| 1. |
- Adlercreutz, Patrick
(author)
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Oxygen supply to immobilized cells : 5. Theoretical calculations and experimental data for the oxidation of glycerol by immobilized Gluconobacter oxydans cells with oxygen or p‐benzoquinone as electron acceptor
- 1986
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In: Biotechnology and Bioengineering. - : Wiley. - 0006-3592 .- 1097-0290. ; 28:2, s. 223-232
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Journal article (peer-reviewed)abstract
- Theoretical calculations of reaction kinetics were done for one‐step reactions catalyzed by cells immobilized in spherical beads. The reactions catalyzed by free cells were assumed to obey Michaelis–Menten kinetics for a one‐substrate reaction. Both external (outside the beads) and internal (inside the beads) mass transfer of the substrate were considered for the immobilized preparations. The theoretical calculations were compared with experimental data for the oxidation of glycerol to dihydroxyacetone by Gluconobacter oxydans cells immobilized in calcium alginate gel. Glycerol was present in excess so that the reaction rate was limited by oxygen. The correlation between experimental data and theoretical calculations was quite good. The calculations showed how the overall effectiveness factor was influenced by, for example, the particle size and the cell density in the beads. In most cases the reaction rate was mainly limited by internal mass transfer of the substrate (oxygen). As shown previously, p‐benzoquinone can replace oxygen as the electron acceptor in this reaction. The same equations for reaction kinetics and mass transfer were used with p‐benzoquinone as the rate‐limiting substrate. Parameters such as diffusivity, maximal reaction rate, and K were, of course, different. In this case also, the correlation between the model and the experimental results was quite good. Much higher production rates were obtained with p‐benzoquinone as the electron acceptor compared to when oxygen was used. The reasons for this fact were that p‐benzoquinone gave a higher maximal reaction rate for free cells and the solubility of p‐benzoquinone was higher than for oxygen. Different methods of increasing the rate of microbial oxidation reactions are discussed.
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| 2. |
- Hahn-Hägerdal, Bärbel, et al.
(author)
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Production of ethanol from lignocellulosic materials
- 1988
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In: Animal Feed Science and Technology. - : Elsevier BV. - 0377-8401. ; 21:2-4, s. 175-182
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Journal article (peer-reviewed)abstract
- In the bioconversion of lignocellulosic materials to ethanol, the cost of the raw material and the cost of the enzymes have been identified as the major costs for the product. In addition, many lignocellulosic materials contain considerable amounts of five-carbon sugars which are not easily fermented to ethanol. The possibility of improving the cost-intensive steps was investigated. The steam pre-treatment of a fast-growing species of Salix (Q082) was optimized with respect to treatment time and temperature, to give the best glucose yield after enzymatic hydrolysis. It was found that the semi-continuous production of cellulolytic enzymes with Trichoderem reesei Rutgers C30 in an aqueous two-phase system (an extractive fermentation system) increased the amount of recoverable enzyme activity compared with a batch process. It was also found that the enzyme consumption in the hydrolysis of cellulolytic materials, in filter paper units (FPU) g−1 reducing sugars (RS), could be considerably reduced by recirculating the cellulolytic enzymes in an aqueous two-phase system combined with an ultra-filtration unit. For the fermentation of pentoses, it was found that the combination of the commercial enzyme glucose isomerase and regular bakers' yeast, Saccharomyces cerevisiae, was superior to xylose fermenting yeasts. Yields and productivities comparable to those obtained in hexose fermentation could be achieved.
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| 3. |
- Larsson, L, et al.
(author)
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The measurement of cell growth in coal slurries
- 1989
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In: Biotechnology Techniques. - 0951-208X. ; 3:5, s. 295-298
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Journal article (peer-reviewed)abstract
- Microbial growth in coal slurries can be detected if surfactant is present in the samples by analysing the protein concentration after disintegration of the cells. Without surfactant present in the samples, the proteins are readily adsorbed on the coal surfaces. A suitable surfactant is sodium dodecyl sulphate at 0.5 to 1% of the sample volume
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| 4. |
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| 5. |
- Mattiasson, Bo, et al.
(author)
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Perfluorochemicals in biotechnology
- 1987
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In: Trends in Biotechnology. - : Elsevier BV. - 0167-7799. ; 5:9, s. 250-254
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Research review (peer-reviewed)abstract
- Gas transport often is a limiting factor in biotechnology. Perfluorochemicals provide a new vehicle for the transport of gases.
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| 6. |
- Mattiasson, Bo, et al.
(author)
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Use of aqueous two-phase systems for recovery and purification in biotechnology
- 1986
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In: Separations, Recovery and Purification in Biotechnology : Recent Advances and Mathematical Modeling - Recent Advances and Mathematical Modeling. - Washington, DC : American Chemical Society. - 9780841209787 - 9780841211513 ; 314, s. 78-92
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Book chapter (peer-reviewed)abstract
- Aqueous two-phase systems are generated by mixing aqueous solutions of two water-soluble polymers, or a polymer and a salt. These systems offer extremely mild conditions for separation of cells, organelles, proteins and other biomolecules, in biochemical processes. Considerable attention has been directed towards the use of the two-phase systems in several areas of biotechnology. The present paper summarizes the state of the art concerning extractive bioconversions for production of small as well as macromolecules, and protein purification using aqueous two-phase system.
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| 7. |
- Olsson, G, et al.
(author)
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Microorganisms for Desulfurization of Coal: the Influence of Leaching Compounds on their Growth
- 1989
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In: Fuel. - 1873-7153. ; 68:10, s. 1270-1274
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Journal article (peer-reviewed)abstract
- An investigation was undertaken to outline how microorganisms suggested for use in coal desulphurization are affected by compounds leached from coal. Three species of the genus Sulfolobus were studied. Sulfolobus acidocaldarius was seen to be affected by compounds leached from coal more negatively than Sulfolobus brierleyi and Sulfolobus solfataricus. It was observed that certain conditions during leaching, such as pH, temperature and leaching time, were important for the concentration of compounds leached from coal. It was seen that compounds leached from coal, in some cases, can improve the growth yield for the microorganisms.
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| 8. |
- Zacchi, Guido, et al.
(author)
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Economic evaluation of enzymatic hydrolysis of phenol-pretreated wheat straw
- 1988
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In: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 32:4, s. 460-466
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Journal article (peer-reviewed)abstract
- Experimental data from the enzymatic hydrolysis of phenol-pretreated Swedish wheat straw have been used to evaluate the cost fractions of capital and utility, enzyme, and raw material. Two different raw material prices and varying enzyme prices have been used. The evaluation is based on an empirical model for the enzymatic hydrolysis and a computer program where utility and equipment, enzyme, and raw material prices can be varied. The optimal residence time for the enzymatic hydrolysis is in the range of 70–110 h. A fed-batch procedure with substrate concentrations higher than 10% oven-dried material (ODM) and enzyme concentrations in the range (6–10) · 106 FPU/ton ODM should be used.
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| 10. |
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