| 91. |
- Schuur, JHB, et al.
(författare)
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Separation of coal-tar constituents from soil particles in a two-liquid-phase slurry system
- 2003
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Ingår i: Environmental Technology. - 1479-487X. ; 24:6, s. 755-765
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Tidskriftsartikel (refereegranskat)abstract
- An evaluation has been made of the capability of rapeseed oil to dissolve polycyclic aromatic hydrocarbon (PAH) crystals in a biphasic system and of its capability to extract PAHs from polluted soil in a two-liquid-phase (TLP) slurry system. Up to 220 g l(-1) of the crystalline hydrocarbons could be dissolved in the organic phase, indicating oil/water-partitioning coefficients of 10(5). When soil from a former gasworks site was treated in a TLP slurry system, it was found that a certain critical amount of vegetable oil had to be added in order to form a free oil phase. Single and multiple extractions gave similar results for multiple short-term and single long-term treatments, with a maximum of 87% for pyrene release. Following a 30-day bioslurry treatment, the total concentration of the 16 EPA PAHs in the soil decreased from 2740 mg kg(-1) to 1366 mg kg(-1). This was followed by one of three different 12-day post-bioslurry treatments. Further bioslurry treatment reduced the final concentration to 1002 mg kg(-1). Abiotic treatment with a surfactant (Brij 30) achieved a reduction to 797 mg kg(-1). Treatment with rapeseed oil gave the best reduction to 343 mg kg(-1).
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| 92. |
- Senthuran, A, et al.
(författare)
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Lactate production in an integrated process configuration: reducing cell adsorption by shielding of adsorbent
- 2004
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 65:6, s. 658-663
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Tidskriftsartikel (refereegranskat)abstract
- The problem of binding of microbial cells to an adsorbent matrix during in situ recovery of bioproducts from a fermentation broth has been addressed by shielding the adsorbent with a thin layer of a non-ionic polymer. Extractive bioconversion of lactic acid by integrating ion-exchange adsorption with the fermentation stage was studied. The effect of coating of the ion-exchanger with agarose on product recovery and cell adsorption was evaluated. Extractive fermentation with both uncoated and coated resin resulted in an increase in reactor productivity as compared to the normal fermentation. The free cell density in the system with agarose-coated beads was similar to that in control fermentation, but was significantly lower in the system with the uncoated ion-exchanger. Electron microscopic scanning of the bead surface after passage of the fermentation broth showed cells attached to the native adsorbent but not to the coated one.
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| 93. |
- Shiomori, Koichiro, et al.
(författare)
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Thermoresponsive properties of sugar sensitive copolymer of N-isopropylacrylamide and 3-(acrylamido)phenylboronic acid
- 2004
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1521-3935 .- 1022-1352. ; 205:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- The copolymer of N-isopropylacrylamide and 3-(acrylamido)phenylboronic acid (82:18, (M) over bar (n)=47000 g. mol(-1)) was prepared by free radical polymerization. The copolymer showed typical thermal precipitation behavior in aqueous solutions, its precipitation temperature (T-P) being increased from 23 to 32degreesC by increasing the pH from 6.5 to 9.7, because of ionization of the phenylboronate units. The pK(a) was evaluated as 8.9+/-0.1 from the effect of pH on T-P. At pH>9, i.e., in the anionic form of the copolymer, T-P was affected by a very low concentration of glucose (5.6 muM, DeltaT(P)=1-1.5degreesC), because of complex formation with a high binding constant. At a higher concentration of polyols (560 muM, pH>8) the increase of T-P was maximal for the copolymer complexes with fructose (7-10degreesC) and decreased in the order: fructose>glucoseapproximate tomannitol>pentaerythritol>galactose>Tris>glycerol. Di- and oligosaccharides (lactose, sucrose, and dextran) caused a slight increase of T-P at pH 7.5-8.7 while no effect was observed at pH>9. Isothermal dissolution of the copolymer suspension in water (27degreesC, pH 8.5) was possible in the. presence of fructose or mannitol but required higher concentrations (1.4-3.6 x 10(3) muM) as compared to those which enabled the shift of T-P in the soluble copolymer. The dissolution rate increased with fructose concentrations.
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| 94. |
- 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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| 95. |
- 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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| 96. |
- Styriakova, I, et al.
(författare)
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Bacterial destruction of mica during bioleaching of kaolin and quartz sand by Bacillus cereus
- 2003
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Ingår i: World Journal of Microbiology & Biotechnology. - 0959-3993. ; 19:6, s. 583-590
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Tidskriftsartikel (refereegranskat)abstract
- Growth and metabolic activities of Bacillus cereus were found to cause the extraction of iron atoms from the octahedral position in mica in the kaolin sample (49%) and in the quartz sands sample (17%) after 3 months of bioleaching, while aluminium removal was only 5%. Mica destruction was detected in kaolin and quartz sands samples by X-ray diffraction analysis and also by i.r. adsorption spectroscopy in quartz sands samples. The structural changes obtained were confirmed by scanning electron microscopy (SEM) analysis. The SEM pictures show a different morphology in the boundary region of mica grains before and after bioleaching. Bacterial destruction effects were feeble in the interlayer sites and were specially directed to split planes, which are occupied by a number of bacterial cells. The biological destruction of mica with phengite composition after iron removal led to development of illite, which was detected by energy-dispersion microanalysis (EDS). Illite development caused also the enrichment of the kaolin sample by fine-grained fraction.
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| 97. |
- Svensson, Mattias, et al.
(författare)
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Startup of an anaerobic single stage digester with a fixed wheat straw bed
- 2001
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Ingår i: 9th World Congress, Anaerobic Digestion 2001, Anaerobic Conversion for Sustainability, Proceedings. - 9076019169 ; , s. 549-551
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The most common form of technology for energy utilization via anaerobic treatment is slurry digestion with a low solids contents, such as sewage sludge or manure. Process control and maintenance are relatively simple, but costs involved with liquid handling and heating favour large, centralised plants. Raising the solids content of a digester to 30% significantly improves the economy of anaerobic digestion, increasing the methane production per volume unit reactor, and avoiding the handling and heating of large volumes of process water. One simple and potentially cheap method of high-solids reactor implementation is a single stage fixed bed reactor, with a solid substrate as the bed and a recycled leachate stream One potential problem with this design is an initial organic acid production during reactor startup, which originates from the easily degradable substrate. A low initial loading rate gives a safer but prolonged startup, and decreases gas production in this period. The choice of substrate strongly influences the probability of clogging. A more careful choice of carrier material allows quicker startup, and reduces the risk of clogging. The material should degrade slowly, to avoid overload during startup, and have a rigid structure in order to avoid clogging. This bed can then be fed from the top with more easily degradable substrate, e.g. crop residue. In this study, we demonstrate startup of a single stage wheat straw (low biodegradability) reactor in a fixed bed.
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| 98. |
- Svensson, Mattias, et al.
(författare)
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The effect of packing density on the startup and operation of an anaerobic single stage fixed wheat straw bed digester
- 2002
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Ingår i: Proceedings of 3rd International Symposium for Anaerobic Digestion of Solid Wastes. ; , s. 14-14
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In Southern Sweden, production of renewable energy from crop residues digestion is viewed as a worthwhile alternative. Also, the process gives valuable mineralised nitrogen as a by-product, which when produced at farm-scale can be recycled for ecological farming. It is difficult to achieve economic utilisation of crop residues in centralised slurry digestion, mainly because of the greater transport costs. Traditional reactor designs have a too low cost efficiency on farm-scale level, and therefore it is essential to introduce technologies and practices leading to economically viable reactor systems on this scale. One very simple reactor design being considered is the vertical column fixed bed digester. This allows relatively high loading rates, combined with a low maintenance requirement. Plant material can be used as a biofilm carrier, and is an inexpensive and highly efficient alternative to traditional support materials, and wheat straw, with its rigid structure and low biodegradability, is a good candidate. In this study, the influence of packing density on startup and single stage semi-batch operation of vertical column fixed bed digesters was examined in one laboratory-scale and three pilot-scale systems.
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| 99. |
|
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| 100. |
- Vargas Calle, Virginia, et al.
(författare)
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Lipase-producing microorganisms from a Kenyan alkaline soda lake
- 2004
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Ingår i: Biotechnology Letters. - 1573-6776. ; 26:2, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- Lipolytic enzyme production of 150 isolated strains from samples of Lake Bogoria (Kenya) was examined. Among these, fifteen isolates were selected on the basis of their lipolytic activities and subjected to morphological and 16S rRNA gene sequencing analyses for their identification. All the microorganisms have been selected under culture conditions with pH ranges between 7-10 and temperatures of 37-55degreesC. Most of them showed optimal growth at 37degreesC and tolerated salinity up to 10% (w/v). Ten of the isolates were Gram-negative, nine of which were closely related to the Pseudomonas cluster and one to the Halomonas cluster sharing high similarity profile with Halomonas desiderata. The remaining Gram-positive isolates were closely related to the Bacillus cluster, and were grouped with Bacillus halodurans, Bacillus alcalophilus and Bacillus licheniformis. Four members of the Bacillus cluster and the Halomonas sp. produced lipolytic activity under alkaline conditions, while others did so at neutral pH values.
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