Degradation of DNA during the autolysis of Saccharomyces cerevisiae

The autolysis of yeast cells has practical implications in the production of fermented foods and beverages and flavourants for food processing. Protein and RNA degradation during yeast autolysis are well described but the fate of DNA is unclear. Yeast cells (Saccharomyces cerevisiae) were autolysed by incubating suspensions at 30'60°C (pH 7.0), and at pH 4.0'7.0 (40°C) for 10'14 days. Up to 55% of total DNA was degraded, with consequent leakage into the extracellular environment of mainly 3'- and 5'-deoxyribonucleotides, and lesser amounts of polynucleotides. The rate and extent of DNA degradation, composition of the DNA degradation products and DNase activity were affected by temperature and pH. The highest amount of DNA degradation occurred at 40°C and pH 7.0, where the highest DNase activity was recorded. DNase activity was lowest at 60°C and pH 4.0, where the proportion of polynucleotides in the degradation products was higher.