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PubMed2005

Non-biodegradable biopolymers from renewable resources: perspectives and impacts.

In recent years the biotechnological production of bulk biopolymers has focused on the synthesis of biodegradable polymers to replace their non-biodegradable counterparts derived from fossil resources. Examples include polyhydroxyalkanoates and polylactic acid, which act as substitutes for polyolefins. By contrast, the biotechnological production of non-biodegradable polymers from renewable resources has so far been scarcely considered, probably because this idea contradicts the paradigm that all natural compounds are biodegradable. Polythioesters, which were recently described as new biopolymers, do not follow this paradigm because although they are produced by bacteria, they are persistent to microbial degradation. Mankind has a need for both non-biodegradable and biodegradable polymers and methods to produce them from renewable resources will be of great value.

Bacteria↗

PubMed2006

Biodegradability of nitrogenous compounds under anaerobic conditions and its estimation.

The anaerobic biodegradability of 23 nitrogenous compounds, including nitrogenous heterocyclic compounds and aliphatic amines, was tested and assessed in integration. These nitrogenous compounds were classified into readily, partially, and poorly biodegradable compounds after calculation of their integrated assessment indices (IAIs), Rules for anaerobic biodegradation of these compounds were also drawn. Stepwise regression and backpropagation artificial neural network (BP-ANN) methods were applied to establish quantitative structure-biodegradability relationships (QSBRs) based on the assessment results. In QSBR models, three molecular structure descriptors-second-order molecular connectivity index (2chi(V3)chi(v)p), and energy of the highest occupied molecular orbital (EHOMO)--were included. After analysis of the sensitivity of variables in QSBR models, it was found that the key molecular structure descriptor affecting anaerobic biodegradability of nitrogenous compounds is EHOMO, which is directly proportional to the anaerobic biodegradability of nitrogenous compounds.

Anaerobiosis↗

PubMed2005

Aerobic biodegradation of organotin compounds in activated sludge batch reactors.

The biodegradation behavior of four organotin (OT) compounds, namely tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT) and triphenyltin (TPhT), was studied in lab-scale activated sludge batch reactors. The activated sludge was spiked with the OT compounds at a level of 100 microg l(-1) as Sn. Determination of the OT compounds by GC-FPD after ethylation in the dissolved and particulate phase revealed that 24 h after the start of the experiments, almost the total of OT compounds has been removed from the dissolved phase and is associated with the suspended solids. Calculation of mass balance in batch reactors showed that OT compounds biodegradation was performed via a sequential dealkylation process. Removals due to biodegradation were differentiated according to the parent compound. In experiments with non-acclimatized biomass, a percentage of 27.1, 8.3, 73.8 and 51.3 was still present as TBT, DBT, MBT and TPhT, respectively, at the end of the experiment (18th day). Half-lives (t1/2) of 10.2 and 5.1 days were calculated for TBT and DBT, respectively, whereas apparent t1/2 values could not be determined for MBT and TPhT (t1/2>18 days). The capacity of activated sludge to biodegrade OT compounds in the absence of supplemental substrate indicated that these compounds can be metabolized as single sources of carbon and energy in activated sludge systems. Excluding TBT, the presence of low concentrations of supplemental substrate did not affect the biodegradation potential of activated sludge. The acclimatization of biomass on OT compounds enhanced significantly biodegradation, resulting in significant decreases of half-lives of OT compounds. As a result in the presence of acclimatized biomass, half-lives of 1.4, 3.6, 9.8 and 5.0 days were calculated for TBT, DBT, MBT and TPhT, respectively.

Biodegradation, Environmental↗

PubMed2006

Determination of biodegradation potential by two culture-independent methods in PAH-contaminated soils.

Biodegradation potentials of polycyclic aromatic hydrocarbons (PAHs) were determined with soil samples collected from various depths of a PAH-contaminated site and of a site nearby where PAHs were not found. Putative dioxygenase genes were amplified by a primer set specific for initial dioxygenases and identified by web-based database homology search. They were further categorized into several groups of which four dioxygenases were selected as probes for DNA hybridization. The hybridization signals according to the presence of putative dioxygenases were positively related to the extent of PAH contamination. However, the signal intensities varied depending on the probes hybridized and moreover were not consistent with PAH biodegradation activities determined by CO2 evolution. Despite widely accepted advantages of molecular biodegradation assessment, our data clearly present the variations of assessment results depending on the genetic information used and suggest that the methodology may tend to underestimate the real biodegradation capacity of a site probably due to the limited dioxygenase database available at the moment. Therefore, the molecular assessment of biodegradation potential should involve a very careful primer and probe design and an extensive microbiological examination of a site of interest to accurately delineate the biodegradation potential of the site.

Amino Acid Sequence↗

PubMed2004

Change of monochloroacetic acid to biodegradable organic acids by hydrothermal reaction.

The feasibility of biodegradability improvement induced from the structural conversion of refractory pollutants by hydrothermal reaction was investigated. Monochloroacetic acid (MCAA) was selected as a preliminary material represented for linear hydrocarbon structured refractory pollutants. Under the tested conditions, MCAA was partially destructed and then converted to biodegradable reaction products by hydrolysis, dehydration and thermal decomposition. The identified products were glycolic acid, citric acid and formic acid. Total organic carbon (TOC) reduction during the structural conversion did not exceed 24%, except the results at the reaction conditions of 350 degrees C and 17 MPa. However, Produced biodegradable organic acids were reduced by thermal decomposition with increasing reaction temperature and time. At the reaction temperature of 250 and 300 degrees C, biodegradability (BOD/COD(Cr)) was reached at 0.51 in 6.9 min and 0.52 in 7.4 min despite the presence of dissociated chlorine ions. The detachment of recalcitrant chlorine ion from MCAA and the production of biodegradable organic acids by hydrothermal reaction were directly related to the biodegradability improvement of reaction products.

Acetates↗

PubMed2006

Aromatic compounds biodegradation under anaerobic conditions and their QSBR models.

Anaerobic biodegradability of 46 kinds of aromatic compounds was tested and assessed in integrate. These aromatic compounds were classified into readily, partially and poorly biodegradable compounds after their integrated assessment indices (IAI) were calculated. Some rules of anaerobic biodegradation of them were drawn. Stepwise regression and backpropagation artificial neural network (BP-ANN) methods were applied to establish quantitative structure biodegradability relationship (QSBR) based on the assessment results. In QSBR models, five molecular structure descriptors, energy of the highest occupied molecular orbital (EHOMO), total energy (TolE), molar refractivity (MR), the logarithm of the partition coefficient for n-octanol/water (LogP), and standard Gibbs free energy (G), were included. After analyzing the sensitivity of variables in QSBR models, it was found that the key molecular structure descriptors affecting anaerobic biodegradability of aromatic compounds were TolE and MR, which were in direct proportion to the anaerobic biodegradability of aromatic compounds.

Bacteria, Anaerobic↗

PubMed2006

Investigation of the proinflammatory potential of biodegradable nanoparticle drug delivery systems in the lung.

Particulate nanocarriers have been praised for their advantageous drug delivery properties in the lung, such as avoidance of macrophage clearance mechanisms and long residence times. However, instilled non-biodegradable polystyrene nanospheres with small diameters and thus large surface areas have been shown to induce pulmonary inflammation. This study examines the potential of biodegradable polymeric nanoparticles composed of poly(lactic-co-glycolic acid) (PLGA) and the novel PLGA derivative, diethylaminopropylamine polyvinyl alcohol-grafted-poly(lactic-co-glycolic acid) (DEAPA-PVAL-g-PLGA), to provoke inflammatory responses in the murine lung after intratracheal instillation. Lactate dehydrogenase (LDH) release, protein concentration, MIP-2 mRNA induction, and polymorphonucleocyte (PMN) recruitment in the bronchial alveolar lavage fluid (BALF) were used to evaluate an inflammatory response in Balb-C mice. Two sizes of polystyrene (PS) nanospheres (diameters: 75 nm and 220 nm) were included in the study for comparison. All nanoparticle suspensions were instilled at concentrations of 1 microg/microl and 2.5 microg/microl, representative of an estimated "therapeutic dose" and a concentrated "dose" of particles. In all experiments, the 75 nm PS particles exhibited elevated responses for the inflammatory markers investigated. In contrast, biodegradable particles of comparable hydrodynamic diameter showed a significantly lower inflammatory response. The most marked differences were observed in the extent of PMN recruitment. While the 75 nm and 220 nm PS nanospheres exhibited 41 and 74% PMN within the total BALF cell population after 24 h, respectively, PMN recruiting in lungs instilled with both types of biodegradable particles did not exceed values of the negative isotonic glucose control. In conclusion, evidence suggests that biodegradable polymeric nanoparticles designed for pulmonary drug delivery may not induce the same inflammatory response as non-biodegradable polystyrene particles of comparable size.

Animals↗

PubMed2004

Modeling of aerobic biodegradation of feces using sawdust as a matrix.

Composting in the bio-toilet system is a continuous thermophilic-aerobic biodegradation process. Unlike to the traditional composting systems, biodegradation rates of organic matter are very important because feces are daily added into the composting reactor of the bio-toilet and an accelerated decomposition is aimed. The models developed for conventional composting processes include simple formulations of biodegradation kinetics and deal mainly with energy and water balances. Therefore, formulation of kinetics that can reasonably describe the biodegradation process in the bio-toilet system is required for better modeling predictions. In this work, a bio-kinetic model was introduced to describe the aerobic biodegradation of feces in the bio-toilet system. This model includes three processes for carbonaceous material degradation and is prepared by using the activated sludge modeling techniques and formulations. Stoichiometric parameters were adopted from literature on activated sludge processes. Kinetic parameters were estimated by conducting batch tests for several organic loadings and by using respirometry, curve-fitting techniques, and sensitivity analysis. Feasibility and applicability of these parameters were assessed by conducting feces intermittent-feeding tests and by simulating the experimental respiration rates. Model, stoichiometric and kinetic parameters proved to be affordable for describing the biodegradation of feces in the bio-toilet system.

Bacteria, Aerobic↗

PubMed2006

Biokinetics of biodegradation of surfactants under aerobic, anoxic and anaerobic conditions.

The present investigation aims at estimating the biodegradation coefficients of surfactants. The biodegradabilities of Triton X-100 and Rhamnolipid were tested under aerobic, nitrate reducing, sulphate reducing and anaerobic conditions using a respirometer. The results indicated that in terms of biodegradability, Rhamnolipid is superior to Triton X-100, since it is biodegradable under all conditions, whereas Triton X-100 is partially biodegradable under aerobic conditions and non-biodegradable under anaerobic, nitrate reducing and sulphate reducing conditions.

Bacteria, Anaerobic↗

PubMed2001

Chemical treatment of an anionic surfactant wastewater: Electrospray-MS studies of intermediates and effect on aerobic biodegradability.

The effect of wet air oxidation on the aerobic biodegradability of a model wastewater containing 1000 mg L(-1) of linear alkylbenzene sulfonate (LAS) has been investigated. Semibatch oxidation experiments were performed temperature of 473 K, oxygen partial pressure of 1.3 MPa and residence times varying from 40 to 390 min, while continuous oxidation experiments were performed at a residence time of 120 min. Oxygen uptake tests were performed to assess the aerobic biodegradability of both the oxidised and the original LAS solutions using cultures that had been adapted to both LAS and oxidation intermediates. The concentration of total organic carbon, chemical oxygen demand and active detergent were followed throughout the wet oxidation and biodegradation experiments, while the main intermediates formed during wet oxidation were identified by means of Electrospray-MS and high performance liquid chromatography. It was found that LAS could be easily oxidised at 473 K to yield a group of molecules with short alkyl chains which do not behave as active detergents. Sulfonated aromatics are produced as intermediates which have had the alkyl chains shortened. The segments of alkyl chains broken off the intermediate compounds appear primarily as short chain organic acids. The original unoxidised 1000 mg L(-1) LAS solution was found to be readily biodegradable in the laboratory aerobic reactors operating at low organic loadings and substrate to microorganism concentration ratios. However, wet oxidation resulted in effluents that were less readily biodegradable than the original LAS with biodegradability decreasing with increasing degree of oxidation. These results suggest that, at the conditions under consideration, a combined chemical pre-oxidations and biological post-treatment process may be less effective in removing LAS than a single-stage biological or chemical process.

Aerobiosis↗

PubMed2002

Biodegradation of oxo-alcohol ethoxylates in the continuous flow activated sludge simulation test.

Biodegradation of two alpha-methyl branched oxo-alcohol ethoxylates (OAE) of different polydispersity: LIAL 125/14 BRD (LIALB) (broad M.W. distribution) and LIAL 125/14 NRD (LIALN) (narrow M.W. distribution), both having an average of 14 oxyethylene subunits (EO) and a C(12-15) alkyl moiety were tested under the continuous flow activated sludge conditions of the classical Husmann plant. Primary biodegradation and concentration of metabolites: free oxo-alcohol fraction (FOA) and poly(ethylene glycols) (PEG), were measured. PEG were divided into two fractions: short-chained PEG (PEGshch) (1-4 EO) and long-chained PEG (PEGlch) (>4 EO). The indirect tensammetric technique combined with an adequate separation was used for analysis. Central fission was found to be a highly dominating pathway, as is the case with fatty alcohol ethoxylates. OAE are highly primarily biodegraded (above 95%). High concentrations of FOA and PEG are formed. Once formed the PEGlch are further fragmented into the PEGshch. Free alcohol fraction compounds are biodegraded sooner when alkyl moiety is shorter. OAE polydispersity has an influence on the kinetics of biodegradation; PEG formed from LIALN are biodegraded slower and to a lower degree than those from LIALB.

Alcohols↗

PubMed2001

Primary biodegradation of veterinary antibiotics in aerobic and anaerobic surface water simulation systems.

The primary aerobic and anaerobic biodegradability at intermediate concentrations (50-5000 microg/l) of the antibiotics olaquindox (OLA), metronidazole (MET), tylosin (TYL) and oxytetracycline (OTC) was studied in a simple shake flask system simulating the conditions in surface waters. The purpose of the study was to provide rate data for primary biodegradation in the scenario where antibiotics pollute surface waters as a result of run-off from arable land. The source of antibiotics may be application of manure as fertilizer or excreta of grazing animals. Assuming first-order degradation kinetics, ranges of half-lives for aerobic degradation of the four antibiotics studied were 4-8 days (OLA), 9.5-40 days (TYL), 14-104 days (MET) and 42-46 days (OTC). OLA and OTC were degraded with no initial lag phase whereas lag phases from 2 to 34 days (MET) and 31 to 40 days (TYL) were observed for other substances. The biodegradation behaviour was influenced by neither the concentrations of antibiotics nor the time of the year and location for sampling of surface water. Addition of 1 g/l of sediment or 3 mg/l of activated sludge from wastewater treatment increased the biodegradation potential which is believed to be the result of increased bacterial concentration in the test solution. Biodegradation was significantly slower in tests conducted in absence of oxygen. Assessments of the toxic properties of antibiotics by studying the influence on the biodegradation rates of 14C-aniline at different concentrations of antibiotics showed that no tests were conducted at toxic concentrations.

Agriculture↗

PubMed2001

Correlation of aerobic biodegradability of sulfonated azo dyes with the chemical structure.

The reported data of biodegradability of variously substituted 25 sulfonated azo dyes were divided into two classes: 8 dyes designated "rapidly biodegradable" and 17 dyes "not rapidly biodegradable", by applying principal components analysis (PCA). The biodegradability of the dyes was modeled with the discriminant technique of two-value regression analysis based on structural descriptors. A statistically significant and biologically meaningful regression model that gives perfect classification was obtained, and the results were compared with the previous qualitative interpretation of the substituent effects on biodegradation. The coefficients of the regression model revealed a significant interaction between ring substituents for biodegradability. The results facilitate understanding of the mechanism of degradation.

Azo Compounds↗

PubMed2002

The use of inert carriers in regulatory biodegradation tests of low density poorly water-soluble substances.

Many poorly water-soluble compounds fail regulatory ready biodegradation tests as the method of test material preparation limits the bioavailability of the chemical. The recognised method for delivery of poorly soluble materials into biodegradability tests consists of coating test material inside the test vessel or onto inert substrates (i.e., glass cover slide, boiling beads, filter paper, or Teflon stir bar) that are placed inside the vessels. Volatile solvents are often used to augment this process. Although these substrates work fairly well for delivering many poorly soluble materials into biodegradability tests, they have not been effective in keeping low density, poorly water-soluble substances in the test medium. Soon after medium is added to the test vessels, these chemicals break loose from the substrates and float on the surface where they have limited contact with micro-organisms in the test medium. Hence, there is a reduced potential for measuring substantial biodegradability in the test. This paper describes the work undertaken to establish a standard method of adding low density, poorly water-soluble substances into test vessels of biodegradability studies to ensure these materials remain in contact with micro-organisms in the test medium. The substances are prepared for testing by adsorption onto silica gel followed by dispersion into the culture medium. This method of delivery may provide greater intra- and inter-laboratory consistency in biodegradability test results for low density, poorly water-soluble substances and it may more closely mimic the probable transport and fate of these substances in the environment.

Biodegradation, Environmental↗

PubMed1999

Decolorization and biodegradability of photocatalytic treated azo dyes and wool textile wastewater.

The photodegradation and biodegradability have been investigated for four non-biodegradable commercial azo dyes, Reactive YellowKD-3G, Reactive Red 15, Reactive Red 24, Cationic Blue X-GRL, an indicator. Methyl Orange, and one industrial wool textile wastewater, using TiO2 suspensions irradiated with a medium pressure mercury lamp. The color removal of dyes solution and dyeing wastewater reached to above 90% within 20-30 min. of photocatalytic treatment. Biochemical oxygen demand (BOD) was found to increase, while chemical oxygen demand (COD), total organic carbon (TOC) decreased, so that the ratio of BOD5/COD of the wastewater increased from original zero up to 0.75. The result implies that photocatalytic oxidation enhanced the biodegradability of the dye-containing wastewater and therefore relationship between decolorization and biodegradability exists. When the color disappeared completely, the wastewater biodegraded normally and could be discharged for further treatment. The experimental results demonstrate that it is possible to combine photocatalysis with conventional biological treatment for the remedy of wastewater containing generally non-biodegradable azo dyes.

Azo Compounds↗

PubMed1999

Biodegradation in laboratory activated sludge plants and aquatic toxicity of herbicides.

The biodegradation and the aquatic toxicity of four herbicides (isoproturon, terbuthylazine, mecoprop, metamitron) were investigated. Laboratory activated sludge plants were used for biodegradation experiments. The biodegradation of mecoprop reached nearly 100%, the other herbicides were not eliminated by biodegradation. The acute Daphnia magna 24-h assay, the algal 72-h inhibition test, and the recently developed lemna growth inhibition 7-d test were applied to evaluate the biological effects of herbicides as original substances. EC 50 and EC 10 values were determined. Algal and lemna test show that isoproturon and terbuthylazine are both much more toxic than mecoprop and metamitron. Daphnids are generally less sensitive against herbicides than plants. Biodegradation and toxicity test were coupled for mecoprop to assess biological long-term effects of possible biodegradation products of this herbicide. The effluents of the laboratory activated sludge units were used in toxicity tests (Daphnia magna 21-d reproduction test, lemna growth inhibition 7-d test). No inhibiting effect on the tested organisms was observed.

2-Methyl-4-chlorophenoxyacetic Acid↗

PubMed2003

Use of tracer tests to evaluate the impact of enhanced-solubilization flushing on in-situ biodegradation.

Tracer tests were conducted to evaluate the effect of a complexing sugar flush (CSF) on in-situ biodegradation potential at a site contaminated by jet fuel, solvents, and other organic compounds. Technical-grade hydroxypropyl-beta-cyclodextrin was used during the CSF study, which was conducted in a hydraulically isolated cell emplaced in a surficial aquifer. In-situ biodegradation potential was assessed with the use of tracer tests, which were conducted prior to and immediately following the CSF study. Ethanol, hexanol, and benzoate were used as the biodegradable tracers, while bromide was used as a nonreactive tracer. The results indicate that the biodegradation of benzoate was similar for both tracer tests. Conversely, the biodegradation of ethanol (23% increase) and hexanol (41% increase) was greater for the post-CSF tracer test. In addition, analysis of core samples collected from within the test cell indicates that the population density of aerobic jet-fuel degraders increased in the vicinity of the injection wells during the CSF. These results indicate that the cyclodextrin flush did not deleteriously affect the indigenous microbial community. This study illustrates that tracer tests can be used to evaluate the impact of remediation activities on in-situ biodegradation potential.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2003

Inverse modeling of BTEX dissolution and biodegradation at the Bemidji, MN crude-oil spill site.

The U.S. Geological Survey (USGS) solute transport and biodegradation code BIOMOC was used in conjunction with the USGS universal inverse modeling code UCODE to quantify field-scale hydrocarbon dissolution and biodegradation at the USGS Toxic Substances Hydrology Program crude-oil spill research site located near Bemidji, MN. This inverse modeling effort used the extensive historical data compiled at the Bemidji site from 1986 to 1997 and incorporated a multicomponent transport and biodegradation model. Inverse modeling was successful when coupled transport and degradation processes were incorporated into the model and a single dissolution rate coefficient was used for all BTEX components. Assuming a stationary oil body, we simulated benzene, toluene, ethylbenzene, m,p-xylene, and o-xylene (BTEX) concentrations in the oil and ground water, respectively, as well as dissolved oxygen. Dissolution from the oil phase and aerobic and anaerobic degradation processes were represented. The parameters estimated were the recharge rate, hydraulic conductivity, dissolution rate coefficient, individual first-order BTEX anaerobic degradation rates, and transverse dispersivity. Results were similar for simulations obtained using several alternative conceptual models of the hydrologic system and biodegradation processes. The dissolved BTEX concentration data were not sufficient to discriminate between these conceptual models. The calibrated simulations reproduced the general large-scale evolution of the plume, but did not reproduce the observed small-scale spatial and temporal variability in concentrations. The estimated anaerobic biodegradation rates for toluene and o-xylene were greater than the dissolution rate coefficient. However, the estimated anaerobic biodegradation rates for benzene, ethylbenzene, and m,p-xylene were less than the dissolution rate coefficient. The calibrated model was used to determine the BTEX mass balance in the oil body and groundwater plume. Dissolution from the oil body was greatest for compounds with large effective solubilities (benzene) and with large degradation rates (toluene and o-xylene). Anaerobic degradation removed 77% of the BTEX that dissolved into the water phase and aerobic degradation removed 17%. Although goodness-of-fit measures for the alternative conceptual models were not significantly different, predictions made with the models were quite variable.

Benzene↗