| 1. |
- Akerberg, C, et al.
(författare)
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A kinetic model for enzymatic wheat starch saccharification
- 2000
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Ingår i: Journal of Chemical Technology and Biotechnology. - 0268-2575. ; 75:4, s. 306-314
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Tidskriftsartikel (refereegranskat)abstract
- A kinetic model describing the enzymatic saccharification of wheat starch by a mixture of ol-amylase and amyloglucosidase has been developed. The model describes the influence of pH, glucose inhibition and starch and enzyme concentration, The results of experimental saccharification under different physical conditions, eg pH and temperature, were used to determine the parameters in the model. The dominant enzyme in the mixture was amyloglucosidase and the maximum rate of saccharification due to this enzyme was found to be optimal at pH 5, and increased Five-Fold when the temperature was increased from 30 to 55 degrees C, Saccharification due to the action of amyloglucosidase was inhibited by the glucose produced and simulation showed that the maximum rate of saccharification decreased by 58% at a starch concentration of 140gdm(-3) compared with a starch concentration much less than 110 gdm(-3) where the effect of glucose inhibition was negligible, (C) 2000 society of Chemical Industry.
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| 2. |
- Akerberg, C, et al.
(författare)
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An economic evaluation of the fermentative production of lactic acid from wheat flour
- 2000
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Ingår i: Bioresource Technology. - 1873-2976. ; 75:2, s. 119-126
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Tidskriftsartikel (refereegranskat)abstract
- A process for the fermentative production of lactic acid from whole-wheat flour consisting of starch and bran containing nutrients is presented and an economical evaluation of the lactic acid production cost performed. Bottlenecks were identified and alternative processes were evaluated and compared. The costs of raw material, the sodium hydroxide in the fermentation step, and the conversion of lactate to lactic acid using electrodialysis were found to contribute considerably to the total production cost. Performing the fermentation step as a batchwise step was economically better than continuous fermentation. The lactic acid production cost can be reduced by lowering the pH and/or by recycling the sodium hydroxide produced by electrodialysis to the fermentor. Using higher wheat flour concentrations reduced the lactic acid production cost and numerical optimisation of the process, with respect to the wheat flour concentration, showed that the optimal concentration corresponded to 116 g glucose/l, which resulted in a production cost of 0.833 US$/kg product. A Monte Carlo simulation of the total production cost for this concentration when the investment and operational cost and the price of the raw material were varied showed that the probability that the production cost could be lower than 0.90 or 1.0 US$/kg was 61% or 91%, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Augustin, Ingo, et al.
(författare)
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HEP Applications Evaluation of the EDG Testbed and Middleware
- 2003
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Konferensbidrag (refereegranskat)abstract
- Workpackage 8 of the European Datagrid project was formed in January 2001 with representatives from the four LHC experiments, and with experiment independent people from five of the six main EDG partners. In September 2002 WP8 was strengthened by the addition of effort from BaBar and D0. The original mandate of WP8 was, following the definition of short- and long-term requirements, to port experiment software to the EDG middleware and testbed environment. A major additional activity has been testing the basic functionality and performance of this environment. This paper reviews experiences and evaluations in the areas of job submission, data management, mass storage handling, information systems and monitoring. It also comments on the problems of remote debugging, the portability of code, and scaling problems with increasing numbers of jobs, sites and nodes. Reference is made to the pioneeering work of Atlas and CMS in integrating the use of the EDG Testbed into their data challenges. A forward look is made to essential software developments within EDG and to the necessary cooperation between EDG and LCG for the LCG prototype due in mid 2003.
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| 4. |
- Mattisson, C, et al.
(författare)
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Diffusion of lysozyme in gels and liquids - A general approach for the determination of diffusion coefficients using holographic laser interferometry
- 2000
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Ingår i: Journal of Chromatography. B. - 1387-2273. ; 743:1-2, s. 151-167
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Tidskriftsartikel (refereegranskat)abstract
- A study on diffusion measurements of the protein lysozyme in liquids and agarose gels, at different pH and ionic strengths, has been performed using holographic laser interferometry. The measurements showed that the diffusive flux was very dependent on pH and ionic strength when the protein was not at its isoelectric point or when the charge of the lysozyme molecules was not screened by ions in the solution. Evaluation of the experimental data with Fick's law, resulted in diffusion coefficients for lysozyme that are strongly dependent on pH and ionic strength. Evaluation of the experimental data using a more general transport model, based on chemical potential gradients instead of concentration gradients resulted in lysozyme diffusion coefficients that are independent of pH and ionic strength. The chemical potential was estimated by using the Poisson-Boltzmann equation. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 5. |
- Mattisson, C, et al.
(författare)
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Light deflection and convection in diffusion experiments using holographic interferometry
- 2001
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 34:20, s. 3088-3096
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Tidskriftsartikel (refereegranskat)abstract
- A study of the effect of light deflection during diffusion studies of ethanol into agarose gel using holographic laser interferometry is presented. Furthermore it also demonstrates how a diffusive flux could give rise to a convective flux in holographic laser interferometry experiments. The convective and diffusive mass transfer is also theoretically compared in both a liquid phase and a gel phase for the ethanol-agarose system used. The current study shows that errors due to light deflection in holographic laser interferometry are extremely small and can be neglected. It also shows the importance of designing the diffusion experiments to avoid natural convection. In gels the convective flow is cancelled by the friction forces between the liquid and the polymer network. However, in the liquid phase the natural convection could occur even though the density differences in the phase are small.
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| 6. |
- Roger, P, et al.
(författare)
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Use of holographic laser interferometry to study the diffusion of polymers in gels
- 2000
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Ingår i: Biotechnology and Bioengineering. - 1097-0290. ; 69:6, s. 654-663
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to demonstrate the potential for holographic interferometry to be used for diffusion studies of large molecules in gels. The diffusion and partitioning of BSA (67,000 g/mol) and pullulans (5,900-112,000 g/mol) in agarose gel were investigated. The gel diffusion coefficients obtained for BSA were higher when distilled water was used as a solvent compared to those obtained with 0.1 M NaCl as the solvent. Furthermore, the gel diffusion coefficient increased with increasing BSA concentration. The same trend was found for liquid BSA diffusion coefficients obtained by DLS. BSA partition coefficients obtained at different agarose gel concentrations (2-6%, w/w) decreased slightly with increasing gel concentration. However, all BSA gel diffusion coefficients measured were significantly lower than those in pure solvent and they decreased with increasing agarose concentration. The gel diffusion coefficients obtained for pullulans decreased with increasing pullulan molecular weight. The same effect from increased molecular weight was seen in the liquid diffusion coefficients measured by DLS. The pullulan partition coefficients obtained decreased with increasing molecular weight. However, pullulans with a larger Stokes' radius than BSA had partition coefficients that were higher or approximately the same as BSA. This implied that the pullulan molecules were more flexible than the BSA molecules. The results obtained for BSA in this study agreed well with other experimental studies. In addition, the magnitude of the relative standard deviation was acceptable and in the same range as for many other methods. The results thereby obtained showed that holographic interferometry is a suitable method for studying diffusion of macromolecules in gels. (C) 2000 John Wiley & Sons, Inc.
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| 7. |
- Tengborg, C, et al.
(författare)
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Influence of enzyme loading and physical parameters on the enzymatic hydrolysis of steam-pretreated softwood
- 2001
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Ingår i: Biotechnology Progress. - : American Chemical Society (ACS). - 1520-6033 .- 8756-7938. ; 17:1, s. 110-117
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Tidskriftsartikel (refereegranskat)abstract
- Softwood is an interesting raw material for the production of fuel ethanol as a result of its high content of hexoses, and it has attracted attention especially in the Northern hemisphere. However, the enzymatic hydrolysis of softwood is not sufficiently efficient for the complete conversion of cellulose to glucose. Since an improvement in the glucose yield is of great importance for the overall economy of the process, the influence of various parameters on the cellulose conversion of steam-pretreated spruce has been investigated. The addition of beta -glucosidase up to 50 IU g(-1) cellulose to the enzymatic hydrolysis process resulted in increased cellulose conversion at a cellulase loading up to 48 FPU g(-1) cellulose. Despite very high enzyme loading (120 FPU g(-1) cellulose) only about 50% of the cellulose in steam-pretreated spruce was converted to glucose when all of the material following pretreatment was used in the hydrolysis step. The influence of temperature, residence time, and pH were investigated for washed pretreated spruce at a dry matter (DM) content of 5% and a cellulase activity of 18.5 FPU g(-1) cellulose. The optimal temperature was found to be dependent on both residence time and pH, and the maximum degree of cellulose conversion, 69.2%, was obtained at 38 degreesC and pH 4.9 for a residence time of 144 h. However, when the substrate concentration was changed from 5% to 2% DM, the cellulose conversion increased to 79.7%. An increase from 5% to 10% DM resulted, however, in a similar degree of cellulose conversion, despite a significant increase in the glucose concentration from 23 g L-1 to 45 g L-1. The deactivation of beta -glucosidase increased with increasing residence time and was more pronounced with vigorous agitation.
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| 8. |
- Tengborg, C, et al.
(författare)
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Reduced inhibition of enzymatic hydrolysis of steam-pretreated softwood
- 2001
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Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 28:9-10, s. 835-844
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Tidskriftsartikel (refereegranskat)abstract
- Softwood constitutes the main source of lignocellulosic material in Sweden which can be used for ethanol production from renewable resources. To make the biomass-to-ethanol process more economically feasible, it is preferable to include the sugar-rich prehydrolysate, i.e. the liquid obtained after the pretreatment step, in the enzymatic hydrolysis of the solid fraction. This study shows that the prehydrolysate inhibits cellulose conversion in the enzymatic hydrolysis step. When the prehydrolysate was included in the enzymatic hydrolysis, the cellulose conversion was reduced by up to 36%. However, this inhibition can be overcome by fermentation of the prehydrolysate prior to enzymatic hydrolysis. (C) 2001 Elsevier Science Inc. All rights reserved.
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