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  • 1
    Electronic Resource
    Electronic Resource
    An investigation into the 19-hydroxylation of androstenedione, cortexolone and progesterone by selected fungi (1985)
    Springer
    Applied microbiology and biotechnology 21 (1985), S. 132-134 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252376
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  • 2
    Electronic Resource
    Electronic Resource
    7 α-Dehydroxylation of cholic acid by Clostridium bifermentans (1981)
    Springer
    Applied microbiology and biotechnology 12 (1981), S. 46-52 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00508118
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrolysis of bile acid conjugates by Clostridium bifermentans (1982)
    Springer
    Applied microbiology and biotechnology 14 (1982), S. 41-45 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00508002
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence that impaired citrate transport into the cell is a contributory factor to extracellular citrate accumulation by a strain of Candida guilliermondii (1993)
    Springer
    Applied microbiology and biotechnology 39 (1993), S. 604-608 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Candida guilliermondii IMK 1 is a mutant strain that accumulates concentrations of citric acid approximately seven times higher than does its parent strain, NRRL Y-448. In contrast to its parent, strain IMK 1 cannot use citrate as the sole carbon source, or assimilate citrate in the presence of glucose. Measurements of membrane ATPase activity show consistently lower values in the mutant strain than in its parent. It is suggested that failure to re-assimilate the excreted citrate is a major contributory factor in the extracellular accumulation of high citrate concentrations, and that this failure is related to a defect in the membrane structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00205060
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of dissolved oxygen tension on 11β- and 19-hydroxylation of Reichstein's Substance S by Pellicularia filamentosa (1982)
    Springer
    Applied microbiology and biotechnology 14 (1982), S. 131-135 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00497887
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  • 6
    Electronic Resource
    Electronic Resource
    Galactose inhibition of citric acid production from glucose by Aspergillus niger (1985)
    Springer
    Applied microbiology and biotechnology 22 (1985), S. 98-102 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Previous work in this laboratory has demonstrated that although Aspergillus niger can readily utilize galactose, no citric acid is produced from this carbon source (Hossain et al. 1984). Experiments were now conducted where galactose was added at various concentrations to synthetic growth medium containing glucose as carbon source, so that the effect of galactose on citric acid production from glucose could be observed. The results showed that the presence of galactose or a product of galactose metabolism caused inhibition of citric acid production, and also reduced the rate of glucose utilization. Enzyme analyses using mycelial cell-free extracts indicated that galactose interfered with the glucose-repression of the key enzyme 2-oxoglutarate dehydrogenase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250027
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of the sugar source on citric acid production by Aspergillus niger (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 393-397 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Under otherwise identical fermentation conditions, the sugar source has been shown to have a marked effect on citric acid production by Aspergillus niger. Sucrose was the most favourable source, followed by glucose and fructose and then lactose. No citric acid was produced from galactose. Strong relationships were observed between citric acid production and the activities of certain enzymes in myccelial cell-free extracts prepared from fermentation samples. When sucrose, glucose, or fructose was the sugar source pyruvate carboxylase activity was high, but 2-oxoglutarate dehydrogenase activity was not detected. When galactose was the sugar source pyruvate carboxylase activity was low, but 2-oxoglutarate dehydrogenase activity was high. It is suggested that whereas glucose and fructose repress 2-oxoglutarate dehydrogenase, thereby causing accumulation of citric acid, galactose does not. The activity of aconitase showed a direct relationship to the citric acid production rate. Thus, the activity was highest when sucrose was the sugar source, and lowest when galactose was the source. It is suggested that when large amounts of citric acid are lost from the cell the activity of aconitase increases as a response to the diminished intracellular supply of its substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00454376
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  • 8
    Electronic Resource
    Electronic Resource
    Model for continuous production of solvents from whey permeate in a packed bed reactor using cells of Clostridium acetobutylicum immobilized by adsorption onto bonechar (1988)
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 323-328 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A mathematical model has been developed to describe the operation of a packed bed reactor for the continuous production of solvents from whey permeate. The model has been used to quantitate the amounts of different physiological/ morphological types of biomass present in the reactor. The majority of biomass is inert, i.e. it neither grows nor produces solvent. Only relatively small amounts of biomass actively grow (vegetative, non-solvent-producing cells), while even smaller amounts are responsible for solvent production (clostridial, solvent-producing cells).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265814
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of glucose on 11β- and 19-hydroxylation of reichstein's substance S by Pellicularia filamentosa (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 211-215 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00510417
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of methanol on citric acid production from galactose by Aspergillus niger (1986)
    Springer
    Applied microbiology and biotechnology 23 (1986), S. 203-205 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of methanol on the ability of several strains of Aspergillus to produce citric acid from galactose has been investigated. In the absence of methanol, very little production (less than 1 g/l) was observed. In the presence of methanol (final concentration 1% v/v), however, citric acid production and yeilds were increased considerably. Strong relationships were observed between citric acid production and the activities of the enzymes 2-oxoglutarate dehydrogenase and pyruvate carboxylase in cell-free extracts. During citric acid production, in the presence of methanol, the activity of 2-oxoglutarate dehydrogenase was low and that of pyruvate carboxylase high. In the absence of methanol, where little citric acid was produced, the reverse was true. It is suggested that the presence of methanol may increase the permeability of the cell to citrate, and the cell responds to the diminished intracellular level by increasing production via repression of 2-oxoglutarate dehydrogenase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261914
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