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PubMed1996

The genus Sphingomonas: physiology and ecology.

Exploitation of the metabolic capabilities of the genus Sphingomonas could provide important commercial benefits to biotechnology. Recent advances have demonstrated that these organisms have unique abilities to degrade refractory contaminants, to serve as bacterial antagonists to phytopathogenic fungi, and to secrete the highly useful gellan exopolysaccharides. Unfortunately, Sphingomonas are also animal pathogens and can readily degrade the copper pipes in drinking water distribution systems. The closely related Zymomonas could be important for commercial ethanol production. These Gram-negative aerobic bacteria are characterized by an outer membrane that contains glycosphingolipids, but lacks lipopolysaccharide. Their distribution in environmental samples has not been systematically examined as yet.

Animals↗
PubMed2004

Protection of mesopore-adsorbed organic matter from enzymatic degradation.

Synthetic mesoporous alumina and silica minerals with uniform pore geometries, and their nonporous analogues, were used to test the role of mineral mesopores (2-50 nm diameter) in protecting organic matter from enzymatic degradation in soils and sediments. Dihydroxyphenylalanine (L-DOPA), a model humic compound, was irreversibly sorbed to both mineral types. The surface area-normalized adsorption capacity was greater for the mesoporous minerals relative to their nonporous analogues. The degradation kinetics of free and mineral-sorbed L-DOPA by the enzyme laccase was monitored in a closed cell via oxygen electrode. Relative to freely dissolved L-DOPA, nonporous alumina-sorbed substrate was degraded, on average, 90% more slowly and to a lesser extent (93%), likely due to laccase adsorption to alumina. In contrast, relative to free L-DOPA, degradation of nonporous silica-sorbed L-DOPA was enhanced by 20% on average. In the case of mesoporous alumina and silica-sorbed L-DOPA, the enzyme activity was 3-40 times lower than that observed for externally sorbed substrate (i.e., L-DOPA sorbed to nonporous minerals). These results provide strong evidence to support the viability of the mesopore protection mechanism for sequestration and preservation of sedimentary organic matter and organic contaminants. Nanopore adsorption/desorption phenomena may aid in explaining the slow degradation of organic contaminants in certain soils and sediments and may have implications for environmental remediation and biotechnological applications.

Adsorption↗
PubMed2005

Effect of agricultural antibiotics on the persistence and transformation of 17beta-estradiol in a Sequatchie loam.

A laboratory incubation study was conducted to investigate the effect of agricultural antibiotics (sulfamethazine, tylosin, and chlortetracycline) on the persistence and transformation of 17beta-estradiol in Sequatchie loam. We measured concentrations of 17beta-estradiol and its primary metabolite (estrone) in soils spiked with antibiotics and 17beta-estradiol. Dehydrogenase activity (DHA) was also measured as an indicator of the total microbial activity of the soils. The presence of antibiotics significantly decreased transformation of 17beta-estradiol to estrone. There was a positive correlation between the DHA and the concentrations of estrone in soil spiked with 17beta-estradiol only, implying that the reaction is mainly catalyzed by dehydrogenases. However, the positive correlation was weakened in soil spiked with 17beta-estradiol and antibiotics together. We recommend that any study evaluating the fate and transport of estrogenic hormones in soil should include the effect of agricultural antibiotics because antibiotics and estrogenic hormones are commonly excreted together in environmental samples.

Anti-Bacterial Agents↗
PubMed2006

Growth conditions impact 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE) accumulation by Cucurbita pepo.

Laboratory experiments were conducted to study the effects of soil moisture content, planting density, plant age, and the growth of multiple generations on the bioconcentration of weathered p,p'-DDE by the plant Cucurbita pepo. As soil moisture content increased from 7.4% to 29.9% (by weight), rates of contaminant accumulation by plant roots were increased by more than a factor of 2. Higher planting density also led to higher uptake, as the root bioconcentration factor (BCF, dry-weight ratio of contaminant concentration in the tissue to that in the soil) increased by 15-fold as the number of plants per pot was raised from 1 to 3. Concentrations of the compound in plant roots were inversely related to plant age, with root BCF declining by approximately a factor of 3 as plants aged from 14 to 28 d. Finally, no change in the bioavailability of the compound was observed in successive generations of plants grown in the same contaminated soil. The results suggest that phytoremediation is influenced by a number of factors and that the cleanup of contaminated soil can be enhanced by an understanding of environmental and other conditions affecting plant growth and bioconcentration.

Biodegradation, Environmental↗
PubMedDate not supplied

Comparative performance studies of water lettuce, duckweed, and algal-based stabilization ponds using low-strength sewage.

A bench-scale continuous-flow wastewater treatment system comprising three parallel lines using duckweed (Spirodela polyrhiza), water lettuce (Pistia stratiotes), and algae (natural colonization) as treatment agents was set up to determine environmental conditions, fecal coliform profiles and general treatment performance. Each line consisted of four ponds connected in series fed by diluted sewage. Influent and effluent parameters measured included environmental conditions, turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrate, nitrite, ammonia, total phosphorus, fecal coliforms, mosquito larvae, and sludge accumulations. Environmental conditions and fecal coliforms profiles were determined in the sediments (0.63 m), suspensions (0.35 m), and surfaces (0.1 m) of each pond. Acidic conditions were observed in the pistia ponds, neutral conditions in duckweed ponds, and alkaline conditions in algal ponds. Fecal coliforms log removals of 6, 4, and 3 were observed in algal, duckweed, and pistia ponds, respectively, in the final effluents, with die-off rates per pond of 2.7, 2.0, and 1.6. Sedimentation accounted for over 99% fecal coliform removal in most of the algal and pistia ponds. BOD removal was highest in the duckweed system, followed by pistia and algae at 95%, 93%, and 25%, respectively. COD removals were 65% and 59%, respectively, for duckweed and pistia, while COD increased in algal ponds by 56%. Nitrate removals were 72%, 70%, and 36%, respectively for duckweed, pistia, and algal ponds. Total phosphorus removals were 33% and 9% for pistia and duckweed systems, while an increase of 19% was observed in the algal treatment system. Ammonia removals were 95% in both pistia and duckweed and 93% in algal systems. Removals of total dissolved solids (TDS) were 70% for pistia, 15% for duckweed, and 9% for algae. Mosquito populations of 11,175/m(2), 3516/m(2), and 96/m(2) were counted in pistia, algal, and duckweed ponds, respectively. Low turbidity and low sludge accumulation characterized the macrophyte ponds. Performance in the removal of fecal coliforms in the algal-based treatment system and organic load removal in both macrophytes and algal-based treatment systems met the Ghana Environmental Protection Agency guideline values.

Animals↗
PubMed2004

[Methodology of enacting standards for remediation of contaminated soils].

Remediation technology for contaminated soils is being developed rapidly in recent years. However, there is a hysteresis in enacting remediation standards for contaminated soils. In particular, no corresponding research has been done in China. Methodology of enacting standards for the remediation of contaminated soils is discussed in order to promote the work in this field. It is emphasized that technological cleanup levels including limits of detection, environmental background levels and regulatory cleanup levels should be fully considered in the enactment of remediation standards.

Biodegradation, Environmental↗
PubMed2000

Microbial degradation of phthalic acid esters under anaerobic digestion of sludge.

The microbial degradation by anaerobic sludge of three phthalates, priority pollutants, listed by both China National Environmental Monitoring Center and the U.S.EPA, namely, dimethyl (DMP), di-n-butyl (DBP) and di-n-octyl (DOP) phthalates was investigated. The experimental results indicated that the biodegradation rate and the biodegradability of three phthalates under anaerobic conditions appeared to be related to the length of the alkyl-side chains. More than 90% of DMP and DBP with the short alkyl-side chain phthalates can be degraded, whereas the DOP degradation appeared to be relatively slow under the same experimental conditions. The quantity of methane produced was measured and the results showed that both the ester groups and the phthalate ring were mineralized at a significant rate. The kinetics study demonstrated that the biodegradation of three phthalates conformed to the first-order model with respect to their concentrations.

Bacteria, Anaerobic↗
PubMed2006

Molecular monitoring of microbial population dynamics during operational periods of anaerobic hybrid reactor treating cassava starch wastewater.

This study characterized the microbial community and population dynamics in an anaerobic hybrid reactor (AHR) treating cassava starch wastewater. Methanogens and nonmethanogens were followed during the start-up and operation of the reactor, and linked to operational and performance data. Biomass samples taken from the sludge bed and packed bed zones of the AHR at intervals throughout the operational period were examined by 16S rRNA fluorescence in situ hybridization (FISH). The start-up seed and the reactor biomass were sampled during the feeding of the wastewater with a chemical oxygen demand (COD) value of 8 g L(-1) and a hydraulic retention time (HRT) of 8 days. These samples were characterized by the predominance of cells with long-rod morphology similar to Methanosaeta spp. Following a sharp operational change, accomplished by increasing the COD concentration of the organic influent from 8 to 10 g L(-1) and reducing the HRT from 8 to 5 days, there was a doubling of the organic loading rate, a reduction of the COD removal efficiency, as well as decreased methane content in the biogas and an accumulation of total volatile acids in the reactor. Moreover, this operational change resulted in a significant population shift from long-rod Methanosaeta-like cells to tetrad-forming Methanosarcina-like cells. The distributions of microbial populations involved in different zones of the AHR were determined. The results showed that nonmethanogens became the predominant population in both sludge and the packed bed zone. However, the percentage of methanogens in the packed bed zone was higher than that in the sludge bed zone. This higher percentage of methanogens was likely caused by the fact that the packed bed zone provided a suitable environmental condition with an appropriate nutrient availability for methanogen growth.

Bacteria, Anaerobic↗
PubMed1997

Bacterial degradation of styrene in waste gases using a peat filter.

A biofiltration process was developed for styrene-containing off-gases using peat as filter material. The average styrene reduction ratio after 190 days of operation was 70% (max. 98%) and the mean styrene elimination capacity was 12 g m-3 h-1 (max. 30 g m-3 h-1). Efficient styrene degradation required addition of nutrients to the peat, adjustment of the pH to a neutral level and efficient control of the humidity. Maintenance of the water balance was easier in a down-flow than in an up-flow process, the former consequently resulting in much better filtration efficiency. The optimum operation temperature was around 23 degrees C, but the styrene removal was still satisfactory at 12 degrees C. Seven different bacterial isolates belonging to the genera Tsukamurella, Pseudomonas, Sphingomonas, Xanthomonas and an unidentified genus in the gamma group of the Proteobacteria isolated from the microflora of active peat filter material were capable of styrene degradation. The isolates differed in their capacity to decompose styrene to carbon dioxide and assimilate it to biomass. No toxic intermediate degradation products of styrene were detected in the filter outlet gas or in growing cultures of isolated bacteria. The use of these isolates in industrial biofilters is beneficial at low styrene concentrations and is safe from both the environmental and public health points of view.

Biodegradation, Environmental↗
PubMed1991

Metabolism of cyanide by Phanerochaete chrysosporium.

The oxidation of veratryl alcohol (3,4-dimethoxybenzyl alcohol) by lignin peroxidase H2 (LiP H2) from the white rot fungus Phanerochaete chrysosporium was strongly inhibited by sodium cyanide. The I50 was estimated to be about 2-3 microM. In contrast, sodium cyanide binds to the native enzyme with an apparent sodium cyanide dissociation constant Kd of about 10 microM. Inhibition of the veratryl alcohol oxidase activity of LiP H2 by cyanide was reversible. Ligninolytic cultures of P. chrysosporium mineralized cyanide at a rate that was proportional to the concentration of cyanide to 2 mM. The N-tert-butyl-alpha-phenylnitrone-cyanyl radical adduct was observed by ESR spin trapping upon incubation of LiP H2 with H2O2 and sodium cyanide. The identity of the spin adduct was confirmed using 13C-labeled cyanide. Six-day-old cultures of the fungus were more tolerant to sodium cyanide toxicity than spores. Toxicity measurements were based on the effect of sodium cyanide on respiration of the fungus as determined by the metabolism of [14C]glucose to [14C]CO2. We propose that this tolerance of the mature fungus was due to its ability to mineralize cyanide and that this fungus might be effective in treating environmental pollution sites contaminated with cyanide.

Alcohol Oxidoreductases↗
PubMed2004

The performances of vegetative treatment systems for highway runoff during dry and wet conditions.

The performances of two different highway runoff treatment systems, a horizontal subsurface flow-constructed wetland and a vegetated balancing pond, are described. Both systems have been assessed by collecting inlet and outlet grab samples during wet and dry weather conditions, and automatically controlled storm event samples have been obtained for the constructed wetland. Removal efficiencies are discussed for BOD (grab samples only), suspended solids, Cd, Cr, Cu, Ni, Pb, Zn, nitrate and sulphate, and explanations are offered for the trends observed under different weather conditions. The large variabilities in the removal efficiencies derived for both treatment systems, based on the analyses of grab samples, make accurate comparisons of the performances difficult and also raise concerns about using this type of sampling approach for this purpose. Treatment systems are required to function satisfactorily during the increased inlet loadings experienced during storm events, and this is shown to be the case for the constructed wetland for the majority of the monitored pollutants. The large removal efficiency ranges for five separate storm events, exhibited by Cu and Pb, are discussed and compared to the other monitored pollutants which showed positive median wet weather removal efficiencies of between 43% and 85%. Despite the existence of performance fluctuations, the generally low monitored inlet concentrations in the highway runoff indicated that the pond discharges did not threaten the environmental quality of the receiving waters.

Biodegradation, Environmental↗
PubMed2004

Mitigating nutrient leaching with a sub-surface drainage layer of granulated tires.

Markets for scrap tires have expanded since the early 1990s with the development of value-added applications such as tire-derived fuel and crumb-rubber-amended asphalt. Granulated tires have also displayed the ability to adsorb volatile organic compounds, indicating that the rubber material can be a useful filter media. Sand-based root zones, typically used for golf course putting green and athletic field construction, lack sufficient cation exchange capacity to restrict nitrogen and phosphorus migration through the root zone and into sub-surface drainage systems. Therefore, the adsorptive properties of tire rubber for retaining nitrogen and phosphorus were studied when applied as a distinct sub-surface drainage or intermediate layer in golf course putting greens. A statistically significant reduction in the concentration of nitrate in leachate was achieved by replacing traditional pea gravel with equally sized granulated tires for the drainage layer media, although the mechanism of nitrate mitigation remains unclear. The results indicate that using granulated tires as a drainage layer or fill material beneath sand-based root zones does not compromise the function of the profile or quality of the vegetation while creating an environmentally beneficial and value-added option for scrap tire reuse.

Biodegradation, Environmental↗
PubMed1999

Effects of moisture and sorption on bioavailability of p-hydroxybenzoic acid to Arthrobacter sp. in soil.

Effects of bioavailability on degradation of 14C-p-hydroxybenzoate were examined using sterile soil inoculated with Arthrobacter sp. Physical accessibility of p-hydroxybenzoate was controlled by varying pore continuity with a range of moisture regimes (-33 to -420 kPa), whereas sorption was controlled via addition of an exchange resin. Arthrobacter sp. accessed 94% of p-hydroxybenzoate in soil at -33 kPa, owing to continuity of soil pores and sufficient cells to exploit available space. A deviation in degradation kinetics at -420 kPa soil was attributed to inaccessible p-hydroxybenzoate in solution. Addition of resin decreased extent of degradation, though the effect diminished as pore continuity decreased. Subtle differences in effects of these processes on degradation kinetics may facilitate their separate treatment in environmental fate models.

Absorption↗
PubMed2006

Comparison of different packing materials for the biofiltration of air toxics.

Four different biofilter packing materials (two porous ceramics, perlite, and open pore polyurethane foam) were compared for the removal of toluene vapors. The focus was on evaluating performance at relatively short gas retention time (13.5 and 27 sec). The reactors were initially operated as biotrickling filters with continuous feeding and trickling of a nutrient solution. After significant plugging of the biotrickling filter beds with biomass was observed, the operation mode was switched to biofiltration with only periodic supply of mineral nutrients. This resulted in stable conditions, which allowed detailed investigations over > 6 months. The reactor packed with cattle bone Porcelite (CBP), a ceramic material containing some macronutrients and micronutrients, exhibited the highest performance. The critical load (i.e., load at which 95% removal occurred) was 29 g m(-3) hr(-1) at a gas retention time of 13.5 sec and 66 g m(-3) hr(-1) at a gas retention time of 27 sec. After the long-term experiment, the packing materials were taken from the reactors and examined. The reactors were divided into three sections, top, middle, and bottom, to determine whether spatial differentiation of biomass occurred. The assays included a double-staining technique to count total and live microorganisms and determination of moisture, protein, and dry weight contents. Microbial community analysis was also conducted by denaturing gradient gel electrophoresis. The results showed that most reactors had a significant fraction of inactive biomass. Comparatively, the CBP biofilter held significantly higher densities of active biomass, which may be the reason for the higher toluene removal performance. The analyses suggest that favorable material properties and the nutrients slowly released by the CBP provided better environmental conditions for the process culture.

Air Pollutants↗
PubMed1993

Starvation-survival of a p-nitrophenol-degrading bacterium.

An environmental actinomycetes, capable of utilizing p-nitrophenol as its sole carbon and nitrogen source, was starved for an 8-week period and showed no reduction in its ability to biodegrade p-nitrophenol. Microscopic examination revealed that starvation of the bacterium resulted in the fragmentation of filaments into individual cells.

Actinomycetaceae↗
PubMed1997

Temperature determines the pattern of anaerobic microbial dechlorination of Aroclor 1260 primed by 2,3,4,6-tetrachlorobiphenyl in Woods Pond sediment.

Reductive dechlorination of the Aroclor 1260 residue in Woods Pond (Lenox, Mass.) sediment samples was investigated for a year at incubation temperatures from 4 to 66 degrees C. Sediment slurries were incubated anaerobically with and without 2,3,4,6-tetrachlorobiphenyl (2346-CB; 350 microM) as a primer for dechlorination of the Aroclor 1260 residue. Dechlorination of the Aroclor residue occurred only in live samples primed with 2346-CB and only at 8 to 34 degrees C and 50 to 60 degrees C. The extent and pattern of polychlorinated biphenyl (PCB) dechlorination were temperature dependent. At 8 to 34 degrees C, the dechlorination resulted in 28 to 65% decreases of the hexathrough nonachlorobiphenyls and corresponding increases in the tri- and tetrachlorobiphenyls. At 12 to 30 degrees C, 30 to 40% of the hexa- through nonachlorobiphenyls were dechlorinated in just 3 months. The optimal temperature for overall chlorine removal was 20 to 27 degrees C. We observed four different microbial dechlorination processes with different but partially overlapping temperature ranges, i.e., Process N (flanked meta dechlorination) at 8 to 30 degrees C, Process P (flanked para dechlorination) at 12 to 34 degrees C, Process LP (unflanked para dechlorination) at 18 to 30 degrees C, and Process T (a very restricted meta dechlorination of specific hepta- and octachlorobiphenyls) at 50 to 60 degrees C. These temperature ranges should aid in the development of strategies for the enrichment and isolation of the microorganisms responsible for each dechlorination process. The incubation temperature determined the relative dominance of the four PCB dechlorination processes and the extent and products of dechlorination. Hence, understanding the effects of temperature on PCB dechlorination at contaminated sites should assist in predicting the environmental fate of PCBs or planning bioremediation strategies at those sites.

Anaerobiosis↗
PubMed2003

Releasing nitrogen from ammoniated lignin by white rot fungus cometabolizes environmental pollutants.

The nitrogen-modified lignocelluloses(NML) produced under oxic ammoniation was metabolized by white rot fungus, NH4(+) -N was released, NO3(-) -N concentration was decreased and total nitrogen loss was blocked within incubation period. During releasing nitrogen from the metabolism of NML, white rot fungus cometabolized recalcitrant environmental pollutants and showed higher degradation capability. Results indicated that this NML complex colonized by white rot fungus might be effective with economic feasibility when they are applied into the vast field ecosystem, it might stabilize NH4+ nitrogen flux and bioremediate the polluted environmental sites.

Ammonia↗