| 1. |
- Brodelius, Peter
(author)
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Permeabilization of Plant Cells for Release of Intracellularly Stored Products: Viability Studies
- 1988
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In: Applied Microbiology and Biotechnology. - 0175-7598 .- 1432-0614. ; 27, s. 561-566
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Journal article (peer-reviewed)abstract
- The effects of various chemical substanceson the permeability of plasma membranesand tonoplasts of three suspension cultures (Catharanthusroseus, Thalictrum rugosum and Chenopodiumrubrum) have been studied. The permeabilityof the plasma membrane is monitoredby measuring the activity of the cytosolic enzymeisocitrate dehydrogenase and the permeability ofthe tonoplast is measured by determining the releaseof substances stored in the vacuoles (inorganicphosphate, berberine and betanin for thethree cell lines, respectively). The minimum concentrationrequired for quantitative release of vacuolarproducts have been established for five differentpermeabilization agents. Cell viability islost upon permeabilization except for treatmentof Catharanthus roseus with DMSO and Triton X-100.
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| 2. |
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| 3. |
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| 4. |
- Sode, K, et al.
(author)
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Continuous Production of Somatomedin C with Immobilized Transformed Yeast Cells
- 1988
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In: Applied Microbiology and Biotechnology. - 0175-7598 .- 1432-0614. ; 28:3, s. 215-221
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Journal article (peer-reviewed)abstract
- Yeast cells producing the growth hormonesomatomedin C (SMC) were constructedand applied in the immobilized form continuouslyfor a period of over 10 days in a flowthroughbioreactor. The construction of theMF~I-SMC fusion vector p336/l is given as wellas the results of the influence of various nutrientseffecting hormone production. Immobilization ofthe transformed yeast cells is described and theirapplication in a continuous bioreactor system.This study demonstrates the feasibility of a longtermand high-level hormone production by immobilizedtransformed yeast. The SMC productivitiesof free cells in batch and immobilized cellsunder continuous conditions were 0.2--0.3 and0.5--0.6 mg per g wet cells and day, respectively.
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| 5. |
- Adlercreutz, Patrick, et al.
(author)
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Characterization of Gluconobacter oxydans immobilized in calcium alginate
- 1985
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In: Applied Microbiology and Biotechnology. - 0175-7598. ; 22:1, s. 1-7
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Journal article (peer-reviewed)abstract
- Gluconobacter oxydans cells were immobilized in calcium alginate and the preparation was used for the oxidation of glycerol to dihydroxyacetone. The characterization was done according to the guidelines given by the Working Party on Immobilized Biocatalysts of the European Federation of Biotechnology. The pH optimum of the preparation was found to be 5.0 and the temperature optimum was 40°C. However, the operational stability was better at 30°C. The glycerol concentration required to obtain half the maximal reaction rate was about 5 mM for both immobilized and free cells. At low concentrations of glycerol and high concentrations of dihydroxyacetone a slight inhibition was noted. No loss of activity of the immobilized preparation was observed after storage for 68 days at +4°C. Investigation of the operational stability revealed a half-life of 5 days. Studies of the influence of particle size and cell densities as well as that of oxygen concentration revealed that the oxygen supply was the rate limiting step.
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| 6. |
- Adlercreutz, Patrick
(author)
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Oxidation of trans- and cis-1,2-cyclohexanediol by Gluconobacter oxydans - Preparation of (R)- and (S)-2-hydroxycyclohexanone
- 1989
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In: Applied Microbiology and Biotechnology. - 0175-7598. ; 30:3, s. 257-263
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Journal article (peer-reviewed)abstract
- The enzymatic oxidation of 1,2-cyclohexanediol and related substrates by Gluconobacter oxydans (ATCC 621) was investigated. At low pH, membrane-bound enzymes were active and at high pH, NAD-dependent, soluble enzymes showed activity. Whole bacterial cells were used to catalyze some bioconversions. Racemic trans-1,2-cyclohexanediol was oxidized at pH 3.5 to give (R)-2-hydroxycyclohexanone (96% e.e.) and at pH 8.0 the same substrate was oxidized to (S)-2-hydroxycyclohexanone (97% e.e.). The latter conversion was severely inhibited by the reaction product while the former was not significantly product inhibited. (S)-2-hydroxycyclohexanone (97% e.e.) was also prepared from cis-1,2-cyclohexanediol by oxidation with G. oxydans cells at pH 3.5 in a reaction which continued to 100% conversion.
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| 7. |
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| 8. |
- Reslow, Mats, et al.
(author)
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Organic solvents for bioorganic synthesis : 1. Optimization of parameters for a chymotrypsin catalyzed process
- 1987
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In: Applied Microbiology and Biotechnology. - 0175-7598. ; 26:1, s. 1-8
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Journal article (peer-reviewed)abstract
- The influence of solvents on enzymatic activity and stability was investigated. As a model reaction the α-chymotrypsin-catalyzed esterification of N-acetyl-l-phenylalanine with ethanol was used. The enzyme was adsorbed on porous glass beads and used in various solvents. Small amounts of water were added to increase the enzymatic activity. These enzyme preparations obeyed. Michaelis-Menten kinetics. Km,app decreased slightly with the log P value of the solvent while Vapp increased markedly with the log P value. Log P values were also useful for generalizing the influence of solvents on enzyme stability. The enzyme preparations showed a markedly higher thermostability in dry solvents having log P values >0.7 than in less hydrophobic solvents. Also the operational stability was better in the more hydrophobic solvents. The amount of water added to the enzyme preparations greatly influenced the initial reaction rates. For some solvents optimal water contents were determined. The thermostability decreased with increasing water content. The observations are summarized in the conclusion that more hydrophobic solvents are preferable to less hydrophobic ones. The log P value gives a good guidance when selecting an organic solvent for enzymatic conversions.
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| 9. |
- Wehtje, Ernst, et al.
(author)
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Activity and operational stability of immobilized mandelonitrile lyase in methanol/water mixtures
- 1988
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In: Applied Microbiology and Biotechnology. - 0175-7598. ; 29:5, s. 419-425
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Journal article (peer-reviewed)abstract
- The enzyme mandelonitrile lyase was covalently immobilized on solid support materials using different methods. Immobilization on porous silica using coupling with glutaraldehyde afforded preparations with high enzyme loading (up to 9% (w/w)). The immobilized enzyme was used in a packed bed reactor for the continuous production of d-mandelonitrile from benzaldehyde and cyanide. The influence of the flow rate, pH, substrate concentrations and enzyme loading on the reaction yield and the enantiomeric purity of the product was investigated. In order to suppress the competing spontaneous reaction, the enzymatic reaction must be rapid. A flow rate of 9.5 ml/min (0.1 M benzaldehyde and 0.3 M HCN) through a 3 ml reactor afforded a 86% yield of mandelonitrile with 92% enantiomeric excess. No leakage of enzyme occurred under continuous operation. One column was used continuously for 200 h without any decrease in yield or enantiomeric purity of the product. High concentrations of benzoic acid were shown to decrease the operational stability of the system.
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