PubMed Health⌕ Search

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 1,315 records · Page 73Linked to original sources
PubMed2002

Transport, deposition and biodegradation of particle bound polycyclic aromatic hydrocarbons in a tidal basin of an industrial watershed.

Polycylic aromatic hydrocarbons (PAHs) are common contaminants in industrial watersheds. Their origin, transport and fate are important to scientists, environmental managers and citizens. The Philadelphia Naval Reserve Basin (RB) is a small semi-enclosed embayment near the confluence of the Schuylkill and Delaware Rivers in Pennsylvania (USA). We conducted a study at this site to determine the tidal flux of particles and particle-bound contaminants associated with the RB. Particle traps were placed at the mouth and inside the RB and in the Schuylkill and Delaware Rivers. There was net particle deposition into the RB, which was determined for three seasons. Spring and fall depositions were highest (1740 and 1230 kg of particles, respectively) while winter deposition was insignificant. PAH concentrations on settling particles indicated a net deposition of 12.7 g PAH in fall and 2.1 g PAH in spring over one tidal cycle. There was no significant PAH deposition in the winter. Biodegradation rates, calculated from 14C-labeled PAH substrate mineralization, could attenuate only about 0.25% of the PAH deposited during a tidal cycle in fall. However, in the spring, biodegradation could be responsible for degrading 50% of the settling PAHs. The RB appears to be a sink for PAHs in this watershed.

Biodegradation, Environmental↗
PubMed1999

Preparation of biodegradable microparticles using solution-enhanced dispersion by supercritical fluids (SEDS).

PURPOSE: We have evaluated a new process, involving solution-enhanced dispersion by supercritical fluids (SEDS), for the production of polymeric microparticles. METHODS: The biodegradable polymers, Poly (DL-lactide-co-glycolide): copolymer composition 50:50 (DL-PLG), Poly (L-lactide) (L-PLA), Poly (DL-lactide) (DL-PLA) and Polycaprolactone (PCL), were used for preparation of microparticles using SEDS. Solutions of the polymers in organic solvents were dispersed and sprayed with supercritical CO2. Extraction of the organic solvents resulted in the formation of solid microparticles. The amounts of highly toxic solvents such as dichloromethane (MC) were reduced in the process. RESULTS: Microparticles were obtained from all polymers. The mean particle size and shape varied with the polymer used. The morphology of the particles was strongly affected by the choice of polymer solvent. Discrete spherical microparticles of DL-PLG were produced with a mean volumetric diameter of 130 microm. The microparticles of the L-PLA were almost spherical, and their size increased from 0.5 to 5 microm as the density of supercritical CO2 decreased. PCL formed microparticles with diameters of 30-210 microm and showed a strong tendency to form films at high pressure. CONCLUSIONS: The SEDS process appears a promising method for production of microparticles from biodegradable polymers without the use of toxic solvents.

Biocompatible Materials↗
PubMed2004

Enhancement of 2,4-dinitrotoluene biodegradation by Burkholderia sp. in sand bioreactors using bacterial hemoglobin technology.

Continuous flow sand column bioreactor experiments were conducted to investigate the effect of 2,4-dinitrotoluene (DNT) concentration (i.e. DNT loading rate) and influent dissolved oxygen (DO) concentration on aerobic biodegradation of DNT by wild type (DNT) and recombinant (YV1) Burkholderia sp., the latter containing plasmid pSC160 which carries the gene (vgb) encoding the hemoglobin (VHb) from the bacterium Vitreoscilla. The experiments were conducted in two continuous flow packed bed sand column bioreactors, one growing the wild type strain and the other growing YV1. Under oxygen-rich feed conditions (6.8 mg DO/L in the feed) with an influent DNT concentration of 99.6 mg/L (DNT loading rate approximately = 9.2 mg/m2/day), the effluent DNT concentration from the wild type bioreactor reached 0.7 mg DNT/L in 40 days whereas it was less than 0.2 mg DNT/L for the YV1 bioreactor in about 25 days. When influent DNT concentration was increased to 214 mg/L (DNT loading rate approximately = 20.3 mg/m2/day) while maintaining the same influent DO level of 6.8 mg/L, the effluent DNT concentration increased to about 5 mg/L for the wild type bioreactor whereas it was maintained at less than 0.2 mg/L for the YV1 bioreactor. Additionally, when influent DO was reduced from 6.8 mg/L to 3.1 mg/L while the influent DNT concentration remained at 214 mg/L, the effluent DNT concentration increased to more than 20 mg/L for the wild type bioreactor but up to only 1.7 mg/L for the YV1 bioreactor. A subsequent increase of influent DO back to 6.6 mg/L reduced the effluent DNT concentration to about 5 mg/L for the wild type bioreactor and to 0.10-0.19 mg/L for the YV1 bioreactor. These results confirm the utility of vgb technology to enhance biodegradation of aromatic compounds under hypoxic conditions and also that this enhancement can be maintained over extended periods of time as evidenced by plasmid stability in Burkholderia YV1.

Biodegradation, Environmental↗
PubMed1994

The behavior of bacteria designed for biodegradation.

Mineralization of organic molecules by microbes is essential for the carbon cycle to operate. The massive mobilization of compounds stored in natural resources, or the introduction of xenobiotics into the biosphere, leads to unidirectional fluxes, which result in the persistance of a number of chemicals in the biosphere, and thus constitute a source of pollution. Molecular biology offers the tools to optimize the biodegradative capacities of microorganisms, accelerate the evolution of "new" activities, and construct totally "new" pathways through the assemblage of catabolic segments from different microbes. Although the number of genetically engineered microbes (GEMs) for potential use in biodegradation is not large, these recombinant microbes function in microcosms according to their design. The survival and fate of recombinant microbes in different ecological niches under laboratory conditions is similar to what has been observed for the unmodified parental strains. rDNA, both on plasmids and on the host chromosome, is usually stably inherited by GEMs. The potential lateral transfer of rDNA from the GEMs to other microbes is significantly diminished, though not totally inhibited, when rDNA is incorporated on the host chromosome. The behavior and fate of GEMs can be predicted more accurately through the coupling of regulatory circuits that control the expression of catabolic pathways to killing genes, so that the GEMs survive in polluted environments, but die when the target chemical is eliminated.

Bacteria↗
PubMed2001

Anaerobic biodegradation of pentachlorophenol in mixtures containing cadmium by two physiologically distinct microbial enrichment cultures.

Anaerobic biodegradation of pentachlorophenol (PCP), in mixtures containing cadmium (Cd), by sulfidogenic (SRB) and methanogenic (MET) enrichment cultures, was studied. Removal of 91-93% of PCP occurred in both SRB- and MET-enriched cultures, in the absence of Cd, within 82 days. The presence of soluble Cd initially decreased the rate of PCP removal by the enrichment cultures, but PCP removal rates improved as the Cd precipitated. GC-MS, 14C-PCP, and 13C-PCP studies confirmed mineralization of PCP by both enrichment cultures, as well as the incorporation of PCP carbon into specific phospholipid fatty acids (PLFAs) of the cell membranes of PCP-degrading anaerobes. This is the first report on anaerobic biodegradation of PCP by SRB- and MET-enriched cultures in the presence, with simultaneous precipitation, of the toxic heavy metal Cd, and of the incorporation of PCP carbons into specific PLFAs of the anaerobic bacterial cells.

Anaerobiosis↗
PubMed1997

Comparison between the evaluation of bacterial regrowth capability in a turbidimeter and biodegradable dissolved organic carbon bioreactor measurements in water.

In recent years, two different approaches to the study of biodegradable organic matter in distribution systems have been followed. The assimilable organic carbon (AOC) indicates the portion of the dissolved organic matter used by bacteria and converted to biomass, which is directly measured as total bacteria, active bacteria or colony-forming units and indirectly as ATP or increase in turbidity. In contrast, the biodegradable dissolved organic carbon (BDOC) is the portion of the dissolved organic carbon that can be mineralized by heterotrophic microorganisms, and it is measured as the difference between the inflow and the outflow of a bioreactor. In this study, at different steps in a water treatment plant, the bacterial regrowth capability was determined by the AOC method that measures the maximum growth rate by using a computerized Monitek turbidimeter. The BDOC was determined using a plug flow bioreactor. Measurements of colony-forming units and total organic carbon (TOC) evolution in a turbidimeter and of colony-forming units at the inflow/outflow of the bioreactor were also performed, calculating at all sampling points the coefficient yield (Y = cfu/delta TOC) in both systems. The correlations between the results from the bioreactor and turbidimeter have been calculated; a high correlation level was observed between BDOC values and all the other parameters, except for Y calculated from bacterial suspension measured in the turbidimeter.

Bacteria↗
PubMed1999

Enhanced biodegradation of phenanthrene by a marine bacterium in presence of a synthetic surfactant.

The biodegradation of phenanthrene by the marine strain Sphingomonas sp. 2MPII (DSMZ 11572) was enhanced by the solubilizating properties of the nonionic surfactant Tween 80. After 197 h of incubation, 85 +/- 4% of the initial amount of phenanthrene (0.4 g l-1) was biodegraded in presence of Tween 80 (0.5 g l-1) as opposed to 52 +/- 5% without this synthetic surfactant. These results confirm that the activity of the strain 2MPII is limited by the bioavailability of the polycyclic aromatic hydrocarbon (PAH) substrate in the aqueous phase. Tween 80 appears to be efficient in increasing the bioavailability of hydrophobic compounds such as PAHs.

Biodegradation, Environmental↗
PubMed2002

Evidence that RDX biodegradation by Rhodococcus strain DN22 is plasmid-borne and involves a cytochrome p-450.

AIMS: To investigate the biodegradation of the explosive compound RDX in Rhodococcus strain DN22, a bacterium previously isolated for its ability to grow on RDX as sole nitrogen source. METHODS AND RESULTS: Analysis of the rates of RDX degradation and nitrite production indicated that 2 mol nitrite were produced per mole RDX degraded. Cells of strain DN22 had the highest activity against RDX during the exponential phase and low activity in the stationary phase. Nitrite production from RDX was inhibited by metyrapone, menadione, piperonyl butoxide, n-octylamine and carbon monoxide and inducible by pyrrolidine, pyridine and atrazine. Acridine orange treatment yielded RDX-minus derivatives of strain DN22 at a curing rate of 1.5% and all of the cured derivatives had lost a large plasmid. CONCLUSIONS: RDX biodegradation in strain DN22 appears to involve a plasmid-encoded cytochrome p-450 enzyme. SIGNIFICANCE AND IMPACT OF THE STUDY: Plasmid-borne RDX degradation genes could potentially be transferred between bacteria. Our research into RDX metabolism in strain DN22 will facilitate future applications of this bacterium for bioremediation.

Acridine Orange↗
PubMed2003

In vivo release of oxytetracycline from a biodegradable controlled-release gel injected subcutaneously in Japanese quail (Coturnix coturnix japonica).

A long-acting, biodegradable, controlled-release formulation of oxytetracycline (CR-OTC) was evaluated in 18 adult Japanese quail (Coturnix coturnix japonica) following a single subcutaneous (s.c.) injection. Prior to characterizing the release of oxytetracycline (OTC) from the CR-OTC, the pharmacokinetic parameters of intravenously (i.v.) administered OTC were determined. Concentrations of free OTC were measured using a bioassay. The plasma concentration-time profile of OTC after a single i.v. injection at 20 mg/kg was best fit to an open two-compartmental model, with the following pharmacokinetic parameters: area under the curve (AUC) = 36.72 mg. h/L, terminal elimination half-life = 2.34 h, clearance (Cl) = 0.545 L/kg/h. Plasma [OTC] was >1.0 micro g/mL for at least 4 h following i.v. injection. The CR-OTC gel was well tolerated at a dosage of 1500 mg/kg s.c. Plasma [OTC] rose to >1.0 micro g/mL within 24 h; it remained >1.0 micro g/mL for at least 10 days in all birds sampled at that time point (n = 9) and for at least 18 days in two of nine birds. Using a deconvolution technique, it was determined that approximately 54.8% of the administered OTC was released from the CR-OTC over the 45-day observation period. This long-acting, biodegradable controlled-release OTC formulation may have potential for the treatment of chlamydophila infections and other OTC-sensitive bacteria in Japanese quail, however further studies are necessary to determine its safety and clinical application.

Animals↗
PubMed2002

Metabolic biomarkers for monitoring anaerobic naphthalene biodegradation in situ.

During the anaerobic biodegradation of naphthalene and methylnaphthalene, unique metabolites are formed by specific microbial carboxylation and ring-reduction reactions. Groundwater samples from an anoxic, shallow aquifer contaminated with gasoline were examined for the presence of these metabolites by extraction, derivatization and gas chromatography coupled to mass spectroscopy. Several metabolites [2-naphthoic acid (2-NA), tetrahydro-2-naphthoic acid (TH-2-NA), hexahydro-2-naphthoic acid (HH-2-NA) and methylnaphthoic acid (MNA)] were found to be present in the groundwater samples. The concentration of 2-NA at each monitoring well was quantified and correlated to the zones of contamination. The presence of the other metabolites in the same wells as 2-NA was used as confirmation that the anaerobic pathway was indeed active. The distribution of metabolites at this site shows that they can be used as biomarkers for demonstrating in situ biodegradation.

Bacteria, Anaerobic↗
PubMed1997

Potentially useful materials for biodegradable ureteric stents.

OBJECTIVES: To develop and test materials that may be useful in the design and further development of biodegradable ureteric stents. MATERIALS AND METHODS: Specimens of two plastics were placed in artificial urine of different pH for 30 days to examine the degree of dissolution of the plastic in alkaline and the stability in acidic conditions. RESULTS: The specimens remained stable in the artificial urine at pH < 7.0 for 30 days and dissolved completely at a pH > or = 7 within 48 h. CONCLUSION: Plastics can be designed which may be useful in the further development of biodegradable ureteric stents. The rate of dissolution could be changed by influencing urinary pH.

Biodegradation, Environmental↗
PubMed1997

Immersion in antibiotic solution prevents bacterial adhesion onto biodegradable prostatic stents.

OBJECTIVE: To determine whether immersion in antibiotic solution reduces or prevents bacterial adhesion onto biodegradable prostatic stents. MATERIALS AND METHODS: Pre-cut segments of polyglycolic acid (PGA) and polylactic acid (PLA) prostatic stents were incubated with two common uropathogenic bacterial strains (Enterococcus faecalis and Escherichia coli) with and without previous immersion in antibiotic solution. Tobramycin, ceftriaxone and ciprofloxacin solutions were used, as these antibiotics are commonly administered for the prophylaxis and treatment of urinary tract infection (UTI). RESULTS: Immersion in ciprofloxacin solution prevented the adherence of both bacterial strains. Immersion in ceftriaxone solution prevented only the adherence of the E. coli strain. Immersion in tobramycin solution had no effect on either of the strains. The stent materials per se did not influence bacterial adhesion. After immersion in ciprofloxacin, the stent segments retained significant antibacterial activity even after one day's incubation in saline. CONCLUSION: Immersion in a suitable antibiotic solution may significantly reduce and even prevent bacterial adhesion onto biodegradable prostatic stents. Preventing bacterial adhesion may reduce the risk of UTI during the use of these devices.

Anti-Bacterial Agents↗
PubMed2002

Evaluation of cellular affinity and compatibility to biodegradable polyesters and Type-II collagen-modified scaffolds using immortalized rat chondrocytes.

Immortalized rat chondrocytes (IRCs) were employed to evaluate the cytocompatibility of different biodegradable polyester scaffolds for chondrocyte seeding and cartilage tissue engineering in vitro due to the limitation of using freshly harvested chondroctyes. Cells were seeded onto the films and the porous substrates as well as into the three-dimensional scaffolds made of the biodegradable polyesters including poly(l-lactide) (PLLA) and two poly(lactide-co-glycolide)s (PLGAs). The materials were characterized by water contact angle, electron spectroscopy for chemical analysis (ESCA), and microscopy. PLGA50/50, one of the PLGAs, had the largest cell numbers at 24 h and 96 h (close to the tissue culture polystyrene control), possibly due to its lower contact angle, higher oxygen/carbon (O/C) atomic ratio, and larger degradation rate. When the surface was further modified by cross-linked Type-II collagen, cell population was significantly enhanced (two- to fourfold). The adhesion and proliferation behavior of IRCs on different materials was parallel to that of rabbit chondrocytes, but was more reproducible in general. IRCs are thus suitable for evaluation of different polymer scaffolds. Despite the favorable cytocompatibility of PLGA50/50, blending with a small portion of PLLA is required for easy fabrication and collagen modification. Scaffolds made of blended materials by freeze-drying procedure with the surface modified by cross-linked Type-II collagen were demonstrated as the ideal templates for chondrocyte seeding in our study.

Animals↗
PubMed1999

Cystic hematoma formation following use of a biodegradable arrow for meniscal repair.

This is a case report of a cystic hematoma formation following the use of a biodegradable arrow for repair of a medial meniscus tear. A literature search found no previous report of this complication. Open hematoma debridement and arrow removal were effective in the treatment of this complication following all-inside meniscal repair with a biodegradable arrow.

Adult↗
PubMed1998

In vitro nerve repair--in vivo. The reconstruction of peripheral nerves by entubulation with biodegradeable glass tubes--a preliminary report.

Biodegradeable "controlled release" inorganic polymer glass tubes can be manufactured to fit the dimensions of any nerve and their rate of solubility can be adjusted to encompass the time taken for nerve regeneration. They have been used in a number of biological applications. The facial nerve was repaired in a group of five sheep by entubulation with biodegradeable glass tubes. The sheep were assessed 10 months after repair and compared with a similar sized group of normal sheep. It was found that while there was a reduction in the peak velocity of conduction in the repaired nerves and in the range of conduction velocities, the minimum conduction velocity was within normal limits. There was a diminution in all of the measured variables of nerve morphometry but in no case did this reach statistical significance. These findings are consistent with the view that regeneration of the nerves had taken place to a degree at least as effective as that seen in nerves of a similar size repaired by conventional means.

Animals↗
PubMed1989

From a synthetic, microporous, compliant, biodegradable small-caliber vascular graft to a new artery.

Microporous, compliant, biodegradable vascular grafts prepared from physical mixtures of polyurethane and poly(L)lactide acid can function as temporary scaffolds for the regeneration of a new arterial wall. In this overview article, the basic ideas behind the properties and construction of these grafts, the basic mechanisms of regeneration, and the scope, limitations, and further prospectives of the use of these biodegradable grafts are reviewed and discussed among literature.

Arteries↗
PubMed1998

Formation of spheroidal aggregates of hepatocytes on biodegradable polymers under continuous-flow bioreactor conditions.

Our laboratory has investigated heterotopic hepatocyte transplantation on biodegradable polymer matrices as an experimental treatment for end-stage liver disease. One of the limitations has been survival of sufficient cell mass after transplantation. We hypothesize that in vitro conditioning of cells within polymer matrices prior to implantation may increase hepatocyte survival and function. In this preliminary study we investigated the effect of continuous flow on hepatocytes and sinusoidal endothelial cells on poly-L-lactic acid (PLLA) discs in vitro. Highly porous PLLA discs were manufactured measuring 18 mm diameter by 1 mm thickness using previously described techniques. Hepatocytes were isolated from adult, male Lewis rats (200-300 g) using a two-step collagenase digestion. Sinusoidal endothelial cells were isolated using a two-step collagenase digestion, differential sedimentation, Percoll gradient centrifugation, and selective adherence. PLLA discs were seeded with hepatocytes alone or with co-cultures of hepatocytes and sinusoidal endothelial cells. Seeded discs were then secured within a flow bioreactor chamber and exposed to continuous flow of culture media at a rate of 20 ml/minute through the chamber. Seeded discs placed in static culture conditions served as controls. Specimens seeded with only hepatocytes were harvested at 24 hours, 48 hours, and 168 hours after seeding. Co-culture specimens were harvested after 168 hours. Specimens were viewed under phase-contrast microscopy and then formalin-fixed and prepared for histologic sectioning. Sections were stained with Hematoxylin and Eosin and then analyzed with light microscopy. Hepatocytes under flow conditions formed spheroidal aggregates of cells of 50 to 200 microns in diameter by 24 hours in culture. Hepatocytes in static conditions showed decreased aggregation of cells and spheroid formation was absent. Co-cultured specimens under flow also showed spheroid formation with endothelial cells lining the outside of hepatocyte spheroids. Co-cultured specimens in static culture showed no spheroid formation and no organization between sinusoidal endothelial cells and hepatocytes. These results suggest that continuous flow increases organization of hepatocytes cultured within biodegradable polymer matrices.

Animals↗