Complete Biodegradation Research Articles

Complete dechlorination and mineralization of pentachlorophenol (PCP) in a hydrogen-based membrane biofilm reactor (MBfR)

Complete biodegradation and mineralization of pentachlorophenol (PCP), a priority pollutant in water, is challenging for water treatment. In this study, a hydrogen (H2)-based membrane biofilm reactor (MBfR) was applied to treat PCP, along with nitrate and sulfate, which often coexist in contaminated groundwater. Throughout 120-days of continuous operation, almost 100% of up to 10 mg/L PCP was removed with minimal intermediate accumulation and in parallel with complete denitrification of 20 mg-N/L nitrate. PCP initially was reductively dechlorinated to phenol, which was then mineralized to CO2 through pathways that began with aerobic activation via monooxygenation by Xanthobacter and anaerobic activation via carboxylation by Azospira and Thauera. Sulfur cycling induced by SO42− reduction affected the microbial community: The dominant bacteria became sulfate-reducers Desulfomicrobium, sulfur-oxidizers Sulfuritalea and Flavobacterium. This study provides insights and a promising technology for bioremediation of water contaminated with PCP, nitrate, and sulfate.

Lipidomic adaptations of the Metarhizium robertsii strain in response to the presence of butyltin compounds

Metarhizium robertsii, a butyltin-resistant filamentous fungus, can rapid and complete biodegradation of di- (DBT) and tributyltin (TBT) under conditions of intensive aeration and ascorbic acid supplementation. In this paper, lipidomic investigations were performed to find the membrane adaptations necessary for effective butyltins degradation. HPLC-MS/MS analysis showed that the phospholipid profile was greatly modified during M. robertsii batch cultivation (pO2 ≥ 20%), contributing to increased membrane fluidity and facilitated mass transfer, which could enhance butyltins biodegradation. Intensified biosynthesis of phospholipids, sphingolipids and ergosterol by the mycelia exposed to butyltins was noted. DIOC6(3) fluorescence intensity for TBT-treated mycelium increased 9-fold pointing to membrane hyperpolarization. Fluorescent studies showed improved membrane rigidity and integrity in response to butyltins presence. Vitamin C supplementation restored membrane composition and dynamic properties, followed by supposed acceleration of transport of monobutyltin and its biodegradation thus protecting the M. robertsii cells against oxidative and nitrosative stress.

Anaerobic co-digestion of petroleum hydrocarbon waste and wastewater treatment sludge

The development of efficient treatment processes for petroleum hydrocarbon waste (PHW) can lead to greater impact in the petroleum industry which has been generating disconcerting amounts of hazardous oily sludge. Traditionally, PHW is thermally remediated to stable non-hazardous soil. In this work, PHW in the form of a semi-solid sludge (hydrocarbons, soil, and water) is treated biochemically in a batch reactor. Contrary to municipal solid waste (MSW), biomass or wastewater treatment sludge (WWTS), PHW lacks the necessary nutrients to biodegrade and may include some heavy metals inhibitors. Therefore, co-digestion, addition of inoculum, and using other additives anaerobically and concurrently with adjustment of the reactor conditions is necessary to stimulate the microbial environment and thereby produce higher specific landfill gas (SLFG) generation. Additionally, hydrogen can also be produced in two stage anaerobic digestion. In this work, multiple samples of PHW and WWTS were collected and analyzed per their proximate/elemental composition and heating values. Then several bench-scale batch reactors were incubated with appropriate PHW and WWTS inoculum to assess their biodegradation. The SLFG generation were the maximum when 60% PHW is co-digested with 40% WWTS at 35 °C under additional hydration in a larger reactor. SLFG in this case reached as high as 130 ml/kg which is in reasonable comparison with the stoichiometric model (153 ml/kg), while inferior to the EPA model (180 ml/kg). Thermogravimetric analysis (TGA) of the digestate before and after the incubation explains the lower SLFG generation as more remaining organic fraction. These experiments set the baseline metrics for future two stage conversion, in which more favorable conditions (higher temperature and water contents) or remediation of inhibitors are pursued for near complete biodegradation.

Complete biodegradation of azo dye in an integrated microbial fuel cell-aerobic system using novel bacterial consortium

In the present work, a commercially used azo dye Remazol navy blue was completely degraded into less toxic intermediates in an integrated microbial fuel cell-aerobic system. A novel defined bacterial consortium comprising of organisms isolated from dye contaminated wastewater has been used as inoculum for this study. As compared to the traditional static incubation method, a rapid decolorization of Remazol navy blue was noticed in the anodic chamber of microbial fuel cell. In low to moderate dye concentrations (25–100 mg/L), almost complete decolorization of Remazol navy blue was achieved within 12 h of microbial fuel cell operation. The first-order kinetic constant of Remazol navy blue decolorization (k) in microbial fuel cell was found to be considerably higher than that of static incubation condition (Kstatic (0.3041) < KMFC (0.5697)). Microbial fuel cells external resistance is found to be a key parameter affecting the reductive decolorization of Remazol navy blue dye with a resistance of 1000 Ω as the optimum giving maximum efficiency. Dye degradation products from each stage of the integrated microbial fuel cell-aerobic system have been analyzed through different analytical techniques such as UV–Vis spectroscopy, Fourier transform infrared spectroscopy and gas chromatography–mass spectrometry analysis. These studies illustrate the reductive degradation of Remazol navy blue in microbial fuel cell treatment stage into different toxic intermediates which were further degraded into simpler compounds in the successive aerobic treatment stage. Phototoxicity study confirms the less toxic nature of the treated effluents as compared to the parent dye.

Strengthening calcium alginate microspheres using polysulfone and its performance evaluation: Preparation, characterization and application for enhanced biodegradation of chlorpyrifos

Bacterial cell immobilization offer considerable advantages over traditional biotreatment systems using free cells. Calcium alginate matrix usually used for bacterial immobilization is susceptible to biodegradation in harsh environment. Current study aimed to produce and characterize stable macrocapsules (MCs) of Chlorpyrifos (CP) degrading bacterial consortium using biocompatible calcium alginate matrix coupled with environmentally stable polysulfone. In current study bacterial consortium capable of CP biodegradation was immobilized using calcium alginate in a form of microcapsule (MC) reinforced by being coated with a synthetic polymer polysulfone (PSf) through phase inversion. Consortium comprised of five bacterial strains was immobilized using optimized concentration of sodium alginate (2.5gL−1), calcium chloride (6gL−1), biomass (600mgL−1) and polysulfone (10gL−1). It has been observed that MCs have high thermal, pH and chemical stability than CAMs. In synthetic media complete biodegradation of CP (100–600mgL−1) was achieved using macrocapsules (MCs) within 18h. CAMs could be reused effectively only upto 5cycles, contrary to this MCs could be used 13 times to achieve more than >96% CP degradation. Shelf life and reusability studies conducted for MCs indicated unaltered biomass retention and CP biodegradation activity (95%) over 16weeks of storage. MCs achieved complete biodegradation of CP (536mgL−1) in real industrial wastewater and reused several times effectively. Metabolites (3,5,6-trichloro-2-pyridinol (TCP), 3,5,6-trichloro-2-methoxypyridine (TMP) and diethyl-thiophosphate (DETP) were traced using GC–MS and possible metabolic pathway was constructed. Study indicated MCs could be used for cleanup of CP contaminated wastewater repeatedly, safely, efficiently for a longer period of time.

Rapid and complete degradation of diclofenac by native soil microorganisms

Abstract Diclofenac one of the widespread xenobiotics, among other organic micropollutants, is persistent accumulating in different habitats like earth, water, plants and even mammalians. Natural microbial communities in soil and water play a key role in fundamental ecological processes such as regulating the fate of pollution released in the environment. As presented in this study varying concentrations of diclofenac between 0.1 and 1.0 g/L solubilized in a low salt medium could be aerobically degraded by forest soil within less than 10 days. In the course of full degradation, a carboxylated diclofenac intermediate could be isolated and identified by LC-MS/MS-TOF. The carboxylated diclofenac might be a key intermediate to enable a complete biodegradation of diclofenac via 2,6-dichloroaniline and carboxylated 2-hydroxyphenylacetic acid by a microbial consortium.

The anaerobic biodegradation of poly(lactic) acid textiles in photosynthetic microbial fuel cells: Self-sustained bioelectricity generation

Poly(lactic) acid (PLA) is a promising material due to the complete biodegradability and environmental-friendly characteristics, but it is difficult to decompose by traditional anaerobic composting. Photosynthetic microbial fuel cells (MFC) are envisaged as a potential bioenergy harvesting techniques in recent years. In this work, the anaerobic biodegradation of PLA textiles for bioelectricity generation was explored in a dual chamber MFC devices using the hybrid anoxygenic photosynthetic bacteria (APB). The result showed that the surface of PLA textiles appeared the widespread damage by SEM micrographs observation, and the corresponding weight loss was 26.67%. The analysis of FT-IR suggested that the breakage process was a biochemical action due to the function of depolymerase. Meanwhile, a stable current density generation of 4.4 ± 0.2 mA/cm2 (500 Ω external resistor) at PLA textiles concentration of 1 g/L was obtained under the shortage of other carbon sources. However, the microbial community structure was obvious difference before and after the test. Moreover, the exploration will provide more potential information for self-sustained bioelectricity generation of MFC.

Biodegradation of Polyaromatic Hydrocarbons by Acclimatized Mixed Culture Using Shake Flask and Roller Bioreactors

The ability of acclimatized mixed culture from sewage waste sludge was tested to biodegrade (PAHs): naphthalene and phenanthrene each with a concentration of 300 mg/L. Sewage sludge was selected as an inexpensive source of mixed culture of microorganisms, usually available in large quantities in wastewater treatment plants. Two types of reactors were employed in the investigation: shake flask and roller bioreactors. Complete biodegradation of naphthalene and phenanthrene was achieved in the shake flask bioreactor after 13 and 14 days of treatment, respectively. The corresponding durations in the roller bioreactor were 11 and 12 days. The obtained results show that the said culture is capable of consuming PAHs as energy and carbon source and have a promising application in bioremediation of PAH contaminated environments. The biodegradation of naphthalene was enhanced when using the roller bioreactor compared to its biodegradation in the shake flask bioreactor. The microorganisms’ specific growth rate was raised from 0.014 to 0.022 h-1 due to the enhanced mixing in the roller bioreactor. No enhancement was observed for phenanthrene biodegradation when using the roller bioreactor: the microorganisms’ specific growth rate was equal to 0.016 h-1 for the shake flask bioreactor compared to 0.012 h-1 for the roller bioreactor. Logistic models were employed for the description of the microorganisms’ growth and the PAHs degradation in both shake flask and roller bioreactor. Additionally, second order inhibition model was used to describe the possible inhibitions. The results obtained from the models well-matched the biodegradation experimental data with R2 of more than 97%.

A process for complete biodegradation of shrimp waste by a novel marine isolate Paenibacillus sp. AD with simultaneous production of chitinase and chitin oligosaccharides

Disposal of chitinaceous waste is a major problem of seafood industry. Most of the known chitinolytic organisms have been studied with respect to pure chitin as substrate. Use of these organisms for degradation of seafood waste has not been explored much. In present study a marine bacterium capable of proficiently degrading shrimp waste with co-production of value added products like chitinase and chitin oligosaccharides was isolated from seafood waste dumping sites. On 16s rRNA and biochemical analysis bacterium was found to be a novel species of genus Paenibacillus.Under optimized condition complete shrimp waste degradation (99%) was achieved along with chitinase yield of 20.01 IUml−1. SEM and FTIR showed the structural changes and breakage of bonds typical to that of chitin, which indicated that this process can be used for the degradation of other chitinaceous material also. Thin layer chromatography revealed the presence of chitin oligosaccharides of various degree of polymerization in the hydrolysate. Complete degradation of shrimp waste by Paenibacillus sp. AD makes it a potential candidate for the bioremediation of seafood waste at large scale. Concomitant production of chitinase and chitin oligosaccharides further makes the process economical and commercially viable.

Invivo characterization of a new type of biodegradable starch microsphere for transarterial embolization.

Transarterial embolization is an established minimally invasive treatment for solid tumors. Unintended inflammation, foreign body reactions and ischemia-triggered neoangiogenesis are clinical drawbacks of permanent embolic materials. The aim of the current study was to characterize a new type of biodegradable starch microsphere with regard to angiographic and histopathological features such as patterns of acute arterial occlusion as well as induction of tissue necrosis, microsphere biodegradation, and inflammation and foreign body reactions during follow-up. Key characteristics of both biodegradable prototypes (L1 and L2; prototype groups) were as follows: microspheres are biodegradable by serum α-amylase, produced from chemically crosslinked potato starch to different extents, in a diameter range of ∼300-800 µm, differing in size distribution and featuring a microsphere deformation of ∼1%. Invivo transarterial embolization with L1 and L2, while applying clinical standard techniques, was performed and compared with clinically established permanent microspheres (Embosphere®500-700 and Embosphere®700-900; control groups). Twenty-four pig kidneys were embolized with the different embolic materials by following the study protocol, and there were no technical failures or complications. Parenchymal necrosis with interstitial calcification was observed in all kidneys independent of the type of embolic material used. Compared with the permanent embolic materials, biodegradable microspheres showed complete (L1) or partial (L2) biodegradation within one week after transarterial embolization, and induced a comparable (L1) or a lower (L2) degree of arterial wall necrosis and a lower degree of inflammation and foreign body reactions. In conclusion, the presented new type of biodegradable microsphere is promising, and could be further evaluated in terms of clinical translation.

Environmental fate of amine oxide: Using measured and predicted values to determine aquatic exposure

Amine oxide (AO) surfactants are used widely in North American household detergents resulting in >44,000mtons disposed down the drain annually. Due to AOs substantial down the drain disposal volume, wide dispersive use, and high aquatic toxicity, there is a need to evaluate ecological exposure and corresponding risk. This study refined the current knowledge regarding the fate of AO disposed down the drain through laboratory simulation studies to evaluate biodegradation in the sewer and during activated sludge wastewater treatment. A monitoring program which measured effluent AO concentrations for the dominant carbon chain lengths, C12 and C14, at 44 wastewater treatment plants (WWTP) across the continental US was also conducted. The study results were then used as input into probabilistic exposure models to predict US receiving stream concentrations. In three separate OECD 314A Sewer Water Die-Away studies AO was rapidly biodegraded with >76% mineralized by study completion and the geometric mean of the primary biodegradation rates being 0.184h−1. Two OECD 303A Activated Sludge WWTP Simulation studies showed rapid and complete biodegradation of AO with ≤0.09% of parent AO remaining in the effluent, ≤0.03% of parent AO sorbed to sludge solids, and >97% complete mineralization of AO. Monitoring at US WWPTs confirmed low levels of AO in effluents with mean C12 and C14AO concentrations of 52.8 and 20.1ng/L respectively. Based on the monitoring data, the 90th percentile concentrations of C12 and C14AO for 7Q10 low flow stream conditions were >2 orders of magnitude lower than the predicted no effect concentrations indicating negligible aquatic risk from AO in US receiving streams. This study verifies that AO is safe for the aquatic environment even at the currently high usage volumes due to rapid biodegradation during transit through the sewer and wastewater treatment.

Improved biodegradation potential of chlorobenzene by a mixed fungal-bacterial consortium

A defined consortium of Ralstonia pickettii L2 (bacterium) and Trichoderma viride LW-1 (fungus) was selected to assess its potential for the enhanced biodegradation of mono-chlorobenzene (CB). At an initial concentration of 220 mg L−1 CB, the developed consortium showed an enhanced degradation rate of 0.50 mg CB·g−1protein·h−1, while the individual Ralstonia sp. L2 and Trichoderma sp. LW-1 showed average degradation rates of 0.34 and 0.32 mg CB·g−1protein·h−1, respectively. A CO2 conversion level of up to 86.3% reflected a possible high mineralization extent of CB by the co-culture. The estimated μmax and vmax values were 0.36 h−1 and 0.41 h−1 for the consortium, which were much higher than the values obtained by each strain individually. 2-Chlorophenol (2-CP) accumulated in the growth medium of strain L2 and inhibited its growth, but it could be consumed quickly by the fungus LW-1, providing a possibility to reach complete biodegradation of CB in a short time. Real-time PCR revealed that bacterium L2 played a major role in the initial stage, and that fungus LW-1 grew well if 2-CP was generated. These results suggest that the fungal-bacterial consortium might be effectively applied for complete biodegradation of CB and have a potential environmental implication in purification of CB-contaminated environments.

Production of Xanthanases by Paenibacillus spp.: Complete Xanthan Degradation and Possible Applications.

Background: A number of microorganisms and their enzymes have been reported as xanthan depolymerizers. Paenibacillus species are well-known polysaccharide hydrolyzing bacteria. However, Paenibacillus alginolyticus and Paenibacillus sp. XD are the only species in the genus which are now known to degrade xanthan. Objectives: Complete biodegradation of the xanthan exopolysaccharide is a rarely found capability among microorganisms. The aim of this study is to survey xanthanase producing bacteria with an appropriate bioactivity for the biopolymer degradation under different environmental conditions. Materials and Methods: The bacteria were isolated based on viscosity reduction of the xanthan solution. Bacterial isolates were identified using rep-PCR (repetitive element-based genomic fingerprinting) and 16S rDNA sequencing. Xanthanases were identified using rep-PCR (repetitive element-based genomic fingerprinting) and 16S rDNA sequencing. Xanthanases were characterized by measuring their activity at different temperatures, pH values, and NaCl concentrations. Degradation of other polysaccharides and xanthan degradation products were investigated based on the screening plate method and TLC (thin-layer chromatography), respectively. Results:Six isolates from different Paenibacillus species with a complete xanthan degrading capability were isolated from Urmia Lake. Phylogenetic analysis placed these strains within the genus Paenibacillus with the closest relatives that were found to be P. nanensis, P. phyllosphaerae, P. agaridevorans, P. agarexedens, and P. taohuashanense. These isolates displayed different levels of the xanthan biodegradation activity in temperatures ranging from 15 to 55°C and pH values from 4 to 11. Xanthanolytic activity was generally prevented in presence of NaCl (> 0.1 mol.L-1). Furthermore, the isolated Paenibacillus spp. could degrade several other polysaccharides including xylan, CMC (carboxymethyl cellulose), starch, alginate, and pectin. Conclusion: Novel strains of the six different Paenibacillus species that were introduced in the present study are able to produce xanthanases with interesting characteristics. In light of the results from this study, special applications, particularly in healthcare, medicine, and the environment is hereby proposed for these enzymes.

Stability of a mixed microbial population in a biological reactor during long term atrazine degradation under carbon limiting conditions

The stability of a mixed bacterial population in a fixed bed reactor for atrazine biodegradation under carbon limiting conditions was examined. A one litre reactor was filled with volcanic scoria and operated as a sequencing batch reactor (SBR) for 66 batches over a period of 230 days. The reactor was inoculated with a mixed atrazine degrading bacterial population and given an atrazine growth medium for start-up, followed by batches of 20 mg/L atrazine in 5 mM phosphate buffer with no additional carbon. Complete (100%) atrazine biodegradation was observed in all batches. Until the 10th batch after start-up, traces of cyanuric acid were observed and 66–70% of the theoretical nitrogen available from atrazine was recovered in the form of ammonium. From the 10th batch onwards, 100% of the theoretical nitrogen available from atrazine was recovered in the form of nitrate with no trace of cyanuric acid observed. After reactor start-up the reactor contained 98% bacteria with the relative abundance of the dominant bacteria comprised of Xanthobacter (25.6%), Variovorax (23%), Ralstonia (12.2%), and Comamonas (8.1%). At the end of reactor operation, 70.8% bacteria and 29.2% archaea were found with Xanthobacter, Ralstonia and Variovorax (1.4%) in much smaller amounts, replaced mainly by Candidatus Nitrososphaera (29.2%), Phyllobacterium (5.5%) and Nitrospira (5.4%).

Aerobic co‐metabolism of 1,1,2,2‐tetrachloroethane by Rhodococcus aetherivorans TPA grown on propane: kinetic study and bioreactor configuration analysis

AbstractBACKGROUND1,1,2,2‐tetrachloroethane (TeCA) has been generally considered as non‐biodegradable under aerobic conditions, while its complete biodegradation was reported with microbial consortia growing anaerobically. This study describes TeCA aerobic co‐metabolic degradation by the propanotroph Rhodococcus aetherivorans strain TPA isolated from a TeCA‐degrading consortium.RESULTSR. aetherivorans TPA was able to grow on aliphatic hydrocarbons from propane to pentane and on gaseous n‐alkane metabolic intermediates. The Michaelis–Menten model allowed a satisfactory fit of the TPA propane utilization rates under resting cell conditions, while the TeCA degradation rates were successfully interpolated with Andrew's inhibition model. A significant propane–TeCA mutual inhibition was observed, although the results did not allow distinguishing between competitive and non‐competitive inhibition. Among different bioreactor options for the on‐site bioremediation of TeCA‐contaminated groundwater, a single suspended‐cell continuous stirred‐tank reactor (CSTR) appeared to be the optimal one.CONCLUSIONSThis study provides for the first time the kinetic and microbiological characterization of a bacterial strain capable of degrading TeCA under aerobic conditions. © 2017 Society of Chemical Industry

Biodegradation of pharmaceuticals and endocrine disruptors with oxygen, nitrate, manganese (IV), iron (III) and sulfate as electron acceptors

Biodegradation of pharmaceuticals and endocrine disrupting compounds was examined in long term batch experiments for a period of two and a half years to obtain more insight into the effects of redox conditions. A mix including lipid lowering agents (e.g. clofibric acid, gemfibrozil), analgesics (e.g. diclofenac, naproxen), beta blockers (e.g. atenolol, propranolol), X-ray contrast media (e.g. diatrizoic acid, iomeprol) as well as the antiepileptic carbamazepine and endocrine disruptors (e.g. bisphenol A, 17α-ethinylestradiol) was analyzed in batch tests in the presence of oxygen, nitrate, manganese (IV), iron (III), and sulfate. Out of the 23 selected substances, 14 showed a degradation of >50% of their initial concentrations under aerobic conditions. The beta blockers propranolol and atenolol and the analgesics pentoxifylline and naproxen showed a removal of >50% under anaerobic conditions. In particular naproxen proved to be degradable with oxygen and under most anaerobic conditions, i.e. with manganese (IV), iron (III), or sulfate. The natural estrogens estriol, estrone and 17β-estradiol showed complete biodegradation under aerobic and nitrate-reducing conditions, with a temporary increase of estrone during transformation of estriol and 17β-estradiol. Transformation of 17β-estradiol under Fe(III)-reducing conditions resulted in an increase of estriol as well. Concentrations of clofibric acid, carbamazepine, iopamidol and diatrizoic acid, known for their recalcitrance in the environment, remained unchanged.

Bioelectroventing: an electrochemical-assisted bioremediation strategy for cleaning-up atrazine-polluted soils.

SummaryThe absence of suitable terminal electron acceptors (TEA) in soil might limit the oxidative metabolism of environmental microbial populations. Bioelectroventing is a bioelectrochemical strategy that aims to enhance the biodegradation of a pollutant in the environment by overcoming the electron acceptor limitation and maximizing metabolic oxidation. Microbial electroremediating cells (MERCs) are devices that can perform such a bioelectroventing. We also report an overall profile of the 14C‐ATR metabolites and 14C mass balance in response to the different treatments. The objective of this work was to use MERC principles, under different configurations, to stimulate soil bacteria to achieve the complete biodegradation of the herbicide 14C‐atrazine (ATR) to 14 CO 2 in soils. Our study concludes that using electrodes at a positive potential [+600 mV (versus Ag/AgCl)] ATR mineralization was enhanced by 20‐fold when compared to natural attenuation in electrode‐free controls. Furthermore, ecotoxicological analysis of the soil after the bioelectroventing treatment revealed an effective clean‐up in < 20 days. The impact of electrodes on soil bioremediation suggests a promising future for this emerging environmental technology.

The current status of biodegradable stent to treat benign luminal disease

Stent implantation is a well-accepted alternative to treat benign luminal disease (BLD). Current stents are often fabricated from plastic, mental and biodegradable materials, and the latter two have wider clinical application. Self-expanding plastic and mental stents possessed many disadvantages such as stent migration, tissue hyperplasia, in-stent restenosis and are difficult to remove, which catalyzes the development of biodegradable stent (BDS). In fact, BDS are not required to be removed upon implementation and leaves no residues in tissue after complete biodegradation compared to metallic or plastic stents. In vascular system, BDS, also termed bioresorbable vascular scaffold (BVS) have also been used to treat luminal stenotic or occlusive lesions in cardiovascular system, peripheral arteries system and veins. In nonvascular system, BDS, with either bare or covered designs, was employed for the treatment of occlusion, stenosis, anastomosis, leak, fistula or perforation of digestive (esophagus, gastrointestinal, biliary, pancreatobiliary, hepatobiliary), respiratory (airway), and urinary (ureteral, urethral). However, the weak radial force, in-stent thrombosis and restenosis become main issues of BDS or BVS and restrict its further clinical application. Therefore, more intensive researches are expected on the strengthening of the radial force of BDS and development of novel drug eluting techniques on its surface to prevent thrombus or restenosis. In this review it is given an updated outline of the use of BDS to treat BLD in a minimal invasive way and explore its advantages and disadvantages for a vast range of fields ranging from cardiovascular to digestive and urinary system. Further discussion to foster the investigation and development of this approach in clinical is also provided.

A pilot-scale coupling of ozonation and biodegradation of 2,4-dichlorophenol-containing wastewater: The effect of biomass acclimation towards chlorophenol and intermediate ozonation products

The effect of pre-ozonation of a synthetic wastewater spiked with 2,4-dichlorophenol prior to a biological treatment was investigated experimentally by using a pilot-scale bioreactor. The pre-ozonated wastewater was characterized by a brown color, probably due to the formation of typical intermediate products such as quinones or their derivatives. Because also under steady conditions a brown effluent of the bioreactor was observed, accompanied with an increased chemical oxygen demand of the effluent, it was assumed that the intermediate products were not completely biodegradable. However, a decreasing sludge volume index indicated the enhanced sludge settleability. Without pre-treatment, the complete biodegradation of 2,4-dichlorophenol occurred. However, due to the presence of small particles, the effluent was not clear, even not after centrifugation. Moreover, the higher sludge volume index indicated the hampered settling of the sludge. Under both investigated circumstances, the nitrification and denitrification process was not affected.

Biodegradation of 5-chloro-2-picolinic acid by novel identified co-metabolizing degrader Achromobacter sp. f1.

Several bacteria have been isolated to degrade 4-chloronitrobenzene. Degradation of 4-chloronitrobenzene by Cupriavidus sp. D4 produces 5-chloro-2-picolinic acid as a dead-end by-product, a potential pollutant. To date, no bacterium that degrades 5-chloro-2-picolinic acid has been reported. Strain f1, isolated from a soil polluted by 4-chloronitrobenzene, was able to co-metabolize 5-chloro-2-picolinic acid in the presence of ethanol or other appropriate carbon sources. The strain was identified as Achromobacter sp. based on its physiological, biochemical characteristics, and 16S rRNA gene sequence analysis. The organism completely degraded 50, 100 and 200mgL-1 of 5-chloro-2-picolinic acid within 48, 60, and 72h, respectively. During the degradation of 5-chloro-2-picolinic acid, Cl- was released. The initial metabolic product of 5-chloro-2-picolinic acid was identified as 6-hydroxy-5-chloro-2-picolinic acid by LC-MS and NMR. Using a mixed culture of Achromobacter sp. f1 and Cupriavidus sp. D4 for degradation of 4-chloronitrobenzen, 5-chloro-2-picolinic acid did not accumulate. Results infer that Achromobacter sp. f1 can be used for complete biodegradation of 4-chloronitrobenzene in remedial applications.