Production of the STA2‐encoded glucoamylase in Saccharomyces cerevisiae is subject to feed‐back control

Three modes of production of the extracellular glucoamylase (GA) in Saccharomyces cerevisiae have been identified: repressed, basal and induced. The repressed mode is found with cells grown in rich media containing non‐limiting concentrations of monosaccharides or disaccharides, including GA‐hydrolysable maltose, as a sole carbon source. Both the basal and the induced modes (spanned by some seven‐fold difference in the rate of GA production) can be displayed by either glucose‐limited or glycerol‐ plus ethanol‐consuming cultures: the induced mode is switched over to the basal one due to a feed‐back inhibition by extracellularly accumulated GA. It is proposed that the feed‐back control involved in GA production can be attenuated by starch which can thus ‘induce’ higher rates of GA production compared to the basal mode.