Growth phase modulation of the productivity of α-galactosidase in budding yeast cultures

The complete utilization of raffinose and melibiose by Saccharomyces cerevisiae requires the synthesis and secretion of an α-galactosidase encoded by a single MEL1 gene. The influence of culture conditions on the productivity of α-galactosidase in batch growth of yeast cells has been investigated. A modulation of the MEL1 gene expression has been observed depending on growth condition, with a maximum of enzyme productivity during a transient physiological phase corresponding to the early stationary phase. Our experiments demonstrate that the highest α-galactosidase productivity observed in the early stationary phase of growth is not associated with a starvation condition, but it is coupled to a particular growth phase. The increase of specific activity of the enzyme occurs mainly for periplasmic and intracellular fractions while the amount of enzyme secreted in the medium remains fairly constant. © 1989.