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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- Axelsson, B., et al.
(författare)
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Lateral forces in wood cutting
- 1991
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Ingår i: Proceedings of the Tenth International Wood Machining Seminar : Oktober 21 - 23, 1991. - : University of California at Berkeley.
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Konferensbidrag (refereegranskat)
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| 6. |
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| 7. |
- Axelsson, B.O.M., et al.
(författare)
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Studies of the main cutting force at and near a cutting edge
- 1993
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Ingår i: European Journal of Wood and Wood Products. - 0018-3768 .- 1436-736X. ; 51:1, s. 43-48
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Tidskriftsartikel (refereegranskat)abstract
- The present work is a study of how various parameters affect the cutting forces at, and near a cutting edge when cutting wood at full speed and with all cutting edges of the tool. Statistical methods from experimental results are used to develop a model
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| 8. |
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| 9. |
- Axelsson, Håkan, et al.
(författare)
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Mätning av aromatiska kolväten med DOAS. En studie av tillförlitlighets- och interferensproblem.
- 1990
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- DOAS-tekniken är en optisk fjärranalysmetod för mätning av luftföroreningar. I det projekt som här avrapporterats har tekniken utvärderats m a p mätning av lätta aromatiska kolväten. Projektet har omfattat såväl litteratur, labb och fältstudier av absorptionsegenskaper som interferenseffekter. Resultaten visar att de lätta aromatiska kolväten har ett gemensamt absorptionsband i nära UV (250-280 mm ) som med fördel kan användas i en DOAS-tillämpning. Utnyttjande detta band, kan flera av aromaterna mätas med en detektionsgräns på några µg/m3. Dock föreligger kraftiga interferenseffekter mellan i synnerhet komponenter med likartad kemisk struktur. Detta problem kan i vissa fall hanteras m h a multipel regressions analys. En förutsättning för detta är dock att inga 'okända' interferande ämnen (lös aromater) förekommer i mätsituationen.
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| 10. |
- 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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