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At least 739 records · Page 41Linked to original sources

PubMed2000

Enhancement of hydrocarbon waste biodegradation by addition of a biosurfactant from Bacillus subtilis O9.

A non-sterile biosurfactant preparation (surfactin) was obtained from a 24-h culture of Bacillus subtilis O9 grown on sucrose and used to study its effect on the biodegradation of hydrocarbon wastes by an indigenous microbial community at the Erlenmeyer-flask scale. Crude biosurfactant was added to the cultures to obtain concentrations above and below the critical micelle concentration (CMC). Lower concentration affected neither biodegradation nor microbial growth. Higher concentration gave higher cell concentrations. Biodegradation of aliphatic hydrocarbons increased from 20.9 to 35.5% and in the case of aromatic hydrocarbons from nil to 41%, compared to the culture without biosurfactant. The enhancement effect of biosurfactant addition was more noticeable in the case of long chain alkanes. Pristane and phytane isoprenoids were degraded to the same extent as n-C17 and n-C18 alkanes and, consequently, no decrease in the ratios n-C17/pri and n-C18/phy was observed. Rapid production of surfactin crude preparation could make it practical for bioremediation of ship bilge wastes.

Bacillus subtilis↗

PubMed2000

Combined ozonation and biodegradation for remediation of mixtures of polycyclic aromatic hydrocarbons in soil.

A study was conducted to investigate the feasibility of a combined treatment (i.e., ozonation and biodegradation) to overcome the inherent bacterial bioavailability limitation, and hence bioremediation limitation, of polycyclic aromatic hydrocarbons in soil. Ozonation was very efficient in the removal of naphthalene, fluorene, phenanthrene, and anthracene, but not for pyrene, chrysene, and benzo(a)pyrene from soil freshly spiked with the hydrocarbons. A similar result was obtained from coal tar-contaminated soil. Elimination of polycyclic aromatic hydrocarbons increased appreciably in sand containing 0.03% organic carbon, indicating the adverse effect of organic carbon on the efficiency of ozone treatment. In spiked and coal tar-contaminated soils, ozonation followed by biodegradation significantly increased the degradation of various polycyclic aromatic hydrocarbons including chrysene and benzo(a)pyrene which were not degraded by the test bacterial consortium alone. In particular, the effect of the combined treatment was more pronounced in coal tar-contaminated soil than in sterile soil spiked with hydrocarbons, probably due to the augmented biological activity of the introduced consortium. The results suggest that a combined treatment including ozonation and biodegradation may be a promising bioremediation technology in soil contaminated with mixtures of polycyclic aromatic hydrocarbons such as former manufactured gas plant sites.

Benzo(a)pyrene↗

PubMed2004

Application of a quartz crystal microbalance to evaluate biodegradability of starch by Bacillus subtilis.

Biodegradation of solution-cast starch films by Bacillus subtilis was monitored using a quartz crystal microbalance (QCM). A starch film was formed on the crystal by solution casting and exposed to the Bacillus subtilis culture in a bioreactor. The high sensitivity of the QCM could monitor small weight changes of the starch films on the crystal in the initial stages of biodegradation by secreted exo-enzymes of the bacterium. The feasibility of this approach as a means of quantification and characterisation of biodegradability of different polymeric materials by selected organisms is discussed.

Bacillus subtilis↗

PubMed1997

Biodegradable block copolymers as injectable drug-delivery systems.

Polymers that display a physicochemical response to stimuli are widely explored as potential drug-delivery systems. Stimuli studied to date include chemical substances and changes in temperature, pH and electric field. Homopolymers or copolymers of N-isopropylacrylamide and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (known as poloxamers) are typical examples of thermosensitive polymers, but their use in drug delivery is problematic because they are toxic and non-biodegradable. Biodegradable polymers used for drug delivery to date have mostly been in the form of injectable microspheres or implant systems, which require complicated fabrication processes using organic solvents. Such systems have the disadvantage that the use of organic solvents can cause denaturation when protein drugs are to be encapsulated. Furthermore, the solid form requires surgical insertion, which often results in tissue irritation and damage. Here we report the synthesis of a thermosensitive, biodegradable hydrogel consisting of blocks of poly(ethylene oxide) and poly(L-lactic acid). Aqueous solutions of these copolymers exhibit temperature-dependent reversible gel-sol transitions. The hydrogel can be loaded with bioactive molecules in an aqueous phase at an elevated temperature (around 45 degrees C), where they form a sol. In this form, the polymer is injectable. On subcutaneous injection and subsequent rapid cooling to body temperature, the loaded copolymer forms a gel that can act as a sustained-release matrix for drugs.

Animals↗

PubMed1995

Production of polyhydroxyalkanoates, a family of biodegradable plastics and elastomers, in bacteria and plants.

In response to problems associated with plastic waste and its effect on the environment, there has been considerable interest in the development and production of biodegradable plastics. Polyhydroxyalkanoates (PHAs) are polyesters that accumulate as inclusions in a wide variety of bacteria. These bacterial polymers have properties ranging from stiff and brittle plastics to rubber-like materials. Because of their inherent biodegradability, PHAs are regarded as an attractive source of nonpolluting plastics and elastomers that can be used for specialty and commodity products. The possibility of producing PHAs in large scale and at a cost comparable to synthetic plastics has arisen from the demonstration of PHA accumulation in transgenic Arabidopsis plants expressing the bacterial PHA biosynthetic genes. Synergism between knowledge of the enzymes and genes contributing to PHA synthesis in bacteria and engineering of plant metabolic pathways will be necessary for the development of crop plants that produce biodegradable plastics.

Acids, Acyclic↗

PubMed2003

The organization of the microbial biodegradation network from a systems-biology perspective.

Microbial biodegradation of environmental pollutants is a field of growing importance because of its potential use in bioremediation and biocatalysis. We have studied the characteristics of the global biodegradation network that is brought about by all the known chemical reactions that are implicated in this process, regardless of their microbial hosts. This combination produces an efficient and integrated suprametabolism, with properties similar to those that define metabolic networks in single organisms. The characteristics of this network support an evolutionary scenario in which the reactions evolved outwards from the central metabolism. The properties of the global biodegradation network have implications for predicting the fate of current and future environmental pollutants.

Bacteria↗

PubMedDate not supplied

Biodegradation of aromatic compounds under mixed oxygen/denitrifying conditions: a review.

Bioremediation of aromatic hydrocarbons in groundwater and sediments is often limited by dissolved oxygen. Many aromatic hydrocarbons degrade very slowly or not at all under anaerobic conditions. Nitrate is a good alternative electron acceptor to oxygen, and denitrifying bacteria are commonly found in the subsurface and in association with contaminated aquifer materials. Providing both nitrate and microaerophilic levels of oxygen may result in oxidation of the stable benzene rings in aromatic contaminants and allow for the intermediates of this oxidation to degrade via denitrification. The effects of using mixed electron acceptors on biodegradation of subsurface contaminants is unclear. Below some critical oxygen threshold, aerobic biodegradation is inhibited, however high levels of oxygen inhibit denitrification. The mechanisms which regulate electron transfer to oxygen and nitrate are complex. This review: 1) describes the factors which may affect the utilization of oxygen and nitrate as dual electron acceptors during biodegradation; 2) summarizes the incidence of dual use of nitrate and oxygen (aerobic denitrification); and 3) presents evidence of the effectiveness of bioremediation under mixed oxygen/nitrate conditions.

Aerobiosis↗

PubMedDate not supplied

Effects of microcosm preparation on rates of toluene biodegradation under denitrifying conditions.

Microcosms were prepared with subsurface material from two aquifers to examine the effects of preparation methods on rates of toluene biodegradation under denitrifying conditions. In both cases, the data fit a zero-order kinetics plot. However, rates of removal were generally proportional to initial toluene concentrations, resulting in similar half-lives. Increasing the solid/liquid mass ratio resulted in decreased lag times in one aquifer material, although in both cases the specific toluene mass removal rate (g toluene g sediment-1 day-1) also decreased. Varying either the initial toluene concentrations or the solid/liquid ratios by two to three orders of magnitude resulted in a half-life variation of only a factor of two, with most of the differences occurring at the extreme ranges of the test variables. These data indicate that similar biodegradation rates might be expected from microcosms prepared with different contaminant concentrations and solid/liquid ratios, which is useful for design of microcosm studies to evaluate biodegradation at field sites.

Anaerobiosis↗

PubMed1998

Change in bacterial community during biodegradation of aniline.

The response of river water microbial communities to chemical compounds was monitored under laboratory conditions using aniline as a model. Bacteria were collected from unpolluted and polluted sites. Bacterial abundance (plate and total direct counting) and its relation to aniline biodegradation was examined. Colony hybridization with 16S rRNA oligonucleotide probes was used to study the changes in microbial community structure during biodegradation of aniline. The changes in bacterial abundance and community structure were related to biodegradation of aniline. Burkholderia-Pseudomonas (rRNA group III), an authentic Alcaligenes group became dominant despite the initial differences in the microbial communities, suggesting that these genera are the main aniline degraders in the aquatic environment.

Alcaligenes↗

PubMedDate not supplied

Microencapsulation of gentamicin in biodegradable PLA and/or PLA/PEG copolymer.

Biodegradable carriers containing gentamicin for local treatment of bone infection were developed. This paper describes the preparation and in vitro evaluation of these biodegradable implants. Poly-L-lactic acid (PLA) and poly-L-lactic acid:polyethylene glycol (PLA/PEG) disk implants containing gentamicin sulphate were obtained by compression of microspheres prepared by a double emulsion process. The mean particle size distribution of the microspheres, based on volume, ranged from 95-270 microm. The gentamicin sulphate loading of the microspheres, after a methylene chloride-water extraction procedure, exceeded 90% of the theoretical value. In vitro dissolution studies on the microspheres and implants with drug loadings 10-40% w/w indicated that the rate of drug release from both PLA and PLA/PEG implants increased, with an increase in drug loading. The release of gentamicin from microspheres was dependent on the properties of PLA and/or PLA/PEG. The PLA/PEG copolymer was more hydrophilic than the PLA homopolymer, and with a smaller pH change in the microenvironment with polymer being degraded. In comparison, the PLA/PEG implant released antibiotic faster and had a larger inhibitory zone based on the Bauer-Kirby experiments used to test the inhibitory activity of antimicrobial devices. Experimental results showed that the biodegradable PLA/PEG gentamicin delivery system had a potential for prophylaxis of post-operative infection.

Anti-Bacterial Agents↗

PubMedDate not supplied

Immune response with biodegradable nanospheres and alum: studies in rabbits using staphylococcal enterotoxin B-toxoid.

In this study, the adjuvant effect of the sustained release biodegradable nanospheres (100-150 nm in diameter) has been compared with alum. Nanospheres were formulated using a biodegradable polylactic polyglycolic acid copolymer (PLGA, 50:50) containing Staphylococcal Enterotoxin B (SEB) toxoid as a model vaccine antigen. Systemic immune response of the nanospheres containing toxoid was studied in rabbits by subcutaneous immunization. The data demonstrated that approximately 30% of the toxoid activity was lost following its encapsulation into nanospheres. Under in vitro conditions, nanospheres demonstrated sustained release of the toxoid. However, only 20% of the antigenic toxoid was released over the first 2 weeks of the release study. Immunization of animals with equal doses of toxoid, either using nanospheres or alum induced a comparable systemic immune response (IgG, IgM and IgA). The immune response reached a maximum level at 7 weeks post-immunization, which then gradually declined with time. The booster dose of toxoid at 19 weeks, either using alum or nanospheres induced similar immune response in both the groups, but was greater than the primary immune response. The studies, thus, suggest that biodegradable nanospheres could be used as a vaccine adjuvant.

Adjuvants, Immunologic↗

PubMedDate not supplied

Biodegradable bromocryptine mesylate microspheres prepared by a solvent evaporation technique. I: Evaluation of formulation variables on microspheres characteristics for brain delivery.

The aim of this study was to formulate biodegradable microspheres containing an anti-parkinsonian agent, bromocryptine mesylate, for brain delivery. The effect of formulation parameters (e.g. polymer, emulsifying agent type and concentration) on the characteristics of the microspheres produced, the efficiency of drug encapsulation, the particle size distribution and in vitro drug release rates from the bromocryptine mesylate microspheres were investigated using a 3(2) factorial design. Bromocryptine mesylate was encapsulated into biodegradable polymers using the following three different polymers; poly(L-lactide), poly(D,L-lactide) and poly(D,L-lactide-co-glycolide). The SEM photomicrographs showed that the morphology of the microspheres greatly depended on the polymer and emulsifying agent. The results indicate that, regardless of the polymer type, increase in emulsifying agent concentration from 0.25-0.75% w/v markedly decreases the particle size of the microspheres. Determination of particle size revealed that the use of 0.75% w/v of emulsifying agent concentration and a polymer solution concentration of 10% w/v resulted in optimum particle size. In order to prepare biodegradable microspheres with high drug content and small particle size, selection of polymer concentration as well as emulsifying agent concentration is critical. Polymer type has a less pronounced effect on the percentage encapsulation efficiency and particle size of microspheres than on the t(50%). The microspheres prepared by all three polymers, at a polymer concentration of 10% w/v and an emulsifying agent concentration of 0.75% w/v with NaCMC:SO (4:1, w/v) mixture was as the optimum formulation.

Biodegradation, Environmental↗

PubMed2003

Analysis of secondary metabolite fate during anaerobic-aerobic azo dye biodegradation in a sequential batch reactor.

A great number of the reported examples of azo dye biodegradation comprise two main steps, the reductive cleavage of the azo bond under anaerobic conditions and the subsequent aerobic mineralization of the produced aromatic amines. Based on this possible metabolism a Sequencing Batch Reactor was chosen to study biologicalcolor removal from simulated cotton textile effluents containing a reactive azo dye. In previous studies high color removal levels of the azo dye Remazol Brilliant Violet 5R were achieved (up to 90% with an initial dye concentration of 100 mg l(-1)) during the anaerobic phase of Sequencing Batch Reactor operation. However, HPLC analyses revealed that the aromatic amines formed in the anaerobic phase were not mineralized during the subsequent aerobic phase. In an attempt to promote the aerobic biodegradation of these aromatic amines three different approaches were tested, the increase of the relative duration of the aerobic phase, the increase of the hydraulic retention time through the decrease of the daily fill flow and finally the increase of the dye/carbon source concentration ratio through the decrease of the fed volumetric organic load. The two aromatic amines directly resulting from azo bond reduction were detected by HPLC analysis. However, a third metabolite with significant peak area was also detected with a time profile suggesting an equilibrium with one of the aromatic amines In spite of the conversions occurring between metabolites during the cycles of the tested approaches, no effective biodegradation of these metabolites was observed during the experimental period of over 810 days.

Anthraquinones↗

PubMed2003

Activated sludge as inoculum for ready biodegradability testing: effect of source.

Results of ready biodegradability tests (RBT) are barely reproducible owing to a well-known lack of definition in inoculum source and quality. In this study, the degree of variability expected when only activated sludges are used as inoculum source was investigated. For this, the characteristics of activated sludges collected in municipal wastewater treatment plants operating at various massic loading rates (MLR; 0.1, 0.5 and 0.9 kgBOD5 kgVSS(-1) d(-1)) were compared. In order to provide suitable cellular densities for RBT, inocula were obtained after settling of activated sludges and analyzed in terms of active and cultivable cell densities, dehydrogenasic activity, BOD5 and a general profile of hydrolytic enzymes. In our analysis, biomass obtained from the High-MLR treatment plant constituted the inoculum having the highest biodegradation potential both with respect to microbial densities and to enzyme activities. This biomass also yielded the fastest biodegradation kinetics in dodecyl benzene sulfonate RBT. An attempt of biomass homogenization of inocula on the basis of cultivable cell density and dehydrogenasic activity gave negative results with this chemical compound. Since, in practice, restriction of activated sludge sources may be difficult, our results emphasize the importance of further studies aimed at homogenization of inoculum quality and quantity.

Biodegradation, Environmental↗

PubMed2004

Biodegradation of Red B dye by Bacillus sp. OY1-2.

Batch tests were employed to investigate the effects of aerobic and anoxic conditions on the biodegradation of Red B dye by Bacillus OY1-2. Results from batch experiments demonstrated anoxic conditions were beneficial for rapid biodegradation of Red B dye in comparison to aerobic conditions. Biodegradation is a major mechanism in the decolorization of Red B dye in comparison with biosorption, which accounted for only 8% of the total decolorization efficiency. Reactors packed with granular activated carbon (GAC) and inoculated with Bacillus OY1-2 were investigated to treat a synthetic wastewater under anoxic conditions. In the absence of cosubstrates, Red B dye was degraded; however, a significant improvement in degradation resulted with the addition of cosubstrates.

Bacillus↗

PubMed2005

Activated sludge is a potential source for production of biodegradable plastics from wastewater.

Increased utilization of synthetic plastics caused severe environmental pollution due to their non-biodegradable nature. In the search for environmentally friendly materials to substitute for conventional plastics, different biodegradable plastics have been developed by microbial fermentations. However, limitations of these materials still exist due to high cost. This study aims at minimization of cost for the production of biodegradable plastics P(3HB) and minimization of environmental pollution. The waste biological sludge generated at wastewater treatment plants is used for the production of P(3HB) and wastewater is used as carbon source. Activated sludge was induced by controlling the carbon: nitrogen ratio to accumulate storage polymer. Initially polymer accumulation was studied by using different carbon and nitrogen sources. Maximum accumulation of polymer was observed with carbon source acetic acid and diammonium hydrogen phosphate (DAHP) as nitrogen source. Further studies were carried out to optimize the carbon: nitrogen ratios using acetic acid and DAHP. A maximum of 65.84% (w/w) P(3HB) production was obtained at C/N ratio of 50 within 96 hours of incubation.

Biodegradation, Environmental↗

PubMed2004

Predicting the biodegradation products of perfluorinated chemicals using CATABOL.

Perfluorinated chemicals (PFCs) form a special category of organofluorine compounds with particularly useful and unique properties. Their large use over the past decades increased the interest in the study of their environmental fate. Fluorocarbons may have direct or indirect environmental impact through the products of their decomposition in the environment. It is a common knowledge that biodegradation is restricted within non-perfluorinated part of molecules: however, a number of studies showed that defluorination can readily occur during biotransformation. To evaluate the fate of PFCs in the environment a set of principal transformations was developed and implemented in the simulator of microbial degradation using the catabolite software engine (CATABOL). The simulator was used to generate metabolic pathways for 171 perfluorinated substances on Canada's domestic substances list. It was found that although the extent of biodegradation of parent compounds could reach 60%, persistent metabolites could be formed in significant quantities. During the microbial degradation a trend was observed where PFCs are transformed to more bioaccumulative and more toxic products. Perfluorooctanoic acid and perfluorooctanesulfonate were predicted to be the persistent biodegradation products of 17 and 27% of the perfluorinated sulphonic acid and carboxylic acid containing compounds, respectively.

Bacteria↗

PubMed1995

CoMFA analysis of biodegradability.

CoMFA (comparative molecular field analysis) has been used to correlate the biodegradability of several classes of compounds. The technique uses an atomic probe to detect the steric and electrostatic fields around a molecule. Good cross-validated correlations were obtained for some series (alcohols, carboxylic acids and linear alkyl benzene sulphonates). Correlations were weaker for esters and benzene sulphonates, and were non-existent for phenols. These results may reflect the unreliability of biodegradation data, but may also be a result of molecular misalignment in the CoMFA procedure. CoMFA appears to be a potentially very useful method for the prediction of biodegradability.

Alcohols↗