| 1. |
- Borde, X, et al.
(författare)
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Synergistic relationships in algal-bacterial microcosms for the treatment of aromatic pollutants.
- 2003
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Ingår i: Bioresource Technology. - 1873-2976. ; 86:3, s. 293-300
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Tidskriftsartikel (refereegranskat)abstract
- The potential of algal–bacterial microcosms was studied for the biodegradation of salicylate, phenol and phenanthrene. The isolation and characterization of aerobic bacterial strains capable of mineralizing each pollutant were first conducted. Ralstonia basilensis was isolated for salicylate degradation, Acinetobacter haemolyticus for phenol and Pseudomonas migulae and Sphingomonas yanoikuyae for phenanthrene. The green alga Chlorella sorokiniana was then cultivated in the presence of the pollutants at different concentrations, showing increasing inhibitory effects in the following order: salicylate85%) was recorded only in the systems inoculated with both algae and bacteria and incubated under continuous lighting. This study presents, to our knowledge, the first reported case of photosynthesis-enhanced biodegradation of toxic aromatic pollutants by algal–bacterial microcosms in a one-stage treatment.
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| 2. |
- Guieysse, Benoit, et al.
(författare)
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Combined UV-biological degradation of PAHs
- 2004
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Ingår i: Chemosphere. - : Elsevier BV. - 1879-1298 .- 0045-6535. ; 55:11, s. 1493-1499
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Tidskriftsartikel (refereegranskat)abstract
- The UV-photolysis of PAHs was tested in silicone oil and tetradecane. In most cases, the degradation of a pollutant provided within a mixture was lower than when provided alone due to competitive effects. With the exception of anthracene, the larger pollutants (4- and 5-rings) were always degraded first, proving that UV-treatment preferentially acts on large PAHs and thereby provides a good complement to microbial degradation. UV-photolysis was also found to be suitable for treatment of soil extract from contaminated soils. The feasibility of UV-biological treatment was demonstrated for the removal of a mixture of phenanthrene and pyrene in silicone oil. UV-irradiation of the silicone oil led to 83% pyrene removal but no phenanthrene photodegradation. Subsequent treatment of the oil in a two-phases partitioning bioreactor (TPPB) system inoculated with Pseudomonas sp. was followed by complete phenanthrene biodegradation but no further pyrene removal. Totally, the combined process allowed 92% removal of the PAH mixture. Further work should focus on characterizing the photoproducts formed and studying the influence of the solvent on the photodegradation process.
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| 3. |
- Guieysse, Benoit, et al.
(författare)
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Influence of the initial composition of algal-bacterial microcosms on the degradation of salicylate in a fed-batch culture
- 2002
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Ingår i: Biotechnology Letters. - 1573-6776. ; 24:7, s. 531-538
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the initial composition of an algal-bacterial microcosm constituted of Chlorella sorokiniana and Ralstonia basilensis was tested for the fed-batch degradation of salicylate at 5 mM. Salicylate degradation was always limited by the O-2 generation rate, which was initially proportional to the algal density, but rapidly became limited by the availability of light once the algae started to grow. The decrease of the salicylate removal rate observed at high algal densities was likely caused by mutual shading within the algal population and the increase of O-2 consumption due to algal dark respiration. With repeated salicylate amendments, all systems converged towards the same characteristics, reaching an optimum rate of salicylate degradation at 1 mmol l(-1) day.
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| 4. |
- Guieysse, Benoit
(författare)
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Innovative Bioreactors for the Degradation of Polycyclic Aromatic Hydrocarbons
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of biological reactors for the treatment of toxic and recalcitrant organic pollutants is a complex task. Firstly, microbial inoculation, acclimation and selection must be optimized to provide the best microflora possible. Secondly, innovative technologies must be developed to overcome the intrinsic low degradation rates of hardly-degradable pollutants in order to allow short treatment times. Finally, since the pollutants involved are often toxic, it is also important to use well-managed treatment system that limit potential process hazards. Efficient inoculum was provided by using a mixture of indigenous soil microflora, most likely containing contaminant-degrading species, and activated sludge sample to provide microbial diversity as a protection against metabolite accumulation and substrate inhibition effects. Both fed-batch and continuous cultivations were suitable for microbial selection. Since the selection of degrading species depends on the origin of the inoculum and the procedure and system used, inoculation, acclimation and selection should be performed each time the treatment of a new effluent or the performance of a new process is studied. Both Suspended-Carrier and Packed-Bed reactors allowed the fast treatment of diluted contaminated effluent. The packed-bed reactor was preferred since it favored the development of very diverse microflora and was based on the use of a cheaper carrier. Special care should be taken in controlling pollutant adsorption to the carriers. Biphasic reactors were found to be suitable for the treatment of concentrated mixtures of contaminants such as soil extracts. Besides reducing the aqueous toxicity of the contaminants, the use of an organic phase in biphasic reactor advantageously permitted to avoid pollutant volatilization and adsorption. However, their large-scale application remains dependent on several improvements. The potential of algae photosynthesis to produce oxygen in-situ in the reactor, which limits the risk for pollutant volatilization, was clearly demonstrated. Emphasis should be given on optimizing photosynthesis efficiency, which depends on the light intensity and the algal population size, rather that the degradation of the pollutants. Since recording pollutant disappearance does not inform about the mechanism of removal and the pollutants involved are toxic, it is very important to monitor microbial activity during the entire process. The rate of disappearance of the electron acceptor used by the microflora could often be well correlated with the microbial activity and the pollutant biodegradation rate. This could lead to the development of biosensors and monitoring strategies suitable for the biological treatment of toxic and recalcitrant pollutants. Finally, although it was often difficult to avoid abiotic removal mechanisms and to monitor microbial degradation, it was still possible to evaluate and control these phenomena in most of the systems described in this thesis work. This clearly demonstrates a very important advantage of ex-situ remediation processes compared to in-situ processes.
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| 5. |
- Munoz, Raul, et al.
(författare)
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Phenenthrene biodegradation by an algal-bacterial consortium in two-phase partitioning bioreactors.
- 2003
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 61:3, s. 261-267
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Tidskriftsartikel (refereegranskat)abstract
- An algal-bacterial consortium formed by Chlorella sorokiniana and a phenanthrene-degrading Pseudomonas migulae strain was able to biodegrade 200-500 mg/l of phenanthrene dissolved in silicone oil or tetradecane under photosynthetic conditions and without any external supply of oxygen. Phenanthrene was only removed when provided in organic solvent, which confirms the potential of two-phase systems for toxicity reduction. Phenanthrene was degraded at highest rates when provided in silicone oil rather than in tetradecane since this solvent probably sequestered the PAH, reducing its mass transfer to the aqueous phase. The influence of phenanthrene concentration, amount of inoculum and light intensity on pollutant removal was also investigated and, under the best conditions, phenanthrene was degraded at 24.2 g mm3·hm1. In addition to being cost-effective and mitigating the release of greenhouse gases into the atmosphere, photosynthetic oxygenation was especially beneficial to the use of two-phase partitioning bioreactors since it prevented solvent emulsification and/or volatilization and evidence was found that the microalgae release biosurfactants that could further enhance phenanthrene degradation.
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| 6. |
- Munoz, Raul, et al.
(författare)
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Photosynthetically oxygenated salicylate biodegradation in a continuous stirred tank photobioreactor
- 2004
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 87:6, s. 797-803
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Tidskriftsartikel (refereegranskat)abstract
- A consortium consisting of a Chlorella sorokiniana strain and a Ralstonia basilensis strain was able to carry out sodium salicylate biodegradation in a continuous stirred tank reactor (CSTR) using exclusively photosynthetic oxygenation. Salicylate biodegradation depended on algal activity, which itself was a function of microalgal concentration, light intensity, and temperature. Biomass recirculation improved the photobioreactor performance by up to 44% but the results showed the existence of an optimal biomass concentration above which dark respiration started to occur and the process efficiency started to decline. The salicylate removal efficiency increased by a factor of 3 when illumination was increased from 50 - 300 muE/M-2 (.)s. In addition, the removal rate of sodium salicylate was shown to be temperature-dependent, increasing from 14 to 27 mg/l(.)h when the temperature was raised from 26.5 to 31.5degreesC. Under optimized conditions (300 muE/m(2) (.)s, 30degreesC, 1 g sodium salicylate/l in the feed and biomass recirculation) sodium salicylate was removed at a maximum constant rate of 87 mg/l.h, corresponding to an estimated oxygenation capacity of 77 mg O-2/l(.)h (based on a BOD value of 0.88 g O-2/g sodium salicylate for the tested bacterium), which is in the range of the oxygen transfer capacity of large-scale mechanical surface aerators. Thus, although higher degradation rates were attained in the control reactor, the photobioreactor is a cost-efficient process which reduces the cost of aeration and prevents volatilization problems associated with the degradation of toxic volatile organic compounds under aerobic conditions. (C) 2004 Wiley Periodicals, Inc.
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| 7. |
- Munoz, Raul, et al.
(författare)
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Salicylate biodegradation by various algal-bacterial consortia under photosynthetic oxygenation.
- 2003
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Ingår i: Biotechnology Letters. - 1573-6776. ; 25:22, s. 1905-1911
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Tidskriftsartikel (refereegranskat)abstract
- Four green microalgae (Chlorella sorokiniana, Chlorella vulgaris, Scenedesmus obliquus and Selenastrum capricornutum), a wild Bolivian microalga strain and two cyanobacteria (Anabaena catenula and Microcystis aeruginosa) were compared for tolerance to salicylate, O2 production capacity and ability to support salicylate degradation by a Ralstonia basilensis strain in symbiotic microcosms with the microalgae. Microcystis aeruginosa had the highest tolerance to salicylate at 500 mg l-1 and 1500 mg l-1 but only produced 0.7 mg O2 l-1 h-1 in the absence of pollutant. Chlorella sorokiniana resisted salicylate at 1500 mg l-1 with the highest O2 production in the absence of salicylate (26 mg l-1 h-1) closely followed by the Bolivian microalga (23 mg l-1 h-1) and Chlorella vulgaris (21 mg l-1 h-1). Selenastrum capricornutum and Anabaena catenula were completely inhibited by salicylate at 500 mg l-1. When inoculated with Ralstonia sp. and supplied with salicylate, Chlorella sorokiniana had the highest removal rate (19 mg l-1 h-1), followed by the wild Bolivian strain (18 mg l-1 h-1) and Chlorella vulgaris (14 mg l-1 h-1).
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| 8. |
- Soares, Ana, et al.
(författare)
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Aerobic biodegradation of nonylphenol by cold-adapted soil bacteria.
- 2003
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Ingår i: Biotechnology Letters. - 1573-6776. ; 25:9, s. 731-738
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Tidskriftsartikel (refereegranskat)abstract
- Three strains capable of mineralizing nonylphenol as sole carbon source were isolated from a sample of contaminated soil and characterized as two Pseudomonas spp. and a Stenotrophomonas sp. The two Pseudomonas spp. expressed characteristics typical of psychrophiles growing optimally of 10 °C and capable of growing at 0 °C. The Stenotrophomonas sp. was more likely psychrotrophic because it had an optimal temperature between 14 and 22 °C although it was not capable of growing at 4 °C. At 14 °C, one of the Pseudomonas spp. exhibited the highest rate of degradation of nonylphenol (4.4 mg l-1 d-1), when compared with axenic or mixed cultures of the isolates. This study represents, to the best of our knowledge, the first reported case of cold-adapted microorganisms capable of mineralizing nonylphenol.
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| 9. |
- Soares, Ana, et al.
(författare)
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Biodegradation of nonylphenol in a continuous packed-bed bioreactor.
- 2003
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Ingår i: Biotechnology Letters. - 1573-6776. ; 25:12, s. 927-933
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Tidskriftsartikel (refereegranskat)abstract
- A packed bed bioreactor, with 170 ml glass bead carriers and 130 ml medium, was tested for the removal of the endocrine disrupter, nonylphenol, with a Sphingomonas sp. The bioreactor was first continuously fed with medium saturated with nonylphenol in an attempt to simulate groundwater pollution. At best, nonylphenol was degraded by 99.5% at a feeding rate of 69 ml h-1 and a removal rate of 4.3 mg nonylphenol day-1, resulting in a 7.5-fold decrease in effluent toxicity according to the Microtox. The bioreactor was then fed with soil leachates at 69 ml h-1 from artificially contaminated soil (1 g nonylphenol kg-1 soil) and a real contaminated soil (0.19 g nonylphenol kg-1 soil). Nonylphenol was always completely removed from the leachates of the two soils. It was removed by 99% from the artificial soil but only 62% from real contaminated soil after 18 and 20 d of treatment, respectively, showing limitation due to nonylphenol adsorption.
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