| 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. |
- Bennett, Neil A., et al.
(författare)
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Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Thermomyces lanuginosus ATCC 46882
- 1998
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 306:3, s. 445-455
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Tidskriftsartikel (refereegranskat)abstract
- An endoxylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) from the culture filtrates of T. lanuginosus ATCC 46882 was purified to homogeneity by DEAE-Sepharose and Bio-Gel P-30 column chromatographies. The purified endoxylanase had a specific activity of 888.8 mumol min-1 mg-1 protein and accounted for approximately 30% of the total protein secreted by this fungus. The molecular mass of native (non-denatured) and denatured endoxylanase were 26.3 and 25.7 kD as, respectively. Endoxylanase had a pI of 3.7 and was optimally active between pH 6.0-6.5 and at 75 degrees C. The enzyme showed > 50% of its original activity between pH 5.5-9.0 and at 85 degrees C. The pH and temperature stability studies revealed that this endoxylanase was almost completely stable between pH 5.0-9.0 and up to 60 degrees C for 5 h and at pH 10.0 up to 55 degrees C for 5 h. Thin-layer chromatography (TLC) analysis showed that endoxylanase released mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-D-glucuronoxylan, O-acetyl-4-O-methyl-D-glucuronoxylan and rhodymenan (a beta-(1-->3)-beta(1-->4)-xylan). Also, the enzyme released an acidic xylo-oligosaccharide from 4-O-methyl-D-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. The enzyme hydrolysed [1-3H]-xylo-oligosaccharides in an endofashion, but the hydrolysis of [1-3H]-xylotriose appeared to proceed via transglycosylation. since the xylobiose was the predominant product. Endoxylanase was not active on pNPX and pNPC at 40 and 100 mM for up to 6 h, but showed some activity toward pNPX at 100 mM after 20-24 h. The results suggested that the endoxylanase from T. lanuginosus belongs to family 11.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- Christakopoulos, Paul, et al.
(författare)
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Controlling simultaneous production of endoglucanase and beta-glucosidase by Fusarium oxysporum in submerged culture
- 1995
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Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 17:8, s. 883-888
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Tidskriftsartikel (refereegranskat)abstract
- The simultaneous production of endoglucanase and β-glucosidase by Fusarium oxysporum was investigated in submerged culture. Consecutive optimization of growth conditions resulted in the correction of large activity differences, observed during production of enzymes, and substantially enhanced low enzyme yields. At optimum growth conditions yields as high as 1650 and 232 U per g of carbon source of endoglucanase and β-glucosidase were obtained respectively competing favourably with those reported for microorganisms grown on the same carbon source. The most important kinetic characteristics of the enzymes were the high temperature optima of endoglucanase (60°C) and β-glucosidase (65°C) and the exceptionally high thermostability of endoglucanase. The latter enzyme retained 50% of the activity at pH 5.0 after approximately 6.5 h at 70°C
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| 6. |
- Christakopoulos, Paul, et al.
(författare)
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Direct conversion of sorghum carbohydrates to ethanol by a mixed microbial culture
- 1993
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Ingår i: Bioresource Technology. - 0960-8524 .- 1873-2976. ; 45:2, s. 89-92
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Tidskriftsartikel (refereegranskat)abstract
- The carbohydrates of sweet sorghum were directly converted to ethanol by a mixed culture of Fusarium oxysporum F3 and Saccharomyces cerevisiae 2541. A number of factors affecting this bioconversion was studied. Optimum ethanol yields of 33·2 g/100 g of total sorghum carbohydrates, corresponding to 10·3 g/100 g of fresh stalks, were obtained. These values represented 68·6% of the theoretical yield based on total polysaccharides and exceeded that based on oligosaccharides of sorghum by 53·7%. The results demonstrated that more than half of the sorghum polysaccharides were directly fermented to ethanol, thus making the process worthy of further investigation.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- Christakopoulos, Paul, et al.
(författare)
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Enhanced acetyl esterase production by Fusarium oxysporum
- 1999
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Ingår i: World Journal of Microbiology & Biotechnology. - 0959-3993 .- 1573-0972. ; 15:4, s. 443-446
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Tidskriftsartikel (refereegranskat)abstract
- Production of acetyl esterase (EC 3.1.1.6) by Fusarium oxysporum strain F3 was enhanced by optimization of growth conditions. Under optimal conditions, activities as high as 0.89 U/ml of culture medium were obtained. The culture filtrate was equally active on p-nitrophenyl acetate and acetylxylan. The enzyme produced 71% deacetylation of acetylxylan in 2 h at 40 ∘C. Activity was optimized at pH6.5 and at 55 ∘C. The respective Km values for p-nitrophenyl acetate and acetylxylan were 0.25 mM and 1.05% (w/v) and the Vm values were 0.65 and 0.43 μmol acetate/min/mg protein.
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| 10. |
- Christakopoulos, Paul, et al.
(författare)
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Enhancement of pH-stability of a low molecular mass endoglucanase from Fusarium oxysporum by protein pegylation
- 1998
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 314:1-2, s. 95-99
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Tidskriftsartikel (refereegranskat)abstract
- The stability of the low molecular mass endoglucanase (23.2 kDa) from Fusarium oxysporum at alkaline pH was enhanced by chemical modification. Two distinct types of amino acid-specific modifiers were used. The first, either cyanuric chloride activated polyethylene glycol (CC–PEG) or polyethylene glycol succinimidyl succinate active ester (SS–PEG), react (more or less specifically) with protein amino groups. The second type, maleimide polyethylene glycol (Mal–PEG), is specific for cysteinyl residues. The enzyme lost almost all of its activity when modified with CC–PEG, whereas no inactivation was observed with SS–PEG and Mal–PEG. The modified endoglucanase showed remarkably enhanced alkaline pH stability. When acting upon cello-oligosaccharides and 4-methylumbelliferyl cello-oligosaccharides, the enzyme preferentially cleaved the internal glycosidic bonds. The modified enzymes mediated a decrease in the viscosity of carboxymethyl cellulose (CMC) associated with the release of only small amounts of reducing sugar. Thus, the modified enzyme retains the endo character of the native enzyme
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