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PubMed2005

Degradation of anthracene and pyrene supplied by microcrystals and non-aqueous-phase liquids.

Polycyclic aromatic hydrocarbons (PAHs) are worldwide environmental pollutants. Their bioavailability is limited by a low aqueous solubility, which causes specific adaptations in degrading bacteria. To compare bacterial degrading behavior, a study was conducted on the mineralization, metabolization and formation of biomass from (14)C-anthracene by Sphingomonas sp. BA2 compared with those from (14)C-pyrene by Gordonia-like strain BP9 and Mycobacterium gilvum VF1. Different conditions of PAH supply were used in the medium: crystals <0.5 mm, microcrystals <<0.1 mm formed by sonication, or PAH solubilized in 2,2,4,4,6,8,8-heptamethylnonane (HMN) or silicone oil. Anthracene supply by crystals and silicone oil led to similar maximum mineralization rates 33 ng ml(-1) h(-1) and the same amount of mineralization (24%) after 168 h. Microcrystals increased the rates and amounts only slightly. HMN decreased the values to less than one-third. In comparison with crystals, microcrystals increased overall pyrene mineralization by strain BP9 from 53% to 58%, with maximum mineralization rates of 160 ng ml(-1) h(-1) and 166 ng ml(-1) h(-1). Silicone oil heavily increased the rate to 292 ng ml(-1) h(-1) and the amount mineralized to 71%, whereas HMN inhibited the degradation by one order of magnitude. A similar degradation behavior showing lower mineralization rates and extent was observed with strain VF1. However, inhibition by HMN was less pronounced. Sonication, leading to decreased PAH crystal size, increased the mass transfer and mineralization rates. PAH supply by silicone oil led to a much higher mass transfer, which may be due to emulsification of the oil, whereas such effects were not observed with HMN.

Alkanes↗

PubMed1995

Some environmental effects on relationships between in sacco degradability of protein and dry matter and chemical composition of Italian ryegrass.

The environmental effects on chemical composition and the rate and extent of crude protein (CP) and dry matter (DM) degradation of Italian ryegrass (Lolium multiflorum Lam.) in the rumen were studied. More intensive nitrogen (N) fertilizing (40, 80 and 140 kg N/ha) increased the content of the water, CP, true proteins and the effective degradability of CP (P < 0.05). Especially in the spring harvest such fertilizing increased the content of acid detergent fibre (ADF), neutral detergent fibre (NDF), cellulose and crude fibre (CF) as well as the rate of DM degradation (P < 0.05) and caused lower DM solubility while the content of hemicellulose was not affected. The most rapid changes due to grass ageing occurred in springtime. The content of DM, ADF, NDF, cellulose, hemicellulose and CF increased with maturity while the degradation rate and effective DM degradability decreased. The season and the trial location influenced the chemical composition of grass and the degradability of both DM and CP (P < 0.05). The closest multiple regression (the lowest RSD) was between the effective protein degradability and CP, NDF, ADF and and acid detergent lignin (ADL) (R2 = 0.97). Relatively good estimation of effective protein degradability was obtained using an exponential regression equation on the basis of CP content (R2 = 0.72), NDF content (R2 = 0.67) or effective DM degradability (R2 = 0.71) while the effective DM degradability may be estimated on the basis of DM solubility (R2 = 0.94), CF content (R2 = 0.93), ADF content (R2 = 0.94), ADL content (R2 = 0.85) or NDF content (R2 = 0.96). When estimating the effective CP and DM degradability from chemical composition, the error that occurs is most evidently influenced by N fertilizing and by time of harvest.

Animals↗

PubMed2006

Corynebacterium glutamicum as a model bacterium for the bioremediation of arsenic.

Arsenic is an extremely toxic metalloid that, when present in high concentrations, severely threatens the biota and human health. Arsenic contamination of soil, water, and air is a global growing environmental problem due to leaching from geological formations, the burning of fossil fuels, wastes generated by the gold mining industry present in uncontrolled landfills, and improper agriculture or medical uses. Unlike organic contaminants, which are degraded into harmless chemical species, metals and metalloids cannot be destroyed, but they can be immobilized or transformed into less toxic forms. The ubiquity of arsenic in the environment has led to the evolution in microbes of arsenic defense mechanisms. The most common of these mechanisms is based on the presence of the arsenic resistance operon (ars), which codes for: (i) a regulatory protein, ArsR; (ii) an arsenite permease, ArsB; and (iii) an enzyme involved in arsenate reduction, ArsC. Corynebacterium glutamicum, which is used for the industrial production of amino acids and nucleotides, is one of the most arsenic-resistant microorganisms described to date (up to 12 mM arsenite and >400 mM arseniate). Analysis of the C. glutamicum genome revealed the presence of two complete ars operons (ars1 and ars2) comprising the typical three-gene structure arsRBC, with an extra arsC1 located downstream from arsC1 (ars1 operon), and two orphan genes (arsB3 and arsC4). The involvement of both ars operons in arsenic resistance in C. glutamicum was confirmed by disruption and amplification of those genes. The strains obtained were resistant to up to 60 mM arsenite, one of the highest levels of bacterial resistance to arsenite so far described. Using tools for the genetic manipulation of C. glutamicum that were developed in our laboratory, we are attempting to obtain C. glutamicum mutant strains able to remove arsenic from contaminated water.

Arsenates↗

PubMed1979

Translocation, distribution, and environmental degradation of hexachlorophene in tomatoes.

The translocation, distribution, metabolism and environmental degradation of hexachlorophene were investigated in tomato plants (Lycopersicon esculentum Mill cv. beefsteak). All plants were grown under standardized conditions and treated with leaf-applied 14C-ring-labeled hexachlorophene (HCP). Treatment time ranged from 0 to 70 days. Autoradiographic analyses were performed on all plants. Selected plant tissues were extracted and chromatographed, using thin layer (TLC) and gas liquid chromatography (GLC). Hexachlorophene was not translocated from the plant leaves. No metabolites of hexachlorophene was found. A slight, but statistically nonsignificant, amount of HCP was lost from the leaves and the inert controls. At the end of the 70-day treatment, based on TLC and regression analysis of thin layer chromatographic plates, averages of 89.5% and 75.9% of the applied HPC remained unaltered on the treated plants and controls, respectively. This indicated that 10.5% and 24.1%, respectively, of the original HCP had been altered. Differences between the treatments and controls were statistically significant after 28 days of exposure. Further analyses of the above data, using gas chromatographic methods, showed that as many as 14 peaks were found in the treated samples and the controls, including the parent material. Ultraviolet photolysis seemed to be the mechanism responsible for alteration of the hexachlorophene. Three extracted chlorinated compounds have been identified by GC-mass spectral (MS) analysis including 2,2'-dihydroxy-3,5',6,6'-tetrachlorodiphenylmethane, 2,2'-dihydroxy-3,5,5',6,6'-pentachlorodiphenylmethane, and 2,2'-dihydroxy-3,3',5,5',6,6'-hexachlorodiphenylmethane (parent HCP). Eleven other electrophylic compounds have been found in various treated plant or control extracts. Further analyses will be necessary to verify the identification of the other degradation products.

Biodegradation, Environmental↗

PubMed1998

Altered biologic activities of commercial polychlorinated biphenyl mixtures after microbial reductive dechlorination.

The reductive dechlorination of polychlorinated biphenyls (PCBs) by anaerobic bacteria has recently been established as an important environmental fate of these compounds. This process removes chlorines directly from the biphenyl ring with replacement by hydrogen, resulting in a product mixture in which the average number of chlorines per biphenyl is reduced. In this study, dechlorination of commercial PCB mixtures (Aroclors 1242 and 1254) by microorganisms eluted from PCB-contaminated sediments of the River Raisin (Michigan) and Silver Lake (Massachusetts) caused a depletion in the proportion of highly chlorinated PCB congeners and an accumulation of lesser-chlorinated congeners. Dechlorination occurred primarily at the meta and, to a much lesser extent, para positions of biphenyl. The concentrations of the coplanar congeners including 3,3',4,4',5-pentachlorobiphenyl, the most potent dioxinlike congener, were significantly lowered by reductive dechlorination. Microbial reductive dechlorination of commercial PCB mixtures caused a substantial reduction in biologic activities in several instances. It significantly lowered or eliminated the inhibitory effects of Aroclors on fertilization of mouse gametes in vitro. Similarly, the dechlorinated product mixtures had substantially lower ethoxyresorufin-O-deethylase induction potencies and showed less ability to induce activating protein 1 transcription factor activity as compared to the unaltered Aroclors. In other assays the same dechlorinated product mixtures demonstrated biologic activities similar to the nondechlorinated Aroclors, including the ability of PCB mixtures to stimulate insulin secretion and cause neutrophil activation. The data presented here establish that the biologic activities of commercial PCB mixtures are altered by microbial reductive dechlorination and that an assessment of their toxic potential requires an array of tests that include the different mechanisms associated with PCBs.

Animals↗

PubMed1999

Studies of the behaviour and fate of the polymer-additives octadecyl-3-(3.5-di-t-butyl-4-hydroxyphenyl)propionate and tri-(2.4-di-t-butylphenyl)phosphite in the environment.

In order to evaluate the environmental risk potential of the polymer-additives octadecyl-3-(3.5-di-t-butyl-4-hydroxyphenyl)propionate (additive 1) and tri-(2.4-di-t-butylphenyl)phosphite (additive 2) we have studied the degradation of the 14C-labelled single components and their release from a polypropylene matrix in abiotic and biotic test systems as well as their transport behaviour in soil. The biotic degradation in waste compost, activated sludge and in soil was studied. In order to conduct release tests, waste disposal material were used as well. The abiotic degradation was effectuated by photooxidation at a catalytic surface. The highest mineralisation rates were obtained by photooxidative degradation of the two test substances. The maximum content of bounded residues was found for additive 1 in soil and for additive 2 in waste compost. In the extracts of soil and compost, the principal metabolites could be identified in the case of additive 1 as 7.9-di-t-butyl-1-oxaspiro[4.5]deca-6.9-dien-2.8-dion and in activated sludge as the methyl ester of 3-(3.5-di-t-butyl-4-hydroxyphenyl) propionic acid. Additive 2 metabolised in all degradation tests nearly completely under formation of two products. The main component was identified as tri-(2.4-di-t-butylphenyl)phosphate. Both polymer-additives were eluated from the chosen soil types. The transport behaviour of additive 1 was independent from the soil type. In all test matrices additive 1 as well as additive 2 were released from polypropylene. Because the amounts of additive 1 and 2 absorbed onto soil particles were taken into account, the highest liberation rates were found in the soil test.

Antioxidants↗

PubMed1988

Microbial ecology of the terrestrial subsurface.

We have presented a current view of the microbial ecology of the terrestrial subsurface by considering primarily the ecology of shallow aquifer sediments. The properties of the aquifer sediments and groundwater determine their ability to support microbial life and control the abundance and activities of microorganisms. Pore size, nutrient limitations, availability of electron acceptors, and large surface area for attachment all may have major effects on microbial abundance and activities in aquifer material. Microorganisms are the predominant forms of life in the subsurface. They will be found wherever enough space, nutrients, and water are available for them to live. Environmental factors such as pH, temperature, hydrostatic pressure, and dissolved salts also may influence subsurface microbial populations, but these factors do not exhibit great extremes in shallow water table aquifers, and thus only in very deep formations might they limit diversity or preclude the existence of microorganisms. Although the presence and activity of microorganisms in most subsurface environments are predictable, only recently have subsurface microbial populations in shallow subsurface zones been characterized. Aseptic sampling methods have been employed and microbiological and biochemical methods have been adapted to determine the types, abundance, and metabolic activities of microorganisms in subsurface material. Bacteria dominate, but eukaryotic microorganisms also are present. Vertical profile studies of a shallow aquifer in Oklahoma showed that active microbial biomass declined with depth to the unsaturated zone, but was variable in saturated sediments. Such a distribution of active biomass may be common in shallow aquifers. Studies on the lateral distribution of microorganisms in shallow and deep aquifers suggest that microorganisms are transported or migrate over fairly long distances in aquifer sediments. Surficial aquifers may be colonized by vertical or lateral transport and migration of surface microorganisms from recharge areas, but microorganisms could also have colonized when sediments were originally deposited. The biological and physical mechanisms controlling the migration of microorganisms in aquifers are not well understood. The function of shallow aquifers was considered with regard to nutritional ecology. Most pristine aquifers are oligotrophic. Heterotrophic life in these unique ecosystems is supported by secondary organic compounds that filter down from the soil above. The quantity and quality of organic nutrients depend on the age of water and rate of recharge of the aquifer.(ABSTRACT TRUNCATED AT 400 WORDS)

Bacteria↗

PubMed2003

Temporal change in culturable phenanthrene degraders in response to long-term exposure to phenanthrene in a soil column system.

Widespread environmental contamination by polycyclic aromatic hydrocarbons (PAH) has led to increased interest in the use of natural attenuation as a clean-up strategy. However, few bioremediation studies have investigated the behaviour of the indigenous PAH-degrading community after long-term exposure to a PAH. In this study, a column packed with sandy loam soil was exposed to a solution saturated with phenanthrene ( approximately 1.2 mg l-1) for a 6-month period to examine the temporal response of the indigenous phenanthrene-degrading community. Initial soil, effluent, and final soil samples were collected and analysed for phenanthrene concentration and culturable phenanthrene degraders. Phenanthrene-degrading isolates were grouped by colony morphology. For each unique group, 16S rDNA polymerase chain reaction was performed, and then sequencing analysis was used to identify the isolate at the genus level. Twenty-five phenanthrene-degrading isolates, potentially representing 19 genera, were obtained from this analysis. Of these, eight genera have not been reported previously to degrade phenanthrene, including Afipia, Janthinobacterium, Leptothrix, Massilia, Methylobacterium, Rhizobium, Sinorhizobium and Thiobacillus. Results indicate that the dominant phenanthrene-degrading population changed over the course of this 6-month experiment. Specifically, the isolates obtained initially from the soil were not subsequently found in either effluent samples or the soil at the end of the experiment. Furthermore, several isolates that were found in the soil at the end of the experiment were not observed in the soil initially or in the effluent samples. This study confirms earlier findings indicating that a diverse community participates in phenanthrene degradation in the environment, and also suggests that the composition of this community is temporally variable.

Bacteria↗

PubMed2005

Degradation of medium-chain-length polyhydroxyalkanoates in tropical forest and mangrove soils.

Bacterial polyhydroxyalkanoates (PHAs) are perceived to be a suitable alternative to petrochemical plastics because they have similar material properties, are environmentally degradable, and are produced from renewable resources. In this study, the in situ degradation of medium-chain-length PHA (PHAMCL) films in tropical forest and mangrove soils was assessed. The PHAMCL was produced by Pseudomonas putida PGA1 using saponified palm kernel oil (SPKO) as the carbon source. After 112 d of burial, there was 16.7% reduction in gross weight of the films buried in acidic forest soil (FS), 3.0% in the ones buried in alkaline forest soil by the side of a stream (FSst) and 4.5% in those buried in mangrove soil (MS). There was a slight decrease in molecular weight for the films buried in FS but not for the films buried in FSst and in MS. However, no changes were observed for the melting temperature, glass transition temperature, monomer compositions, structure, and functional group analyses of the films from any of the burial sites during the test period. This means that the integral properties of the films were maintained during that period and degradation was by surface erosion. Scanning electron microscopy of the films from the three sites revealed holes on the film surfaces which could be attributed to attack by microorganisms and bigger organisms such as detritivores. For comparison purposes, films of polyhydroxybutyrate (PHB), a short-chain-length PHA, and polyethylene (PE) were buried together with the PHAMCL films in all three sites. The PHB films disintegrated completely in MS and lost 73.5% of their initial weight in FSst, but only 4.6% in FS suggesting that water movement played a major role in breaking up the brittle PHB films. The PE films did not register any weight loss in any of the test sites.

Biodegradation, Environmental↗

PubMed2001

Influence of ferrous iron and ph on carbon tetrachloride degradation by Methanosarcina thermophila.

The influence of environmental conditions on the biological transformation of a contaminant must be well understood to optimize remediation processes. One factor that impacts the biological transformation of carbon tetrachloride (CT) is elemental iron (Fe0). Previous research has shown that Fe0 increases the methanogenic CT degradation rate by providing H2 for cell growth and dechlorination. As Fe0 oxidizes it also increases the pH and Fe2+ levels, which may also impact the biological transformation of CT. Experiments were performed with Methanosarcina thermophila to investigate the influence of these factors on CT degradation. The transformation of CT and CF was greatly influenced by pH, with the rate of CT and CF degradation increasing with increasing pH. After 6 h, > 90% of the CT had been degraded in the treatments containing cells at a pH of 8.5, whereas only about 51% of the CT had been degraded in similar treatments at a pH of 5.5. Fe2+ did not significantly influence the degradation of CT; however, 60% less CF was formed in systems containing cells+Fe2+ than in systems containing cells only. In addition. Fe2+ promoted rapid transformation of CF when added to treatments containing cells. The product distribution after 9 days in all systems containing cells was very similar, with 98.04 +/- 5.46% (two-sided 95% confidence interval) of the originally fed CT present as soluble products. These results show that pH and Fe2+ influence the degradation of CT and CF, although transiently. Because the residence time of contaminants in Fe0 barriers varies with the thickness of the barrier, it is likely that this influence will be important for some flow-through systems. This implies that a combined Fe0/organism remediation system may have previously unrealized advantages (due to pH and Fe2+ changes).

Biodegradation, Environmental↗

PubMed2006

Characterization and reactivity assessment of organic substrates for sulphate-reducing bacteria in acid mine drainage treatment.

Acid mine drainage (AMD), which contains high concentrations of sulphate and dissolved metals, is a serious environmental problem. It can be treated in situ by sulphate reducing bacteria (SRB), but effectiveness of the treatment process depends on the organic substrate chosen to supply the bacteria's carbon source. Six natural organic materials were characterized in order to investigate how well these promote sulphate reduction and metal precipitation by SRB. Maple wood chips, sphagnum peat moss, leaf compost, conifer compost, poultry manure and conifer sawdust were investigated in terms of their carbon (TOC, TIC, DOC) and nitrogen (TKN) content, as well as their easily available substances content (EAS). Single substrates, ethanol, a mixture of leaf compost (30% w/w), poultry manure (18% w/w), and maple wood chips (2% w/w), and the same mixture spiked with formaldehyde were then tested in a 70-day batch experiment to evaluate their performance in sulphate reduction and metal removal from synthetic AMD. Metal removal efficiency in batch reactors was as high as 100% for Fe, 99% for Mn, 99% for Cd, 99% for Ni, and 94% for Zn depending on reactive mixtures. Early metal removal (0-12d) was attributed to the precipitation of (oxy)hydroxides and carbonate minerals. The lowest metal and sulphate removal efficiency was found in the reactor containing poultry manure as the single carbon source despite its high DOC and EAS content. The mixture of organic materials was most effective in promoting sulphate reduction, followed by ethanol and maple wood chips, and single natural organic substrates generally showed low reactivity. Formaldehyde (0.015% (w/v)) provided only temporary bacterial inhibition. Although characterization of substrates on an individual basis provided insight on their chemical make-up, it did not give a clear indication of their ability to promote sulphate reduction and metal removal.

Acids↗

PubMed2005

Evaluation of trickle-bed air biofilter performance under periodic stressed operating conditions as a function of styrene loading.

Trickle-bed air biofilters (TBABs) are suitable for treating volatile organic compounds (VOCs) at a significantly high practical loading because of their controlled environmental conditions. The application of TBAB for treating styrene-contaminated air under periodic backwashing and cyclical nonuse periods at a styrene loading of 0.64-3.17 kg chemical oxygen demand (COD)/m3 x day was the main focus of this study. Consistent long-term efficient performance of TBAB strongly depended on biomass control. A periodic in situ upflow with nutrient solution under media fluidization, that is, backwashing, was approached in this study. Two different nonuse periods were employed to simulate a shutdown for equipment repair or during weekends and holidays. The first is a starvation period without styrene loading, and the second is a stagnant period, which reflects no flow passing through the biofilter. For styrene loadings up to 1.9 kg COD/m3 x day, removal efficiencies consistently above 99% were achieved by conducting a coordinated biomass control strategy, that is, backwashing for 1 hr once per week. Under cyclical nonuse periods for styrene loadings up to 1.27 kg COD/m3 x day, stable long-term performance of the biofilter was maintained at more than 99% removal without employing backwashing. No substantial impact of nonuse periods on the biofilter performance was revealed. However, a coordinated biomass control by backwashing subsequently was unavoidable for attaining consistently high removal efficiency at a styrene loading of 3.17 kg COD/m3 x day. As styrene loading was increased, reacclimation of the biofilter to reach the 99% removal efficiency following backwashing or the nonuse periods was delayed. After the non-use periods, the response of the biofilter was a strong function of the biomass in the bed. No significant difference between the effects of the two different nonuse periods on TBAB performance was observed during the study period.

Air Movements↗

PubMed2006

[Co-expression of Rhodococcus sp. DS-3 dszABC and dszD gene with incompatible plasmids in Escherichia coli].

Biological dusulfurizaion of petroleum feedstocks and products may offer an attractive alternative to reduce sulfur oxide emissions that cause serious environmental pollution. Dibenzothiophene (DBT), a model of organic sulfur compound in petroleum, can be microbially desulfurized without degradation of the organic structure by 4S pathway. Three desulfurization enzymes (DszA, DszB and DszC) and flavin reductase (DszD) are involved in sulfur-specific DBT desulfurization. DszA and DszC are FMNH2-dependent monoxygenases, FMNH2 is provided from the freely diffusible FMNH2 pool in the cell, and is replenished by DszD. So, co-expression of the desulfurization enzymes and flavin reductase can enhance the rate of sulfur removal. In the present work two incompatible plasmids: pBADD and paN2 were constructed. The paN2 allows Escherichia coli to liberate the sulfur of DBT and DBTs and pBADD produces a flavin reductase. They were co-expressed in Escherichia coli B121 (DE3). The soluble products of DszA, DszB, DszC and DszD accounted for 7.6%, 3.5%, 3.1% and 18% of the total proteins in co-expressed system. The desulfurization rate of lysate of E. coli BL21- pBADD + paN2 is 12.03 micromol/(h x mg) Dsz protein and about 5.4-fold of that of E. coli BL2-paN2. Experiment were also conducted using resting cell with the 0.6 wt% DBT in n-hexadecane as model diesel oil. After 24 hours reaction, 0.42 mmol/L (about 84%) DBT was converted to 2-HBP by E. coli BL21- pBADD + paN2, however, there was only 0.08 mmol/L (about 16%) DBT was desulfurized by E. coli BL2-paN2. The maximum desulfurization rate of E.coli BL21-pBADD + paN2 is about 67 micromol/h. The result shows that DszD enhances the rate of 2-HBP production when co-expressed in vivo with the desulfurization enzymes.

Bacterial Proteins↗

PubMed1996

Mobilization of PAH and PCB from contaminated soil using a digestive tract model.

Environmental contaminants are mainly incorporated by ingestion. In general only those contaminants mobilized by the digestive juices are available for absorption in the digestive tract, while pollutants still fixed to indigestible particles leave the body without any effect. To evaluate the different health risks arising from the ingestion of individual types of polluted soil or other materials, we developed an in vitro test system which simulates the transition of pollutants from contaminated materials into digestive juices by means of a standardized artificial gastro-intestinal model. The test system simulates the influence of the acidic environment of the stomach (gastric model) followed by the neutral or slightly alkaline environment of the small intestine (gastro-intestinal model). Investigations on small amounts of polluted soil, sewage sludge, asphalt, metal scrap and blast sand showed that the mobilization of polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) by artificial gastric juice reaches 3% up to 22% of the pollutant concentration introduced into the test system. Elutions of the contaminated materials under gastric and subsequently under intestinal conditions with bile concentrations of 3 g/l resulted in PAH- and PCB-mobilizations in the range of 5% up to 40%. The degree of mobilization depends considerably on supplementary food material added to the test system. Lyophilized milk increased the fraction of mobilized PAH and PCB to 40%-85%. Application of the test system on 22 different contaminated soils showed that the mobilization of PAH under gastro-intestinal conditions with the addition of lyophilized milk ranged from 7% up to 95%, and the mobilization of PCB ranged from 32% up to 83%. This indicates that the test system can be a useful tool for evaluating the individual health risks arising from polluted soil or other materials.

Animals↗

PubMed2004

Removal and recovery of nickel(II) from aqueous solution by loofa sponge-immobilized biomass of Chlorella sorokiniana: characterization studies.

The biosorption process for the removal of nickel(II) by loofa sponge-immobilized biomass of Chlorella sorokiniana (LIBCS), a newly developed immobilized biosorbent, was characterized. Effects of environmental factors on metal uptake capacity of LIBCS were studied and compared with free biomass of C. sorokiniana (FBCS). Nickel(II) removal by LIBCS was found to be influenced by pH of the solution, initial metal concentration, and biomass concentration. The biosorption of nickel(II) ions by both LIBCS and FBCS increased as the initial concentration of nickel(II) ions increased in the medium. No loss to biosorption capacity of LIBCS for nickel(II) was found due to the presence of loofa sponge, indeed as compared to FBCS an increase of 25.3% was noted in the biosorption capacity of LIBCS. Maximum biosorption capacities for FBCS and LIBCS were found as 48.08 and 60.38 mg nickel(II)/g, respectively, whereas the amount of nickel(II) ions adsorbed on the plain loofa sponge was 6.1mg/g. During these biosorption studies, LIBCS exhibited excellent physical and chemical stability without any significant release/loss of microalgal biomass from loofa sponge matrix. The kinetics of nickel(II) removal was extremely fast reaching at equilibrium in about 15 min for LIBCS and 20 min for FBCS. The biosorption equilibrium was well described by the Langmuir and Freundlich adsorption isotherms. The biosorption capacities were found to be solution pH dependent and the maximum adsorption was found at a solution pH 4-5. The LIBCS could be regenerated using 75 mM HCl, with up to 98% recovery. The LIBCS were shown to be robust and stable with little decrease in the nickel(II) uptake capacity when used in consecutive seven biosorption-desorption cycles. Continuous removal of nickel(II) from electroplating effluent by LIBCS packed in fixed bed column bioreactor confirm the possibility of developing a biological treatment process for the removal of toxic metals from authentic wastewater.

Adsorption↗

PubMed2005

Ecotoxicological evaluation of diesel-contaminated soil before and after a bioremediation process.

Evaluation of contaminated sites is usually performed by chemical analysis of pollutants in soil. This is not enough either to evaluate the environmental risk of contaminated soil nor to evaluate the efficiency of soil cleanup techniques. Information on the bioavailability of complex mixtures of xenobiotics and degradation products cannot be totally provided by chemical analytical data, but results from bioassays can integrate the effects of pollutants in complex mixtures. In the preservation of human health and environment quality, it is important to assess the ecotoxicological effects of contaminated soils to obtain a better evaluation of the healthiness of this system. The monitoring of a diesel-contaminated soil and the evaluation of a bioremediation technique conducted on a microcosm scale were performed by a battery of ecotoxicological tests including phytotoxicity, Daphnia magna, and nematode assays. In this study we biostimulated the native microflora of soil contaminated with diesel by adding nutrients and crop residue (corn straw) as a bulking agent and as a source of microorganisms and nutrients; in addition, moisture was adjusted to enhance diesel removal. The bioremediation process efficiency was evaluated directly by an innovative, simple phytotoxicity test system and the diesel extracts by Daphnia magna and nematode assays. Contaminated soil samples were revealed to have toxic effects on seed germination, seedling growth, and Daphnia survival. After biostimulation, the diesel concentration was reduced by 50.6%, and the soil samples showed a significant reduction in phytotoxicity (9%-15%) and Daphnia assays (3-fold), confirming the effectiveness of the bioremediation process. Results from our microcosm study suggest that in addition to the evaluation of the bioremediation processes efficiency, toxicity testing is different with organisms representative of diverse phylogenic levels. The integration of analytical, toxicological and bioremediation data is necessary to properly assess the ecological risk of bioremediation processes.

Animals↗

PubMed2005

[Filtering capacity of Anodonta woodiana and its feeding selectivity on phytoplankton].

Lake eutrophication associated with algal bloom has become a major environmental challenge in China. Filter feeding organisms, e.g., silver carp, bighead carp, and zebra mussel, have been widely used to manipulate water environment through their top-down effects. The bivalve Anodonta woodiana is widely distributed across China, and has been used for bio-manipulation of some water bodies. In situ experiments were performed in a bay of Lake Dianchi and its surrounding ponds to study the filtering capacity and the filter feeding rate of Anodonta woodiana in these aguatic habitats, and to determine the controlling factors. The results showed that there was a relationship between filtration rate and total suspended substances measured in laboratory during August and September 2001 when the water temperature was 20 +/- 2 degrees C, which was expressed as y = 4 380.41 e(- 0.0184x) (R2 = 0.621, P < 0.05) based on at least squares analyses. The filtration rate was strongly related to the body weight by measuring in laboratory over 24 hours during August 2001 when the water temperature was 20 +/- 2 C. At least squares analyses gave the equation y = 2 904.16 + 12 076.24e(-0.0034x) (R2 = 0.9825, P = < 0.05). A slight variation of filtration rate was found over 24 hours, which could be explained by the bivalves' adaptation to the experimental circumstances rather than the daily change of its filtration feeding. In general, the filtration capacity of natural Anodonta woodiana population in the water bodies was very limited, as a result of its small population size. No significant selective feeding on algae was found by contrasting the relative abundance of algae in the habitats and the guts of Anodonta woodiana. The feeding selectivity on algae was neither correlated with the size of algae, nor with the initial abundance of algae in water column.

Animals↗

PubMed2002

Degradation characteristics of toluene, benzene, ethylbenzene, and xylene by Stenotrophomonas maltophilia T3-c.

Stenotrophomonas maltophilia T3-c, isolated from a biofilter for the removal of benzene, toluene, ethylbenzene, and xylene (BTEX), could grow in a mineral salt medium containing toluene, benzene, or ethylbenzene as the sole source of carbon. The effect of environmental factors such as initial toluene mass, medium pH, and temperature on the degradation rate of toluene was investigated. The cosubstrate interactions in the BTEX mixture by the isolate were also studied. Within the range of initial toluene mass (from 23 to 70 pmol), an increased substrate concentration increased the specific degradation of toluene by S. maltophilia T3-c. The toluene degradation activity of S. maltophilia T3-c could be maintained at a broad pH range from 5 to 8. The rates at 20 and 40 degrees C were 43 and 83%, respectively, of the rate at 30 degrees C. The specific degradation rates of toluene, benzene, and ethylbenzene by strain T3-c were 2.38, 4.25, and 2.06 micromol/g-DCW/hr. While xylene could not be utilized as a growth substrate by S. maltophilia T3-c, the presence of toluene resulted in the cometabolic degradation of xylene. The specific degradation rate of toluene was increased by the presence of benzene, ethylbenzene, or xylene in binary mixtures. The presence of toluene or xylene in binary mixtures with benzene increased the specific degradation rate of benzene. The presence of ethylbenzene in binary mixtures with benzene inhibited benzene degradation. The presence of more than three kinds of substrates inhibited the specific degradation rate of benzene. All BTEX mixtures, except tri-mixtures of benzene, ethylbenzene, and xylene or mixtures of all four substrates, had little effect on the degradation of ethylbenzene by S. maltophilia T3-c. The utilization preference of the substrates by S. maltophilia T3-c was as follows: ethylbenzene was degraded fastest, followed by toluene and benzene. However, the specific degradation rates of substrates, in order, were benzene, toluene, and ethylbenzene.

Benzene↗