Abstract
Trials were undertaken to elucidate the stimulating effect of sodium humate on yeast multiplication and the intensity of their fermentation. This effect appears specifically at pH non-optimal for the medium. No correlation was found between this effect and the complex-forming properties of various natural and synthetic humate fractions or the concentration of phosphate and calcium ions in the medium. Application of cystein as reducing agent, aeration of the medium and addition of detergents to it did not substitute the effect of humate. Tannin and gibberellin, on the other hand, stimulated cell proliferation and fermentation at non-optimal pH, remaining almost without influence at optimal pH, similarly as does humate.