OPTIMIZING ENZYME-PRODUCTION BY BAKERS-YEAST IN CONTINUOUS-CULTURE - PHYSIOLOGICAL KNOWLEDGE USEFUL FOR PROCESS DESIGN AND CONTROL

Saccharomyces cerevisiae was grown in aerobic continuous culture on a defined minimal medium, with glucose (40 g.l(-1)) as the growth-limiti ng carbon source, to acquire knowledge useful in process design and fo r model-based control. Steady-state concentrations of biomass, glucose , ethanol and activities of model products alcohol dehydrogenase, hexo kinase, malate dehydrogenase, glucose-6-phosphate dehydrogenase and is o-citrate dehydrogenase were determined at dilution rates (D) between 0.06 h(-1) and 0.323 h(-1) (close to mu(max)). Enzyme activities showe d productivity trends related to the transition from oxidative to oxid o-reductive growth. Conclusions are drawn from the data with regard to designing a new process for production of intracellular enzymes. Issu es of process stability as well as productivity are discussed.