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PubMed2006

Aquatic risk assessment of alcohol ethoxylates in North America and Europe.

An environmental risk assessment for alcohol ethoxylates (AE) is presented that integrates wastewater treatment plant monitoring, fate, and ecotoxicity research with a new application of mixture toxicity theory based on simple similar concentration addition of AE homologs in a species-sensitivity distribution (SSD) context. AEs are nonionic surfactants composed of a homologous series of molecules that range in alkyl chain length from 12 to 18 carbons and ethoxylates from 0 to 18 units. Chronic ecotoxicity of AE is summarized for 17 species in 60 tests and then normalized to monitoring data for AE mixtures. To do so, chronic aquatic toxicity was first expressed as EC10 per species (the concentration predicted to cause a 10% reduction in an important ecological endpoint). Normalization integrated several new quantitative structure-activity relationships for algae, daphnids, fish, and mesocosms and provided an interpretation of toxicity test data as a function of individual homologs in an AE mixture. SSDs were constructed for each homolog and the HC5 (hazardous concentration protective of 95% of species based on a small biological effect [the chronic EC10]) was predicted. Total mass of AE in monitored effluents from 29 sites in Europe, Canada, and the United States averaged 6.8, 2.8, and 3.55 microg/L, respectively. For risk assessment purposes, correction of exposure to account for fatty alcohol derived from sources other than AE and for sorbed components based on experimental evidence was used to determine AE concentrations in undiluted (100%) effluents from North America and Europe. Exposure and effect findings were integrated in a toxic unit (TU)-based model that considers the measured distribution of individual AE homologs in effluent with their corresponding SSDs. Use of environmentally relevant exposure corrections (bioavailability and accounting for AE-derived alcohol) resulted in TUs ranging from 0.015 to 0.212. Low levels of risk are concluded for AE in the aquatic environments of Europe and North America.

Adsorption↗

PubMed2003

Destruction of cyanide in gold mill effluents: biological versus chemical treatments.

In gold mining, cyanide has been the preferred lixiviant worldwide since 1887. Although cyanide can be destroyed and recovered by several processes, it is still widely discussed and examined due to its potential toxicity and environmental impact. Biological treatment of cyanide is a well-established process and has been commercially used at gold mining operations in North America. Biological treatment processes facilitate growth of microorganisms that are essential for the treatment. The present review describes the advances in the use of biological treatment for the destruction of cyanide in gold mill effluents.

Bacteria↗

PubMed2002

Cadmium biosorption by Sphingomonas paucimobilis biomass.

Among microorganisms isolated in Bangkok, the gram-negative bacterium Sphingomonas paucimobilis exhibited the greatest cadmium tolerance. It was able to survive in the medium containing cadmium as high as 200 mg/l. However, concentrations of cadmium at 25-200 mg/l inhibited its growth. The biosorption properties for cadmium of this bacterial biomass and the effects of environmental factors (i.e., biosorbent type, initial pH and biosorbent concentration) on the cadmium biosorption were explored. The results showed that the cadmium removal capacity of living cells was markedly higher than that of nonliving cells. Cadmium biosorption by S. paucimobilis biomass was also affected by the initial pH and biosorbent concentration.

Adsorption↗

PubMed1986

Rapid assay for screening and characterizing microorganisms for the ability to degrade polychlorinated biphenyls.

We designed a rapid assay that assesses the polychlorinated biphenyl (PCB)-degradative competence and congener specificity of aerobic microorganisms, identifies strains capable of degrading highly chlorinated biphenyls, and distinguishes among those that degrade PCBs by alternative pathways. Prior attempts to assay PCB-degradative competence by measuring disappearance of Aroclors (commercial PCB mixtures) have frequently produced false-positive findings because of volatilization, adsorption, or absorption losses. Furthermore, these assays have generally left the chemical nature of the competence obscure because of incomplete gas chromatographic resolution and uncertain identification of Aroclor peaks. We avoided these problems by using defined mixtures of PCB congeners and by adopting incubation and extraction methods that prevent physical loss of PCBs. Our assay mixtures include PCB congeners ranging from dichloro- to hexachlorobiphenyls and representing various structural classes, e.g., congeners chlorinated on a single ring (2,3-dichlorobiphenyl), blocked at 2,3 sites (2,5,2'5'-tetrachlorobiphenyl), blocked at 3,4 sites (4,4'-dichlorobiphenyl), and lacking adjacent unchlorinated sites (2,4,5,2',4',5'-hexachlorobiphenyl). The PCB-degrative ability of microorganisms is assessed by packed-column gas chromatographic analysis of these defined congener mixtures following 24-h incubation with resting cells. When tested with 25 environmental isolates, this assay revealed a broad range of PCB-degradative competence, highlighted differences in congener specificity and in the extent of degradation of individual congeners, predicted degradative competence on commercial PCBs, and (iv) identified strains with superior PCB-degradative ability.

Alcaligenes↗

PubMed1997

Environmental fate assessment of two synthetic polycarboxylate polymers.

In order to estimate the proportion which may enter the aquatic environment and characterize exposure potential, the environmental fate properties of two polycarboxylate polymers in activated sludge were determined. The polycarboxylates studied were a polymer emulsion (PE), a high-molecular-weight polymer (MW 50,000-60,000), and a resin polymer (RP), a low-molecular-weight polymer (MW 4500 to 9000). Both polymers exhibited a high degree of sorption to sludge solids in a series of sorption/ desorption studies, indicating a high potential for removal during wastewater treatment. In isotherm tests, the adsorption coefficient, Koc, was 1060 and 2730 for the RP and the PE, respectively. The biodegradation of the two polymers was measured under aerobic conditions in a 60-day semicontinuous activated sludge test and in a 60-day modified Sturm test using 14C-labeled compounds. In both studies, polymers accumulated in sludge solids over time and there was no evidence of significant biodegradation, although small amounts of radiolabeled CO2 were produced, suggesting the potential for biodegradation. Testing confirmed that the lack of biodegradation was not due to inhibition of microbial respiration by the polymers. High removals of PE and RP during wastewater treatment were confirmed in a field study at a facility receiving polymer inputs from households and manufacturing plants.

Biodegradation, Environmental↗

PubMed1991

Degradation of dioxane, tetrahydrofuran and other cyclic ethers by an environmental Rhodococcus strain.

By enrichment and isolation techniques bacterial strains with the capacity to grow on aliphatic cyclic ethers (dioxane, tetrahydrofuran, 1,3-dioxolane) have been isolated. Six strains that degrade tetrahydrofuran were classified as belonging to the genus Rhodococcus. One of two strains that degrade dioxane instead of or in combination with tetrahydrofuran was further characterized and a hypothetical catabolic pathway comprising an initial 2-hydroxylation and several oxidation steps is postulated.

Biodegradation, Environmental↗

PubMed2004

Transcriptional regulation of plant cell wall degradation by filamentous fungi.

Plant cell wall consists mainly of the large biopolymers cellulose, hemicellulose, lignin and pectin. These biopolymers are degraded by many microorganisms, in particular filamentous fungi, with the aid of extracellular enzymes. Filamentous fungi have a key role in degradation of the most abundant biopolymers found in nature, cellulose and hemicelluloses, and therefore are essential for the maintenance of the global carbon cycle. The production of plant cell wall degrading enzymes, cellulases, hemicellulases, ligninases and pectinases, is regulated mainly at the transcriptional level in filamentous fungi. The genes are induced in the presence of the polymers or molecules derived from the polymers and repressed under growth conditions where the production of these enzymes is not necessary, such as on glucose. The expression of the genes encoding the enzymes is regulated by various environmental and cellular factors, some of which are common while others are more unique to either a certain fungus or a class of enzymes. This review summarises our current knowledge on the transcriptional regulation, focusing on the recently characterized transcription factors that regulate genes coding for enzymes involved in the breakdown of plant cell wall biopolymers.

Biodegradation, Environmental↗

PubMed2005

Pilot project of mechanical-biological treatment of waste in Brazil.

By mechanical-biological treatment (MBT) of residual municipal solid waste the behaviour of landfills can be significantly improved. After MBT the organic content (COD and BOD5), total organic carbon, and total nitrogen in the leachate, as well as the gas production rate, are reduced to values lower than 90% of the fresh untreated waste. The volume of the stabilized material to be disposed on landfills decreases enormously, by up to 70%. The monitoring effort for a landfill constructed under these conditions is reduced to a minimum and the stabilized material can be used in other ways, as material for reforestation, for cover material or for thermal utilization to produce energy. Environmental conditions are important in MBT, as well as waste characteristics. This paper describes the results of a pilot project of MBT performed in Rio de Janeiro, Brazil. The results have shown that this technology can be used successfully in developing countries, with economy for the society and important results for the environment.

Air Pollution↗

PubMed2007

Alkane hydroxylases involved in microbial alkane degradation.

This review focuses on the role and distribution in the environment of alkane hydroxylases and their (potential) applications in bioremediation and biocatalysis. Alkane hydroxylases play an important role in the microbial degradation of oil, chlorinated hydrocarbons, fuel additives, and many other compounds. Environmental studies demonstrate the abundance of alkane degraders and have lead to the identification of many new species, including some that are (near)-obligate alkanotrophs. The availability of a growing collection of alkane hydroxylase gene sequences now allows estimations of the relative abundance of the different enzyme systems and the distribution of the host organisms.

Alkanes↗

PubMed2001

The fate and persistence of trifluoroacetic and chloroacetic acids in pond waters.

The environmental fate of trichloro-, dichloro-, and monochloroacetic acids, and trifluoroacetic acid was investigated using field aquatic microcosms and laboratory sediment-water systems. Trifluoroacetic acid was extremely persistent and showed no degradation during a one-year field study, though it appeared to undergo transient partitioning within an unknown pond phase as the temperature of the surroundings was reduced. Of the three chloroacetic acids, trichloro had the longest residence time (induction and decay) (approximately 40 d), dichloro the shortest (approximately 4 d), and monochloro an intermediate residence time (approximately 14 d). Laboratory studies suggest that the biodegradation of trichloro-, dichloro-, and monochloroacetic acids leads primarily to the formation of chloride and oxalic, glyoxalic, and glycolic acids, respectively.

Acetates↗

PubMed1999

Bacteria designed for bioremediation.

Although many environmental pollutants are efficiently degraded by microorganisms, others persist and constitute a severe health hazard. In some instances, persistence is a consequence of the inadequate catabolic potential of the available microorganisms. Gene technology, combined with a solid knowledge of catabolic pathways and microbial physiology, enables the experimental evolution of new or improved catabolic activities for such pollutants.

Bacteria↗

PubMed2002

Photocatalytic atrazine degradation by synthetic minerals, atmospheric aerosols, and soil particles.

In this work, the photocatalytic atrazine degradation by seven synthetic minerals and five environmental particle samples was examined to investigate a possible contribution of photocatalysis to the abiotic degradation of atrazine in the environment. Particle suspensions containing 500 ng/L atrazine were irradiated with a sun simulator, and the atrazine degradation was monitored by enzyme-linked immunosorbent assay (ELISA). Atrazine detection by ELISA proved to be an useful analytical tool because of low cross-reactivity of atrazine metabolites and high sensitivity with detection limits in the lower nanograms per liter range. The atrazine degradation followed first-order kinetics, and the obtained rate coefficients were compared with the rate of direct photolysis. Known photocatalysts, such as TiO2 and ZnO, showed the expected fast photocatalytic degradation (k = 27-327 x 10(-3) min(-1)) of atrazine. The degradation rates detected upon irradiation of titanium-, zinc-, or iron-containing minerals were orders of magnitudes lower (k = 0.15-0.70 x 10(-3) min(-1)) but still significantly faster than direct photolysis without particles (k = 0.10 x 10(-3) min(-1)). With environmental particle samples (soot, fly ash, sand, road dust, and volcanic ash), however, no significant photocatalytic activity was observed (k = 0.07-0.16 x 10(-3) min(-1)). The atrazine degradation rates were in the range of direct photolysis. Thus photocatalysis by aerosol or soil particles appears not to enhance abiotic atrazine degradation in the environment.

Aerosols↗

PubMed1986

Linear alkylbenzene sulfonates (LAS) in sewage sludges, soils and sediments: analytical determination and environmental safety considerations.

Linear Alkylbenzenesulphonates (LAS), a major anionic surfactant used in laundry products, can be measured specifically in the environment by instrumental analysis. In addition to a desulphonation-gas chromatography approach, a method based on high performance liquid chromatography has been developed. The main features of the methods are outlined, and LAS concentrations measured in sewage sludge, sediments and sludge amended soils are reported. Knowledge of usage volumes, sewage treatment practices and environmental transport and transformation mechanisms has been used to predict concentrations of LAS. These calculated concentrations were found to agree well with those actually measured in the environment. Both measured and calculated ambient concentrations of LAS are below those which could produce potentially adverse effects in representative surface water, benthic and terrestrial organisms.

Alkanes↗

PubMed1991

Collection and management of fecal wastes for space missions.

An improved type of human waste collection subsystem has been developed for Space Station Freedom which is designed to meet the challenges of zero gravity collection and system performance. Fecal collection is followed by passive storage for relatively short duration missions. The benefits of utilizing components in solid wastes as part of a partial or completely closed Environmental Control and Life Support System (ECLSS) become more apparent as the duration of the mission increases. The purpose of this review is to summarize the development issues associated with the current waste management subsystem for Space Station Freedom. Also reviewed are current ideas associated with the evolutionary development of this waste management subsystem for longer duration missions.

Biodegradation, Environmental↗

PubMed2004

Bacterial transcriptional regulators for degradation pathways of aromatic compounds.

Human activities have resulted in the release and introduction into the environment of a plethora of aromatic chemicals. The interest in discovering how bacteria are dealing with hazardous environmental pollutants has driven a large research community and has resulted in important biochemical, genetic, and physiological knowledge about the degradation capacities of microorganisms and their application in bioremediation, green chemistry, or production of pharmacy synthons. In addition, regulation of catabolic pathway expression has attracted the interest of numerous different groups, and several catabolic pathway regulators have been exemplary for understanding transcription control mechanisms. More recently, information about regulatory systems has been used to construct whole-cell living bioreporters that are used to measure the quality of the aqueous, soil, and air environment. The topic of biodegradation is relatively coherent, and this review presents a coherent overview of the regulatory systems involved in the transcriptional control of catabolic pathways. This review summarizes the different regulatory systems involved in biodegradation pathways of aromatic compounds linking them to other known protein families. Specific attention has been paid to describing the genetic organization of the regulatory genes, promoters, and target operon(s) and to discussing present knowledge about signaling molecules, DNA binding properties, and operator characteristics, and evidence from regulatory mutants. For each regulator family, this information is combined with recently obtained protein structural information to arrive at a possible mechanism of transcription activation. This demonstrates the diversity of control mechanisms existing in catabolic pathways.

Bacteria↗

PubMed1994

Designing microorganisms for the treatment of toxic wastes.

The genetic design of novel metabolic routes offers exciting possibilities for biological research and biotechnology, both in the exploration of the metabolic/evolutionary potential of cells and in the development of innovative applications. In this chapter, we review recent advances in the development of genetic tools and strategies for the design of new microorganisms for elimination of environmental pollutants. These include the design of regulated gene expression circuits that provide high levels of catalytic activity, even under environmental conditions that ordinarily repress expression of catabolic genes; the rational alteration of relevant properties of proteins that qualitatively or quantitatively restrict catabolic activities; the judicious assembly of gene blocks encoding selected metabolic modules to create novel metabolic routes and combinations of routes; and the design of microorganisms exhibiting properties that contribute to better process development.

Bacteria↗

PubMed2002

[Bioremediation of low-level radionuclide contaminated soils and water].

Different anthroponic factors have led up to increasing background concentrations of radionuclides in human ecosystems. As long as these radionuclides enter into soil-water substrates, they can pose hazards to human health through different pathways. Since most conventional chemical or physical procedures are not practical for dealing with low-level radionuclides in the water-soil substrates, new remediation technologies are being developed to tackle the problem. Bioremediation has attracted much attention because of its many advantages such as low cost and less environmental disturbance. The present paper summarizes the sources of radionuclides and introduces the concept of low-level radionuclide bioremediation. The state of the art in the field of bioremediation of low-level radionuclide contaminated water-soil substrates has also been reviewed and summarized in this paper. On the basis of above mentioned discussions the future developing trends were put forward.

Biodegradation, Environmental↗

PubMed2006

Degradation of malathion by Pseudomonas during activated sludge treatment system using principal component analysis (PCA).

Popular descriptive multivariate statistical method currently employed is the principal component analyses (PCA) method. PCA is used to develop linear combinations that successively maximize the total variance of a sample where there is no known group structure. This study aimed at demonstrating the performance evaluation of pilot activated sludge treatment system by inoculating a strain of Pseudomonas capable of degrading malathion which was isolated by enrichment technique. An intensive analytical program was followed for evaluating the efficiency of biosimulator by maintaining the dissolved oxygen (DO) concentration at 4.0 mg/L. Analyses by high performance liquid chromatographic technique revealed that 90% of malathion removal was achieved within 29 h of treatment whereas COD got reduced considerably during the treatment process and mean removal efficiency was found to be 78%. The mean pH values increased gradually during the treatment process ranging from 7.36-8.54. Similarly the mean ammonia-nitrogen (NH3-N) values were found to be fluctuating between 19.425-28.488 mg/L, mean nitrite-nitrogen (NO3-N) ranging between 1.301-2.940 mg/L and mean nitrate-nitrogen (NO3-N) ranging between 0.0071-0.0711 mg/L. The study revealed that inoculation of bacterial culture under laboratory conditions could be used in bioremediation of environmental pollution caused by xenobiotics. The PCA analyses showed that pH, COD, organic load and total malathion concentration were highly correlated and emerged as the variables controlling the first component, whereas dissolved oxygen, NO3-N and NH3-N governed the second component. The third component repeated the trend exhibited by the first two components.

Biodegradation, Environmental↗