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  • 1985-1989  (3)
  • 1988  (2)
  • 1987  (1)
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  • 1985-1989  (3)
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  • 1
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of various culture conditions on growth kinetics of an homofermentative strain of the lactic acid bacterium Streptococcus cremoris were investigated in batch cultures, in order to facilitate the production of this organism as a starter culture for the dairy industry. An optimal pH range of 6.3–6.9 was found and a lactose concentration of 37 g·l-1 was shown to be sufficient to cover the energetic demand for biomass formation, using the recommended medium. The study of the effect of lactic acid concentration on growth kinetics revealed that the end-product was not the sole factor affecting growth. The strain was characterized for its tolerance towards lactic acid and a critical concentration of 70 g·l-1 demonstrated. With the product yield of 0.9 g·g-1 at non-lactose limiting conditions the lactic acid concentration of 33 g·l-1 could not explain the low growth rates obtained, implicating a nutritional limitation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5044
    Keywords: Lipophilic amines distribution ; Ajmalicine release ; pH gradients ; Catharanthus roseus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During growth, Catharanthus roseus cells exhibit an acidification of the culture medium that may be controlled by Ca2+. With a view to enhance the productivity of alkaloids by plant cells, the effect of extracellular pH modifications on the excretion processes has been investigated. Ca2+ dependent proton pumping leads to the release of various lipophilic amine-like compounds (benzylamine, methylamine, nicotine) initially accumulated by the cells, but also facilitates the excretion of endogenous ajmalicine. Once released in the medium, these compounds are however taken up again by the cells, probably as the charged form. For the alkaloid contained in C. roseus some evidence suggests that the diffusible form comes from the cytosolic compartment and not from the storage vacuoles. This appears to be a major production limitation to the use of pH gradients in order to favour alkaloid excretion.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5044
    Keywords: Catharanthus roseus ; cell suspension culture ; enzyme activities ; carbon dioxide partial pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro enzyme activities of glycolysis, pentose-phosphate pathway and dark CO2 fixation were assayed in batch cultures of heterotrophic Catharanthus roseus cells under various gassing rates and partial pressures of carbon dioxide. Detrimental effects of low pCO2 culture conditions on the growth characteristics could be linked to marked changes in levels of enzymes of primary metabolism during growth. The enzyme levels observed during the early stages of growth were found to be more stable when a constant pCO2 (20 mbar) was maintained and enabled exponential growth to be reached more rapidly. The importance of carbon dioxide as a “conditioning factor” of the culture medium is discussed.
    Type of Medium: Electronic Resource
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