Proteomics-based mechanistic study of sub-lethally injured Saccharomyces cerevisiae by pulsed electric fields

Abstract

The pulsed electric fields (PEF) technology has been widely applied to inactivate spoilage and pathogenic microorganisms in food products because of its conspicuous advantages. However, the inevitable production of sub-lethally injured microorganisms limited its further application and development. In the present study, we investigated the mechanisms underlying the PEF-induced inactivation and sublethal damage of microorganisms to enhance the bactericidal effect of PEF treatments. In our work, Saccharomyces cerevisiae was used as a model organism, and the lethal and sublethal injury of microorganisms induced by PEF was estimated using non-selective and selective media. We found that PEF treatment with 20 kV/cm intensity for 200 or 400 μs, or with 15 kV/cm intensity for 400 μs, caused more sub-lethally injured cells. The PEF with 55 °C treatment produced the highest inactivation rate and the lowest sublethal injury rate. Then two-dimensional electrophoresis with mass spectrometry analysis was conducted to analyze the protein differences of S. cerevisiae under different PEF treatments. Compared with the PEF treatment (20 kV/cm, 200 μs) alone, many proteins changed significantly after PEF combined with 55 °C mild heat treatment, including several heat shock proteins. Finally, the heat shock protein 104 (Hsp104) of S. cerevisiae was knocked out, which led to a decrease in sub-lethally injured cells and an increase in inactivation rate after PEF treatment. Our findings provide critical information for developing more effective PEF-based microbial inactivation approaches in food processing.