Application of Controlled Heat Stress To Alter the Proteome, Amino Acid Content, and Cellular Structure of Yeast...

Autolysis of yeast cells can be induced by exposure to extreme stress, including high temperatures. This study investigated the cellular responses to heat stress during autolysis. Saccharomyces cerevisiae was heated to 60 °C either very rapidly (<4.5 min) or gradually (∼2.5 h) and then held at 60 °C for 24 h and analyzed using proteomics, electron microscopy, and biochemical analyses. Extensive proteomic remodeling occurred under both heating regimes, with 139 proteins enriched and 98 reduced by at least 10-fold. Protein markers linked to heat stress, autophagy, apoptosis, and necrosis suggested these processes occurred before cell death. While the amino acid profiles remained unchanged regardless of the heating rate, gradually heated yeast developed thicker cell walls and fragmented vacuoles, which contributed to greater protein release (90% versus 50% for rapid heating). Thus, gradual heat stress enhanced protein yield without altering the amino acid profile, providing valuable insights for improving industrial yeast extract production.