| 1. |
- Axelsson, Anders, et al.
(författare)
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Economic evaluation of the hydrolysis of lactose using immobilized beta-galactosidase
- 1990
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Ingår i: Applied Biochemistry and Biotechnology. - 1559-0291. ; 24-5, s. 679-693
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Tidskriftsartikel (refereegranskat)abstract
- A computer program for preliminary cost estimates of free and immobilized enzyme systems has been developed. The cost for the hydrolysis of lactose by β-galactosidase fromAspergillus oryzae has been calculated for a batch tank reactor, with free (BTRF) and immobilized (BTRI) enzymes, a continuously stirred tank reactor (CSTR) and a plug-flow tubular reactor (PFTR), considering the mass transfer behavior and deactivation of the enzyme. Enzyme immobilization is economically feasible, compared with a system with free enzymes, despite a very high cost for the enzyme attachment. At a half-life time of 80 d, the PFTR gives the lowest cost (0.48 SEK/kg lactose), but the cost for the BTRI is just slightly higher (0.66 SEK/kg lactose) and still much lower than the BTRF (2.10 SEK/kg lactose).
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| 2. |
- Axelsson, Anders, et al.
(författare)
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Performance of batch and continuous reactors with co-immobilized yeast and beta-galactosidase
- 1991
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575 .- 1097-4660. ; 52:2, s. 227-241
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Tidskriftsartikel (refereegranskat)abstract
- The anaerobic fermentation of deproteinized whey with beta-galactosidase coimmobilized with Saccharomyces cerevisiae in calcium alginate gel beads for the production of ethanol has been studied in a continuous horizontal packed bed reactor (HPBR). The results are compared with batch experiments in a stirred tank reactor. The immobilized yeast cells are exposed to conditions that vary with time and location in the reactor, making a true steady state impossible. In spite of a very low specific growth rate-of the order of 0.01 h-1 in the first section of the HPBR-the yeast cell growth, accompanied by bead expansion in this section, was high enough to create a cell concentration gradient along the reactor. The continuous reactor is preferable to the batch reactor as the galactose conversion is more efficient. The highest volumetric productivity obtained in the HPBR was 125 mol ethanol m-3 h-1 (6 g ethanol dm-3 h-1) at a substrate concentration of 164 mol m-3 lactose (56 g dm-3) and a dilution rate of 0.21 h-1, corresponding to a space velocity of 0.51 dm3 dm-3 gel h-1. The ethanol yield from consumed glucose and galactose was 80%. The ethanol yield from lactose was only 70%, as only 75% of the galactose was consumed while all the lactose and glucose were converted.
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| 3. |
- Axelsson, Anders, et al.
(författare)
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Simulation of batch and continuous reactors with co-immobilized yeast and β-galactosidase
- 1991
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575 .- 1097-4660. ; 52:4, s. 481-497
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Tidskriftsartikel (refereegranskat)abstract
- A reaction-diffusion model was used to simulate a co-immobilized system utilizing the numerical method of orthogonal collocation. The production of ethanol from deproteinized whey using beta-galactosidase co-immobilized with Saccharomyces cerevisiae in calcium alginate gel beads was chosen as a model system. Calculated concentrations of lactose, glucose, galactose and ethanol were compared with experimental data for a batch reactor and a continuous horizontal packed-bed reactor. The mathematical model has been used to analyse the influence of internal and external mass transfer for the continuous reactor. The external mass transfer was shown to be of minor importance. The introduction of baffles decreased the backmixing in the horizontal packed-bed reactor. Internal mass transfer was found to be the main cause of the reduction in the apparent reaction rate. Thus, much of the expected increase in reaction rate is diminished by mass transfer hindrance when the cell concentration is increased.
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| 4. |
- Carlsson, F, et al.
(författare)
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Mathematical modelling and parametric studies of affinity chromatography
- 1994
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Ingår i: Computers & Chemical Engineering. - 1873-4375. ; 18:suppl. 1, s. 657-661
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Tidskriftsartikel (refereegranskat)abstract
- In this study a model based on mass transfer and sorption rate constants with physical significance is used for simulation of affinity chromatography, The simulation program has been used to perform a parametric analysis of the adsorption of lysozyme on Cibacron Blue-Sepharose CL-6B. The influence of process parameters as well as physical parameters on the chromatography process was investigated. The external and the internal mass transfer as well as the sorption rate were found to contribute to the control of the overall rate of the system. The most important process parameter was the radius of the beads. The optimum bead size was found to be around 50 mu m.
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| 5. |
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| 6. |
- Eklund, R, et al.
(författare)
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Optimization of temperature and enzyme concentration in the enzymatic saccharification of steam-pretreated willow
- 1990
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Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 12:3, s. 225-228
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Tidskriftsartikel (refereegranskat)abstract
- The effect of temperature and enzyme concentration on the enzymatic hydrolysis of steam-pretreated willow was investigated to obtain the optimal hydrolysis conditions. The willow was pretreated at 220°C for 10 min according to the results of earlier optimization studies of the steam-pretreatment conditions for high glucose yields. The concentrations of two commercial enzymes, Celluclast 2L and Novozyme 188, were varied in the range 0–20% (based on oven-dry substrate). A maximum in the conversion of cellulose to glucose was obtained using a mixture of 15% Celluclast and 3% Novozyme, corresponding to an activity of 11.4 FPU g−1 substrate. Higher enzyme concentrations did not increase the initial hydrolysis rate nor affect the final glucose yield. The effects of temperature in the range 40°C to 60°C were investigated. The temperature affects both the initial hydrolysis rate and the final glucose yield. The highest glucose yield was obtained at 40°C. The yield decreased with increasing temperature, due to increased enzyme deactivation at higher temperatures, while the initial reaction rate increased with increasing temperatures.
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| 7. |
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| 8. |
- Galbe, Mats, et al.
(författare)
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Adsorption of cellulases on steam-pretreated willow
- 1990
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Ingår i: Applied Biochemistry and Biotechnology. - 1559-0291. ; 24-5, s. 87-101
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of cellulases on steam-pretreated willow has been measured for2, 4, and 8 wt% willow and with varying enzyme concentrations (2–100 wt% based on substrate). The enzyme concentration was measured as soluble protein, filter paper activity (FPA), CMC-ase activity, and activity toward willow. The adsorption data were modeled with a Langmuir isotherm. The maximum adsorption capability depends on the method for measurement of the enzyme concentration. The lowest value, 470 mg enzyme/g willow, was obtained for the soluble protein and the highest value, 650 mg/g, for the FPA. For technical applications, a single isotherm can be used for calculation of the adsorption capability of steam-treated willow.
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| 9. |
- Galbe, Mats, et al.
(författare)
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Simulation of ethanol production processes based on enzymatic hydrolysis of lignocellulosic materials using ASPEN PLUS
- 1992
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Ingår i: Applied Biochemistry and Biotechnology. - 1559-0291. ; 34-5, s. 93-104
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Tidskriftsartikel (refereegranskat)abstract
- The process simulator ASPEN PLUS was used for simulation of an ethanol production process based on enzymatic hydrolysis of lignocellulosic materials. The effect of water recycling, necessary to reduce the amount of waste water and to increase the ethanol concentration in the feed to the distillation, was investigated. For a process based on 20 t/h raw material, the amount of waste water can be reduced from 70.7 t/h, without recycling, to 7.1 t/h. Furthermore, the ethanol concentration in the distillation feed increased from 2.5 to 10%. The concentration of byproducts and possible inhibitors increased by a factor of 20-40 in the hydrolysis and fermentation steps. This gives new conditions for future hydrolysis and fermentation experiments.
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| 10. |
- Galbe, Mats, et al.
(författare)
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Simulation of ethanol production processes based on enzymatic hydrolysis of woody biomass
- 1994
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Ingår i: Computers & Chemical Engineering. - : Elsevier BV. - 1873-4375 .- 0098-1354. ; 18:Suppl. 1, s. 687-691
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Tidskriftsartikel (refereegranskat)abstract
- The process simulator ASPEN PLUS was used for simulation of an ethanol production process based on enzymatic hydrolysis of lignocellulosic materials. Various process configurations were studied to increase the overall yield of ethanol and to reduce the energy consumption in the process. An increased utilization of the pentosan fraction was achieved by a complex recycling of streams in the process. This increased the total overall yield from 56% to 70%. Internal recycling of an ethamol containing stream increased the ethanol concentration in the distillation feed from 2.6 to 7.1 wt% which decreased the energy consumption in the distillation from 8 to 2 MW. The recycling will however result in increased concentrations of byproducts and inhibitors which requires future investigation of how these new conditions will affect the performance in the hydrolysis and fermentation steps.
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