Morphological and metabolic changes in the yeast Kluyveromyces marxianus var. marxianus NRRLy2415 during fermentation of lactose

Graeme M. Walker, Joseph D. O'Neill

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    Abstract

    Oxygen availability has been identified as a major factor in governing the morphology of the lactose‐fermenting yeast, Kluyveromyces marxianus var. marxianus (formerly fragilis) NRRLy2415. In this particular strain, filamentous cells (F forms) predominate during the initial stages of aerobic propagation whilst budding yeast cells (Y forms) predominate during anaerobiosis. In other K. marxianus strains, and in Candida pseudotropicalis, budding cells predominate irrespective of oxygen availability. Increased cellular cytochrome contents and oxygen uptake rates accompanied Y to F (yeast to filamentous) transitions in K. marxianus NRRLy2415, suggesting that functional mitochondria are involved in controlling dimorphism in this yeast. This was further supported by the observation that respiratory inhibitors such as chloramphenicol prevented filamentation and promoted formation of respiratory‐deficient budding cells. During aerobic batch cultivation. K. marxianus displayed physiological variability in which cells were initially filamentous and respiratory but latterly were yeast‐like and fermentative, suggesting that growth rate as well as oxygen availability affected cell physiology. This was supported by the finding that during growth in lactose‐limited chemostat culture, the morphology and respiratory activity of K. marxianus varied with the specific growth rate of cells. In addition, the fermentation rates of F and Y forms varied, although maximum ethanol yields were not significantly different between the two morphologies. These results have implications for the more eflcient conversion of lactose to ethanol in commercial fermentations of cheese whey.
    Original languageEnglish
    Pages (from-to)75-89
    Number of pages15
    JournalJournal of Chemical Technology and Biotechnology
    Volume49
    Issue number1
    DOIs
    Publication statusPublished - 1990

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    Kluyveromyces marxianus
    lactose
    fermentation
    yeasts
    oxygen
    cells
    Candida kefyr
    ethanol
    cell physiology
    cheese whey
    anaerobiosis
    chloramphenicol
    cytochromes
    dimorphism
    specific growth rate
    mitochondria
    uptake mechanisms

    Cite this

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    title = "Morphological and metabolic changes in the yeast Kluyveromyces marxianus var. marxianus NRRLy2415 during fermentation of lactose",
    abstract = "Oxygen availability has been identified as a major factor in governing the morphology of the lactose‐fermenting yeast, Kluyveromyces marxianus var. marxianus (formerly fragilis) NRRLy2415. In this particular strain, filamentous cells (F forms) predominate during the initial stages of aerobic propagation whilst budding yeast cells (Y forms) predominate during anaerobiosis. In other K. marxianus strains, and in Candida pseudotropicalis, budding cells predominate irrespective of oxygen availability. Increased cellular cytochrome contents and oxygen uptake rates accompanied Y to F (yeast to filamentous) transitions in K. marxianus NRRLy2415, suggesting that functional mitochondria are involved in controlling dimorphism in this yeast. This was further supported by the observation that respiratory inhibitors such as chloramphenicol prevented filamentation and promoted formation of respiratory‐deficient budding cells. During aerobic batch cultivation. K. marxianus displayed physiological variability in which cells were initially filamentous and respiratory but latterly were yeast‐like and fermentative, suggesting that growth rate as well as oxygen availability affected cell physiology. This was supported by the finding that during growth in lactose‐limited chemostat culture, the morphology and respiratory activity of K. marxianus varied with the specific growth rate of cells. In addition, the fermentation rates of F and Y forms varied, although maximum ethanol yields were not significantly different between the two morphologies. These results have implications for the more eflcient conversion of lactose to ethanol in commercial fermentations of cheese whey.",
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    T1 - Morphological and metabolic changes in the yeast Kluyveromyces marxianus var. marxianus NRRLy2415 during fermentation of lactose

    AU - Walker, Graeme M.

    AU - O'Neill, Joseph D.

    PY - 1990

    Y1 - 1990

    N2 - Oxygen availability has been identified as a major factor in governing the morphology of the lactose‐fermenting yeast, Kluyveromyces marxianus var. marxianus (formerly fragilis) NRRLy2415. In this particular strain, filamentous cells (F forms) predominate during the initial stages of aerobic propagation whilst budding yeast cells (Y forms) predominate during anaerobiosis. In other K. marxianus strains, and in Candida pseudotropicalis, budding cells predominate irrespective of oxygen availability. Increased cellular cytochrome contents and oxygen uptake rates accompanied Y to F (yeast to filamentous) transitions in K. marxianus NRRLy2415, suggesting that functional mitochondria are involved in controlling dimorphism in this yeast. This was further supported by the observation that respiratory inhibitors such as chloramphenicol prevented filamentation and promoted formation of respiratory‐deficient budding cells. During aerobic batch cultivation. K. marxianus displayed physiological variability in which cells were initially filamentous and respiratory but latterly were yeast‐like and fermentative, suggesting that growth rate as well as oxygen availability affected cell physiology. This was supported by the finding that during growth in lactose‐limited chemostat culture, the morphology and respiratory activity of K. marxianus varied with the specific growth rate of cells. In addition, the fermentation rates of F and Y forms varied, although maximum ethanol yields were not significantly different between the two morphologies. These results have implications for the more eflcient conversion of lactose to ethanol in commercial fermentations of cheese whey.

    AB - Oxygen availability has been identified as a major factor in governing the morphology of the lactose‐fermenting yeast, Kluyveromyces marxianus var. marxianus (formerly fragilis) NRRLy2415. In this particular strain, filamentous cells (F forms) predominate during the initial stages of aerobic propagation whilst budding yeast cells (Y forms) predominate during anaerobiosis. In other K. marxianus strains, and in Candida pseudotropicalis, budding cells predominate irrespective of oxygen availability. Increased cellular cytochrome contents and oxygen uptake rates accompanied Y to F (yeast to filamentous) transitions in K. marxianus NRRLy2415, suggesting that functional mitochondria are involved in controlling dimorphism in this yeast. This was further supported by the observation that respiratory inhibitors such as chloramphenicol prevented filamentation and promoted formation of respiratory‐deficient budding cells. During aerobic batch cultivation. K. marxianus displayed physiological variability in which cells were initially filamentous and respiratory but latterly were yeast‐like and fermentative, suggesting that growth rate as well as oxygen availability affected cell physiology. This was supported by the finding that during growth in lactose‐limited chemostat culture, the morphology and respiratory activity of K. marxianus varied with the specific growth rate of cells. In addition, the fermentation rates of F and Y forms varied, although maximum ethanol yields were not significantly different between the two morphologies. These results have implications for the more eflcient conversion of lactose to ethanol in commercial fermentations of cheese whey.

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