Yeast-metal interactions: impact on brewing and distilling fermentations

Abstract

[Abstract]: In brewing and distilling fermentations, key metal ions are magnesium and zinc, which act as co-factors for important glycolytic enzymes and also as modulators of yeast stress. In addition to their effects on enzymes, metal ions may have marked effects on stability and dynamics of cell membranes, leading to downstream effects on cell permeability and signalling systems. Occasionally, the bioavailability of certain key minerals may be limiting and this can adversely affect yeast fermentation processes. For example, zinc levels may decrease during mashing and wort boiling as the metal ion becomes complexed in precipitated trub. Consequently, zinc levels in wort may become compromised leading to impaired fermentation performance. This paper reviews previous work on the impact of magnesium and calcium on industrial yeasts and also describes the uptake and utilisation of zinc by brewing and distilling yeasts under conditions varying from deficit to oversupply. In addition, it discusses the impact of yeast-zinc interactions on the progress and efficiency of brewing and distilling fermentations, the status of cell membrane systems, and the influence of metals in governing yeast responses to environmental stress.