefore, the biodegradability of eight EPSs, six of which were produced by lactic acid bacteria, was compared with microorganisms from human feces or soil. EPS-degradation was determined from the decrease in polysaccharide-sugar concentration and by high-performance size exclusion chromatography (HPSEC). Xanthan, clavan, and the EPSs produced by Streptococcus thermophilus SFi 39 and SFi 12 were readily degraded, in contrast to the EPSs produced by Lactococcus lactis ssp. cremoris B40, Lactobacillus sakei 0-1, S. thermophilus SFi20, and Lactobacillus helveticus Lh59. Clearly, the susceptibility of exopolysaccharides to biological breakdown can differ greatly, implying that the physiological effects of these compounds may also vary a lot. Received: 23 August 1999 / Accepted: 5 October 1999     

Biodegradability of Erika fuel oil

The biodegradation of the fuel oil resulting from the Erika wreck was studied by computerized gas chromatography in laboratory cultures over 80 days. The total extent of biodegradation was around 11%. The degraded compounds were the molecules of the light cracking fraction used to dilute the distillation residue, as well as n-alkanes and part of the branched alkanes. Part of the polycyclic aromatic hydrocarbons PAH and alkyl PAH was also degraded. The very low biodegradability of the Erika fuel is attributable to its chemical composition. The product is rich in components that are inherently resistant or refractory to microbial metabolism such as resins, asphaltenes and polycyclic saturated and aromatic hydrocarbons.     

糖蜜酒精废液厌氧生物降解性能的BMP分析

在中温条件下,对pH值和营养比例两个影响因素进行了糖蜜酒精废液的BMP分析,探讨酒精废液在厌氧消化过程中产甲烷量、COD浓度的变化情况,以及COD去除率与产气量、pH值之间的关系。研究结果表明,厌氧处理法能够使糖蜜酒精废液的有机负荷大大降低,CODcr去除率最高可达90．6％;在调节营养比例的条件下,pH=8．5时甲烷菌活性最佳,其中COD．P=300：1的产甲烷量最高。