Stress Tolerance of Baker’s Yeast During Bread-Making Processes

Abstract

During the fermentation of dough and the production of baker’s yeast, cells of baker’s yeast are exposed to numerous and multiple environmental stresses including freeze–thaw, high-sucrose, and air-drying, the so-called baking-associated stresses. In addition, such stress conditions could induce oxidative stress in yeast cells with an increase in reactive oxygen species level because of the denaturation of proteins including antioxidant enzymes and the severe damage to the mitochondrial membrane or respiratory chain. To avoid lethal damage, baker’s yeast cells need to acquire a variety of stress-tolerant mechanisms, such as the induction of stress proteins, accumulation of stress protectants or compatible solutes, change of membrane composition, and repression of translation, by regulating the corresponding gene expression via stress-triggered signal transduction pathways. For example, proline and trehalose are important compounds involved in the stress tolerance of baker’s yeast. In fact, the engineering of proline and trehalose metabolism is a promising approach for the development of stress-tolerant baker’s yeast. Moreover, the multiomics approach such as comprehensive phenomics and functional genomics is promising for the identification of novel genes required for the stress tolerance. To further improve the fermentation ability or the production efficiency of yeasts, however, the detailed mechanisms underlying the stress response, adaptation, and tolerance of yeast cells should be understood. We believe that not only baker’s yeast, but also other important industrial yeasts with higher tolerance to various stresses, could contribute to the yeast-based industry for the effective production of bread doughs and alcoholic beverages or a breakthrough in bioethanol production.