Behaviour of Candida utilis during growth in relation to Mg2+ and K+ concentration in sugar cane molasses

Magnesium and potassium ions are present in sugar cane molasses in a concentration of about 0.3% and 2.5%, respectively, which is high enough to support biomass production from Candida utilis. Culture broth with 40 g/l of total reducing substances supplemented by the addition of 1 ppm of Mg²⁺ leads to a higher yield (Y x/s) in batch fermentation experiments. The subsequent addition of Mg²⁺ up to 10 ppm decreases the yield coefficient from 0.53 to 0.42 without affecting the growth rate. Fermentation media supplemented with 1 to 10 ppm of K⁺ decreased both the yield coefficient and the specific growth rate. A Mg/K ratio of about 0.1 seems to be optimal for yeast biomass propagation.