| 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. |
- Alkasrawi, Malek, et al.
(författare)
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Recirculation of process streams in fuel ethanol production from softwood based on simultaneous saccharification and fermentation
- 2002
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Ingår i: Applied Biochemistry and Biotechnology. - 0273-2289 .- 1559-0291. ; 98, s. 849-861
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Konferensbidrag (refereegranskat)abstract
- The effect of process stream recirculation on ethanol production from steam- pretreated softwood based on simultaneous saccharification and fermentation (SSF) was investigated for two process configurations. In the first configuration, a part of the stillage stream after distillation was recycled and, in the second configuration, the liquid after SSF was recycled. The aim was to minimize the energy consumption in the distillation of the fermentation broth and in the evaporation of the stillage, as well as the use of fresh water. However, recirculation leads to an increased concentration of nonvolatiles in the first configuration, and of both volatiles and nonvolatiles in the second configuration. These substances might be inhibitory to the enzymes and the yeast in SSF. When 60% of the fresh water was replaced by stillage, the ethanol yield and the productivity were the same as for the configuration without recirculation. The ethanol production cost was reduced by 17%. In the second configuration, up to 40% of the fresh water could be replaced without affecting the final ethanol yield, although the initial ethanol productivity decreased. The ethanol production cost was reduced by 12%. At higher degrees of recirculation,fermentation was clearly inhibited, resulting in a decrease in ethanol yield while hydrolysis seemed unaffected.
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| 4. |
- Alkasrawi, Malek, et al.
(författare)
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The effect of Tween-20 on simultaneous saccharification and fermentation of softwood to ethanol
- 2003
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Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 33:1, s. 71-78
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneous sacchatification and fermentation (SSF) of steam-pretreated wood constitutes an attractive process configuration for ethanol production from biomass. However, the high enzyme addition in SSF contributes to a high process cost. In this study we explore the effect of the non-ionic surfactant Tween-20 as an additive in SSE Tween-20 addition at 2.5 g/l had several positive effects on SSF: (i) the ethanol yield was increased by 8%; (ii) the amount of enzyme loading could be reduced by 50%, while maintaining a constant yield; (iii) the enzyme activity increased in the liquid fraction at the end of SSF, probably by preventing unproductive binding of the cellulases to lignin, which could facilitate enzyme recovery; (iv) the time required to attain maximum ethanol concentration was reduced. Surfactants as an additive in SSF can significantly lower the operational cost of the process. However, less expensive surfactants must be investigated. (C) 2003 Elsevier Science Inc. All rights reserved.
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| 5. |
- Bollok, M, et al.
(författare)
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Simultaneous saccharification and fermentation of steam-pretreated spruce to ethanol
- 2000
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Ingår i: Applied Biochemistry and Biotechnology. - 1559-0291. ; 84-6, s. 69-80
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Tidskriftsartikel (refereegranskat)abstract
- Ethanol production was studied in simultaneous saccharification and fermentation (SSF) of steam-pretreated spruce at 42 degrees C, using a thermotolerant yeast. Three yeast strains of Kluyveromyces marxianus were compared in test fermentations. SSF experiments were performed with the best of these on 5% (w/w) of substrate, at a cellulase loading of 37 filter paper units/g of cellulose, and a beta-glucosidase loading of 38 IU/ g of cellulose. The detoxification of the substrate and the lack of pH control in the experiments increased the final ethanol concentration. The final ethanol yield was 15% lower compared to SSF with Saccharomyces cerevisiae at 37 degrees C, owing to the cessation of ethanol fermentation after the first 10 h.
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| 6. |
- Choteborska, P, et al.
(författare)
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Processing of wheat bran to sugar solution
- 2004
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Ingår i: Journal of Food Engineering. - 0260-8774. ; 61:4, s. 561-565
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Tidskriftsartikel (refereegranskat)abstract
- In accordance to better exploitation of raw material for bioethanol production we try to find the method for saccharification of problematic cover part of grain, so called bran. The bran consists of three main components: residual starch, hemicellulose and cellulose. Whereas hydrolysis of starch is easy and well solved, there are questions how to optimise hydrolysis of all polysaccharides together, including hernicellulose and cellulose. The bran was treated with starch degrading enzymes (Termamyl 120 L and AMG 300 L) in order to remove the starch from the solid particles and use the starch-free residue for hydrolysis of hernicelluloses to pentoses. This starch-free residue (SFR) was treated with sulphuric acid and high temperature during exact time. Different times of pre-treatment (10-50 min), different temperatures (110-180degreesC) and different concentrations of sulphuric acid (1-4% of weight of slurry) were tested, as well as presence of furfural and 5-hydroxy-methyl-2-furaldehyd (HMF), substances causing inhibition of fermentation, was evaluated. The best yield of sugars (52.1 g/100 g of SFR) was achieved by using 1% of sulphuric acid at 130degreesC for 40 min and this method generates very low content of furfural and HMF (0.28 g/l, resp. 0.05 g/l). (C) 2003 Elsevier Ltd. All rights reserved.
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| 7. |
- Galbe, Mats, et al.
(författare)
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A review of the production of ethanol from softwood
- 2002
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 59:6, s. 618-628
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Forskningsöversikt (refereegranskat)abstract
- Ethanol produced from various lignocellulosic materials such as wood, agricultural and forest residues has the potential to be a valuable substitute for, or complement to, gasoline. One of the major resources in the Northern hemisphere is softwood. This paper reviews the current status of the technology for ethanol production from softwood, with focus on hemicellulose and cellulose hydrolysis, which is the major problem in the overall process. Other issues of importance, e.g. overall process configurations and process economics are also considered.
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| 8. |
- Ingesson, H, et al.
(författare)
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The effect of shaking regime on the rate and extent of enzymatic hydrolysis of cellulose
- 2001
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Ingår i: Journal of Biotechnology. - 1873-4863. ; 88:2, s. 177-182
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Tidskriftsartikel (refereegranskat)abstract
- In an attempt to elucidate the effect of mixing on the rate and extent of enzymatic hydrolysis of cellulosic substrates, alpha -cellulose was hydrolysed using a commercial cellulase preparation at varying levels of substrate concentration (2.5,5 and 7.5% (w/v)) and by using three shaking regimes: continuous at low-speed (25 rpm), continuous at high-speed (150 rpm) and an intermittent regime comprised of high and low-speed shaking intervals. The continuous, high-speed shaking produced the highest conversion yields, whereas the intermittent and low-speed shaking regimes resulted in lower conversions. After 72 h, at all shaking regimes (150 rpm, 25 rpm and intermittent), using a low substrate concentration (2.5%) produced conversion yields (82, 79 and 80%) higher than those obtained at high (7.5%) substrate concentration (68, 63 and 68%). As the substrate concentration increased, the conversion yields at intermittent shaking gradually approached those resulting from high-speed shaking. Thus, it appears that intermittent shaking could be a beneficial process option as it can reduce the mixing energy requirements while producing reasonably high conversion yields. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 9. |
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| 10. |
- Karlsson, David, et al.
(författare)
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Electronic speckle pattern interferometry: A tool for determining diffusion and partition coefficients for proteins in gels
- 2002
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Ingår i: Biotechnology Progress. - : Wiley. - 1520-6033 .- 8756-7938. ; 18:6, s. 1423-1430
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to demonstrate electronic speckle pattern interferometry (ESPI) as a powerful tool in determining diffusion coefficients and partition coefficients for proteins in gels. ESPI employs a CCD camera instead of a holographic plate as in conventional holographic interferometry. This gives the advantage of being able to choose the reference state freely. If a hologram at the,reference state is taken and compared to a hologram during the diffusion process, an interferometric picture can be generated that describes the refraction index gradients and thus the concentration gradients in the gel as well as in the liquid. MATLAB is then used to fit Fick's law to the experimental data to obtain the diffusion coefficients in gel and liquid. The partition coefficient is obtained from the same experiment from the flux condition at the interface between gel and liquid. This makes the comparison between the different diffusants more reliable than when the measurements are performed in separate experiments. The diffusion and partitioning coefficients of lysozyme, BSA, and IgG in 4% agarose gel at pH 5.6 and in 0.1 M NaCl have been determined. In the gel the diffusion coefficients were 11.2 +/- 1.6, 4.8 +/- 0.6, and 3.0 +/- 0.3 m(2)/s for lysozyme, BSA, and IgG, respectively. The partition coefficients were determined to be 0.65 +/- 0.04, 0.44 +/- 0.06, and 0.51 +/- 0.04 for lysozyme, BSA, and IgG, respectively. The current study shows that ESPI is easy to use and gives diffusion coefficients and partition coefficients for proteins with sufficient accuracy from the same experiment.
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