Metals in yeast fermentation processes

This chapter reviews the mineral nutrition of yeasts employed in fermentation processes, with a particular focus on the roles of magnesium, calcium, and zinc in the physiology of industrial strains of the yeast Saccharomyces cerevisiae. In yeast cell physiology, these roles are multifarious and can affect significantly the progress and efficiency of industrial fermentations. The chapter discusses some of the salient points for the cell physiology of S. cerevisiae: metal ion “bioavailability” in fermentation media is more important than total levels of metals; high calcium levels are detrimental; metal-preconditioned yeasts may improve fermentative metabolism; stress affects metal ion homeostasis and some metals can counteract physiological stress. It is evident that many metals strongly influence yeast fermentation performance, and more careful attention should be paid to minerals in fermentation feedstocks than has hitherto been the case. Also, by physiologically adapting starter yeast cultures, benefits may accrue in terms of improved fermentations.