SEARCH · PubMed Health

Results for “Biodegradation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources

PubMed2005

Monitoring of accelerated naphthalene-biodegradation in a bioaugmented soil slurry.

The effect of microbial inoculation on the mineralization of naphthalene in a bioslurry treatment was evaluated in soil slurry microcosms. Inoculation by Pseudomonas putida G7 carrying the naphthalene dioxygenase (nahA) gene resulted in rapid mineralization of naphthalene, whereas indigenous microorganisms in the PAH-contaminated soil required a 28 h adaptation period before significant mineralization occurred. The number of nahA-like gene copies increased in both the inoculated and non-inoculated soil as mineralization proceeded, indicating selection towards naphthalene dioxygenase producing bacteria in the microbial community. In addition, 16S rRNA analysis by denaturing gradient gel electrophoresis (DGGE) analysis showed that significant selection occurred in the microbial community as a result of biodegradation. However, the indigenous soil bacteria were not able to compete with the P. putida G7 inoculum adapted to naphthalene biodegradation, even though the soil microbial community slightly suppressed naphthalene mineralization by P. putida G7.

Biodegradation, Environmental↗

PubMed2005

Fate and biodegradability of sulfonated aromatic amines.

Ten sulfonated aromatic amines were tested for their aerobic and anaerobic biodegradability and toxicity potential in a variety of environmental inocula. Of all the compounds tested, only two aminobenzenesulfonic acid (ABS) isomers, 2- and 4-ABS, were degraded. The observed degradation occurred only under aerobic conditions with inocula sources that were historically polluted with sulfonated aromatic amines. Bioreactor experiments, with non-sterile synthetic wastewater, confirmed the results from the aerobic batch degradation experiments. Both ABS isomers were degraded in long-term continuous experiment by a bioaugmented enrichment culture. The maximum degradation rate in the aerobic bioreactor was 1.6-1.8 g 1(-1) d(-1) for 2-ABS and a somewhat lower value for 4-ABS at hydraulic retention times (HRT) of 2.8-3.3 h. Evidence for extensive mineralization of 2- and 4-ABS was based on oxygen uptake and carbon dioxide production during the batch experiments and the high levels of chemical oxygen demand (COD) removal in the bioreactor. Furthermore, mineralization of the sulfonate group was demonstrated by high recovery of sulfate. The sulfonated aromatic amines did not show any toxic effects on the aerobic and anaerobic bacterial populations tested. The poor biodegradability of sulfonated aromatic amines indicated under the laboratory conditions of this study suggests that these compounds may not be adequately removed during biological wastewater treatment.

Aerobiosis↗

PubMed2006

Inhibition of biogas production by alkyl benzene sulfonates (LAS) in a screening test for anaerobic biodegradability.

The effect of the inoculum source on the digestion of linear alkylbenzene sulfonates (LAS) under anaerobic conditions has been investigated. The potential for primary and ultimate LAS biodegradation of anaerobic sludge samples obtained from wastewater treatment plants (WWTPs) of different geographical locations was studied applying a batch test system. It was found that only 4-22% of the LAS added to the batch anaerobic digesters was primarily transformed suggesting a poor primary degradation of the LAS molecule in anaerobic discontinuous systems. Regarding ultimate biodegradation, the addition of LAS to the batch anaerobic digesters caused a reduction on the extent of biogas production. Significant differences in the inhibition extent of the biogas production were observed (4-26%) depending on the sludge used as inoculum. Effect of the surfactant on the anaerobic microorganisms was correlated with its concentration in the aqueous phase. Sorption of LAS on anaerobic sludge affects its toxicity by depletion of the available fraction of the surfactant. LAS content on sludge was related to the total amount of calcium and magnesium extractable ions. The presence of divalent cations promote the association of LAS with anaerobic sludge reducing its bioavailability and the extent of its inhibitory effect on the biogas production.

Alkanesulfonic Acids↗

PubMed2006

Biodegradation kinetics of 2,4,6-trichlorophenol by an acclimated mixed microbial culture under aerobic conditions.

The objective of this study was to achieve a better quantitative understanding of the kinetics of 2,4,6-trichlorophenol (TCP) biodegradation by an acclimated mixed microbial culture. An aerobic mixed microbial culture, obtained from the aeration basin of the wastewater treatment plant, was acclimated in shake flasks utilizing various combinations of 2,4,6-TCP (25-100 mg l(-1)), phenol (300 mg l(-1)) and glycerol (2.5 mg l(-1)) as substrates. Complete primary TCP degradation and a corresponding stoichiometric release of chloride ion were observed by HPLC and IEC analytical techniques, respectively. The acclimated cultures were then used as an inoculum for bench scale experiments in a 4 l stirred-tank reactor (STR) with 2,4,6-TCP as the sole carbon/energy (C/E) source. The phenol acclimated mixed microbial culture consisted of primarily Gram positive and negative rods and was capable of degrading 2,4,6-TCP completely. None of the predicted intermediate compounds were detected by gas chromatography in the cell cytoplasm or supernatant. Based on the disappearance of 2,4,6-TCP, degradation was well modelled by zero-order kinetics which was also consistent with the observed oxygen consumption. Biodegradation rates were compared for four operating conditions including two different initial 2,4,6-TCP concentrations and two different initial biomass concentrations. While the specific rate constant was not dependent on the initial 2,4,6-TCP concentration, it did depend on the initial biomass concentration (X (init)). A lower biomass concentration gave a much higher zero-order specific degradation rate. This behaviour was attributed to a lower average biomass age or cell retention time (theta(x)) for these cultures. The implications of this investigation are important for determining and predicting the potential risks associated with TCP, its degradation in the natural environment or the engineering implications for ex situ treatment of contaminated ground water or soil.

Acclimatization↗

PubMed2006

Characterisation of biodegradation capacities of environmental microflorae for diesel oil by comprehensive two-dimensional gas chromatography.

In contaminated soils, efficiency of natural attenuation or engineered bioremediation largely depends on biodegradation capacities of the local microflorae. In the present study, the biodegradation capacities of various microflorae towards diesel oil were determined in laboratory conditions. Microflorae were collected from 9 contaminated and 10 uncontaminated soil samples and were compared to urban wastewater activated sludge. The recalcitrance of hydrocarbons in tests was characterised using both gas chromatography (GC) and comprehensive two-dimensional gas chromatography (GCxGC). The microflorae from contaminated soils were found to exhibit higher degradation capacities than those from uncontaminated soil and activated sludge. In cultures inoculated by contaminated-soil microflorae, 80% of diesel oil on an average was consumed over 4-week incubation compared to only 64% in uncontaminated soil and 60% in activated sludge cultures. As shown by GC, n-alkanes of diesel oil were totally utilised by each microflora but differentiated degradation extents were observed for cyclic and branched hydrocarbons. The enhanced degradation capacities of impacted-soil microflorae resulted probably from an adaptation to the hydrocarbon contaminants but a similar adaptation was noted in uncontaminated soils when conifer trees might have released natural hydrocarbons. GCxGC showed that a contaminated-soil microflora removed all aromatics and all branched alkanes containing less than C(15). The most recalcitrant compounds were the branched and cyclic alkanes with 15-23 atoms of carbon.

Alkanes↗

PubMed2006

Simultaneous biodegradation of methyl parathion and carbofuran by a genetically engineered microorganism constructed by mini-Tn5 transposon.

A genetically engineered microorganism (GEM) capable of simultaneous degrading methyl parathion (MP) and carbofuran was successfully constructed by random insertion of a methyl parathion hydrolase gene (mpd) into the chromosome of a carbofuran degrading Sphingomonas sp. CDS-1 with the mini-transposon system. The GEM constructed was relatively stable and cell viability and original degrading characteristic was not affected compared with the original recipient CDS-1. The effects of temperature, initial pH value, inoculum size and alternative carbon source on the biodegradation of MP and carbofuran were investigated. GEM cells could degrade MP and carbofuran efficiently in a relatively broad range of temperatures from 20 to 30 degrees C, initial pH values from 6.0 to 9.0, and with all initial inoculation cell densities (10(5)-10(7) CFU ml(-1)), even if alternative glucose existed. The optimal temperature and initial pH value for GEM cells to simultaneously degrade MP and carbofuran was at 30 degrees C and at pH 7.0. The removal of MP and carbofuran by GEM cells in sterile and non-sterile soil were also studied. In both soil samples, 50 mg kg(-1) MP and 25 mg kg(-1) carbofuran could be degraded to an undetectable level within 25 days even if there were indigenous microbial competition and carbon sources effect. In sterile soil, the biodegradation rates of MP and carbofuran were faster, and the decline of the inoculated GEM cells was slower compared with that in non-sterile soil. The GEM constructed in this study was potential useful for pesticides bioremediation in natural environment.

Biodegradation, Environmental↗

PubMed2006

Biosorption and biodegradation of pentachlorophenol (PCP) in an upflow anaerobic sludge blanket (UASB) reactor.

In order to understand the fate of PCP in upflow anaerobic sludge blanket reactor (UASB) more completely, the sorption and biodegradation of pentachlorophenol (PCP) by anaerobic sludge granules were investigated. The anaerobic granular sludge degrading PCP was formed in UASB reactor, which was seeded with anaerobic sludge acclimated by chlorophenols. At the hydraulic retention time (HRT) of 20-22 h, and PCP loading rate of 200-220 mg l(-1) d(-1), UASB reactor exhibited good performance in treating wastewater which containing 170-180 mg l(-1) PCP and the PCP removal rate of 99.5% was achieved. Sequential appearance of tetra-, tri-, di-, and mono-chlorophenol was observed in the reactor effluent after 20 mg l(-1) PCP introduction. Sorption and desorption of PCP on the anaerobic sludge granules were all fitted to the Freundlich isotherm equation. Sorption of PCP was partly irreversible. The Freundlich equation could describe the behavior of PCP amount sorbed by granular sludge in anaerobic reactor reasonably well. The results demonstrated that the main mechanism leading to removal of PCP on anaerobic granular sludge was biodegradation, not sorption or volatization.

Adsorption↗

PubMed2006

Biodegradability of tetrabromobisphenol A and tribromophenol by activated sludge.

Laboratory reactor systems based on the conventional (aerobic) activated sludge process and on the contact (anaerobic) process were operated almost one year in order to develop a biological process for the degradation of the fire retardant tetrabromobisphenol A (TBBPA) and to find out if its degradation might result in the formation of the endocrine disruptor bisphenol A (BPA). The reactors were fed a TBBPA waste mixture containing also tribromophenol (TBP), and added with contaminated sediments that might have contained indigenous bacteria exposed to these compounds. Various organic compounds were used as potential electron donors to enhance growth of halorespiring bacteria that would debrominate the TBBPA and make it available for further aerobic mineralization. In spite of the various operating strategies applied and the different carbon sources added, no TBBPA biodegradation has been observed and no accumulation of intermediates such as BPA in any of the aerobic or anaerobic reactors has been detected. TBP on the other hand, was found to be easily biodegraded by aerobic cultures simulating the activated sludge process. This was linked to consistent accumulation of bromides, released to the liquid following TBP breakdown.

Bacteria, Aerobic↗

PubMed1993

Autologous vein supported with a biodegradable prosthesis for arterial grafting.

To evaluate the potential of a supporting, compliant, biodegradable prosthesis to function as a temporary protective scaffold for autologous vein grafts in the arterial circulation, we implanted vein grafts into the carotid arteries of rabbits, either with (composite grafts) or without (control grafts) such a supporting prosthesis, and evaluated them up to 6 weeks. The control vein grafts showed edema and severe medial disruption with infiltration of polymorphonuclear cells on day 1. Over the study, irregular fibrocyte formation resulted in the formation of a fibrotic vein wall. In contrast, the composite vein grafts showed preservation of smooth muscle cell layers and elastic laminae with a minor inflammatory response. Regular proliferation of fibroblasts, which in some areas were circularly oriented, was observed. We conclude that a supporting, compliant, biodegradable prosthesis can function as a protective scaffold for vein grafts in the arterial circulation, thus reducing damage to the vein graft wall and allowing gradual arterialization.

Animals↗

PubMed1994

Sciatic nerve regeneration navigated by laminin-fibronectin double coated biodegradable collagen grafts in rats.

Biodegradable type I collagen tube grafts filled longitudinally with laminin and fibronectin double coated collagen fiber bundles (L-F grafts) were implanted to promote sciatic nerve regeneration in rats. Grafts filled with uncoated collagen fibers were used as control. A 1 cm defect on the right sciatic nerve was filled with a graft in the manner of bridging. Thirty days after implantation, several newly developed nerve fasciculi were found at the middle portion of the L-F grafts in contrast to no developed nerves in the controls. After 60 days, the middle and distal portions of both grafts included well-developed nerve tissues with prominent myelinated and unmyelinated nerve fibers surrounded by perineural cells, but the control distal portion showed fewer nerve fibers. All artificial collagen elements were completely degraded and absorbed at 30 days, and new nerve tissues surrounded by an epineurium successfully connected the proximal stump to the distal stump of the initially separated nerve. Descending and ascending action potentials were evoked in all grafts at 60 days. These results indicated that laminin and fibronectin may promote the growth of axons in biodegradable collagen grafts, which guided nerve regeneration well and allowed the formation of epineurium.

Animals↗

PubMed1989

Patency and long-term biological fate of a two-ply biodegradable microarterial prosthesis in the rat.

This study was undertaken to determine the long-term performance of a two-ply biodegradable, compliant microarterial prosthesis for its ability to function successfully as a temporary scaffold for the regeneration of a neoartery. Two-ply microarterial prostheses (internal diameter 1.5 mm, length 1 cm), prepared from a polyurethane-based (PU) material, were implanted into the abdominal aorta of rats (n = 22) and were evaluated at 3 months (n = 6), 6 months (n = 6) and one year (n = 10) after implantation, by means of macroscopic inspection, light microscopy and electron microscopy. All implants were patent and all, except two with a very small local dilatation at one year, were normally shaped. Arterial pulsations were reduced but still visible in all implants. In all implants a neoartery had regenerated: (1) a complete neointima composed of endothelial cells, (2) a neomedia composed of smooth muscle cells surrounded with elastin and collagen and of comparable thickness to rat media, and (3) a neoadventitia composed of fibrohistiocytic tissue that had organised the graft wall. In 2 out of the 10 one-year implants, smooth muscle cells were predominantly circularly arranged as in normal arterial tissue; in all other implants smooth muscle cells were predominantly longitudinally arranged. These results demonstrate that two-ply biodegradable PU-based prostheses have a good long-term performance when implanted into rat abdominal aortas.

Animals↗

PubMed1987

Peripheral nerve regeneration with entubulation repair: comparison of biodegradeable nerve guides versus polyethylene tubes and the effects of a laminin-containing gel.

These experiments present quantitative data concerning peripheral nerve regeneration in vivo. We used entubulation repair as a model to compare two different types of tubular prostheses, one nonbiodegradable and the other biodegradable. We modified the microenvironment of the regenerating axons within the tubular prostheses by adding a laminin-containing gel to the interior of the tube at the time of initial implantation. The data demonstrate that specific manipulations to the microenvironment of regenerating peripheral axons have quantitative effects on the rate and extent of nerve regeneration. Such effects were dependent on the composition of the tubular prosthesis and varied according to the survival time of the animals. For instance, the laminin gel within the biodegradable tubes enhanced nerve regeneration at 2 weeks but was inhibitory at 6 weeks. Furthermore, such manipulations may have different effects on the number of myelinated axons found within the regenerating nerve cable versus the number of primary motor and sensory neurons giving rise to such axons. We concluded that: the presence of a laminin-containing gel significantly increased the initial rate at which axons from primary sensory and motor neurons cross a transection site; an initial delay in axonal outgrowth at early time points did not necessarily predict diminished outgrowth at later times; and because of the potential for axonal branching the number of myelinated axons found in the midportion of a tubular prosthesis did not always correlate with the number of primary motor and sensory neurons which gave rise to those axons.

Animals↗

PubMed1977

Evaluation and comparisons of biodegradable substances as osteogenic agents.

This study compared the osteogenic potential and tissue compatibility of biodegradable copolymers--PLA/PGA--and a biodegradable ceramic--Ca3(PO4)2. These compounds were placed in experimentally created defects in rat tibias, both in combination and singly, and evaluated at 14, 28, and 42 days. The ceramic served as a format to result in uniform osteogenesis throughout the defect. The copolymer implants resulted in a more gradual bone formation, progressing slowly from the would peripheries. The ceramic and copolymer combination behaved little differently from the copolymer alone. All experimental materials were extremely tissue tolerant, with minimal inflammation and no foreign-body reactions.

Animals↗

PubMed1995

Anaerobic biodegradability testing of surfactants.

Anionic and nonionic surfactants (5-50 mg C/g solids/L medium) were screened for anaerobic microbial decomposition to methane in an automated pressure transducer serum bottle assay system at 35C using municipal digester solids as a source of anaerobic bacteria. Analysis of the headspace gas recovered from tests with linear primary alcohol sulfates (A45S and A24S) and a linear alcohol ethoxylate (LAE-8) showed that these compounds were readily degraded (60-85% of the theoretical methane, TM) after a 15-30 day lag period at 50 ppm C. The extent of degradation of a branched alkyl phenol ethoxylate (NPE-9) was lower (30-40% TM). A survey of intact nonionic and anionic surfactants present in municipal digester sludges in the U.S. showed that these materials were present at levels of 0.5-8 mg CTAS or MBAS/g dry solids. A surfactant which was slower to biodegrade (NPE-9) at 50 ppm C was readily metabolized to methane when tested at 5 and 10 mg C/g solids/L. The pressure transducer serum bottle method described may be used to test biodegradability and inhibitory effects on methanogenesis at surfactant concentrations (e.g. 5 ppm C/g solids) typically present in digesters.

Bacteria, Anaerobic↗

PubMed1995

Biodegradation of toluene diamine (TDA) in activated sludge acclimated with aniline and TDA.

The biodegradability of toluene diamine (TDA) which has been regarded as a "recalcitrant compound" was examined in activated sludges. In this study, a microorganic-enzyme system which metabolized TDA was obtained by acclimating the activated sludge with aniline and TDA. In the sludge subject to be 200 days' acclimation, the considerable increase in respiration rate with the addition of TDA, accompanied the sharp decrease in its concentration. This indicated that TDA was metabolized fortuitously. The rate of biodegradation of TDA in the absence of aniline was first order with respect to its concentration when the initial TDA concentration was less than about 5 mg/l. The rate constant in this relation was proportional to mixed liquor suspended solid (MLSS). However, when the initial TDA concentration exceeded 5 mg/l, the plots were deviated from a first order rate equation.

Aniline Compounds↗

PubMed1996

Effects of ryegrass on biodegradation of hydrocarbons in soil.

The effects of growing ryegrass (Lolium perenne L.) on the biodegradation of hydrocarbons was studied in laboratory scale soil columns. Degradation of hydrocarbons as well as bacterial numbers, soil respiration rates and soil dehydrogenase activities were determined. In the rhizosphere soil system, aliphatic hydrocarbons disappeared faster than in unvegetated columns. Abiotic loss by evaporation was of minor significance. Elimination of pollutants was accompanied by an increase in microbial numbers and activities. The microbial plate counts and soil respiration rates were substantially higher in the rhizosphere than in the bulk soil. The results indicate that biodegradation of hydrocarbons in the rhizosphere is stimulated by plant roots.

Biodegradation, Environmental↗

PubMed1989

Ability of the phototrophic bacterium Rhodospirillum rubrum to produce various poly (beta-hydroxyalkanoates): potential sources for biodegradable polyesters.

Studies have been carried out in order to optimize growth and culture conditions for the intracellular formation of poly(beta-hydroxyalkanoates) (PHA) in the phototrophic, purple, non-sulphur bacterium Rhodospirilum rubrum. Its potential to produce novel copolymers was investigated. Recently, it has become of industrial interest to evaluate these polyesters as potentially biodegradable plastics for a wide range of possible applications. On an industrial scale, the use of photosynthetic bacteria could harness sunlight as an energy source for the production of these materials. R. rubrum was grown anaerobically in the light on different linear and branched beta-hydroxycarboxylic acids and various n-alkanoic acids. Under nitrogen-limiting conditions a PHA content of up to 45% of cellular dry weight was detected. When R. rubrum was grown on different concentrations of various n-alkanoic acids, intracellular PHA production was detected on all acids used. In most of the cases, the storage polymer contained beta-hydroxybutyrate (HB) and beta-hydroxyvalerate (HV) monomer units. Grown on n-alkanoic acids with a chain length of four carbon atoms and more, R. rubrum produced a copolymer containing the beta-hydroxyhexanoate (HC) repeating unit in addition to the HB and HV monomer. Using beta-hydroxyheptanoic acid as the carbon source, a polyester which contained HB, HV, HC, and beta-hydroxyheptanoate was formed. These copolyesters represent a novel class of biodegradable thermoplastics. The results demonstrate the metabolic flexibility of R. rubrum to form many different types of polyesters which might substitute plastics synthesized from petrochemicals.

Ammonia↗

PubMed1985

Interaction of biodegradable beta-whitlockite ceramics with bone tissue: an in vivo study.

The biodegradation of different porous beta-whitlockite materials are studied by in vivo experiments, radiographic follow-ups and light microscopy observations. The materials were implanted in rabbit tibiae for 16 month. Micropores play an important role in the biodegradation rate. The resorbing materials evoke an inflammation with plasma cells. The resorption starts in the medulla, and the phagocytosed particles are removed to the lymph nodes. Normal bone function can be restored after all the implant material is resorbed.

Animals↗