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  • 1
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Fungi which have been previously shown to hydrolyse glycocholic acid, with liberation of the free bile acid, have now been shown to be similarly capable of hydrolysing glycodeoxycholic acid. Sodium taurocholate, however, is much less susceptible and its hydrolysis has been demonstrated with only one of the selected fungi, Penicillium chrysogenum, growing in a medium containing the conjugate as the sole sulphur source. It is concluded that the nature of the amino acid moiety is important in determining the ease of hydrolysis of bile acid conjugates by whole cells of the fungi under test.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Statistically designed experiments were used to identify variables important in the 7α-dehydroxylation of cholic acid to deoxycholic acid by strains of Clostridium bifermentans in pH-controlled anaerobic fermentation. Deoxycholic acid yields were highest in the presence of 10% CO2 and near pH 7 but were largely unaffected by the strain of organism used, time of bile acid substrate addition, mode of gas delivery, presence of thioglycollate, or the use of OH− ion or HCO 3 − ion for pH control. However, dehydroxylation was enhanced, and the redox potential remained relatively high, when temperatures were low, inoculum size small, and growth inhibitors were present. Deoxycholic acid yields of up to 40% were observed but the formation of 7-ketodeoxycholic acid side product could not be entirely prevented.
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  • 3
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Two strains of Clostridium bifermentans have been investigated for their ability to hydrolyse bile acid conjugates under conditions suited to further transformation of the free acids liberated. In batch fermentation at 0.5 g/l substrate concentration, growing cells effected the near-quantitative hydrolysis of glycodeoxycholate, taurodeoxycholate and taurocholate within 48 h; glycocholate was 88% hydrolysed. At substrate concentration greater than 1.0 g/l however, taurine conjugates were less well hydrolysed. Further transformation of the liberated cholic acid to deoxycholic acid and/or 7-ketodeoxycholic acid was achieved, but quantitative conversion was not observed.
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The 11β- and 19-hydroxylation enzyme(s) of Pellicularia filamentosa IFO 6298 have been shown to be inducible by Reichstein's Substance S. By using the protein synthesis inhibitor, cycloheximide, in fermenter culture the effects of dissolved oxygen tension (DOT) on enzyme induction and enzyme expression have been separately investigated. For both hydroxylations, an optimum DOT for induction has been shown at 15% of saturation, while the optimum for expression is at 30% of saturation. The results have been verified in the absence of cycloheximide. Thus, maximum rates of hydroxylation are achieved when induction is performed at low DOT, followed by elevation to ensure maximum expression.
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  • 5
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Experiments in batch-fermenters have demonstrated that the 11β- and 19-hydroxylation of Reichstein's Substance S by Pellicularia filamentosa ceases in the absence of glucose. The effects of glucose consumption rate and growth rate on hydroxylation have been investigated using chemostat cultures. With glucose-limited cultures, increased hydroxylation rates were observed with increased glucose consumption rates. With nitrogen-limited cultures, however, some form of glucose-repression exists. The maximum rate of hydroxylation occurred at a glucose consumption rate at which the culture was just nitrogen-limited. The growth rate had no major importance.
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  • 6
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary An investigation was performed to recognise a fungus capable of 19-hydroxylating the steroids androstenedione, cortexolone and progesterone, in high yield with little or no side reactions. The fungi selected for study belong to a group which has been previously reported to possess 19-hydroxylation ability. Pellicularia filamentasa f. sp. microsclerotia IFO 6298 and P. filamentosa f.sp. sasakii IFO 5254 both 19-hydroxylated cortexolone, but 19-hydroxylated products were not detected using either androstenedione or progesterone as substrate. When 19-hydroxylating cortexolone, both strains of P. filamentosa produced 11β-hydroxycortexolone as a by-product, but P. filamentosa f.sp. microsclerotia IFO 6298 was superior in terms of 19-hydroxylation and the relative amounts of the two products.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A range of fungi have been investigated for their ability to hydrolyse glycocholic acid to yield cholic acid. Using thin-layer chromatography the majority of fungi tested have been shown to possess this ability. In the case of Cochliobolus intermedius IMI 52980 the product of hydrolysis has been isolated and characterised as cholic acid. The same organism has been demonstrated to grow using glycocholic acid as the sole source of carbon and nitrogen.
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  • 8
    ISSN: 1572-9567
    Keywords: corresponding states ; petroleum fractions ; viscosity prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We predict the viscosity of petroleum fractions using extended corresponding states. Our model builds upon the TRAPP procedure, which is the most advanced approach to predict transport properties of straight-chain nonpolar hydrocarbons and their mixtures. We perform comparisons with experimental viscosity data for pure hydrocarbons, treating them as nonstandard components; we find deviations of 10–15%. We also extend the model to predict the transport properties of petroleum fractions and compare with an experimental database of more than 80 crude oils, including highly aromatic petroleum fractions. The model predicts the viscosity of the crude oil fractions within experimental uncertainty.
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  • 9
    ISSN: 1572-9567
    Keywords: corresponding states ; petroleum fractions ; propane ; viscosity, thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A corresponding-states model for the transport properties of petroleum fractions is presented. The model requires only the API specific gravity and the mean average boiling point as input parameters. The extended correspanding-states model uses propane as a reference fluid, and new generalized shape factor expressions that are functions of the acentric factor and the reduced temperature are presented. Also presented are new correlating functions for the viscosity and thermal conductivity of the reference fluid that can be extrapolated well below the freezing point of propane. The performance of the model is demonstrated by comparing with experimental data for viscosity and thermal conductivity of petroleum fractions.
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron Letters 7 (1966), S. 741-742 
    ISSN: 0040-4039
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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