Publications (26)153.86 Total impact
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Article: Shell biofilm nitrification and gut denitrification contribute to emission of nitrous oxide by the invasive freshwater mussel Dreissena polymorpha (zebra mussel).
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ABSTRACT: Nitrification in shell biofilms and denitrification in the gut of the animal accounted for N(2)O emission by Dreissena polymorpha (Bivalvia), as shown by gas chromatography and gene expression analysis. The mussel's ammonium excretion was sufficient to sustain N(2)O production and thus potentially uncouples invertebrate N(2)O production from environmental N concentrations.Applied and environmental microbiology 04/2012; 78(12):4505-9. · 3.69 Impact Factor -
Article: Sulfur, iron-, and calcium cycling associated with naturalelectric currents running through marine sediment
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ABSTRACT: Natural electric currents running through marine sediments have recently been found to couple oxygen reduction at the surface to sulfide oxidation in deeper anoxic layers. Here we show that such spatial separation of oxidation and reduction processes causes non-conventional sulfur, iron, and calcium mobilization and reallocation. Reduced marine sediment was incubated with overlying oxic water and the vertical distribution of solutes and solids was analyzed after 45–150 days. As much as 44% of sediment oxygen consumption was driven by electric currents, and electrogenic oxidation of sulfide to sulfate with concurrent proton generation resulted in significant dissolution of iron sulfides and calcium carbonates in the anoxic layers of the sediment. Most of the mobilized iron diffused to the oxic zone where it formed oxidized iron minerals. Calcium precipitated in the oxic zone as magnesium-calcite. The electric coupling of biogeochemical processes in distant regions thus generates unique chemical conditions in marine sediments whereby key elements are mobilized and relocated, probably along with trace elements and nutrients. We suggest that such electrically coupled biogeochemistry flourishes in marine sediments after transient oxygen depletion, leaving distinct signatures of such events in the geological record.Geochimica et Cosmochimica Acta 01/2012; · 4.26 Impact Factor -
Article: Bacterial community structure of a full-scale biofilter treating pig house exhaust air.
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ABSTRACT: Biological air filters represent a promising tool for treating emissions of ammonia and odor from pig facilities. Quantitative fluorescence in situ hybridization (FISH) and 16S rRNA gene sequencing were used to investigate the bacterial community structure and diversity in a full-scale biofilter consisting of two consecutive compartments (front and back filter). The analysis revealed a highly specialized bacterial community of limited diversity, dominated by a few groups of Betaproteobacteria (especially Comamonas) and diverse Bacteroidetes. Actinobacteria, Gammaproteobacteria, and betaproteobacterial ammonia oxidizers (Nitrosomonas eutropha/Nitrosococcus mobilis-lineage) were also quantitatively important. Only a few quantitative differences existed between the two filter compartments at the group level, with a lower relative abundance of Actinobacteria and a higher relative abundance of the Cytophaga-Flavobacteria group in the back filter compared to the front filter. These results confirmed the N. eutropha/Nc. mobilis-lineage as the main ammonia oxidizers in pig house air filters and allowed first hypotheses for the key organisms involved in odor removal.Systematic and Applied Microbiology 07/2011; 34(5):344-52. · 3.37 Impact Factor -
Article: The effect of systematic medication review in elderly patients admitted to an acute ward of internal medicine.
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ABSTRACT: Elderly patients are vulnerable to medication errors and adverse drug events due to increased morbidity, polypharmacy and inappropriate interactions. The objective of this study was to investigate whether systematic medication review and counselling performed by a clinical pharmacist and clinical pharmacologist would reduce length of in-hospital stay in elderly patients admitted to an acute ward of internal medicine. A randomized, controlled study of 100 patients aged 70 years or older was conducted in an acute ward of internal medicine in Denmark. Intervention arm: a clinical pharmacist conducted systematic medication reviews after an experienced medical physician had prescribed the patients' medication. Information was collected from medical charts, interview with the patients and database registrations of drug purchase. Subsequently, medication histories were conferred with a clinical pharmacologist and advisory notes recommending medication changes were completed. Physicians were not obliged to comply with the recommendations. Control arm: medication was reviewed by usual routine in the ward. Primary end-point was length of in-hospital stay. In addition, readmissions, mortality, contact to primary healthcare and quality of life were measured at 3-month follow-up. In the intervention arm, the mean length of in-hospital stay was 239.9 hr (95% CI: 190.2-289.6) and in the control arm: 238.6 hr (95% CI: 137.6-339.6), which was neither a statistical significant nor a clinically relevant difference. Moreover, no differences were observed for any of the secondary end-points. Systematic medication review and medication counselling did not show any effect on in-hospital length of stay in elderly patients when admitted to an acute ward of internal medicine.Basic & Clinical Pharmacology & Toxicology 05/2010; 106(5):422-7. · 2.18 Impact Factor -
Article: Distribution, ecology and molecular identification of Thioploca from Danish brackish water sediments.
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ABSTRACT: The distribution of Thioploca populations was investigated in Danish fjords, brackish lakes and coastal waters. Thioploca was found in three geographically distinct populations, where biomasses reached 33.8+/-14.3 g wet weight m(-2) (mean+/-SD). Mats or lawns were not formed at the sediment surfaces and Thioploca biomasses peaked 4-7 cm into the sediment and extended down to 18 cm depth. Morphology and 16S rRNA gene sequences classified all populations as Thioploca ingrica. A sequence divergence of 1.7-2.2% indicated that T. ingrica comprise at least two genotypes. Physiological analysis showed that T. ingrica accumulate nitrate in concentrations of approximately 3 mM and that bicarbonate and acetate are used as a carbon source. The presence of oxygen promoted carbon incorporation, but T. ingrica could survive up to 3 months without an external supply of nitrate or oxygen. Thioploca ingrica populations were exclusively found close to river outlets in a bioturbated sediment with separate sulphidic spots and worm burrow walls containing nitrate and oxygen. It is hypothesized that the subsurface T. ingrica have a special advantage in this heterogeneous environment using their sheath surrounding the bacterial trichomes when navigating between electron donor and acceptor.FEMS Microbiology Ecology 03/2010; 73(1):110-20. · 3.41 Impact Factor -
Article: Electric currents couple spatially separated biogeochemical processes in marine sediment.
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ABSTRACT: Some bacteria are capable of extracellular electron transfer, thereby enabling them to use electron acceptors and donors without direct cell contact. Beyond the micrometre scale, however, no firm evidence has previously existed that spatially segregated biogeochemical processes can be coupled by electric currents in nature. Here we provide evidence that electric currents running through defaunated sediment couple oxygen consumption at the sediment surface to oxidation of hydrogen sulphide and organic carbon deep within the sediment. Altering the oxygen concentration in the sea water overlying the sediment resulted in a rapid (<1-h) change in the hydrogen sulphide concentration within the sediment more than 12 mm below the oxic zone, a change explicable by transmission of electrons but not by diffusion of molecules. Mass balances indicated that more than 40% of total oxygen consumption in the sediment was driven by electrons conducted from the anoxic zone. A distinct pH peak in the oxic zone could be explained by electrochemical oxygen reduction, but not by any conventional sets of aerobic sediment processes. We suggest that the electric current was conducted by bacterial nanowires combined with pyrite, soluble electron shuttles and outer-membrane cytochromes. Electrical communication between distant chemical and biological processes in nature adds a new dimension to our understanding of biogeochemistry and microbial ecology.Nature 02/2010; 463(7284):1071-4. · 36.28 Impact Factor -
Article: Widespread occurrence of nitrate storage and denitrification among Foraminifera and Gromiida.
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ABSTRACT: Benthic foraminifers inhabit a wide range of aquatic environments including open marine, brackish, and freshwater environments. Here we show that several different and diverse foraminiferal groups (miliolids, rotaliids, textulariids) and Gromia, another taxon also belonging to Rhizaria, accumulate and respire nitrates through denitrification. The widespread occurrence among distantly related organisms suggests an ancient origin of the trait. The diverse metabolic capacity of these organisms, which enables them to respire with oxygen and nitrate and to sustain respiratory activity even when electron acceptors are absent from the environment, may be one of the reasons for their successful colonization of diverse marine sediment environments. The contribution of eukaryotes to the removal of fixed nitrogen by respiration may equal the importance of bacterial denitrification in ocean sediments.Proceedings of the National Academy of Sciences 01/2010; 107(3):1148-53. · 9.68 Impact Factor -
Article: Distribution and rate of microbial processes in an ammonia-loaded air filter biofilm.
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ABSTRACT: The in situ activity and distribution of heterotrophic and nitrifying bacteria and their potential interactions were investigated in a full-scale, two-section, trickling filter designed for biological degradation of volatile organics and NH(3) in ventilation air from pig farms. The filter biofilm was investigated by microsensor analysis, fluorescence in situ hybridization, quantitative PCR, and batch incubation activity measurements. In situ aerobic activity showed a significant decrease through the filter, while the distribution of ammonia-oxidizing bacteria (AOB) was highly skewed toward the filter outlet. Nitrite oxidation was not detected during most of the experimental period, and the AOB activity therefore resulted in NO(2)(-), accumulation, with concentrations often exceeding 100 mM at the filter inlet. The restriction of AOB to the outlet section of the filter was explained by both competition with heterotrophic bacteria for O(2) and inhibition by the protonated form of NO(2)(-), HNO(2). Product inhibition of AOB growth could explain why this type of filter tends to emit air with a rather constant NH(3) concentration irrespective of variations in inlet concentration and airflow.Applied and environmental microbiology 05/2009; 75(11):3705-13. · 3.69 Impact Factor -
Article: Physiology and behaviour of marine Thioploca.
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ABSTRACT: Among prokaryotes, the large vacuolated marine sulphur bacteria are unique in their ability to store, transport and metabolize significant quantities of sulphur, nitrogen, phosphorus and carbon compounds. In this study, unresolved questions of metabolism, storage management and behaviour were addressed in laboratory experiments with Thioploca species collected on the continental shelf off Chile. The Thioploca cells had an aerobic metabolism with a potential oxygen uptake rate of 1760 micromol O2 per dm(3) biovolume per h, equivalent to 4.4 nmol O2 per min per mg protein. When high ambient sulphide concentrations (approximately 200 microM) were present, a sulphide uptake of 6220+/-2230 micromol H2S per dm(3) per h, (mean+/-s.e.m., n=4) was measured. This sulphide uptake rate was six times higher than the oxidation rate of elemental sulphur by oxygen or nitrate, thus indicating a rapid sulphur accumulation by Thioploca. Thioploca reduce nitrate to ammonium and we found that dinitrogen was not produced, neither through denitrification nor through anammox activity. Unexpectedly, polyphosphate storage was not detectable by microautoradiography in physiological assays or by staining and microscopy. Carbon dioxide fixation increased when nitrate and nitrite were externally available and when organic carbon was added to incubations. Sulphide addition did not increase carbon dioxide fixation, indicating that Thioploca use excess of sulphide to rapidly accumulate sulphur rather than to accelerate growth. This is interpreted as an adaptation to infrequent high sulphate reduction rates in the seabed. The physiology and behaviour of Thioploca are summarized and the adaptations to an environment, dominated by infrequent oxygen availability and periods of high sulphide abundance, are discussed.The ISME Journal 04/2009; 3(6):647-57. · 7.38 Impact Factor -
Article: Nitrous oxide emission by aquatic macrofauna.
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ABSTRACT: A large variety of aquatic animals was found to emit the potent greenhouse gas nitrous oxide when nitrate was present in the environment. The emission was ascribed to denitrification by ingested bacteria in the anoxic animal gut, and the exceptionally high N(2)O-to-N(2) production ratio suggested delayed induction of the last step of denitrification. Filter- and deposit-feeding animal species showed the highest rates of nitrous oxide emission and predators the lowest, probably reflecting the different amounts of denitrifying bacteria in the diet. We estimate that nitrous oxide emission by aquatic animals is quantitatively important in nitrate-rich aquatic environments like freshwater, coastal marine, and deep-sea ecosystems. The contribution of this source to overall nitrous oxide emission from aquatic environments might further increase because of the projected increase of nitrate availability in tropical regions and the numeric dominance of filter- and deposit-feeders in eutrophic ecosystems.Proceedings of the National Academy of Sciences 04/2009; 106(11):4296-300. · 9.68 Impact Factor -
Article: Physiology and behaviour of marine Thioploca
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ABSTRACT: Among prokaryotes, the large vacuolated marine sulphur bacteria are unique in their ability to store, transport and metabolize significant quantities of sulphur, nitrogen, phosphorus and carbon compounds. In this study, unresolved questions of metabolism, storage management and behaviour were addressed in laboratory experiments with Thioploca species collected on the continental shelf off Chile. The Thioploca cells had an aerobic metabolism with a potential oxygen uptake rate of 1760 μmol O2 per dm3 biovolume per h, equivalent to 4.4 nmol O2 per min per mg protein. When high ambient sulphide concentrations (~200 μM) were present, a sulphide uptake of 6220±2230 μmol H2S per dm3 per h, (mean±s.e.m., n=4) was measured. This sulphide uptake rate was six times higher than the oxidation rate of elemental sulphur by oxygen or nitrate, thus indicating a rapid sulphur accumulation by Thioploca. Thioploca reduce nitrate to ammonium and we found that dinitrogen was not produced, neither through denitrification nor through anammox activity. Unexpectedly, polyphosphate storage was not detectable by microautoradiography in physiological assays or by staining and microscopy. Carbon dioxide fixation increased when nitrate and nitrite were externally available and when organic carbon was added to incubations. Sulphide addition did not increase carbon dioxide fixation, indicating that Thioploca use excess of sulphide to rapidly accumulate sulphur rather than to accelerate growth. This is interpreted as an adaptation to infrequent high sulphate reduction rates in the seabed. The physiology and behaviour of Thioploca are summarized and the adaptations to an environment, dominated by infrequent oxygen availability and periods of high sulphide abundance, are discussed.Keywords: nitrate metabolism, oxygen uptake, phosphate, sulphide uptake, ThioplocaThe ISME Journal 03/2009; 3(6):647-657. · 7.38 Impact Factor -
Article: A Method for Estimating Mass-Transfer Coefficients in a Biofilter from Membrane Inlet Mass Spectrometer Data
Journal of the Air & Waste Management Association. 02/2009; 59(2):155-162. -
Article: [Treatment of community-acquired pneumonia--treatment].
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ABSTRACT: Penicillin is the drug of choice for treatment of community-acquired pneumonia (CAP) in Denmark. The primary determinant for therapeutic activity of penicillin is ''penicillin time'' (T>MIC), i.e. time with penicillin concentration above minimum inhibitory concentration. Eradication of S. pneumoniae requires T>MIC above 40-50%. The second determinant for therapeutic activity is the ratio between maximum penicillin concentration in serum and MIC (Cmax/MIC). Considering penicillin pharmacokinetics, intravenous penicillin 2 million units four times a day is recommended as empirical treatment of CAP.Ugeskrift for laeger 02/2008; 170(3):127-30. -
Article: Nitrogen transformations in stratified aquatic microbial ecosystems.
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ABSTRACT: New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a microm-mm scale. A large and ever-expanding knowledge base about nitrogen fixation, nitrification, denitrification, and dissimilatory reduction of nitrate to ammonium, and about the microorganisms performing the processes, has been produced by use of these techniques. During the last decade the discovery of anammmox bacteria and migrating, nitrate accumulating bacteria performing dissimilatory reduction of nitrate to ammonium have given new dimensions to the understanding of nitrogen cycling in nature, and the occurrence of these organisms and processes in stratified microbial communities will be described in detail.Antonie van Leeuwenhoek 12/2006; 90(4):361-75. · 2.09 Impact Factor -
Article: Evidence for complete denitrification in a benthic foraminifer.
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ABSTRACT: Benthic foraminifera are unicellular eukaryotes found abundantly in many types of marine sediments. Many species survive and possibly reproduce in anoxic habitats, but sustainable anaerobic metabolism has not been previously described. Here we demonstrate that the foraminifer Globobulimina pseudospinescens accumulates intracellular nitrate stores and that these can be respired to dinitrogen gas. The amounts of nitrate detected are estimated to be sufficient to support respiration for over a month. In a Swedish fjord sediment where G. pseudospinescens is the dominant foraminifer, the intracellular nitrate pool in this species accounted for 20% of the large, cell-bound, nitrate pool present in an oxygen-free zone. Similarly high nitrate concentrations were also detected in foraminifera Nonionella cf. stella and a Stainforthia species, the two dominant benthic taxa occurring within the oxygen minimum zone of the continental shelf off Chile. Given the high abundance of foraminifera in anoxic marine environments, these new findings suggest that foraminifera may play an important role in global nitrogen cycling and indicate that our understanding of the complexity of the marine nitrogen cycle is far from complete.Nature 10/2006; 443(7107):93-6. · 36.28 Impact Factor -
Article: Impact of bacterial NO3(-) transport on sediment biogeochemistry.
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ABSTRACT: Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3(-) reduction from denitrification to dissimilatory NO3(-) reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H2S with NO3(-) and transported S0 to the sediment surface for aerobic oxidation.Applied and Environmental Microbiology 12/2005; 71(11):7575-7. · 3.83 Impact Factor -
Article: Errors in the medication process: frequency, type, and potential clinical consequences.
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ABSTRACT: To investigate the frequency, type, and consequences of medication errors in more stages of the medication process, including discharge summaries. A cross-sectional study using three methods to detect errors in the medication process: direct observations, unannounced control visits, and chart reviews. With the exception of errors in discharge summaries all potential medication error consequences were evaluated by physicians and pharmacists. A randomly selected medical and surgical department at Aarhus University Hospital, Denmark. Eligible in-hospital patients aged 18 or over (n = 64), physicians prescribing drugs and nurses dispensing and administering drugs. Frequency, type, and potential clinical consequences of all detected errors compared with the total number of opportunities for error. We detected a total of 1065 errors in 2467 opportunities for errors (43%). In worst case scenario 20-30% of all evaluated medication errors were assessed as potential adverse drug events. In each stage the frequency of medication errors were-ordering: 167/433 (39%), transcription: 310/558 (56%), dispensing: 22/538 (4%), administration: 166/412 (41%), and finally discharge summaries: 401/526 (76%). The most common types of error throughout the medication process were: lack of drug form, unordered drug, omission of drug/dose, and lack of identity control. There is a need for quality improvement, as almost 50% of all errors in doses and prescriptions in the medication process were caused by missing actions. We assume that the number of errors could be reduced by simple changes of existing procedures or by implementing automated technologies in the medication process.International Journal for Quality in Health Care 03/2005; 17(1):15-22. · 1.96 Impact Factor -
Article: Kinetics, diffusional limitation and microscale distribution of chemistry and organisms in a CANON reactor.
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ABSTRACT: In the Completely Autotrophic Nitrogen removal Over Nitrite (CANON) process, aerobic and anaerobic ammonia oxidizing bacteria cooperate to remove ammonia in one oxygen-limited reactor. Kinetic studies, microsensor analysis, and fluorescence in situ hybridization on CANON biomass showed a partial differentiation of processes and organisms within and among aggregates. Under normal oxygen-limited conditions ( approximately 5 microM O2), aerobic ammonia oxidation (nitrification) was restricted to an outer shell (<100 microm) while anaerobic ammonia oxidation (anammox) was found in the central anoxic parts. Larger type aggregates (>500 microm) accounted for 68% of the anammox potential whereas 65% of the nitrification potential was found in the smaller aggregates (<500 microm). Analysis with O2 and NO2- microsensors showed that the thickness of the activity zones varied as a function of bulk O2 and NO2- concentrations and flow rate.FEMS Microbiology Ecology 01/2005; 51(2):247-56. · 3.41 Impact Factor -
Article: Microscale distribution of nitrification activity in sediment determined with a shielded microsensor for nitrate.
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ABSTRACT: Microprofiles of O(2) and NO(3) were measured simultaneously in freshwater sediment with microsensors which were completely free from electrical interference because of coaxial designs. Depth profiles of nitrification (NO(3) production) and denitrification (NO(3) consumption) were subsequently determined by computer simulation of the measured microprofiles. The nitrifying bacterial community responded very quickly to changes in environmental conditions, and new steady-state microprofiles of O(2) and NO(3) were usually approached within a few hours after perturbation. Nitrification started quickly after introduction of O(2) in previously anoxic layers, suggesting prolonged survival of the nitrifiers during anaerobiosis. Changes in the availability of O(2) and NH(4) greatly affected the nitrification profile, and there was a high rate of coupled nitrification-denitrification under conditions in which nitrification occurred right above the oxic-anoxic interface. Addition of C(2)H(2) rapidly removed the NO(3) peaks, indicating that NO(3) production was due mainly to autotrophic nitrification.Applied and Environmental Microbiology 11/1993; 59(10):3287-96. · 3.83 Impact Factor -
Article: Nitrification and denitrification in lake and estuarine sediments measured by the N dilution technique and isotope pairing.
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ABSTRACT: The transformation of nitrogen compounds in lake and estuarine sediments incubated in the dark was analyzed in a continuous-flowthrough system. The inflowing water contained NO(3), and by determination of the isotopic composition of the N(2), NO(3), and NH(4) pools in the outflowing water, it was possible to quantify the following reactions: total NO(3) uptake, denitrification based on NO(3) from the overlying water, nitrification, coupled nitrification-denitrification, and N mineralization. In sediment cores from both lake and estuarine environments, benthic microphytes assimilated NO(3) and NH(4) for a period of 25 to 60 h after darkening. Under steady-state conditions in the dark, denitrification of NO(3) originating from the overlying water accounted for 91 to 171 mumol m h in the lake sediments and for 131 to 182 mumol m h in the estuarine sediments, corresponding to approximately 100% of the total NO(3) uptake for both sediments. It seems that high NO(3) uptake by benthic microphytes in the initial dark period may have been misinterpreted in earlier investigations as dissimilatory reduction to ammonium. The rates of coupled nitrification-denitrification within the sediments contributed to 10% of the total denitrification at steady state in the dark, and total nitrification was only twice as high as the coupled process.Applied and Environmental Microbiology 08/1993; 59(7):2093-8. · 3.83 Impact Factor
Top co-authors
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Institutions
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1993–2012
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Aarhus University
- Department of Ecology and Genetics
Aars, Region North Jutland, Denmark
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2009–2011
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Aalborg University
- Department of Biotechnology, Chemistry and Environmental Engineering
Aalborg, Region North Jutland, Denmark
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