Strategies of Freezing Tolerance in Yeast: Genes’ Rapid Response for Accumulation of Stress Protectants

Production of frozen ready-to-bake bakery products has gained significant attention during the past few years. However, the freezing process during the production of frozen bakery products may decrease the quality especially in the case of suppression of the activity of baker yeast. Great improvements in the quality of frozen bakery products may be achieved by increasing the stability of yeast during freezing storage. Many microorganisms have different kinds of mechanisms to suppress environmental, freezing or thawing stresses. In this review paper, reported strategies which are used for rising tolerance of microorganisms, especially yeast, are reviewed. One of the introduced protective procedures is the accumulation of special intra-cellular metabolites by some microorganisms. Two main key metabolites in this regard are trehalose and proline (which act as an osmoprotectant and decrease the melting point of DNA), which are introduced in this review article. Also, cloning strategies for increasing their bioaccumulation are pointed out, and their mechanisms of action are described. Finally, overexpression of SNR84 gene as an another microbial strategy for surviving in harsh environmental conditions is (small nucleolar RNAs) mentioned, which leads to ribosomal pseudouridines (responsible for freezing tolerance and decreasing growth rate of organisms).