Old yeasts, young beer—The industrial relevance of yeast chronological life span

Abstract

Much like other living organisms, yeast cells have a limited lifespan, both in terms of the maximal length of time a cell can stay alive (chronological lifespan) as well as the maximal number of cell divisions it can undergo (replicative lifespan). Over the past years, intensive research revealed that the lifespan of yeast depends both on the genetic background of the cells as well as on environmental factors. Specifically, the presence of stress factors, reactive oxygen species and the availability of nutrients profoundly impact lifespan, and signaling cascades involved in the response to these factors, including the TOR and cAMP/PKA pathways, play a central role. Interestingly, yeast lifespan also has direct implications for its use in industrial processes. In beer brewing, for example, the inoculation of finished beer with live yeast cells, a process called “bottle conditioning” helps improve the product’s shelf life by clearing undesirable carbonyl compounds such as furfural and 2‐methylpropanal that cause staling. However, this effect depends on the reductive metabolism of living cells and is thus inherently limited by the cells’ chronological lifespan. Here, we review the mechanisms underlying chronological lifespan in yeast. We also discuss how this insight connects to industrial observations and ultimately opens new routes towards superior industrial yeasts that can help improve a product’s shelf life, and thus contribute to a more sustainable industry.