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  • 1
    Electronic Resource
    Electronic Resource
    Effect of aerobiosis on fermentation and key enzyme levels during growth of Pichia stipitis, Candida shehatae and Candida tenuis on d-xylose (1989)
    Springer
    Archives of microbiology 152 (1989), S. 143-147 
    Details
    ISSN: 1432-072X
    Keywords: d-Xylose fermentation ; Aeration level ; Xylose reductase ; Xylitol dehydrogenase ; Yeast ; Candida shehatae ; Candida tenuis ; Pichia stipitis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between the degree of aerobiosis, xylitol production and the initial two key enzymes of d-xylose metabolism were investigated in the yeasts Pichia stipitis, Candida shehatae and C. tenuis. Anoxic conditions severely curtailed growth and retarded ethanol productivity. This, together with the inverse relationship between xylitol accumulation and aeration level, suggested a degree of redox imbalance. The ratios of NADH- to NADPH-linked xylose reductase were similar in all three yeasts and essentially independent of the degree of aerobiosis, and thus did not correlate with their differing capacities for ethanol production, xylitol accumulation or growth under the different conditions of aerobiosis. Under anoxic conditions the enzyme activity of Pichia stipitis decreased significantly, which possibly contributed to its weaker anoxic fermentation of xylose compared to C. shehatae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00456092
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  • 2
    Electronic Resource
    Electronic Resource
    Thermomyces lanuginosus: properties of strains and their hemicellulases (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 27 (2003), S. 0 
    Details
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The non-cellulolytic Thermomyces lanuginosus is a widespread and frequently isolated thermophilic fungus. Several strains of this fungus have been reported to produce high levels of cellulase-free β-xylanase both in shake-flask and bioreactor cultivations but intraspecies variability in terms of β-xylanase production is apparent. Furthermore all strains produce low extracellular levels of other hemicellulases involved in hemicellulose hydrolysis. Crude and purified hemicellulases from this fungus are stable at high temperatures in the range of 50–80°C and over a broad pH range (3–12). Various strains are reported to produce a single xylanase with molecular masses varying between 23 and 29 kDa and pI values between 3.7 and 4.1. The gene encoding the T. lanuginosus xylanase has been cloned and sequenced and is shown to be a member of family 11 glycosyl hydrolases. The crystal structure of the xylanase indicates that the enzyme consists of two β-sheets and one α-helix and forms a rigid complex with the three central sugars of xyloheptaose whereas the peripheral sugars might assume different configurations thereby allowing branched xylan chains to be accepted. The presence of an extra disulfide bridge between the β-strand and the α-helix, as well as to an increase in the density of charged residues throughout the xylanase might contribute to the thermostability. The ability of T. lanuginosus to produce high levels of cellulase-free thermostable xylanase has made the fungus an attractive source of thermostable xylanase with potential as a bleach-boosting agent in the pulp and paper industry and as an additive in the baking industry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0168-6445(03)00018-4
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  • 3
    Electronic Resource
    Electronic Resource
    Fps1p controls the accumulation and release of the compatible solute glycerol in yeast osmoregulation (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The accumulation of compatible solutes, such as glycerol, in the yeast Saccharomyces cerevisiae, is a ubiquitous mechanism in cellular osmoregulation. Here, we demonstrate that yeast cells control glycerol accumulation in part via a regulated, Fps1p-mediated export of glycerol. Fps1p is a member of the MIP family of channel proteins most closely related to the bacterial glycerol facilitators. The protein is localized in the plasma membrane. The physiological role of Fps1p appears to be glycerol export rather than uptake. Fps1Δ mutants are sensitive to hypo-osmotic shock, demonstrating that osmolyte export is required for recovery from a sudden drop in external osmolarity. In wild-type cells, the glycerol transport rate is decreased by hyperosmotic shock and increased by hypo-osmotic shock on a subminute time scale. This regulation seems to be independent of the known yeast osmosensing HOG and PKC signalling pathways. Mutants lacking the unique hydrophilic N-terminal domain of Fps1p, or certain parts thereof, fail to reduce the glycerol transport rate after a hyperosmotic shock. Yeast cells carrying these constructs constitutively release glycerol and show a dominant hyperosmosensitivity, but compensate for glycerol loss after prolonged incubation by glycerol overproduction. Fps1p may be an example of a more widespread class of regulators of osmoadaptation, which control the cellular content and release of compatible solutes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01248.x
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of the osmotic-stress response inSaccharomyces cerevisiae: osmotic stress and glucose repression regulate glycerol-3-phosphate dehydrogenase independently (1994)
    Springer
    Current genetics 25 (1994), S. 12-18 
    Details
    ISSN: 1432-0983
    Keywords: Osmotic stress ; Glycerol ; Glycerol-3-phosphate dehydrogenase ; Glucose repression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Micro-organisms have developed systems to adapt to sudden changes in the environment. Here we describe the response of the yeastSaccharomyces cerevisiae to osmotic stress. A drop in the water activity (aw) of the medium following the addition of NaCl led to an immediate shrinkage of the cells. During the 2 h following the osmotic shock the cells partially restored their cell volume. This process depended on active protein synthesis. During the recovery period the cells accumulated glycerol intracellularly as a compatible solute and very little glycerol was leaking out of the cell. We have investigated in more detail the enzymes of glycerol metabolism and found that only the cytoplasmic glycerol-3-phosphate dehydrogenase was strongly induced. The level of induction was dependent on the yeast strain used and the degree of osmotic stress. The synthesis of cytoplasmic glycerol-3-phosphate dehydrogenase is also regulated by glucose repression. Using mutants defective in glucose repression (hxk2Δ), or derepression (snf1Δ), and with invertase as a marker enzyme, we show that glucose repression and the osmotic-stress response system regulate glycerol-3-phosphate dehydrogenase synthesis independently. We infer that specific control mechanisms sense the osmotic situation of the cell and induce responses such as the production and retention of glycerol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712960
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of respiratory inhibitors on the fermentative ability of Pichia stipitis, Pachysolen tannophilus and Saccharomyces cerevisiae under various conditions of aerobiosis (1988)
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 67-71 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The growth and ethanol production by the d-xylose-fermenting yeasts Pichia stipitis and Pachysolen tannophilus under various conditions of aerobiosis responded similarly to the addition of the respiratory inhibitors potassium cyanide (KCN), antimycin A (AA), sodium azide and rotenone. However, the d-glucose-fermenting yeast Saccharomyces cerevisiae differed markedly from these yeasts in response to the inhibitors. In general the growth of the d-xylose-fermenting yeasts was inhibited by the respiratory inhibitors while ethanol production was either stimulated (especially when oxygen was available) or unaffected or inhibited by rotenone or AA or KCN and sodium azide, respectively. However, by exception KCN and AA stimulated ethanol production under aerobic conditions by Pichia stipitis and Pachysolen tannophilus respectively. Stimulatory or inhibitory effects by respiratory inhibitors were less marked in S. cerevisiae. These data suggest that unimpaired mitochondrial function is necessary for growth on d-xylose and optimal d-xylose fermentation. A requirement for membrane generated energy during d-xylose utilisation is indicated by 2,4-dinitrophenol inhibition of growth and fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00258353
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  • 6
    Electronic Resource
    Electronic Resource
    Utilization of glucose and cellobiose by Candida wickerhamii (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 281-286 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Candida wickerhamii produced ethanol under aerated and nonaerated conditions when grown on glucose but only under non-aerated conditions when grown on cellobiose. When the yeast was grown on 20 g·l−1 glucose in fermentation flasks, the substrate was completely utilized and 9.2 g·l−1 ethanol was produced. When 100 g·l−1 glucose was used, only 60% of the substrate was consumed and 23.4 g·l−1 ethanol was produced fermentatively whereas 31 g·l−1 ethanol was produced in an aerated fermenter. Ethanol toxicity was confirmed by adding ethanol to the culture. No ethanol was produced at added ethanol concentrations of 24 g·l−1 or higher although growth occurred even in the presence of 74 g·l−1 ethanol. The fermentation of glucose and cellobiose (20 g·l−1) was completed in 24 h and 125 h with specific growth rates of 0.29 and 0.06 h−1 respectively. β-Glucosidase was produced when grown on either glucose or cellobiose but the differential rate of enzyme production was 64 fold higher on cellobiose. Increased aeration stimulated enzyme production. β-Glucosidase was present in the fermentation broth and associated with the cells under non-aerated conditions and almost exclusively cell-associated under aerated conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00508021
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  • 7
    Electronic Resource
    Electronic Resource
    Nutritional, temperature, pH, and oxygen requirements of Candida wickerhamii (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 334-338 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A defined growth medium was determined for the cellobiose fermenting yeast Candida wickerhamii. Biotin and calcium pantothenate were required for growth while thiamine stimulated growth and ethanol production. The optimum temperature and pH for growth and ethanol production were 30°C and between pH 3 and pH 5 respectively. Oxygen availability played an important role in the fermentation of cellobiose and glucose. The optimum oxygen transfer rate for maximum ethanol production from glucose was 1.75 mmol (g dry biomass · h)−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00499499
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  • 8
    Electronic Resource
    Electronic Resource
    Diauxic utilization of glucose-cellobiose mixtures by Candida wickerhamii (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 369-373 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Glucose and cellobiose are the principle sugars released during cellulose hydrolysis. The utilization of mixtures of these sugars (10 g·l−1) by Candiada wickerhamii in batch cultures under aerobic and non-aerated conditions was investigated. Glucose was utilized first followed by cellobiose after a diauxic lag. Ethanol was produced from glucose under both aerobic and non-aerated conditions. Following glucose depletion under aerobic conditions, ethanol (produced during growth on glucose) and cellobiose were utilized simultaneously. Under non-aerated conditions ethanol was produced from cellobiose after the diauxic lag. When the glucose concentration was increased from 2 to 8 g·l−1 in glucose: cellobiose mixtures (total sugar 10 g·l−1), decreases of 66–91% were observed in the specific rates of growth, ethanol production, β-glucosidase production and sugar utilization on cellobiose as well as an increase in the diauxic time lag under aerobic and non-aerated conditions. After depletion of glucose, the viability of C. wickerhamii decreased during cellobiose utilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00504747
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  • 9
    Electronic Resource
    Electronic Resource
    The oxygen requirements of yeasts for the fermentation of d-xylose and d-glucose to ethanol (1988)
    Springer
    Applied microbiology and biotechnology 28 (1988), S. 63-68 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of oxygen availability on d-xylose and D-glucose metabolism by Pichia stipitis, Candida shehatae and Pachysolen tannophilus was investigated. Oxygen was not required for fermentation of d-xylose or d-glucose, but stimulated the ethanol production rate from both sugars. Under oxygen-limited conditions, the highest ethanol yield coefficient (Ye/s) of 0.47 was obtained on d-xylose with. P. stipitis, while under similar conditions C. shehatae fermented d-xylose most rapidly with a specific productivity (qpmax) of 0.32 h-1. Both of these yeasts fermented d-xylose better and produced less xylitol than. P. tannophilus. Synthesis of polyols such as xylitol, arabitol, glycerol and ribitol reduced the ethanol yield in some instances and was related to the yeast strain, carbon source and oxygen availability. In general, these yeasts fermented d-glucose more rapidly than d-xylose. By contrast Saccharomyces cerevisiae fermented d-glucose at least three-fold faster under similar conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250500
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  • 10
    Electronic Resource
    Electronic Resource
    An investigation of d-{1-13C} xylose metabolism in Pichia stipitis under aerobic and anaerobic conditions (1988)
    Springer
    Applied microbiology and biotechnology 28 (1988), S. 293-296 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The uptake of d-{1-13C} xylose, the accumulation of intermediates and the distribution of the label in ethanol in Pichia stipitis under aerobic and anaerobic conditions were investigated by nuclear magnetic resonance spectroscopy. The rate-limiting step of d-xylose metabolism under aerobic conditions appeared to be uptake, whereas under anaerobic conditions it was the conversion of xylitol to xylulose. The yeast showed no preference to either the alpha-or beta-forms of d-xylose. Under anaerobic conditions only {2-13C{ ethanol was detected and this suggests that NADH but not NADPH was used as cofactor in the conversion of xylose to xylitol. d-Xylose is most likely metabolised by the pentose phosphate pathway in this yeast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250458
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