MAGNESIUM-LIMITED GROWTH OF SACCHAROMYCES-CEREVISIAE

The growth response of Saccharomyces cerevisiae to magnesium limitatio n when propagated aerobically in batch culture under conditions of glu cose repression was hyperbolic, thus indicating a Monod relationship T he saturation coefficient, K-s, was 36 mu M magnesium, and exogenous m agnesium requirements for optimal yeast growth rate were established i n minimal medium. An investigation into growth and metabolism of S. ce revisiae over a range of growth rates using a magnesium-limited chemos tat revealed that at growth rates less than mu(max), cells exhibited a physiological state characteristic of non-carbon-limited growth. This was exemplified by an increase in the biomass yield from increased ma gnesium availability and alterations in the relative contributions of fermentation and respiration to the overall respirofermentative activi ty as the growth rate increased reward mu(max). Studies on the growth behaviour of S. cerevisiae when cells were released from magnesium lim itation within a chemostat suggested that magnesium primarily exerts i ts influence on cell division cycle progression in this yeast.