| 1. |
- Alkasrawi, Malek, et al.
(författare)
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Influence of strain and cultivation procedure on the performance of simultaneous saccharification and fermentation of steam pretreated spruce
- 2006
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 38:1-2, s. 279-286
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Tidskriftsartikel (refereegranskat)abstract
- Yeast to be used in simultaneous saccharification and fermentation (SSF) of lignocelluloses materials has to be prepared in a separate cultivation step. The effects of the cultivation procedure on the performance of SSF of steam pretreated softwood were studied in the current work. The yeast used in the SSF was either directly commercially available Baker's yeast (as packaged yeast) or the same strain of yeast produced from the hydrolysate obtained in the pretreatment of the softwood material. A second strain of Saccharomyces cerevisiae TMB3000. isolated from spent sulphite liquor, was also compared with the commercial Baker's yeast. The strains were tested in SSF at substrate loads of 3, 5 and 8% dry weight of water insoluble material. Final ethanol yields were above 85% of the theoretical (based on the available hexoses) in all cases, except for the package yeast for the 8% substrate load, in which case the final yield was less than 65%. The cultivation procedure was found to have a significant impact on the performance during SSF, as well as in small-scale fermentations of hydrolysate liquor without solid material. The Baker's yeast cultivated on the hydrolysate from the steam pretreatment had in all cases a higher productivity, in particular at the highest substrate load. Cultivated Baker's yeast had a slightly higher productivity than TMB3000. The results suggest that the adaptation of the yeast to the inhibitors present in the medium is an important factor that must be considered in the design of SSF processes.
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| 2. |
- Andersson, Alexandra, et al.
(författare)
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Comparison of diafiltration and size-exclusion chromatography to recover hemicelluloses from process water from thermomechanical pulping of spruce
- 2007
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Ingår i: Applied Biochemistry and Biotechnology. - : Springer Science and Business Media LLC. - 1559-0291 .- 0273-2289. ; 137:1-12, s. 971-983
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Tidskriftsartikel (refereegranskat)abstract
- Hemicelluloses constitute one of the most abundant renewable resources on earth. To increase their utilization, the isolation of hemicelluloses from industrial biomass side-streams would be beneficial. A method was investigated to isolate hemicelluloses from process water from a thermomechanical pulp mill. The method consists of three steps: removal of solids by microfiltration, preconcentration of the hemicelluloses by ultrafiltration, and purification by either size-exclusion chromatography (SEC) or diafiltration. The purpose of the final purification step is to separate hemicelluloses from small oligosaccharides, monosaccharides, and salts. The ratio between galactose, glucose, and mannose in oligo- and polysaccharides after preconcentration was 0.8: 1: 2.8, which is similar to that found in galactoglucomannan. Continuous diafiltration was performed using a composite fluoro polymer membrane with cutoff of 1000 Da. After diafiltration with four diavolumes the purity of the hemicelluloses was 77% (gram oligo- and polysaccharides/gram total dissolved solids) and the recovery was 87%. Purification by SEC was performed with 5, 20, and 40% sample loadings, respectively and a flow rate of 12 or 25 mL/min (9 or 19 cm/h). The purity of hemicelluloses after SEC was approx 82%, and the recovery was above 99%. The optimal sample load and flow rate were 20% and 25 mL/min, respectively. The process water from thermomechanical pulping of spruce is inexpensive. Thus, the recovery of hemicelluloses is not of main importance. If the purity of 77%, obtained with diafiltration, is sufficient for the utilization of the hemicelluloses, diafiltration probably offers a less expensive alternative in this application.
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| 3. |
- Foglia, Domenico, et al.
(författare)
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Integration study on a two-stage fermentation process for the production of biohydrogen
- 2009
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Ingår i: Chemical Engineering Transactions. - 1974-9791. ; 18, s. 345-350
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Konferensbidrag (refereegranskat)abstract
- In order to make the hydrogen economy fully sustainable, renewable resources have to be employed for its production. Simulation models, developed with Aspen Plus to calculate mass and energy balances, will be used to integrate the process steps necessary to produce pure hydrogen from biomass in a 2-stage fermentation process. The main challenge is the reduction of water and heat demand connected to the low substrate concentration in the fermentation steps; the easiest solution is to partly recirculate outgoing process streams. Electrolyte equilibrium was considered during simulation of different recirculation options to evaluate important effects on the pH and on the system osmolality. The results show that certain recirculation options can reduce the heat and water demand significantly.
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| 4. |
- Galbe, Mats, et al.
(författare)
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Pretreatment of Lignocellulosic Materials for Efficient Bioethanol Production
- 2007
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Ingår i: Advances in Biochemical Engineering/Biotechnology. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0724-6145. - 9783540736509 ; 108, s. 41-65
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Bokkapitel (refereegranskat)abstract
- Second-generation bioethanol produced from various lignocellulosic materials, such as wood, agricultural or forest residues, has the potential to be a valuable substitute for, or a complement to, gasoline. One of the crucial steps in the ethanol production is the hydrolysis of the hemicellulose and cellulose to monomer sugars. The most promising method for hydrolysis of cellulose to glucose is by use of enzymes, i.e. cellulases. However, in order to make the raw material accessible to the enzymes some kind of pretreatment is necessary. During the last few years a large number of pretreatment methods have been developed, comprising methods working at low pH, i.e. acid based, medium pH (without addition of catalysts), and high pH, i.e. with a base as catalyst. Many methods have been shown to result in high sugar yields, above 90% of theoretical for agricultural residues, especially for corn stover. For more recalcitrant materials, e.g. softwood, acid hydrolysis and steam pretreatment with acid catalyst seem to be the methods that can be used to obtain high sugar and ethanol yields. However, for more accurate comparison of different pretreatment methods it is necessary to improve the assessment methods under real process conditions. The whole process must be considered when a performance evaluation is to be made, as the various pretreatment methods give different types of materials. (Hemicellulose sugars can be obtained either in the liquid as monomer or oligomer sugars, or in the solid material to various extents; lignin can be either in the liquid or remain in the solid part; the composition and amount/concentration of possible inhibitory compounds also vary.) This will affect how the enzymatic hydrolysis should be performed(e.g. with or without hemicellulases), how the lignin is recovered and also the use of the lignin co-product.
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| 5. |
- Galbe, Mats, et al.
(författare)
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Process Engineering Economics of Bioethanol Production
- 2007
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Ingår i: Advances in Biochemical Engineering/Biotechnology. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0724-6145. - 9783540736509 ; 108, s. 303-327
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Bokkapitel (refereegranskat)abstract
- This work presents a review of studies on the process economics of ethanol production from lignocellulosic materials published since 1996. Our objective was to identify the most costly process steps and the impact of various parameters on the fi- nal production cost, e.g. plant capacity, raw material cost, and overall product yield, as well as process configuration. The variation in estimated ethanol production cost is considerable, ranging from about 0.13 to 0.81 US$ per liter ethanol. This can be explained to a large extent by actual process differences and variations in the assumptions underlying the techno-economic evaluations. The most important parameters for the economic outcome are the feedstock cost, which varied between 30 and 90US$ per metric ton in the papers studied, and the plant capacity, which influences the capital cost. To reduce the ethanol production cost it is necessary to reach high ethanol yields, as well as a high ethanol concentration during fermentation, to be able to decrease the energy required for distillation and other downstream process steps. Improved pretreatment methods, enhanced enzymatic hydrolysis with cheaper and more effective enzymes, as well as improved fermentation systems present major research challenges if we are to make lignocellulose-based ethanol production competitive with sugar- and starch-based ethanol. Process integration, either internally or externally with other types of plants, e.g. heat and power plants, also offers a way of reducing the final ethanol production cost.
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| 6. |
- Galbe, Mats, et al.
(författare)
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Production of ethanol from biomass - Research in Sweden
- 2005
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Ingår i: Journal of Scientific and Industrial Research. - 0022-4456. ; 64:11, s. 905-919
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Tidskriftsartikel (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. This paper reviews the research activities in Sweden on development of the technology for ethanol production from lignocellulosics. The paper focuses on hemicellulose and cellulose hydrolysis and fermentation as well as on process integration and techno-economic evaluation of the overall process.
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| 7. |
- Hahn-Hägerdal, Bärbel, et al.
(författare)
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Bio-ethanol - the fuel of tomorrow from the residues of today
- 2006
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Ingår i: Trends in Biotechnology. - : Elsevier BV. - 0167-7799. ; 24:12, s. 549-556
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Forskningsöversikt (refereegranskat)abstract
- The increased concern for the security of the oil supply and the negative impact of fossil fuels on the environment, particularly greenhouse gas emissions, has put pressure on society to find renewable fuel alternatives. The most common renewable fuel today is ethanol produced from sugar or grain (starch); however, this raw material base will not be sufficient. Consequently, future large-scale use of ethanol will most certainly have to be based on production from lignocellulosic materials. This review gives an overview of the new technologies required and the advances achieved in recent years to bring lignocellulosic ethanol towards industrial production. One of the major challenges is to optimize the integration of process engineering, fermentation technology, enzyme engineering and metabolic engineering.
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| 8. |
- Hoyer, Kerstin, et al.
(författare)
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Production of fuel ethanol from softwood by simultaneous saccharification and fermentation at high dry matter content
- 2009
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575 .- 1097-4660. ; 84:4, s. 570-577
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The production of bio-ethanol from softwood is considered a promising alternative to fossil fuels in Sweden. In order to make fuel ethanol economically competitive with fossil fuels, it is important to reduce the production cost, which can be done by increasing the dry matter content of the fermentation medium, thus reducing the energy demand in the final distillation of the fermentation broth. Running simultaneous saccharification and fermentation l at higher dry matter content has, however, been found to decrease the ethanol yield. RESULTS: The use of different stirrer types and stirring speeds in the present study has shown to have an influence on the final ethanol yield in SSF with 10% water-insoluble solids (WIS). Also, higher concentration of pretreatment hydrolysate, i.e., with increased inhibitor concentration, at the same WIS resulted in a decreased ethanol yield. However, despite stirring problems and high inhibitor concentration, ethanol was produced at 12% WIS with an ethanol yield in the SSF step of 81% of the theoretical based on the content of fermentable sugars in the fermentor. CONCLUSION: The decrease in ethanol yield in SSF at high dry matter content has been shown to be a combined effect of increased mass transfer resistance and increased inhibitor concentration in the fermentation broth. (c) 2008 Society of Chemical Industry
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| 9. |
- Jakobsson, Niklas, et al.
(författare)
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Using computer simulation to assist in the robustness analysis of an ion-exchange chromatography step
- 2005
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1063:1-2, s. 99-109
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a methodology to gain process knowledge and assist in the robustness analysis of an ion-exchange step in a protein purification process using a model-based approach. Factorial experimental design is common practice in industry today to obtain robustness characterization of unit operations with respect to variations in process parameters. This work aims at providing a better insight into what process variations affect quality and to further reduce the experimental work to the regions of process variation that are of most interest. This methodology also greatly increases the ability to predict process performance and promotes process understanding. The model calibration part of the methodology involves three consecutive steps to calibrate a steric mass action (SMA) ion-exchange chromatography model. Firstly, a number of gradient elution experiments are performed. Secondly, experimental breakthrough curves have to be generated for the proteins if the adsorption capacity of the medium for each component is not known. Thirdly, a multi-component loading experiment is performed to calibrate the multi-component effects that cannot be determined from the single-component experiments. The separation process studied in this work is the separation of polyclonal IgG from a mixture containing IgG, myoglobin and BSA. The calibrated model is used to simulate six process variations in a full factorial experiment. The results of the simulations provide information about the importance of the different process variations and the simulations are also used to determine the crucial points for the process parameter variations. The methodology can be used to assist in the robustness analysis normally performed in the pharmaceutical industry today as it is able to predict the impact on process performance resulting from variations in salt concentration, column load, protein concentration and flow rate. (C) 2004 Elsevier B.V. All rights reserved.
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| 10. |
- Kempe, Henrik, et al.
(författare)
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Determination of diffusion coefficients of proteins in stationary phases by frontal chromatography
- 2006
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 93:4, s. 656-664
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Tidskriftsartikel (refereegranskat)abstract
- A strategy to determine effective diffusion coefficients of proteins in chromatographic gels is presented in this article. An experimental methodology based on frontal liquid chromatography was combined with a numerical methodology based on a mathematical model describing the chromatographic process including the extra-column dispersion, the dispersion due to the packed bed, the external mass transfer from the bulk phase to the stationary phase, and the diffusive transport within the stationary phase. The methodology has several advantages compared to previously reported methods to determine diffusion coefficients in that no other equipment than an HPLC is required, any class of stationary phases can be investigated as long as the experiments are performed under non-binding conditions, and no modification, e.g., moulding of slabs or membranes, to the stationary phase is required. To show the applicability of the methodology, the effective diffusion coefficients of lysozyme, bovine serum albumin, and immunoglobulin gamma in Sepharose (TM) CL-4B were determined and shown to be comparable with those determined with other methods. (c) 2005 Wiley Periodicals, Inc.
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