Dried Yeast: Impact of Dehydration and Rehydration on Brewing Yeast DNA Integrity

Abstract

As a consequence of fluidized bed drying, yeast cells may be exposed to a series of physiological stresses, of which the most evident is water loss. Desiccation can lead to cell wall crenellation, cytoplasmic crowding, loss of DNA supercoiling, membrane disruption, phase transitions, and ultimately cell death. Although the dehydrated phenotype has been well characterized, the sequence of events that causes damage to the cell has not been widely reported. Here we investigate the impact of dehydration and rehydration on the stability of the brewing yeast genome, including both the chromosomal and mitochondrial DNA (mtDNA). Analysis of rehydrated and control yeast populations for chromosome length polymorphisms (karyotyping), DNA sequence changes (PCR analysis of interdelta sequences), gross mitochondrial damage (presence of respiratory deficient mutants), and mitochondrial sequence changes (mtDNA RFLP [restriction fragment length polymorphisms]) indicated that the genetic constitution of dried yeast is not affected by the drying process. Active dried yeast (ADY) populations also demonstrated an enhanced tolerance to mutagen challenge (targeted at mtDNA), suggesting that the susceptibility of mtDNA to change is not associated with fluidized bed drying. These results demonstrate that the genetic stability of ADY is comparable to control populations.