Induced autolysis ofSaccharomyces cerevisiae: Morphological effects, rheological effects, and dynamics of accumulation of extracellular hydrolysis products

Abstract

Changes in the internal structure ofSaccharomyces cerevisiae cells and accumulation of proteins and nucleic components in extracellular fluid as decomposition products were studied in the 40–75°C temperature range under the effect of various membranotrophic additives. Autolysis was shown to be a two-step process: The first step consists of the restructuring of cell endostructures and the activation of lytic enzymes, which is accompanied by reduction of cell volume and system viscosity; the second step directly follows the first step and consists of hydrolysis of cell components and release of hydrolysis products into extracellular space. Duration of the first step depends on the temperature and the plasmolyzer. Hydrophilic additives (ethanol, ethyl acetate) were most effective during the first step at 60–65°C, whereas hydrophobic additives (lecithin, lauric acid) were most effective at 55°C. In the second step, the temperature optimum of protease activity in the control (without additives) was 60°C, that of nuclease activity was 70°C. Additives reduce the temperature optimum of endoenzymatic activity. Cell morphology was studied at various stages of autolysis by electron and phase-contrast microscopy.