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At least 649 records · Page 36Linked to original sources

PubMed2005

Biodegradation of lindane by Pleurotus ostreatus via central composite design.

The degradation of lindane was studied in liquid-agitated cultures using a commercial strain of the fungus Pleurotus ostreatus as the biodegrading organism. The biodegradation was accomplished with the action of extracellular oxidative enzymes, produced by the fungus to decompose woody substrates. Enzyme activities of manganese peroxidase and laccase were measured in a liquid mineral medium. An orthogonal Central Composite Design of experiments was used to construct second-order response surfaces with the fungus growth, final pH and the lindane biodegradation as optimization parameters. The initial lindane concentration, the nitrogen content, the incubation time and the temperature were used as design factors. Optimal conditions found for all these parameters will be used for the continuation of this project aiming at the bioremediation of contaminated sites with persistent organic pollutants such as lindane.

Biodegradation, Environmental↗

PubMed2004

Biodegradation of phenanthrene in soil-slurry systems with different mass transfer regimes and soil contents.

The effect of soil contents and mass transfer rates on soil bioremediation was investigated. Phenanthrene, a 3-ring polycyclic aromatic hydrocarbon (PAH), was chosen as a model target compound. The biodegradation tests were performed in soil-slurry systems at two distinct mass transfer rates: fast in flasks tests at 150 rpm and slow in roller-bottle tests at 2 rpm. The rate of phenanthrene biodegradation was similar at low soil content (2 wt.%) in both slurry systems, but the rates at high soil contents (6 and 18 wt.%) were higher in the roller-bottle tests. The maximum utilization rate constant for sorbed-phase biodegradation obtained from curve fitting using a mathematical model was decreased in the flask tests with increasing soil content, while not decreased in the roller-bottle tests.

Adsorption↗

PubMed2005

Biodegradation and mineral weathering controls on bulk electrical conductivity in a shallow hydrocarbon contaminated aquifer.

Geochemical and stable carbon isotope data from closely spaced vertical intervals in a hydrocarbon-impacted aquifer were used to assess the relationship between biodegradation, mineral weathering, and enhanced bulk conductivity zones. The results show that depth zones of enhanced bulk conductivity in the contaminated aquifer had higher total dissolved solids (TDS) compared to background groundwater. The higher TDS in contaminated groundwater were due to elevated ion concentrations from enhanced mineral weathering. Depth intervals with higher concentrations of major cations overlapped with zones with higher total petroleum hydrocarbons, which were the same zones where reduction of nitrate, iron, manganese, sulfate, and methanogenesis was occurring. Hence, the zones of higher bulk conductivity may be explained by mineral weathering related to hydrocarbon biodegradation. Our results suggest that biodegradation of hydrocarbons may impart changes to the aquifer geochemistry that can be indirectly observed using geophysical techniques. We therefore argue for inclusion of geophysical investigations as part of natural attenuation assessment programs.

Biodegradation, Environmental↗

PubMed2006

Biodegradation of hydrocarbons vapors: Comparison of laboratory studies and field investigations in the vadose zone at the emplaced fuel source experiment, Airbase Vaerløse, Denmark.

The natural attenuation of volatile organic compounds (VOCs) in the unsaturated zone can only be predicted when information about microbial biodegradation rates and kinetics are known. This study aimed at determining first-order rate coefficients for the aerobic biodegradation of 13 volatile petroleum hydrocarbons which were artificially emplaced as a liquid mixture during a field experiment in an unsaturated sandy soil. Apparent first-order biodegradation rate coefficients were estimated by comparing the spatial evolution of the resulting vapor plumes to an analytical reactive transport model. Two independent reactive numerical model approaches have been used to simulate the diffusive migration of VOC vapors and to estimate degradation rate coefficients. Supplementary laboratory column and microcosm experiments were performed with the sandy soil at room temperature under aerobic conditions. First-order kinetics adequately matched the lab column profiles for most of the compounds. Consistent compound-specific apparent first-order rate coefficients were obtained by the three models and the lab column experiment, except for benzene. Laboratory microcosm experiments lacked of sensitivity for slowly degrading compounds and underestimated degradation rates by up to a factor of 5. Addition of NH3 vapor was shown to increase the degradation rates for some VOCs in the laboratory microcosms. All field models suggested a significantly higher degradation rate for benzene than the rates measured in the lab, suggesting that the field microbial community was superior in developing benzene degrading activity.

Bacteria↗

PubMed2025

Detoxifying biotransformation of chloramphenicol by Exiguobacterium sp. CAP4 and its bioaugmentation of chloramphenicol biodegradation in simulated wastewater.

The extensive use of chloramphenicol (CAP) in livestock leads the accumulation of CAP in livestock manures, threatening environmental and human health. Therefore, eliminating or reducing CAP concentration in manures before its re-utilization and application through microbial remediation is necessary. Exiguobacterium sp. CAP4, isolated from the plastisphere in duck manures, was capable of degrading CAP with the biodegradation efficiency of 97.8 % at initial CAP concentration of 5 mg/L within 4 days. A total of twenty-four biotransformation products were determined, including two novel transformation products, TP166 and TP203, enriched the integrity of CAP biodegradation pathways. Furthermore, the biotransformation process was proposed as a detoxifying process through biotransformation products toxicity evaluation. Notably, Exiguobacterium sp. CAP4 successfully colonized in the cow manures after inoculation, and bioaugmented the biodegradation of CAP in virgin cow manures. This study significantly extended our understanding of the CAP biotransformation fate, and provided a promising bacterial strain for bioremediation of CAP containing wastewater in situ.

Chloramphenicol↗

PubMed2003

Effect of additional carbon source on naphthalene biodegradation by Pseudomonas putida G7.

Addition of a carbon source as a nutrient into soil is believed to enhance in situ bioremediation by stimulating the growth of microorganisms that are indigenous to the subsurface and are capable of degrading contaminants. However, it may inhibit the biodegradation of organic contaminants and result in diauxic growth. The objective of this work is to study the effect of pyruvate as another carbon source on the biodegradation of polynuclear aromatic hydrocarbons (PAHs). In this study, naphthalene was used as a model PAH, ammonium sulfate as a nitrogen source, and oxygen as an electron acceptor. Pseudomonas putida G7 was used as a model naphthalene-degrading microorganism. From a chemostat culture, the growth kinetics of P. putida G7 on pyruvate was determined. At concentrations of naphthalene and pyruvate giving similar growth rates of P. putida G7, diauxic growth of P. putida G7 was not observed. It is suggested that pyruvate does not inhibit naphthalene biodegradation and can be used as an additional carbon source to stimulate the growth of P. putida G7 that can degrade polynuclear aromatic hydrocarbons.

Biodegradation, Environmental↗

PubMed2004

Anaerobic biodegradation of an organic by-products leachate by interaction with different mine tailings.

Deinking by-products from paper recycling have been used as cover materials on acid-producing tailings. Due to residual cellulose, anaerobic degradation leads to the production of an organic-rich leachate, which may percolate through the tailings. This study aims at describing the influence of the tailings' characteristics on the attenuation of organic matter in leachate and at discussing the degradation mechanisms. To this end, leachate was mixed with different types of tailings, including three unoxidized tailings with varying acid generation potentials and one tailing in three states of oxidation. Regularly, selected biochemical parameters were analyzed to access the evolution of organic components. The results show that when leachate from deinking by-products was placed in contact with tailings, phase and acid-base balance reactions took place in the beginning. Subsequently, oxidation-reduction reactions dominated the chemistry of the system. The type, the constituents, and the state of oxidation of the mine tailings condition the mechanisms of biodegradation of organic components. Methanogenesis was predominant in the control sample (pure organic leachate) but was absent in all leachate-tailings mixtures. No biodegradation was observed in the liquid phase for oxidized tailings and the organic concentration remained constant for unoxidized tailings, independently of the acid-generation potential. The biodegradation efficiency was optimal when the leachate was in contact with a mixture of oxidized and unoxidized tailings due to sulfate-reduction.

Acids↗

PubMed2004

Biodegradation of 2,4-dinitrotoluene using poultry litter leachate.

Various micro-organisms are known to degrade 2,4-dinitrotoluene (DNT) through pathways involving intermediates. Addition of nutrients stimulates the biodegradation process. Poultry litter has a consortia of micro-organisms along with many nutrients. The objective was to study the DNT biodegradation using poultry litter in an aqueous medium. Complete biodegradation of 10-50 ppm 2,4-DNT solutions was observed after two days interaction with poultry litter leachate without the formation of any intermediates. No degradation was observed using autoclaved litter leachate.

Animals↗

PubMed2004

Use of poultry litter for biodegradation of soil contaminated with 2,4- and 2,6-dinitrotoluene.

Pseudomonas sp. and Pseudomonas putida can utilize dinitrotoluene (DNT) as N-source after the enzymatic removal of nitro groups from the aromatic ring. Addition of nutrients is known to stimulate the biodegradation process. Poultry litter has consortia of microorganisms (including Pseudomonas) along with many nutrients. The objective of this research was to study the biodegradation of 2,4- and 2,6-DNT contaminated soil (from Badger Army Ammunition Plant) using poultry litter. Complete biodegradation of both 2,4- and 2,6-DNT in the soil was observed after 1-day interaction with poultry litter. No degradation was observed using autoclaved litter.

Air Pollutants, Occupational↗

PubMed2006

Evaluation of biodegradability and oxidation degree of hospital wastewater using photo-Fenton process as the pretreatment method.

In this work, the photo-Fenton process was used for the pretreatment of hospital wastewater with the objective of improving its overall biodegradability and determining the degree of increased oxidation. The chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD5), total organic carbon (TOC) and toxicity towards the gram negative marine bioluminescent bacteria of the species V. fischeri were selected as the environmental sum parameters to follow the performance of this process. The enhancement of biodegradability, evaluated in terms of the BOD5/COD ratio, increased from 0.3 to 0.52 and the oxidation degree, calculated in terms of AOS, leveled up from -1.14 to +1.58 at the optimum conditions; a dosage ratio of COD:H2O2:Fe(II) at 1:4:0.1, and a reaction pH of 3. The reduction in the inhibition percentage from the toxicity test indicated the safe levels for micro-organisms in degrading the residual organic substance in this method. Almost total removal percentages of COD, BOD5, and TOC were found by a sequential activated sludge process for the pre-treated wastewater. Results obtained from this work indicated that the photo-Fenton process could be a suitable pretreatment method in reducing toxicity of pollutants and enhancing biodegradability of hospital wastewaters treated in a coupled photochemical-biological system.

Aerobiosis↗

PubMed2004

Biodegradable polymer with collagen microsponge serves as a new bioengineered cardiovascular prosthesis.

OBJECTIVE: Biodegradable materials with autologous cell seeding have attracted much interest as potential cardiovascular grafts. However, pretreatment of these materials requires a complicated and invasive procedure that carries the risk of infection. To avoid these problems, we sought to develop a biodegradable graft material containing collagen microsponge that would permit the regeneration of autologous vessel tissue. The ability of this material to accelerate in situ cellularization with autologous endothelial and smooth muscle cells was tested with and without precellularization. METHODS: Poly(lactic-co-glycolic acid) as a biodegradable scaffold was compounded with collagen microsponge to form a vascular patch material. These poly(lactic-co-glycolic acid)-collagen patches with (n = 10) or without (n = 10) autologous vessel cellularization were used to patch the canine pulmonary artery trunk. Histologic and biochemical assessments were performed 2 and 6 months after the implantation. RESULTS: There was no thrombus formation in either group, and the poly(lactic-co-glycolic acid) scaffold was almost completely absorbed in both groups. Histologic results showed the formation of an endothelial cell monolayer, a parallel alignment of smooth muscle cells, and reconstructed vessel wall with elastin and collagen fibers. The cellular and extracellular components in the patch had increased to levels similar to those in native tissue at 6 months. CONCLUSIONS: The poly(lactic-co-glycolic acid)-collagen microsponge patch with and without precellularization showed good histologic findings and durability. This patch shows promise as a bioengineered material for promoting in situ cellularization and the regeneration of autologous tissue in cardiovascular surgery.

Animals↗

PubMed2007

Biodegradation of petroleum products in experimental plots in Antarctic marine sediments is location dependent.

Clean sediment collected from O'Brien Bay, East Antarctica, was artificially contaminated with a mix of Special Antarctic Blend diesel fuel and lubricating oil and deployed in two uncontaminated locations (O'Brien and Sparkes Bays) and a previously contaminated bay (Brown Bay) to evaluate whether a history of prior contamination would influence the biodegradation process. Detailed analysis of the hydrocarbon composition in the sediment after 11 weeks revealed different patterns of degradation in each bay. Biodegradation indices showed that hydrocarbon biodegradation occurred in all three bays but was most extensive in Brown Bay. This study shows that even within a relatively small geographical area, the longevity of hydrocarbons in Antarctic marine sediments can be variable. Our results are consistent with faster natural attenuation of spilt oil at sites with previous exposure to oil but further work is needed to confirm this. Such information would be useful when evaluating the true risk and longevity of oils spills.

Antarctic Regions↗

PubMed2006

Aerobic and anaerobic biodegradation of phenol derivatives in various paddy soils.

Microbiological degradation of phenol and some of its alkyl-derivatives (p-cresol, 4-n-propylphenol, 4-i-propylphenol, 4-n-butylphenol, 4-sec-butylphenol, 4-t-butylphenol, and 4-t-octylphenol) was examined under both aerobic and anaerobic conditions in seven Japanese paddy soils. Aerobic biodegradation of phenol derivatives was detected in all the paddy soils examined. The half-lives ranged from 2 to 19 days. The aerobic degradation rate of 4-t-octylphenol was correlated inversely with the total carbon contents of paddy soils, and there were significant inverse correlations between the aerobic degradation rate and the size of alkyl groups of alkylphenols. Anaerobic biodegradation of phenol and p-cresol was detected in three soils with the half-lives ranging from 24 to 260 days for phenol and from 11 to 740 days for p-cresol, respectively. The three soils were characterized by low contents of nitrate and iron oxides. Other soil properties did not show any significant correlations with the anaerobic degradation rates. In one soil, we found for the first time anaerobic biodegradation of 4-n-propylphenol. However, the other five compounds (4-i-propylphenol, 4-n-butylphenol, 4-sec-butylphenol, 4-t-butylphenol and 4-t-octylphenol) were not degraded over 224 days of incubation. These results suggest that phenol and all the alkylphenols were degraded within several days when paddy soil is not flooded and so under aerobic conditions. Under flooded and anaerobic conditions, 4-n-propylphenol would be degraded as well as phenol and p-cresol while alkylphenols with long and branched alkyl chains were hardly degraded at all.

Agriculture↗

PubMed2006

Identifying model pollutants to investigate biodegradation of hazardous XOCs in WWTPs.

Xenobiotic organic compounds (XOCs) in wastewater treatment plant (WWTP) effluents might cause toxic effects in ecosystems. Several investigations have emphasized biodegradation as an important removal mechanism to reduce pollution with XOCs from WWTP effluents. The aim of the study was to design a screening tool to identify and select hazardous model pollutants for the further investigation of biodegradation in WWTPs. The screening tool consists of three criteria: The XOC is present in WWTP effluents, the XOC constitutes an intolerable risk in drinking water or the environment, and the XOC is expected to be biodegradable in WWTPs. The screening tool was tested on bisphenol A (BPA), carbamazepine (CBZ), di(2ethylhexyl)-phthalate (DEHP), 17beta-estradiol (E2), estrone (E1), 17alpha-ethinyloetradiol (EE2), ibuprofen, naproxen, nonylphenol (NP), and octylphenol (OP). BPA, DEHP, E2, E1, EE2, and NP passed all criteria in the screening tool and were selected as model pollutants. OP did not pass the filter and was rejected as model pollutant. CBZ, ibuprofen, and naproxen were not finally evaluated due to insufficient data.

Biodegradation, Environmental↗

PubMed2005

Biodegradable municipal solid waste: characterization and potential use as animal feedstuffs.

Five different fractions of the biodegradable municipal solid waste (BMSW) were evaluated as potential animal feedstuffs. For each source of waste (meat waste (MW), fish waste (FW), fruit and vegetables waste (FVW), restaurant waste (RW), household waste (HW)), samples were obtained from small shops (butchers, fishmongers, fruit and vegetable shops), restaurants and a MSW treatment plant (household waste). The chemical composition, microbiological characterization, dioxins, furans, PCB's and mineral content were determined for every type of waste fraction. The analysed biodegradable waste presented high moisture content (from 60% to 90%). Some fractions were dense in one nutrient: meat waste in ether extract, fish waste in crude protein, fruit and vegetable waste in nitrogen free extract. The other studied fractions (restaurant fraction and household fraction) presented a more balanced composition, but the presence of toxic concentrations of contaminants such as metals was higher than European legislation permitted values in animal feeding. From a microbiological standpoint, a heat treatment at 65 degrees C for 20 min was sufficient to ensure microbiological quality of the samples. This treatment was also advisable to reduce the moisture content: a lower moisture content facilitates the waste handling and processing and, therefore, the inclusion of these waste fractions in commercial animal diets. This paper presents a potential alternative for the recovery of organic matter content in municipal solid waste. The results obtained in this research and the feedstuffs legislation in force related to animal feed, indicated that some of the studied biodegradable waste fractions (meat waste, fruit and vegetable waste and fish waste) could be considered as alternatives to typical raw materials used in animal feeds.

Animal Feed↗

PubMed2004

Temperature effect on aerobic biodegradation of feces using sawdust as a matrix.

Temperature is one of the most important factors affecting microbial growth and biological reactions. In this study, the effect of temperature on aerobic biodegradation of feces is described through the comparison and analysis of experimental oxygen utilization rates (OUR) profiles obtained from batch tests conducted at several temperatures covering mainly mesophilic and thermophilic ranges. Additionally, the temperature effect was incorporated into the bio-kinetic model introduced by Lopez Zavala et al. (Water Res 38(5) (2004) 1327) and simulation of experimental OUR profiles was conducted. Results show that mesophilic and thermophilic microorganisms behaved differently to temperature; additionally, results suggest that the optimum temperature from the viewpoint of feces biodegradability is within the thermophilic range, nearly 60 degrees C. The enzymatic activity of microorganisms at 70 degrees C was remarkably diminished. For better predictions in the mesophilic range, two fractions of slowly biodegradable organic matter were identified, easily hydrolyzable organic matter (X(Se)) and slowly hydrolyzable organic matter (X(Ss)).

Bacteria, Aerobic↗

PubMed2004

Effects of oxygen on biodegradation of benzoate and 3-chlorobenzoate in a denitrifying chemostat.

A mixed microbial culture degraded a mixture of benzoate (863 mg/L), 3-chlorobenzoate (3-CB) (69.7 mg/L), and pyruvate (244 mg/L) under denitrifying conditions in a chemostat. Biodegradation under denitrifying conditions was stable, complete (effluent concentrations below detection limits), and proceeded without the production of toxic intermediates like chlorocatechols. The addition of oxygen at mass input rates of 6.2%, 15.5%, and 43.9% of the mass input rate of chemical oxygen demand (COD) (337 mg COD/h) did not induce the synthesis of aerobic biodegradation pathways and thus did not disrupt biodegradation. Rather, the oxygen was used as a terminal electron acceptor, displacing a stoichiometric amount of nitrate, leading to microaerobic conditions (dissolved oxygen concentration <0.050 mg/L) in which oxygen utilization and denitrification occurred simultaneously. The reduction of nitrate occurred fully to N(2) gas with no accumulation of nitrite, nitrous oxide, or nitric oxide, although the ability of the culture to transfer electrons to the nitrogen oxides decreased as the oxygen input was increased. The anoxic benzoate uptake capability was unaffected by the increase in oxygen addition, but the anoxic 3-CB uptake capability increased, as did the level of benzoyl-CoA reductase in the cells.

Anti-Infective Agents↗

PubMed2005

Mineralization of some natural refractory organic compounds by biodegradation and ozonation.

The objective of this study was to explore the extent of mineralization, reduction in color and reduction of COD of gallic acid, tannin and lignin by ozonation and a combination of aerobic biodegradation and ozonation. Ozonation of pure aliquots (phase I experiments) resulted in the decline in TOC, COD, COD/TOC ratio, UV absorbance at 280 nm and color of the three model compounds investigated, with COD removals of greater than 80% and high removals (>90%) of UV absorbance at 280 nm and color observed in all cases at an ozone dose of 6 mg ozone/mg initial TOC or higher. Aerobic biodegradation of pure gallic acid, tannin and lignin aliquots resulted in COD decline of approximately 36-38%. Subsequent ozonation (phase II experiments) resulted in further decline in TOC, COD, COD/TOC ratio, and increase in UV absorbance at 280 nm and color removals. COD and TOC removals comparable to phase I experiments were obtained with 30-40% lower ozone absorption in phase II experiments. The biodegradation step was quite effective in removing specific UV absorbance at 280 nm, with up to 75% removal observed. Subsequent ozonation increased overall specific UV absorbance at 280 nm to greater than 90%.

Bacteria, Aerobic↗