| 1. |
- Agnantiari, G., et al.
(författare)
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A Purified α-galactosidase from aspergillus niger with enhanced kinetic characteristics
- 1991
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Ingår i: Acta Biotechnologica. - : Wiley. - 0138-4988 .- 1521-3846. ; 11:5, s. 479-484
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular α-galactosidase from Aspergillus niger was purified 128-fold over the crude extract by gel filtration, ion exchange chromatography and chromatofocusing. Certain substrates and end products affected enzyme activity. Among the former p-nitrophenyl-α-galactopyranoside (PNPG) inhibited the enzyme at 1.4 mM while melibiose did not inhibit α-galactosidase at concentrations up to 50 mM. Enzymic end products such as glucose did not inhibit the enzyme at concentrations up to 100 mM while galactose exhibited a competitive inhibition with a Ki = 1.29 mM. The kinetic characteristics of the enzyme compared favourably to other microbial α-galactosidases and make it suitable for food process applications.
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| 2. |
- Caridis, K A, et al.
(författare)
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Control of catalase production and purity by altering certain nutritional factors of Alternaria alternata growth medium
- 1991
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Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 13:1, s. 35-38
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Tidskriftsartikel (refereegranskat)abstract
- Both activity level of catalase and presence of glucose oxidase as an impurity were controlled by the type and concentration of nitrogen and carbon source in the culture medium of Alternaria alternata. It was possible to produce glucose oxidase-free catalase at activity levels competing favourably with those reported for other catalase hyperproducing microorganisms.
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| 3. |
- Christakopoulos, Paul, et al.
(författare)
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Direct conversion of straw to ethanol by Fusarium oxysporum : Effect of cellulose crystallinity
- 1991
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Ingår i: Enzyme and microbial technology. - 0141-0229 .- 1879-0909. ; 13:3, s. 272-274
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Tidskriftsartikel (refereegranskat)abstract
- Wheat straw was successfully fermented to ethanol by Fusarium oxysporum F3 in a one-step process. Cellulose crystallinity was found to be a major factor in the bioconversion process. Ethanol yields increased linearly with decreasing crystallinity index. Approximately 80% of straw carbohydrates were converted directly to ethanol with a yield of 0.28 g ethanol/g−1 of straw when the crystallinity index was reduced to 23.6%.
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| 4. |
- Christakopoulos, Paul, et al.
(författare)
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Direct ethanol conversion of pretreated straw by Fusarium oxysporum
- 1991
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 35:3, s. 297-300
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Tidskriftsartikel (refereegranskat)abstract
- Factors affecting the direct conversion of alkali pretreated straw to ethanol by Fusarium oxysporum F3 were investigated and the alkali level used for pretreatment and the degree of delignification of straw were found to be the most important. A linear correlation between ethanol yield and both the degree of straw delignification and the alkali level was observed. At optimum delignified straw concentration (4% w/v), a maximum ethanol yield of 0·275 g ethanol g−1 of straw was obtained corresponding to 67·8% of the theoretical yield.
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| 5. |
- Christakopoulos, Paul, et al.
(författare)
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Exceptionally thermostable α- and β-galactosidase from Aspergillus niger separated in one step
- 1990
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 25:6, s. 210-212
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular alpha- and-beta-galactosidases from a strain of Aspergillus niger were separated and purified in one step by cation exchange chromatography. Both enzymes had acidic pH (3.5-4.0) and high temperature (65-degrees-C) optima and an exceptionally high thermostability. Thus, -alpha-galactosidase had an activity half-time of 104 min at 60-degrees-C whereas at the same temperature the respective value for-beta-galactosidase was 835 min. At optimum conditions of activity the apparent K(m) values of alpha- and beta-galactosidase were 0.44mM and 1.1mM respectively. Both the high temperature optima and thermostability properties of the enzymes make them particularly suitable for high temperature processes.
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| 6. |
- 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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| 7. |
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| 8. |
- Koullas, D.P., et al.
(författare)
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Effect of alkali delignification on wheat straw saccharification by fusarium oxysporum cellulases
- 1993
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 4:1, s. 9-13
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Tidskriftsartikel (refereegranskat)abstract
- The effect of alkaline delignification of wheat straw on the chemical composition and the subsequent enzymic hydrolysis of the pretreated straw are reported. Both hot (120°°C) and cold (20–36°°C) delignification were investigated, using either aqueous or organic alkaline solutions. The treated lignocellulosic materials were hydrolyzed by the cellulases of Fusarium oxysporum strain F3. Both delignification and saccharification yield showed linear relationships with the level of alkali used. Under the chosen experimental conditions 70–100% hydrolysis was achieved either by hot or cold delignification. Delignification to at least 50% appeared crucial for total polysaccharide conversion.
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| 9. |
- Lezinou, V., et al.
(författare)
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Simultaneous saccharification and fermentation of sweet sorghum carbohydrates to ethanol in a fed-batch process
- 1994
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Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 16:9, s. 983-988
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Tidskriftsartikel (refereegranskat)abstract
- The simultaneous saccharification and fermentation (SSF) of sweet sorghum carbohydrates to ethanol by Fusarium oxysporum F3 alone or in mixed culture with Saccharomyces cerevisiae 2541 or Zymomonas mobilis CP4 in a fed-batch fermentation process was studied. While SSF was adequately carried out by the first microorganism the process achieved its maximum value by the mixed culture of the fungus and yeast. Under optimum conditions, ethanol yields and concentrations as high as 29.7 g of ethanol per 100 g of dry sorghum stalk and 7.5 % (w/v) respectively were obtained. These values together with the high yield of sorghum crop in Greece make this process promising and worthy of further investigation for the production of fuel bioethanol
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| 10. |
- Tsitsimpikou, C., et al.
(författare)
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Studies of the effect of organic solvents on the stability of β-glucosidase from Fusarium oxysporum
- 1994
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Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 16:1, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- The effect of organic solvents on the stability of β-glucosidase in a powder form, isolated fromFusarium oxysporum, has been studied using several organic solvents of different degree of hydrophobicity. It was found that β-glucosidase remains quite stable after a prolonged incubation in the presence of most of the organic solvents used, even at temperatures as high as 70°C. Only dimethyformamide (DMF) and tetrahydrofuran (THF) reduce considerably the enzyme activity in a short preincubation period. Studies on the effect of the pH of the buffer used prior to lyophilization, as well as of exogenous added water to the incubation mixture, on enzyme stability show that it is more stable in pH 5.0 and in the lowest water content. In addition it was found that the presence of glucose in the lyophilization procedure gives a significant protection to the enzyme when it is incubated for 30 h in pentanol and n-hexane.
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