Acknowledgement: A Novel Method of Inducing and Retaining Cell Cycle Synchronization in Cultures of Saccharomyces cerevisiae

Journal of the ASBC 72(2):102-109, 2014. J. Blake Layfield, Lucas R. Vann, and John D. Sheppard

In conventional fermentation, at any one time, individual yeast cells are randomly distributed with respect to the stage of their growth and division cycle. The observed metabolic performance is, therefore, the result of an average of the entire population. In contrast, a synchronous population is characterized by cells that are aligned with respect to their metabolic processes, traversing the cell cycle and dividing mostly in unison. In this study, a novel method for inducing and retaining cell cycle synchronization in yeast cultures (diploid and polyploid-type) was developed using a simple and natural phased expansion method, in which the volume of the culture was increased step-wise at time periods equal to the cell doubling time. Results indicate that this method was effective in producing yeast cultures with a high degree of synchrony, verified by cell counts and fluorescent cytometry. When stored in relatively small volumes at –80°C in glycerol, the cultures maintained their synchrony upon thawing. Experiments were also conducted at the lab-scale to assess the potential use of synchronous cultures in brewing applications. The incorporation of phased seed expansion and periodic feeding of the yeast culture provided increased metabolic uniformity within the population and reduced variability in fermentation performance.