| 31. |
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| 32. |
- Hatti-Kaul, Rajni, et al.
(författare)
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Release of protein from biological host.
- 2003
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Ingår i: Isolation and Purification of Proteins. - 9780824747596 - 9780824707262 ; , s. 1-27
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 33. |
- Håkansson, Kristina, et al.
(författare)
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A biosensor for the analysis of acetonitrile
- 2004
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Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 19:7, s. 721-726
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Tidskriftsartikel (refereegranskat)abstract
- A biosensor for monitoring acetonitrile was constructed. A mixed culture was taken from a degradation reactor and mounted on top of a Clark electrode. The amperometric biosensor was placed in a flow-through cell and integrated into a flow injection system. The metabolic response in terms of oxygen consumption was well correlated to the concentration of acetonitrile in standard solutions. However, when the reaction products, acetic acid and ammonia, were also present, the response was erratic, due to the additional metabolic reaction on acetate. By introducing a hydrophobic barrier it was possible to eliminate the negative influence of these charged products and thus to improve the operational selectivity of the sensor. The biosensor showed good stability for analysis during at least 6 days and future work will focus on using it for monitoring and control of degradation processes. (C) 2003 Elsevier B.V. All rights reserved.
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| 34. |
- Håkansson, Kristina, et al.
(författare)
-
Microbial degradation of acetonitrile using a suspended-carrier biofilm process
- 2002
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Ingår i: Biotechnology Letters. - 1573-6776. ; 24:4, s. 287-291
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Tidskriftsartikel (refereegranskat)abstract
- A microbial process for the destruction of acetonitrile has been developed. Suitable microorganisms were enriched from activated sludge by cultivation with a high selection pressure when acetonitrile was the sole source of carbon and nitrogen. The process is based on cultivating the microorganisms as a biofilm on plastic carriers. These are utilised in a stirred-tank reactor with continuous feeding of 40-150 mM acetonitrile and an outlet for spent medium. The observed efficiency in the conversion process was from 53-100%, depending on the organic load. To improve the capacity and reliability of the process, a two-step process was developed with two stirred-tank reactors coupled in series. With such an arrangement, conversion efficiencies from 92-100% were achieved when the organic load was 2 g acetonitrile l(-1) d(-1) in the first reactor.
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| 35. |
- Ivanov, Alexander, et al.
(författare)
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Conjugation of penicillin acylase with the reactive copolymer of N-isopropylacrylamide: a step towards thermosensitive industrial biocatalyst.
- 2003
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Ingår i: Biotechnology Progress. - : Wiley. - 1520-6033 .- 8756-7938. ; 19:4, s. 1167-1175
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Tidskriftsartikel (refereegranskat)abstract
- Conjugation of penicillin acylase (PA) to poly-N-isopropylacrylamide (polyNIPAM) was studied as a way to prepare a thermosensitive biocatalyst for industrial applications to antibiotic synthesis. Condensation of PA with the copolymer of NIPAM containing active ester groups resulted in higher coupling yields of the enzyme (37%) compared to its chemical modification and copolymerization with the monomer (9% coupling yield) at the same NIPAM:enzyme weight ratio of ca. 35. A 10-fold increase of the enzyme loading on the copolymer resulted in 24% coupling yield and increased by 4-fold the specific PA activity of the conjugate. Two molecular forms of the conjugate were found by gel filtration on Sepharose CL 4B: the lower molecular weight fraction of ca. 106 and, presumably, cross-linked protein-polymer aggregates of MW > 107. Michaelis constant for 5-nitro-3-phenylacetamidobenzoic acid hydrolysis by the PA conjugate (20 M) was found to be slightly higher than that of the free enzyme (12 M), and evaluation of Vmax testifies to the high catalytic efficiency of the conjugated enzyme. PolyNIPAM-cross-linked PA retained its capacity to synthesize cephalexin from D-phenylglycin amide and 7-aminodeacetoxycephalosporanic acid. The synthesis-hydrolysis ratios of free and polyNIPAM-cross-linked enzyme in cephalexin synthesis were 7.46 and 7.49, respectively. Thus, diffusional limitation, which is a problem in the industrial production of -lactam antibiotics, can be successfully eliminated by cross-linking penicillin acylase to a smart polymer (i.e., polyNIPAM).
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| 36. |
- Ivanov, Alexander, et al.
(författare)
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Photosensitive copolymer of N-isopropylacrylamide and methacryloyl derivative of spyrobenzopyran
- 2002
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Ingår i: Polymer. - 0032-3861. ; 43:13, s. 3819-3823
-
Tidskriftsartikel (refereegranskat)abstract
- The copolymer of N-isopropylacrylamide (NIPAM) and methacryloyl derivative of spirobenzopyran (MSBP) with a molecular weight of 21 000 g/mol and the average molar MSBP content of 1.9% was prepared by free radical polymerization. The copolymer displayed its phase transition in water in the temperature range of 30-50 degreesC. UV irradiation of its aqueous solution caused photoinduced transformation of MSBP units into their coloured merocyanine forms, while the cloud point of the irradiated copolymer shifted by ca. 10 degreesC to lower temperatures. During a long-term exposure to daylight (20 days) the copolymer gradually elapsed to its colourless spiropyran form, the process being ca. 100-times slower than that for monomeric MSBP. Due to the slow reverse isomerization of its merocyanine form and low solubility in water at room temperature the UV irradiated copolymer could be quantitatively separated from aqueous solution by centrifugation. (C) 2002 Published by Elsevier Science Ltd.
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| 37. |
- Ivanov, Alexander, et al.
(författare)
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Synthesis of boronate-contaming copolymers of N,N-dimethylacrylamide, their interaction with poly(vinyl alcohol) and rheological behaviour of the gels
- 2004
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 45:8, s. 2495-2505
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Tidskriftsartikel (refereegranskat)abstract
- Cross-linking of polyvinylalcohol (PVA) by boronate-containing copolymer of N,N-dimethylacrylamide (DMAA, 1) was studied and compared to cross-linking of PVA by borate buffers in weakly alkaline solutions. The copolymer of M-w = 19,000 g mor(-1) containing 9 mol% N-acryloyl-m-aminophenylboronic acid (NAAPBA, 2) was prepared by free radical polymerization of the monomers, exhibiting copolymerization constants r(1) = 0.84 and r(2) = 2.2. Due to multipoint interaction of the copolymer with PVA via monodiols, the intermolecular cross-linking required for seven-fold and 10-fold lower boron concentrations as compared to borate buffers of pH 8.6 and 7.5, respectively. In theological measurements, PVA-copolymer gels exhibited storage moduli (G'(max) comparable to those of PVA-borate gels prepared at 7.5-fold higher boron concentration and the same pH 8.6, what testified to the similar concentration of cross-links in the gels. Therefore, DMAA-NAAPBA copolymer is a more effective cross-linker of PVA than borate. The PVA-copolymer gel exhibited much higher relaxation time (97 s) compared to PVA-borate gels (less than or equal to20 s) indicating a longer lifetime of junction zones. The 'shape stability, of the gel is suggested to originate in the structure of junctions, containing several boronate-diol complexes, between the macromolecules of PVA and the copolymer. (C) 2004 Elsevier Ltd. All rights reserved.
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| 38. |
- Ivinova, Olga, et al.
(författare)
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Influence of complexing polyanions on the thermostability of basic protiens.
- 2003
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Ingår i: Macromolecular Bioscience. - : Wiley. - 1616-5195 .- 1616-5187. ; 3:3-4, s. 210-215
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Tidskriftsartikel (refereegranskat)abstract
- Lysozyme (Lyz), chymotrypsinogen (Cht), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were used as model proteins capable of forming water-soluble polyelectrolyte complexes with linear synthetic polyanions. The complex formation with sodium poly(methacrylate) (PMA), sodium poly(acrylate) (PAA), sodium poly(anetholsulfonate) (PAS), and potassium poly(vinylsulfate) (PVS) markedly reduced the temperature of protein denaturation, Tmax, as determined by differential scanning calorimetry (DSC). The effect of sodium poly(styrenesulfonate) (PSS) on Lyz was so drastic that the protein melting peak was not observed at all during DSC measurements. The temperature shift, most pronounced for Lyz, increased upon substitution of the polyanions according to the following series: PMA < PVS < PAA < PAS < PSS. Decomposition of the complexes by addition of either sodium chloride or poly(N-ethyl-4-vinylpyridinium) cation completely restored the initial Tmax of the protein (except for PSS and PAS). The complex formation slightly affected the enzyme activity up to temperatures close to Tmax of the polyanion-protein complex. On further heating, the activity of the complex decreased steeply, whereas the free enzyme maintained a high activity. The data obtained strongly suggest that the protein-polyelectrolyte interactions in solution, while leaving the thermostability and activity of the proteins practically unaffected over a rather wide temperature range, result in the effective denaturation of proteins once a certain critical temperature is achieved. This finding appears to be crucial for further development of immobilized enzymes in biotechnology and essential for understanding mechanisms and principles of the functioning of proteins immobilized on charged matrices in vivo.
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| 39. |
- Jantsch, Tor Gunnar, et al.
(författare)
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A simple spectrophotometric method based on pH-indications for monitoring partial and total alkalinity in anaerobic processes
- 2003
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Ingår i: Environmental Technology. - 1479-487X. ; 24:9, s. 1061-1067
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Tidskriftsartikel (refereegranskat)abstract
- Partial alkalinity, as a measure of bicarbonate concentration, and total alkalinity, as a measure of the concentration of bicarbonate and volatile fatty acids, are useful parameters for monitoring anaerobic digestion processes. This paper reports a new method based on pH-indicators and spectrophotometric measurements for the monitoring of partial and total alkalinity. The method was used in an off-line procedure for monitoring of an anaerobic process and displayed less than 5% deviation from the traditional method of measuring partial and total alkalinity, as well as being rapid and reproducible. A flow injection analysis system based on the method was used on-line for monitoring overload in a UASB reactor, which demonstrated changes in alkalinity not easily registered using traditional methods.
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| 40. |
- Jantsch, Tor Gunnar, et al.
(författare)
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An automated spectrophotometric system for monitoring buffer capacity in anaerobic digestion processes
- 2004
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Ingår i: Water Research. - : Elsevier BV. - 1879-2448 .- 0043-1354. ; 38:17, s. 3645-3650
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic digestion is a suitable method for the treatment of wastewater and organic wastes, yielding biogas as a useful by-product. A common way of preventing instability problems and avoiding acidification in anaerobic digesters is to keep the organic load to the digester far below its maximum capacity. An improved way of operating digesters would be to use monitoring and control systems for increased organic load under controlled conditions such that the digester performance is improved. The partial alkalinity, which indicates the bicarbonate concentration, has in many cases been found to be a suitable parameter to monitor. Here, an automated monitoring system for alkalinity measurements is described. It is shown to be applicable for measuring a wide range of bicarbonate concentrations. The system shows potential for monitoring anaerobic digesters as it responds to the alkalinity of digester effluent, as well as being stable over a relatively long time span with few maintenance requirements. (C) 2004 Elsevier Ltd. All rights reserved.
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