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PubMed2001

Use of molecular techniques in bioremediation.

In a practical sense, biotechnology is concerned with the production of commercial products generated by biological processes. More formally, biotechnology may be defined as "the application of scientific and engineering principles to the processing of material by biological agents to provide goods and services" (Cantor, 2000). From a historical perspective, biotechnology dates back to the time when yeast was first used for beer or wine fermentation, and bacteria were used to make yogurt. In 1972, the birth of recombinant DNA technology moved biotechnology to new heights and led to the establishment of a new industry. Progress in biotechnology has been truly remarkable. Within four years of the discovery of recombinant DNA technology, genetically modified organisms (GMOs) were making human insulin, interferon, and human growth hormone. Now, recombinant DNA technology and its products--GMOs are widely used in environmental biotechnology (Glick and Pasternak, 1988; Cowan, 2000). Bioremediation is one of the most rapidly growing areas of environmental biotechnology. Use of bioremediation for environmental clean up is popular due to low costs and its public acceptability. Indeed, bioremediation stands to benefit greatly and advance even more rapidly with the adoption of molecular techniques developed originally for other areas of biotechnology. The 1990s was the decade of molecular microbial ecology (time of using molecular techniques in environmental biotechnology). Adoption of these molecular techniques made scientists realize that microbial populations in the natural environments are much more diverse than previously thought using traditional culture methods. Using molecular ecological methods, such as direct DNA isolation from environmental samples, denaturing gradient gel electrophoresis (DGGE), PCR methods, nucleic acid hybridization etc., we can now study microbial consortia relevant to pollutant degradation in the environment. These techniques promise to provide a better understanding and better control of environmental biotechnology processes, thus enabling more cost effective and efficient bioremediation of our toxic waste and contaminated environments.

Bacteria↗
PubMed2005

Degradation of xenobiotic compounds by lignin-degrading white-rot fungi: enzymology and mechanisms involved.

White-rot fungi (WRF) are ubiquitous in nature with their natural ability to compete and survive. WRF are the only organisms known to have the ability to degrade and mineralize recalcitrant plant polymer lignin. Their potential to degrade second most abundant carbon reserve material lignin on the earth make them important link in global carbon cycle. WRF degrade lignin by its unique ligninolytic enzymatic machinery including lignin peroxidase, manganese peroxidase, laccase, cellobiose dehydrogenase, H2O2-generating enzymes, etc. The ligninolytic enzymes system is non-specific, extracellular and free radical based that allows them to degrade structurally diverse range of xenobiotic compounds. Lignin peroxidase and manganese peroxidase carry out direct and indirect oxidation as well as reduction of xenobiotic compounds. Indirect reactions involved redox mediators such as veratryl alcohol and Mn2+. Reduction reactions are carried out by carboxyl, superoxide and semiquinone radicals, etc. Methylation is used as detoxification mechanism by WRF. Highly oxidized chemicals are reduced by transmembrane redox potential. Degradation of a number of environmental pollutants by ligninolytic system of white rot fungi is described in the present review.

Basidiomycota↗
PubMed2005

Cr(VI) detoxification by Desulfovibrio vulgaris strain Hildenborough: microbe-metal interactions studies.

Toxic heavy metals constitute a worldwide environmental pollution problem. Bioremediation technologies represent efficient alternatives to the classic cleaning-up of contaminated soil and ground water. Most toxic heavy metals such as chromium are less soluble and toxic when reduced than when oxidized. Sulfate-reducing bacteria (SRB) are able to reduce heavy metals by a chemical reduction via the production of H2S and by a direct enzymatic process involving hydrogenases and c3 cytochromes. We have previously reported the effects of chromate [Cr(VI)] on SRB bioenergetic metabolism and the molecular mechanism of the metal reduction by polyhemic cytochromes. In the current work, we pinpoint the bacteria-metal interactions using Desulfovibrio vulgaris strain Hildenborough as a model. The bacteria were grown in the presence of high Cr(VI) concentration, where they accumulated precipitates of a reduced form of chromium, trivalent chromium [Cr(III)], on their cell surfaces. Moreover, the inner and outer membranes exhibited precipitates that shared the spectroscopic signature of trivalent chromium. This subcellular localization is consistent with enzymatic metal reduction by cytochromes and hydrogenases. Regarding environmental significance, our findings point out the Cr(VI) immobilization mechanisms of SRB; suggesting that SRB are highly important in metal biogeochemistry.

Biodegradation, Environmental↗
PubMed2000

Pseudomonas aeruginosa rhamnolipids: biosynthesis and potential applications.

Pseudomonas aeruginosa produces and secretes rhamnose-containing glycolipid biosurfactants called rhamnolipids. This review describes rhamnolipid biosynthesis and potential industrial and environmental applications of rhamnolipids. Rhamnolipid production is dependent on central metabolic pathways, such as fatty acid synthesis and dTDP-activated sugars, as well as on enzymes participating in the production of the exopolysaccharide alginate. Synthesis of these surfactants is regulated by a very complex genetic regulatory system that also controls different P. aeruginosa virulence-associated traits. Rhamnolipids have several potential industrial and environmental applications including the production of fine chemicals, the characterization of surfaces and surface coatings, as additives for environmental remediation, and as a biological control agent. Realization of this wide variety of applications requires economical commercial-scale production of rhamnolipids.

Biodegradation, Environmental↗
PubMed1977

Chlorinated benzenes in the environment.

Chlorinated benzenes are composed of twelve chemical species: one mono-, three di-, three tri-, three tetra-, one penta-, and one hexachlorobenzene. Most of these are not only important intermediates for various kinds of chemicals but are also extensively employed for various applications singly or in combination. For example, 1,4-dichlorobenzene is used chiefly against termites in soil; trichlorobenzenes are used as solvents for pesticides and also as heat transfer agents with PCBs; the mixture of trichlorobenzene and tetrachlorobenzene is applied in controlling shellfish predators; and hexachlorobenzene is applied to wheat as a fungicide in some countries and as an additive to rubber products. The annual production (1973) of monochlorobenzene, 1,2-dichlorobenzene, and 1,4-dichlorobenzene in Japan was about 23,000, 9000, and 20,000, tons, respectively. Production volumes of other chlorinated benzenes are not well known but are assumed to be smaller than those of the above three compounds. The total annual production of chlorinated benzenes far surpasses the peak production of PCBs (7000 tons/year) which are known as a ubiquitous pollutant in this country. Since chlorinated benzenes have a chemical structure and properties similar to those of PCBs and PCTs, it seemed necessary to direct our attention to environmental contamination by these materials. The present paper describes only the occurrence and the fate of these materials. Toxicity and biological impact are not referred to here.

Air Pollution↗
PubMed1996

Safety evaluation of a lipase expressed in Aspergillus oryzae.

A programme of studies was conducted to establish the safety of a lipase artificially expressed in Aspergillus oryzae to be used in the detergent industry and as a processing aid in the baking industry. Laboratory animal studies were used to assess general and inhalation toxicity, skin sensitization, and skin and eye irritation. Its potential to cause mutagenicity and chromosomal aberrations was assessed in microbial and tissue culture in vitro studies. The pathogenicity of A. oryzae, the organism used to produce the lipase, was also assessed in laboratory animals. Basic ecotoxicity in a variety of test species was studied. General and inhalation toxicity was low. There was evidence of mild skin irritation. There was no evidence of eye irritation, skin sensitization, mutagenic potential, chromosomal aberrations, exotoxicity or notable pathogenicity. Comparison of these results with human exposure levels and previously published data indicates that the lipase appears safe for consumers in the given applications, requires no special occupational health precautions in manufacture and is of low environmental impact. Furthermore, the organism used in production of the lipase hs no notable pathogenicity.

Administration, Inhalation↗
PubMedDate not supplied

Persistence of estrogenic hormones in agricultural soils: I. 17Beta-estradiol and estrone.

The persistence and pathways of dissipation of 17beta-estradiol and estrone in soil were established in laboratory microcosm incubations. [4-14C]-17beta-Estradiol dissipation and mineralization rates were determined over a range of temperatures and moistures, and this compound was rapidly removed in soil conditions typical of a temperate growing season. 17beta-Estradiol was oxidized to estrone in both autoclaved and nonsterile loam, silt loam, and sandy loam soils, suggesting an abiological transformation. In contrast, estrone was stable in autoclaved soil, suggesting that its removal was microbially mediated. Both [4-14C]-17beta-estradiol and [4-14C]-estrone formed non-extractable residues, and soil-bound residues were only slowly mineralized, suggesting that their bioavailability was low. Determination of total estrogenicity in soil extracts by means of a recombinant yeast assay indicated that there were no other estrogenic compounds produced during 17beta-estradiol dissipation, and that total estrogenicity was rapidly dissipated below the detection limit. We suggest that environmental studies evaluating the movement and persistence of estrogenic hormones from animal wastes should include estrone in their analyses.

Agriculture↗
PubMed2001

Comparison of different life-cycle impact assessment methods for aquatic ecotoxicity.

Human and ecotoxicity impact categories are problematic to quantify within life-cycle impact assessment (LCIA) because their local scope makes them difficult to aggregate with the traditional global-impact categories used in life-cycle assessment (LCA). For being able to assess local impacts such as toxicity, LCIA developers increasingly include fate modeling into LCA. This article follows this development by comparing different LCIA methods for aquatic ecotoxicology and by investigating the importance of fate within LCIA, the necessity of considering freshwater and seawater compartments separately, and the key degradation and intermedia transfer processes involved. The methods are compared by assessing an example study of domestic clothes washing in former West Germany. Four LCIA methods are selected and applied to four substances emitted during the washing process. The conclusion is that the consideration of environmental fate does matter and that aquatic ecotoxic impacts can differ significantly for the same substance in freshwater and in marine ecosystems. The way (bio)degradation, photolysis, volatilization, and transfer from agricultural soils are considered plays an important role as do the system boundaries chosen. This means that the LCIA methodology should remain flexible so that appropriate methods can be chosen for different applications. Fate models being developed in the environmental risk assessment of chemicals can contribute to the further improvement of LCIA methods.

Agriculture↗
PubMed2005

Generation of polluted waters from mining wastes in a uranium deposit.

Dump consisting of 9500 tons of rich-in-pyrite mining wastes located in the uranium deposit Curilo, Western Bulgaria, was, after rainfall, an intensive source of acid drainage waters. These waters had a pH in the range of about 1.7-4.5 and contained radionuclides (uranium, radium), heavy metals (copper, zinc, cadmium, lead, nickel, cobalt, iron, and manganese), arsenic and sulphates in concentrations usually much higher than the relevant permissible levels for waters intended for use in the agriculture and/or industry. The generation of these polluted waters was studied under real field conditions for a period of about seven years during different climatic seasons. It was found that the dump was inhabited by a diverse microflora in which some acidophilic chemolithotrophic bacteria were the prevalent microorganisms. The solubilization of the above-mentioned pollutants from the dump material was connected mainly with the oxidation of pyrite and other sulphide minerals by these bacteria. Their activity depended on some essential environmental factors such as temperature, pH, and water, oxygen and nutrient contents in the dump.

Acid Rain↗
PubMed1983

Biomaterials for drug delivery systems.

Drug delivery systems have unusual materials requirements which derive mainly from their therapeutic role: to administer drugs over prolonged periods of time at rates that are independent of patient-to-patient variables. The chemical nature of the surfaces of such devices may stimulate biorejection processes which can be enhanced or suppressed by the simultaneous presence of the drug that is being administered. Selection of materials for such systems is further complicated by the need for compatibility with the drug contained within the system. A review of selected drug delivery systems is presented. This leads to a definition of the technologies required to develop successfully such systems as well as to categorize the classes of drug delivery systems available to the therapist. A summary of the applications of drug delivery systems will also be presented. There are five major challenges to the biomaterials scientist: (1) how to minimize the influence on delivery rate of the transient biological response that accompanies implantation of any object; (2) how to select a composition, size, shape, and flexibility that optimizes biocompatibility; (3) how to make an intravascular delivery system that will retain long-term functionality; (4) how to make a percutaneous lead for those delivery systems that cannot be implanted but which must retain functionality for extended periods; and (5) how to make biosensors of adequate compatibility and stability to use with the ultimate drug delivery system-a system that operates with feedback control.

Biocompatible Materials↗
PubMed2002

Bacterial chemotaxis to pollutants and plant-derived aromatic molecules.

There is accumulating evidence that motile bacteria are chemotactically attracted to environmental pollutants that they can degrade. Chemotaxis, the ability of motile bacteria to detect and respond to specific chemicals in the environment, can increase an organism's chances of locating useful sources of carbon, nitrogen and energy, and could thus play an important role in the biodegradation process. Recent evidence demonstrating that chemotaxis and biodegradation genes are coordinately regulated suggests that these processes are intimately linked in nature.

Bacteria↗
PubMed2006

Evaluation of the effects of various culture conditions on Cr(VI) reduction by Shewanella oneidensis MR-1 in a novel high-throughput mini-bioreactor.

The growth and Cr(VI) reduction by Shewanella oneidensis MR-1 was examined using a mini-bioreactor system that independently monitors and controls pH, dissolved oxygen (DO), and temperature for each of its 24, 10-mL reactors. Independent monitoring and control of each reactor in the cassette allows the exploration of a matrix of environmental conditions known to influence S. oneidensis chromium reduction. S. oneidensis MR-1 grew in minimal medium without amino acid or vitamin supplementation under aerobic conditions but required serine and glycine supplementation under anaerobic conditions. Growth was inhibited by DO concentrations >80%. Lactate transformation to acetate was enhanced by low concentration of DO during the logarithmic growth phase. Between 11 and 35 degrees C, the growth rate obeyed the Arrhenius reaction rate-temperature relationship, with a maximum growth rate occurring at 35 degrees C. S. oneidensis MR-1 was able to grow over a wide range of pH (6-9). At neutral pH and temperatures ranging from 30 to 35 degrees C, S. oneidensis MR-1 reduced 100 microM Cr(VI) to Cr(III) within 20 min in the exponential growth phase, and the growth rate was not affected by the addition of chromate; it reduced chromate even faster at temperatures between 35 and 39 degrees C. At low temperatures (<25 degrees C), acidic (pH < 6.5), or alkaline (pH > 8.5) conditions, 100 microM Cr(VI) strongly inhibited growth and chromate reduction. The mini-bioreactor system enabled the rapid determination of these parameters reproducibly and easily by performing very few experiments. Besides its use for examining parameters of interest to environmental remediation, the device will also allow one to quickly assess parameters for optimal production of recombinant proteins or secondary metabolites.

Biodegradation, Environmental↗
PubMed2004

Environmental genomics: exploring the unmined richness of microbes to degrade xenobiotics.

Increasing pollution of water and soils by xenobiotic compounds has led in the last few decades to an acute need for understanding the impact of toxic compounds on microbial populations, the catabolic degradation pathways of xenobiotics and the set-up and improvement of bioremediation processes. Recent advances in molecular techniques, including high-throughput approaches such as microarrays and metagenomics, have opened up new perspectives and pointed towards new opportunities in pollution abatement and environmental management. Compared with traditional molecular techniques dependent on the isolation of pure cultures in the laboratory, microarrays and metagenomics allow specific environmental questions to be answered by exploring and using the phenomenal resources of uncultivable and uncharacterized micro-organisms. This paper reviews the current potential of microarrays and metagenomics to investigate the genetic diversity of environmentally relevant micro-organisms and identify new functional genes involved in the catabolism of xenobiotics.

Bacteria↗
PubMed2004

Long-range transport and global fractionation of POPs: insights from multimedia modeling studies.

The long-range transport of persistent organic pollutants (POPs) is investigated with two multimedia box models of the global system. ChemRange is a purely evaluative, one-dimensional steady-state (level III) model; CliMoChem is a two-dimensional model with different temperatures, land/water ratios and vegetation types in different latitudinal zones. Model results are presented for three case studies: (i) the effect of atmospheric aerosol particles on the long-range transport of POPs, (ii) the effect of oceanic deposition on the long-range transport of different PCB congeners, (iii) the global fractionation of different PCB congeners. The model results for these case studies show: (i) the low atmospheric half-lives estimated for several organochlorine pesticides are likely to be inconsistent with the observed long-range transport of these compounds; (ii) export to the deep sea reduces the potential for long-range transport of highly hydrophobic compounds (but does not remove these chemicals from the biosphere); (iii) there are different meanings of the term global fractionation that refer to different aspects of the fractionation process and need to be distinguished. The case-study results further indicate that the influences of varying environmental conditions on the physicochemical properties and the degradation rate constants of POPs need to be determined.

Air Movements↗
PubMed1997

Dechlorination of lindane by the cyanobacterium Anabaena sp. strain PCC7120 depends on the function of the nir operon.

Nitrate is essential for lindane dechlorination by the cyanobacteria Anabaena sp. strain PCC7120 and Nostoc ellipsosporum, as it is for dechlorination of other organic compounds by heterotrophic microorganisms. Based on analyses of mutants and effects of environmental factors, we conclude that lindane dechlorination by Anabaena sp. requires a functional nir operon that encodes the enzymes for nitrate utilization.

Anabaena↗
PubMed1987

Experimental evolution of catabolic pathways of bacteria.

Experimental evolution of catabolic pathways offers considerable potential for accelerating the evolution of bacteria able to degrade toxic industrial chemicals, and this may be useful for combatting environmental pollution. The principal strategies that have been successfully followed to evolve useful catabolic routes for aromatic compounds in soil bacteria are analysed.

Bacteria↗