| 1. |
- Caridis, Konstantina-Anna, et al.
(författare)
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Simultaneous production of glucose oxidase and catalase by Alternaria alternata
- 1991
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598 .- 1432-0614. ; 34:6, s. 794-797
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Tidskriftsartikel (refereegranskat)abstract
- A number of factors affecting simultaneous production of cell-bound glucose oxidase and catalase by the fungus Alternaria alternata have been investigated. Consecutive optimization of the type and concentration of nitrogen and carbon source, the initial pH and growth temperature resulted in a simultaneous increase in glucose oxidase and catalase by 780% and 68% respectively. Two second-order equations, describing the combined effect of pH and temperature on the activity of each enzyme, revealed that glucose oxidase had its optima at pH 7.9 and 32.3°C and catalase at pH 8.5 and 18.1°C. Under certain growth conditions, yields as high as 23.5 and 18,100 units/g carbon source for glucose oxidase and catalase, respectively, were simultaneously obtained.
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| 2. |
- Christakopoulos, Paul, et al.
(författare)
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On the mechanism of direct conversion of cellulose to ethanol by Fusarium oxysporum : Effect of cellulase and β-glucosidase
- 1990
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598 .- 1432-0614. ; 33:1, s. 18-20
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the three main enzymes involved in cellulose saccharification, namely cellobiohydrolase, carboxymethylcellulase and beta-glucosidase, on the direct conversion of cellulose to ethanol by Fusarium oxysporum F3 were investigated. Ethanol production was not affected when the activity of the former two enzymes was varied within a wide range. By contrast, beta-glucosidase markedly affected ethanol production showing an optimum level of 0.7-0.8 unit/ml growth medium. A significant decrease of cellulose bioconversion time to ethanol was obtained when beta-glucosidase activity was adjusted to this optimal level at the beginning of the fermentation process.
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| 3. |
- Christakopoulos, Paul, et al.
(författare)
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Production and characterization of extracellular lipase from Calvatia gigantea
- 1992
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598 .- 1432-0614. ; 38:2, s. 194-197
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Tidskriftsartikel (refereegranskat)abstract
- A number of factors affecting production of extracellular lipase by the edible fungus Calvatia gigantea were investigated. Consecutive optimization of carbon and nitrogen sources, initial pH of culture medium and growth temperature resulted in an increase in lipase activity of 87%. Under optimum conditions, activities as high as 22.4 units ml−1 of culture medium were obtained, competing favourably with most activities reported for other lipase hyperproducing microorganisms. The enzyme was optimally active at pH 7.0 and 30°C and had, at optimum pH, half-lives of 75.7 and 22.9 min at 45 and 55°C. Both high activity and kinetic characteristics of the enzyme make this process worthy of further investigation.
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| 4. |
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| 5. |
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| 6. |
- Holmberg, Erland, et al.
(författare)
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Reaction conditions for the resolution of 2-methylalkanoic acids in esterification and hydrolysis with lipase from Candida cylindracea
- 1991
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 35:5, s. 572-578
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated resolution of 2-methylalkanoic acids using lipase from Candida cylindracea as a catalyst. The resolution of 2-methyldecanoic acid was more successful than that of 2-methylbutyric acid both by esterification and hydrolysis. This indicates that the resolution of the acid is dependent on the chain length of the acid moiety. The chain length of the alcohol moiety of the ester affected the resolution of the long-chain acid only. Using esterification, (R)-2-methyldecanoic acid was produced in an enantiomeric excess (e.e.) of 95% (E = 40). If the enantiomeric ratio is low (E = 3.6), as in the resolution of 2-methylbutyric acid, esterification combined with a high equilibrium conversion could be used to yield the remaining acid in a high e.e. In the hydrolytic reactions, the e.e. and the equilibrium conversion were dependent on the pH and the presence of CaCl2. When octyl 2-methyldecanoate was hydrolysed at pH 8.0 in the presence of CaCl2, the (S)-acid was formed with an e.e. of 80% (E = 9), but when the hydrolysis was carried out at pH 7.5 without CaCl2, a very low e.e. and a low equilibrium conversion were observed. The latter conditions allowed the esterification of 2-methyldecanoic acid with 1-octanol even in aqueous medium.
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| 7. |
- Pietikäinen, Pekka, et al.
(författare)
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Influence of the reaction medium on the product distribution of peroxidase-catalysed oxidation of p-cresol
- 1990
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 33:4, s. 455-458
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Tidskriftsartikel (refereegranskat)abstract
- p-Cresol was oxidized by hydrogen peroxide in a reaction catalysed by horseradish peroxidase and the low molecular weight products were investigated. In aqueous media Pummerer's ketone (I) was the dominating product but in organic media the product distribution was quite different; 2,2'-dihydroxy-5,5'-dimethyldiphenyl (II) was the main low molecular weight product. Similar product distributions were obtained with peroxidase adsorbed on a solid support and suspended in toluene and with peroxidase solubilized in a microemulsion containing the same solvent. The best selectivity for the formation of (II) was obtained when the enzyme was adsorbed on Celite and suspended in water-saturated chloroform with 0.5% (v/v) extra water added. The yield of low molecular weight products in this case was 28%; of this fraction, 95% was (II).
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| 8. |
- Svensson, Ingemar, et al.
(författare)
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Interesterification of phosphatidylcholine with lipases in organic media
- 1990
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 33:3, s. 255-258
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Tidskriftsartikel (refereegranskat)abstract
- Lipases were investigated with respect to their ability to catalyse the incorporation of fatty acids into phosphatidylcholine (PC) by interesterification reactions. The enzymes were dried onto solid support materials and the conversions were carried out in water-saturated toluene. Three lipases (two fungal and one plant enzyme) had the desired activity; immobilized lipase from Mucor miehei (Lipozyme) was the most active enzyme. The Lipozyme-catalysed interesterification was selective for the sn-1 position of PC and during 48 h of reaction around 50% of the fatty acids in this position were replaced with heptadecanoic acid, a fatty acid which was practically absent in the original phospholipid. Due to adsorption on the support material and the competing hydrolysis reaction the total amount of PC in the reaction solution decreased to about 40% of the original amount. Higher interesterification rates were obtained with free fatty acids as acyl donors than with fatty acid esters.
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| 9. |
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