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 37 records · Page 2Linked to original sources

PubMed1991

Effects of surfactant adsorption and biodegradability on the distribution of bacteria between sediments and water in a freshwater microcosm.

A microcosm containing resuspended river sediment was used to investigate the effect of anionic surfactants on the distribution of bacteria between planktonic and attached populations. Freshwater river sediment containing viable bacteria was preequilibrated in the microcosm, which was subsequently supplemented with biodegradable or recalcitrant surfactants and a non-surface-active carbon and energy source. Population dynamics of both free-living and attached bacteria were measured by epifluorescence microscopy with simultaneous analysis of the residual solution concentration of the xenobiotic carbon source. The addition of the readily biodegradable anionic surfactants sodium decyl sulfate and sodium dodecyl sulfate in separate experiments caused an increase in the number of attached bacteria and a concomitant decrease in the number of free-living bacteria. As biodegradation of the surfactants progressed, these trends reversed and the bacterial populations had returned to their preaddition values by the time when biodegradation was completed. In contrast, sodium tetradecyl sulfate or sodium dodecane sulfonate did not stimulate bacterial association with sediment, nor were they biodegraded in the microcosm. Sodium pyruvate, a non-surface-active carbon and energy source, was readily utilized but caused no bacterial attachment to the sediment. These results indicate that for an anionic surfactant to induce bacterial attachment to river sediment, it must be biodegradable. The bacterial attachment to the sediment appears to be reversible and may be dependent on the accumulation of the surfactant at the surface or as a result of alteration of the surface free energies.

Adsorption↗

PubMed1991

Biodegradation of pentachlorophenol in soil: the response to physical, chemical, and biological treatments.

The effects of physical, chemical, and biological treatments on biodegradation of pentachlorophenol (PCP) were studied in a silt-loam soil contaminated with 175 mg PCP/kg and uniformly 14C-labelled PCP. Biodegradation of 14C-labelled PCP and technical-grade PCP were monitored over 210 days incubation. Mineralization of labelled PCP was significantly (p=0.05) influenced by soil treatments. Negligible biodegradation occurred in either the sterile control soil or the uninoculated control soil, with less than 1% of added 14C recovered as 14 CO2. Inoculation of unamended soil with a strain of Flavobacterium (ATCC 39723) known to degrade PCP increased biodegradation of PCP; approximately 60% of the [14C]PCP was recovered as 14CO2. Increased soil water content (60% versus 30% w/w) enhanced biodegradation (67% recovery of 14C as CO2), while increased chloride ion concentration and anoxic conditions were inhibitory (20 and 1% recoveries, respectively). Residual soil PCP concentrations were also influenced by various treatments. In the sterile control soil and noninoculated control, after 210 days incubation, concentrations of PCP were 143 and 1223 mg/kg, respectively, while the PCP concentration in the inoculated soil was 21 mg/kg. When soil organic matter was increased by adding finely ground red clover leaf and stem material, the residual PCP concentration was reduced to 6 mg/kg after 210 days. Increased soil water content resulted in a residual PCP concentration of 5 mg/kg. High-pressure liquid chromatography of soil extracts revealed no accumulation of partial PCP degradation products. The results indicated that biodegradation of PCP in soil was significantly influenced by various soil amendments.

Biodegradation, Environmental↗

PubMed1986

Compliance and biodegradation of vascular grafts stimulate the regeneration of elastic laminae in neoarterial tissue: an experimental study in rats.

Microporous vascular grafts that are compliant and biodegradable can function as scaffolds for the regeneration of the arterial wall in small-caliber arteries. The purpose of this study was to determine the specific influence of both compliance and biodegradation of microporous vascular grafts on this regeneration, especially on the regeneration of elastic laminae. Therefore we implanted three different types of microporous vascular grafts into the abdominal aorta of rats. These grafts were (I) compliant, biodegradable (group I; n = 6), (II) compliant, biostable (group II; n = 8), and (III) noncompliant, biodegradable (group III; n = 8). Six weeks after implantation the implants were evaluated by means of light microscopy and electron microscopy. The compliance of the implants, as indicated by arterial pulsations, was well maintained in group I but not in group II. In all groups a neomedia had regenerated, composed of smooth muscle cells that were predominantly longitudinally arranged. Elastic laminae were present almost throughout the neomedia in group I, restricted to the luminal layers of the neomedia in group II, and totally absent in the neomedia of group III. These results demonstrate that both compliance and biodegradation stimulate the regeneration of elastic laminae in neoarterial tissue. Because of the compliance of microporous vascular grafts, smooth muscle cells are mechanically stimulated by the arterial pulsations to produce elastin arranged in laminae. Because of the biodegradation of these grafts, compliance is maintained, which therefore favors the regeneration of elastic laminae.

Animals↗

PubMed1992

Adsorption of polycyclic aromatic hydrocarbons (PAHs) by soil particles: influence on biodegradability and biotoxicity.

Polycyclic aromatic hydrocarbon (PAH) biodegradation was investigated in contaminated soils from two different industrial sites under simulated land treatment conditions. Soil samples from a former impregnation plant (soil A) showed high degradation rates of PAHs by the autochthonous microorganisms, whereas PAHs in material of a closed-down coking plant (soil B) were not degraded even after inoculation with bacteria known to effectively degrade PAHs. As rapid PAH biodegradation in soil B was observed after PAHs were extracted and restored into the extracted soil material, the kind of PAH binding in soil B appears to completely prevent biodegradation. Sorption of PAHs onto extracted material of soil B follows a two-phase process (fast and slow); the latter is discussed in terms of migration of PAHs into soil organic matter, representing less accessible sites within the soil matrix. Such sorbed PAHs are suggested to be non-bioavailable and thus non-biodegradable. By eluting soil B with water, no biotoxicity, assayed as inhibition of bioluminescence, was detected in the aqueous phase. When treating soil A analogously, a distinct toxicity was observed, which was reduced relative to the amount of activated carbon added to the soil material. The data suggest that sorption of organic pollutants onto soil organic matter significantly affects biodegradability as well as biotoxicity.

Adsorption↗

PubMed1989

Expert systems survey on biodegradation of xenobiotic chemicals.

To determine the feasibility of developing an expert system for biodegradability assessment, a survey was conducted in which biodegradation experts were asked to estimate rates and products of degradation for 50 chemicals. These chemicals, which varied widely in structure, were considered representative of the spectrum of premanufacture notice chemicals subject to EPA review under the Toxic Substances Control Act. There was substantial agreement among the 22 experts on both sites of initial attack and rates of degradation. The approximate order in which various groups were viewed as contributing to aerobic biodegradability is as follows: ester, amide, anhydride greater than hydroxyl greater than carboxyl, epoxide, site of unsaturation greater than benzene ring, methyl, methylene. Hydrolyzable groups, azo bonds, halogens, and nitro groups were preferred sites of anaerobic attack. Among the negative influences on aerobic biodegradability were molecular mass, branching, halogenation, and nitrogen heterocycles. Results also indicate that estimates of removal by biodegradation in aerobic wastewater treatment and time for aerobic ultimate and primary degradation were well correlated, and that the predictive value of such correlations could be improved using correction factors for certain classes of chemicals. The results lend support to existing rules of thumb, but also offer additional insight that will prove useful in designing a prototype system.

Biodegradation, Environmental↗

PubMed1990

Quantitative structure-activity relationships for biodegradation.

Quantitative structure-activity relationships (QSARs) between biodegradation rates of organic compounds and chemical structure parameters are reviewed. Although a number of such relationships have been developed, they in general only apply to restricted ranges of compounds, limiting their value as predictors of biodegradation rates. For many of these classes of chemicals relationships have been reported with different structural descriptors, varying from macroscopic physical properties to molecular structure parameters. More information on the mechanism and rate-determining steps of biodegradation, which can lead to a better-founded choice of descriptors, and more biodegradation rate data are required to further develop QSARs for biodegradation.

Biodegradation, Environmental↗

PubMed1992

Screening methods for assessment of biodegradability of chemicals in seawater--results from a ring test.

An international ring test involving 14 laboratories was organized on behalf of the Commission of the European Economic Communities (EEC) with the purpose of evaluating two proposed screening methods for assessment of biodegradability in seawater: (a) a shake flask die-away test based primarily on analysis of dissolved organic carbon and (b) a closed bottle test based on determination of dissolved oxygen. Both tests are performed with nutrient-enriched natural seawater as the test medium and with no inoculum added other than the natural seawater microflora. The test methods are seawater versions of the modified OECD screening test and the closed bottle test, respectively, adopted by the Organization for Economic Cooperation and Development (OECD) and by the EEC as tests for "ready biodegradability." The following five chemicals were examined: sodium benzoate, aniline, diethylene glycol, pentaerythritol, and 4-nitrophenol. Sodium benzoate and aniline, which are known to be generally readily biodegradable consistently degraded in practically all tests, thus demonstrating the technical feasibility of the methods. Like in previous ring tests with freshwater screening methods variable results were obtained with the other three compounds, which is believed primarily to be due to site-specific differences between the microflora of the different seawater samples used and to some extent also to differences in the applied concentrations of test material. A positive result with the screening methods indicates that the test substance will most likely degrade relatively rapidly in seawater from the site of collection, while a negative test result does not preclude biodegradability under environmental conditions where the concentrations of chemicals are much lower than the concentrations applied for analytical reasons in screening tests. Nevertheless, the screening tests are considered useful and cost-effective tools for an initial assessment of biodegradability in marine environments.

Aniline Compounds↗

PubMedDate not supplied

Estimation of aqueous solubility of organic molecules by the group contribution approach. Application to the study of biodegradation.

A reliable and generally applicable aqueous solubility estimation method for organic compounds based on a group contribution approach has been developed. Two models have been established based on two different sets of parameters. One has a higher accuracy, while the other has a more general applicability. The prediction potentials of these two models have been evaluated through cross-validation experiments. For model I, the mean cross-validated r2 and SD for 10 such cross-validation experiments were 0.946 and 0.503 log units, respectively. While for model II, they were 0.953 and 0.546 log units, respectively. Applying our models to estimate the water solubility values for the compounds in an independent test set, we found that model I can be applied to 13 out of 21 compounds with a SD equal to 0.58 log unit and model II can be applied to all the 21 compounds with a SD equal to 1.25 log units. Our models compare favorably to all the current available water estimation methods. A program based on this approach has been written in FORTRAN77 and is currently running on a VAX/VMS system. The program can be applied to estimate the water solubility of the water solubility of any organic chemical with a good or fairly good accuracy except for except for electrolytes. Applying our aqueous solubility estimation models to biodegradation studies, we found that although the water solubility was not the sole factor controlling the rate of biodegradation, ring compounds with greater solubilities were more likely to biodegrade at a faster rate. The significance of the relationship between water solubility and biodegradation activity has been illustrated by predicting the biodegradation activity of 27 new chemicals based solely on their estimated solubility values.

Biodegradation, Environmental↗

PubMed1985

Biodegradation of [14C]phenol in secondary sewage and landfill leachate measured by double-vial radiorespirometry.

Double-vial radiorespirometry was used to estimate the biodegradation rates of 14C-labeled phenol in a landfill leachate and a secondary treated domestic wastewater. Rates were found to be comparable for each material at each of the three concentrations tested. Sewage microorganisms immediately began biodegrading the [14C]phenol; landfill leachate microorganisms required a lag period before maximum biodegradation of the [14C]phenol. The apparent rate of [14C]phenol biodegradation was 2.4 times faster in the sewage than in the landfill leachate. Double-vial radiorespirometry was shown to be an effective method for screening biodegradation rates in aquifers.

Biodegradation, Environmental↗

PubMed1975

Screening test for assessment of ultimate biodegradability: linear alkylbenzene sulfonates.

A relatively simple shake-flask system for determining CO2 evolution was developed to assess the ultimate biodegradability by soil and sewage micro-organisms of chemicals which enter the environment. Linear alkylbenzene sulfonates (LAS) were used as model compounds to evaluate the method and were found to undergo substantial biodegradation in this dilute system. At the 30 mg/liter test concentration, higher-molecular-weight LAS compounds were biodegraded at a slower rate and to a lesser extent than lower-molecular-weight LAS, an effect which was eliminated or greatly reduced upon incremental addition of the LAS to the test medium during the first week of incubation. LA35S was used to demonstrate rapid LAS desulfonation, and 14CO2 evolution studies with (14C) benzene ring-labeled LAS indicated concomitant biodegradation of the entire LAS molecule as well as the LAS aromatic component. The test can be employed to examine numerous compounds at the same time and is readily adapted to studies of the effect of variation in temperature and oxygen concentration on biodegradation.

Bacteria↗

PubMed1992

Biodegradable fixation of distal humeral physeal fractures.

Polyglycolic acid (PGA) has been used worldwide as a biodegradable suture material since 1970. Biodegradable polyglycolide implants were introduced in osteofixation of cancellous bone fractures in 1985. From September 1987 to September 1989, 19 consecutive children with physeal fractures of the distal humerus necessitating open reduction and internal fixation were treated by transphyseal biodegradable fixation using 1.5 x 60-mm2 self-reinforced polyglycolide (SR-PGA) pins. Included were nine displaced fractures of the lateral humeral condyle, five severe avulsions of the medial epicondyle of the humerus, four displaced fractures of the humeral capitellum, and one intraarticular fracture of the medial condyle of the humerus. After accurate reduction, two smooth Kirschner pins 1.5 mm in diameter were introduced across the growth plate for temporary fixation. The metallic pins then were removed one by one and subsequently replaced with the cylindrical SR-PGA pins 1.5 mm in diameter. After operation, a padded plaster splint was worn for four weeks. Neither secondary displacement nor signs of growth disturbance were seen during the 26-month follow-up time (mean, 17.2 months). Not only the reduction of the costs but also the psychological aspects should be considered when dealing with biodegradable fixation of physeal fractures in children. Transphyseal biodegradable fixation has established itself as a procedure of choice for handling simple physeal fractures.

Adolescent↗

PubMed1989

Brain biocompatibility of a biodegradable, controlled-release polymer in rats.

We report the biocompatibility in the rat brain of a controlled-release, biodegradable polymer, the polyanhydride poly-[bis(p-carboxyphenoxy)propane-sebacic acid] copolymer (PCPP-SA) in a 20:80 formulation. The biodegradable polyanhydride can be used for drug delivery directly into the brain, circumventing the difficulties posed by the blood-brain barrier and avoiding the consequences of having to administer toxic doses systematically to reach therapeutic doses in the central nervous system. The tissue reaction in the presence of PCPP-SA was compared to that seen with other standard neurosurgical implants. Fifty-six adult Sprague-Dawley rats were assigned to one of seven groups and underwent bilateral frontal lobe implantation of PCPP-SA (42 hemispheres), Surgicel (oxidized regenerated cellulose) (35 hemispheres), or Gelfoam (absorbable gelatin sponge) (35 hemispheres). None of the animals showed any behavioral changes or neurological deficits suggestive of either systemic or localized toxicity from the biodegradable polyanhydride, all surviving to the scheduled data of sacrifice. PCPP-SA evoked a well localized inflammatory reaction, comparable to that of Surgicel, which resolved as the PCPP-SA polymer degraded over five weeks. The biodegradable polyanhydride has been shown in this study to be nontoxic and biocompatible in the rat brain, when compared to standard neurosurgical implants.

Animals↗

PubMed1988

Antibiotic release from an experimental biodegradable bone cement.

An experimental biodegradable bone cement [poly(propylene fumarate)-methylmethacrylate] (PPF-MMA) has been compared in vivo with polymethylmethacrylate (PMMA) as a carrier agent for local release of antibiotics. This approach is potentially applicable to the treatment of chronic osteomyelitis where the clinical goal is to achieve sustained high concentrations of antibiotics locally in the infected bone. In our experiments, gentamicin- and vancomycin-impregnated cylindrical PMMA and PPF-MMA cement specimens were implanted subcutaneously in rats, and blood and wound fluid samples were obtained over a 2-week period. Antibiotic levels were determined using immunoassays, and microbiologic activity was confirmed with agar diffusion techniques. The biodegradable PPF-MMA cement achieved and maintained considerably higher wound antibiotic levels than did PMMA cement. Vancomycin levels for the PPF-MMA cement were greater than 20 times those for the PMMA cement at all sampling times from 24 h to 14 days. For both cements, the serum antibiotic concentrations remained safely below maximum levels recommended for parenteral therapy. Mechanical testing of the PPF-MMA cement showed that admixture of 3% by weight of antibiotic did not adversely affect material properties. We conclude that this experimental biodegradable bone cement (PPF-MMA) can be used as a carrier to achieve high sustained local levels and low serum levels of antibiotics. Because it is biodegradable and thus does not require a secondary procedure for removal, it has special potential for use in treatment of chronic osteomyelitis.

Administration, Topical↗

PubMed1991

Respirometric analysis of the biodegradation of organic contaminants in soil and water.

Client-funded bench-scale investigations concerning the likelihood of successfully applying biological remediation to hazardous wastes must be cost-effective, and they usually need only determine if biodegradation is likely to occur on site. To assess the potential for stimulating biodegradation, biochemical oxygen demand (BOD) was used to continuously monitor bacterial respiration during growth on mixed organic wastes from contaminated water and soil. Continuously collected oxygen-consumption data provided information on the overall metabolic activity of the resident bacterial population and permitted direct observation of the cessation of microbial respiratory activity and, thus, the termination of aerobic degradation. The correlation of biological oxygen utilization with biodegradation was confirmed using independent analytical methods. Continuous, long-term BOD analysis was applied to bench-scale studies to assess the biodegradation of mixed organic wastes from contaminated sites and industrial waste effluents. This information was used to make an initial determination regarding the need to further explore bioremediation as a potential remedial-action technology using on-site, pilot-scale testing.

Bacteria↗

PubMed1991

QSARs and PARs for biodegradation of PCBs.

Relationships between the biodegradation rate constants of a number of polychlorinated biphenyls (PCBs) and hydrophobic and electronic structural parameters are compared. There is no simple relationship with octanol-water partition coefficients, indicating that the biodegradation rates of PCBs are probably not determined by their rates of permeation through the bacterial membranes. Biodegradation rate constants correlated much better with both the electronic and hydrophobic properties of the chlorine substituents, which suggests that the reactivity and possibly enzyme binding of PCBs control their biodegradation rates.

Acinetobacter↗

PubMed1991

Biodegradation of refractory hydrocarbon biomarkers from petroleum under laboratory conditions.

Biomarkers are of great value in petroleum exploration because they provide essential information about the geological history of oils and source rocks. Steranes are of particular importance as they can be related to naturally occurring precursors. These compounds generally experience intense biodegradation, however, which alters their original distribution and obscures the information that they carry regarding oil maturity and source material. In an attempt to identify the microorganisms responsible for this degradation, we have investigated the capacity of 73 aerobic bacteria to degrade steranes present in Rozel Point (Utah) oil. Seven Gram-positive strains, belonging to a limited number of genera, were found to be active. Using Nocardia sp. SEBR 16, which caused the most extensive alteration, we have determined biodegradation rates for several isomers of steranes and methylsteranes. The preference for alteration of different isomers reflects that observed in natural environments, suggesting that the degradation intermediates could be used as indicators of the extent of the biodegradation in an oil. In addition, the microorganisms used here might be effective in biodegrading oil spills.

Arthrobacter↗

PubMed1992

A rapid in situ respiration test for measuring aerobic biodegradation rates of hydrocarbons in soil.

An in situ test method to measure the aerobic biodegradation rates of hydrocarbons in contaminated soil is presented. The test method provides an initial assessment of bioventing as a remediation technology for hydrocarbon-contaminated soil. The in situ respiration test consists of ventilating the contaminated soil of the unsaturated zone with air and periodically monitoring the depletion of oxygen (O2) and production of carbon dioxide (CO2) over time after the air is turned off. The test is simple to implement and generally takes about four to five days to complete. The test was applied at eight hydrocarbon-contaminated sites of different geological and climatic conditions. These sites were contaminated with petroleum products or petroleum fuels, except for two sites where the contaminants were primarily polycyclic aromatic hydrocarbons. Oxygen utilization rates for the eight sites ranged from 0.02 to 0.99 percent O2/hour. Estimated biodegradation rates ranged from 0.4 to 19 mg/kg of soil/day. These rates were similar to the biodegradation rates obtained from field and pilot studies using mass balance methods. Estimated biodegradation rates based on O2 utilization were generally more reliable (especially for alkaline soils) than rates based on CO2 production. CO2 produced from microbial respiration was probably converted to carbonate under alkaline conditions.

Aerobiosis↗

PubMed1992

Use of biodegradable plates and screws in a rabbit model.

During the last decade, rigid internal fixation with miniplates and screws has gained widespread acceptance in the correction of both congenital and acquired craniomaxillofacial deformities. Recent studies have proposed that the currently employed metallic plates and screws may require removal because of potential facial growth restriction in growing children. Others have reported bone resorption under the plate due to stress shielding, infection, extrusion, and palpability in regions where there is minimal tissue coverage. Because these implants are radiopaque, they generate significant that interfere with radiological studies and with radiation therapy in patients undergoing treatment for malignancies. There is no question that the use of a biodegradable plating system would eliminate each of these potential or real problems, because stability is necessary only for a reasonably short period until the fracture segments have become united. We report the initial phase of a long-term study examining various materials that will be available for fabrication of a biodegradable plate and screw system. We evaluated a commercially developed biodegradable plate and screw system to treat zygomatic arch fractures in a rabbit model. Fractures were surgically created at the midpoint of each zygomatic arch. The experimental animals were then divided into three equal groups. Fractures in the first group were permitted to heal without any form of stabilization. In the second group, segments were secured with standard titanium plates and screws. Biodegradable plates and screws were employed for stabilization in the experimental group. Animals were then killed, and radiographs were obtained at 2, 4, 6, and 8 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗