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PubMed2006

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost.

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost was reported for the first time. Batch tests were carried out to analyze influences of several environmental factors on biohydrogen production from wheat straw wastes. The performance of biohydrogen production using the raw wheat straw and HCl pretreated wheat straw was then compared in batch fermentation tests. The maximum cumulative hydrogen yield of 68.1 ml H2/g TVS was observed at 126.5 h, the value is about 136-fold as compared with that of raw wheat straw wastes. The maximum hydrogen production rate of 10.14 ml H2/g TVS h was obtained by a modified Gompertz equation. The hydrogen content in the biogas was 52.0% and there was no significant methane observed in this study. In addition, biodegradation characteristics of the substrate were also discussed. The experimental results showed that the pretreatment of the substrate plays a key role in the conversion of the wheat straw wastes into biohydrogen by the composts generating hydrogen.

Animals↗

PubMed2002

Deactivation of the biological activity of paraquat in the soil environment: a review of long-term environmental fate.

During the many years of paraquat usage, wide ranges of investigations of its environmental impact have been conducted. Much of this information has been published, but key, long-term field studies have not previously been presented and assessed. The purpose of this review is to bring together and appraise this information. Due to the nature of paraquat residues in soils, the major part (some 99.99%) of a paraquat application that reaches the soil within the typical Good Agricultural Practice (GAP) is strongly adsorbed to soils of a wide variety of textures. This is in equilibrium with an extremely low concentration in soil solution. However, the paraquat in soil solution is intrinsically biodegradable, being rapidly and completely mineralized by soil microorganisms. The deactivation of the biological activity of paraquat in soils, due to sorption, has been investigated thoroughly and systematically. It is recognized that the determination of total soil residues by severe extraction procedures provides no insight into the amount of paraquat biologically available in soil. Consequently, the key assay developed for this purpose, namely, the strong adsorption capacity-wheat bioassay (SAC-WB) method, has proved to be valuable for determination of the adsorption capacity relevant to paraquat for any particular soil. This method has been validated in the field with a series of long-term (>10 years) trials in different regions of the world. These trials have also shown that, following repeated applications of very high levels of paraquat in the field, residues not only reach a plateau but also subsequently decline. This demonstrates that the known biodegradation of paraquat in soil pore water plays an important role in field dissipation. The biological effects of paraquat in the field have been assessed under unrealistically high treatment regimes. These trials have demonstrated that the continued use of paraquat under GAP conditions will have no detrimental effects on either crops or soil-dwelling flora and fauna. Any such effects can occur only under extreme use conditions (above the SAC-WB), which do not arise in normal agricultural practice.

Adsorption↗

PubMed1993

Biology, ecology, and biotechnological applications of anaerobic bacteria adapted to environmental stresses in temperature, pH, salinity, or substrates.

Anaerobic bacteria include diverse species that can grow at environmental extremes of temperature, pH, salinity, substrate toxicity, or available free energy. The first evolved archaebacterial and eubacterial species appear to have been anaerobes adapted to high temperatures. Thermoanaerobes and their stable enzymes have served as model systems for basic and applied studies of microbial cellulose and starch degradation, methanogenesis, ethanologenesis, acetogenesis, autotrophic CO2 fixation, saccharidases, hydrogenases, and alcohol dehydrogenases. Anaerobes, unlike aerobes, appear to have evolved more energy-conserving mechanisms for physiological adaptation to environmental stresses such as novel enzyme activities and stabilities and novel membrane lipid compositions and functions. Anaerobic syntrophs do not have similar aerobic bacterial counterparts. The metabolic end products of syntrophs are potent thermodynamic inhibitors of energy conservation mechanisms, and they require coordinated consumption by a second partner organism for species growth. Anaerobes adapted to environmental stresses and their enzymes have biotechnological applications in organic waste treatment systems and chemical and fuel production systems based on biomass-derived substrates or syngas. These kinds of anaerobes have only recently been examined by biologists, and considerably more study is required before they are fully appreciated by science and technology.

Adaptation, Physiological↗

PubMed1994

Utilization of 2-phosphonobutane-1,2,4-tricarboxylic acid as source of phosphorus by environmental bacterial isolates.

Six bacterial strains able to degrade aerobically 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) were isolated. The bacteria used PBTC as sole source of phosphorus in the presence of an alternative source of carbon. The microorganisms were taken from various ecosystems, e.g. river water, river sediment and activated sludge. PBTC up to a concentration of 1 mM (270 mg/l) was completely degraded by a defined mixed culture.

Bacteria↗

PubMed2003

Carbohydrate-derived chlorinated compounds in ECF bleaching of hardwood pulps: formation, degradation, and contribution to AOX in a bleached kraft pulp mill.

Five monochlorinated compounds derived from glucuronoxylan were identified in the liquid process streams of a kraft pulp mill producing hardwood pulp with ECF bleaching, representing ca. 15-20% of the AOX of the bleaching filtrates. The environmental risk of such compounds is negligible because a major fraction (70-80%) is degraded during effluent mixing and neutralization, and about 20-30% is degraded during the biological treatment of the mixed effluent. Only less than 3.5% (0.009-0.017 kg/ tAD) of the compounds formed in the bleaching leave the mill in the final effluent.

Biodegradation, Environmental↗

PubMed2006

Discharge of three benzotriazole corrosion inhibitors with municipal wastewater and improvements by membrane bioreactor treatment and ozonation.

A set of three benzotriazole corrosion inhibitors was analyzed by liquid chromatography-mass spectrometry in wastewaters and in a partially closed water cycle in the Berlin region. Benzotriazole (BTri) and two isomers of tolyltriazole (TTri) were determined in untreated municipal wastewater with mean dissolved concentrations of 12 microg/L (BTri), 2.1 microg/L (4-TTri), and 1.3 microg/L (5-TTri). Removal in conventional activated sludge (CAS) municipal wastewater treatment ranged from 37% for BTri to insignificant removal for 4-TTri. In laboratory batch tests 5-TTri was mineralized completely and 4-TTri was mineralized to only 25%. This different behavior of the three benzotriazoles was confirmed by following the triazoles through a partially closed water cycle, into bank filtrate used for drinking water production, where BTri (0.1 microg/L) and 4-TTri (0.03 microg/ L) but no 5-TTri were detected after a travel time of several months. The environmental half-life appears to increase from 5-TTri over BTri to 4-TTri. Treatment of municipal wastewater by a lab-scale membrane bioreactor (MBR) instead of CAS improved the removal of BTri and 5-TTri but could not avoid their discharge. Almost complete removal was achieved by ozonation of the treatment plant effluent with 1 mg O3/mg DOC.

Biodegradation, Environmental↗

PubMed2001

In situ bioremediation of soil contaminated with oil and heavy metals.

An experimental plot of soil contaminated with crude oil and heavy metals (copper, zinc and cadmium) was subjected to bioremediation using the activity of the indigenous soil microflora. The oil was light, rich in paraffins and with a very low content of asphaltene-resinous substances. Copper, zinc and cadmium were present mainly as sulfide minerals but also in forms more amenable to biological and chemical leaching. Their contents in the soil exceeded approximately 1.5-3 times the relevant permissible levels. The soil microflora contained different oil-degrading and metal-solubilizing microorganisms. The activity of this microflora was enhanced by suitable changes in the levels of some essential environmental factors such as oxygen, water and nutrient contents in the soil. The oil content in the plot was decreased from the initial 12.50 g/kg dry soil to 1.25 g/kg dry soil within 8 months of treatment. Simultaneously, the contents of copper, zinc and cadmium were decreased below the relevant permissible levels for soil of such type.

Bacteria↗

PubMed2002

Biotechnology and bioremediation: successes and limitations.

With advances in biotechnology, bioremediation has become one of the most rapidly developing fields of environmental restoration, utilizing microorganisms to reduce the concentration and toxicity of various chemical pollutants, such as petroleum hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phthalate esters, nitroaromatic compounds, industrial solvents, pesticides and metals. A number of bioremediation strategies have been developed to treat contaminated wastes and sites. Selecting the most appropriate strategy to treat a specific site can be guided by considering three basic principles: the amenability of the pollutant to biological transformation to less toxic products (biochemistry), the accessibility of the contaminant to microorganisms (bioavailability) and the opportunity for optimization of biological activity (bioactivity). Recent advances in the molecular genetics of biodegradation and studies on enzyme-tailoring and DNA-shuffling are discussed in this paper.

Biodegradation, Environmental↗

PubMed2002

Polycyclic aromatic hydrocarbons: environmental pollution and bioremediation.

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed and relocated in the environment as a result of the incomplete combustion of organic matter. Many PAHs and their epoxides are highly toxic, mutagenic and/or carcinogenic to microorganisms as well as to higher systems including humans. Although various physicochemical methods have been used to remove these compounds from our environment, they have many limitations. Xenobiotic-degrading microorganisms have tremendous potential for bioremediation but new modifications are required to make such microorganisms effective and efficient in removing these compounds, which were once thought to be recalcitrant. Metabolic engineering might help to improve the efficiency of degradation of toxic compounds by microorganisms. However, efficiency of naturally occurring microorganisms for field bioremediation could be significantly improved by optimizing certain factors such as bioavailability, adsorption and mass transfer. Chemotaxis could also have an important role in enhancing biodegradation of pollutants. Here, we discuss the problems of PAH pollution and PAH degradation, and relevant bioremediation efforts.

Animals↗

PubMed2004

Chemical databases evaluated by order theoretical tools.

Data on environmental chemicals are urgently needed to comply with the future chemicals policy in the European Union. The availability of data on parameters and chemicals can be evaluated by chemometrical and environmetrical methods. Different mathematical and statistical methods are taken into account in this paper. The emphasis is set on a new, discrete mathematical method called METEOR (method of evaluation by order theory). Application of the Hasse diagram technique (HDT) of the complete data-matrix comprising 12 objects (databases) x 27 attributes (parameters + chemicals) reveals that ECOTOX (ECO), environmental fate database (EFD) and extoxnet (EXT)--also called multi-database databases--are best. Most single databases which are specialised are found in a minimal position in the Hasse diagram; these are biocatalysis/biodegradation database (BID), pesticide database (PES) and UmweltInfo (UMW). The aggregation of environmental parameters and chemicals (equal weight) leads to a slimmer data-matrix on the attribute side. However, no significant differences are found in the "best" and "worst" objects. The whole approach indicates a rather bad situation in terms of the availability of data on existing chemicals and hence an alarming signal concerning the new and existing chemicals policies of the EEC.

Biodegradation, Environmental↗

PubMedDate not supplied

ATSDR evaluation of health effects of chemicals. IV. Polycyclic aromatic hydrocarbons (PAHs): understanding a complex problem.

Polycyclic Aromatic Hydrocarbons (PAHs) are a group of chemicals that are formed during the incomplete burning of coal, oil, gas, wood, garbage, or other organic substances, such as tobacco and charbroiled meat. There are more than 100 PAHs. PAHs generally occur as complex mixtures (for example, as part of products such as soot), not as single compounds. PAHs are found throughout the environment in the air, water, and soil. As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals, including PAHs (ATSDR, 1995), found at facilities on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) and which pose the most significant potential threat to human health, as determined by ATSDR and the Environmental Protection Agency (EPA). These profiles include information on health effects of chemicals from different routes and durations of exposure, their potential for exposure, regulations and advisories, and the adequacy of the existing database. Assessing the health effects of PAHs is a major challenge because environmental exposures to these chemicals are usually to complex mixtures of PAHs with other chemicals. The biological consequences of human exposure to mixtures of PAHs depend on the toxicity, carcinogenic and noncarcinogenic, of the individual components of the mixture, the types of interactions among them, and confounding factors that are not thoroughly understood. Also identified are components of exposure and health effects research needed on PAHs that will allow estimation of realistic human health risks posed by exposures to PAHs. The exposure assessment component of research should focus on (1) development of reliable analytical methods for the determination of bioavailable PAHs following ingestion, (2) estimation of bioavailable PAHs from environmental media, particularly the determination of particle-bound PAHs, (3) data on ambient levels of PAHs metabolites in tissues/fluids of control populations, and (4) the need for a critical evaluation of current levels of PAHs found in environmental media including data from hazardous waste sites. The health effects component should focus on obtaining information on (1) the health effects of mixtures of PAHs particularly their noncarcinogenic effects in humans, and (2) their toxicokinetics. This report provides excerpts from the toxicological profile of PAHs (ATSDR, 1995) that contains more detailed information.

Animals↗

PubMed2005

Practical considerations on the use of predictive models for regulatory purposes.

Interest in the use of quantitative structure-activity relationships (QSARs) for regulatory purposes has been growing steadily over the years, and many models have been evaluated under the guidance and acceptability criteria defined at the Setubal workshop held in March 2002. This work explores some of the practical issues related to the use of QSARs for regulatory purposes using results obtained from rat oral lethality and fish acute toxicity estimates generated from computational models (including TOPKAT, MCASE, OASIS, and ECOSAR). Using data submitted under the Environmental Protection Agency's (EPA's) High Production Volume (HPV) Challenge Program, the results on the quality of the estimations are compared using a standard statistical review and an additional classification approach in which the hazard predictions were grouped using well-defined regulatory criteria (those used in EPA's New Chemical Program). Our results indicate that an evaluation of a model's regulatory applicability and predictive power is ultimately dependent on the specific criteria used in the assessment process. This work also discusses the practical difficulties associated with defining the domain of a predictive model using the estimates of four different ready biodegradation models and experimental data submitted under the EPA's New Chemical program. Our results suggest that the method a model employs for its predictions is as important as the training set in determining its domain of applicability. Together, these results highlight the challenges associated with developing reliable and easily applied acceptability criteria for the regulatory use of QSAR models.

Biodegradation, Environmental↗

PubMed1995

Integrated approach for environmental assessment of new and existing substances.

To ensure the environmental safety of new and existing substances, the environmental fate and potential effects resulting from their release into the environment must be assessed. This requires the development of reasonable, consistent, and effective methods to conduct environmental risk assessments and to prioritize testing for these substances. This assessment must integrate fate and effects at the point-of-entry; it should also extend to an assessment of the potential to persist, and the consequences of increases in exposure concentrations, and to bioaccumulate. The conventional environmental risk assessment approach is used to assess the fate and effects of a substance at its point-of-entry into the environment. In this paper, an approach is presented for conducting quantitative environmental risk assessments of new and existing substances that builds on this conventional approach by including quantitative assessment of the potential for, and consequences of, persistence and bioaccumulation. The approach is described for aquatic, sediment, and terrestrial environments. For each environmental compartment, the approach includes (i) classification of the substance, based on environmental partitioning processes, to ensure that the appropriate data are collected and models used; (ii) a fate assessment to understand the ultimate fate of the substance after entry into the environment or "an environmental compartment" and to predict the exposure concentration of the substance at point-of-entry; (iii) a persistence assessment which determines the potential for increase in the exposure concentration as a result of repeated additions of the substance; (iv) effects assessment; (v) environmental risk assessment to examine the potential for adverse impact on ecosystems; and (vi) a bioaccumulation assessment to evaluate the potential for direct and indirect effects on the species of interest due to bioaccumulation. The assessment approach is illustrated using data for a hypothetical consumer product substance that is disposed down-the-drain.

Animals↗

PubMed2005

Natural cyanide degradation and impact on Ili River drainage areas from a Goldmine in Xinjiang autonomous region, China.

The Ili River is a very important river to the northwest of China and Kazakhstan. The Axi Goldmine is located in the upstream of a branch of the Ili River. The cyanide from the goldmine effluent is a threat to the downstream areas. According to our study, the natural degradation of cyanide conforms to a negative exponential equation in the tailings impoundment, second wastewater pond and even in the receiving streams if the dilution action from other streams were deducted. In the combined action of dilution and natural decomposing, the cyanide from the goldmine effluent does not pose a hazard to the trunk of the Ili River in the normal producing states. The equations of cyanide degradation in the streams and the hydrology parameters could be used to assess the environmental impact on the downstream areas if accidental discharges of cyanide occurred. The available way of decreasing the cyanide impact on the streams is to increase the rate of recycled water so that the lower the wastewater level in the tailing impoundment and the second wastewater pond, the lower is the amount of leakage of wastewater to the streams.

Biodegradation, Environmental↗

PubMed2004

Development of biobased products.

Research conducted over the past seven years by the biotechnology byproducts consortium (BBC) addresses its mission to investigate the opportunities to add value to agricultural products, byproducts and coproducts and to manage the wastewater arising from agribusinesses in an environmentally favorable way. Since a wide variety of research approaches have been taken, the results are collected in five topic groups: (1) bioremediation that includes anaerobic fermentations of wastes to produce methane and hydrogen, the genetics of methanogenesis and in situ remediation of contaminated aquifer systems, landfill leachates and industrial effluents; (2) land application of fermentation byproducts and their use in animal feeds; (3) biocatalytic studies of transformations of components of corn and soybean oils, peroxidases present in plant products, such as soybean hulls; (4) biochemical reactions for the production of de-icers from industrial water streams, biodiesel production from fats and greases, biodegradable plastics from polymerizable sugar derivatives, single cell foods derived from fungal growth on waste streams, and bacterial polysaccharides from Erwinia species; (5) separation and recovery of components by membrane technologies.

Animal Feed↗

PubMed1999

Biodeterioration of granite monuments by Ochrolechia parella (L.) mass: an FT Raman spectroscopic study.

Ochrolechia parella is one of the most abundant lichens colonizing granite monuments in the region of Galicia (N.W. Spain). Its interaction with granite used in the construction of four ancient monuments was studied using FT Raman spectroscopy to evaluate the production of calcium oxalate by this lichen and the relationship of this production with different environmental conditions, particularly humidity. The results obtained showed that Ochrolechia parella is an aggressive colonizer, causing chemical disturbances to the granite through the formation of both calcium oxalate monohydrate and dihydrate. Apothecial development appears to be related to the production of calcium oxalate, and humidity determines the state of hydration of the calcium oxalate in the thallus.

Architecture↗

PubMed2005

Suicidal genetically engineered microorganisms for bioremediation: need and perspectives.

In the past few decades, increased awareness of environmental pollution has led to the exploitation of microbial metabolic potential in the construction of several genetically engineered microorganisms (GEMs) for bioremediation purposes. At the same time, environmental concerns and regulatory constraints have limited the in situ application of GEMs, the ultimate objective behind their development. In order to address the anticipated risks due to the uncontrolled survival/dispersal of GEMs or recombinant plasmids into the environment, some attempts have been made to construct systems that would contain the released organisms. This article discusses the designing of safer genetically engineered organisms for environmental release with specific emphasis on the use of bacterial plasmid addiction systems to limit their survival thus minimizing the anticipated risk. We also conceptualize a novel strategy to construct "Suicidal Genetically Engineered Microorganisms (SGEMs)" by exploring/combining the knowledge of different plasmid addiction systems (such as antisense RNA-regulated plasmid addiction, proteic plasmid addiction etc.) and inducible degradative operons of bacteria.

Bacteria↗

PubMed2001

Diversity of the Burkholderia cepacia complex and implications for risk assessment of biological control strains.

The Burkholderia cepacia complex (Bcc) consists of several species of closely related and extremely versatile gram-negative bacteria found naturally in soil, water, and the rhizosphere of plants. Strains of Bcc have been used in biological control of plant diseases and bioremediation, while some strains are plant pathogens or opportunistic pathogens of humans with cystic fibrosis. The ecological versatility of these bacteria is likely due to their unusually large genomes, which are often comprised of several (typically two or three) large replicons, as well as their ability to use a large array of compounds as sole carbon sources. The original species B. cepacia has been split into eight genetic species (genomovars), including five named species, but taxonomic distinctions have not enabled biological control strains to be clearly distinguished from human pathogenic strains. This has led to a reassessment of the risk of several strains registered by the U.S. Environmental Protection Agency for biological control. We review the biology of Bcc bacteria, especially how our growing knowledge of Bcc ecology and pathogenicity might be used in risk assessment. The capability of this bacterial complex to cause disease in plants and humans, as well as to control plant diseases, affords a rare opportunity to explore traits that may function in all three environments.

Biodegradation, Environmental↗