Metabolomics analysis of freeze–thaw tolerance enhancement mechanism of ε-poly-l-lysine on industrial yeast

Antimicrobial polycationic peptide ε-poly-l-lysine (ε-PL) enhanced the freeze-thaw tolerance of industrial yeast; the enhancement mechanism of ε-PL on yeast was studied. Results showed that a ε-PL coating was observed in ε-PL-treated yeast. After 4 times of freeze-thaw, the cell viability, glycerol content, and CO2 production of 0.6 mg/mL ε-PL-treated yeast were higher than those of untreated yeast, specifically, the cell viability of ε-PL-treated yeast was 87.6%, and that of untreated yeast was 68.5%. Metabolomic results showed that the enhancement mechanism of ε-PL on yeast was related to the promotion of cell membrane-related fatty acid synthesis pathways before freeze-thaw treatment, and the promotion of trehalose biosynthesis and glycerophospholipid metabolism pathways after freeze-thaw. Furthermore, ε-PL induced inhibition of the tricarboxylic acid cycle, resulting in a longer stationary phase at the beginning of the freeze-thaw and ultimately providing a higher level of freeze-thaw stress tolerance than untreated yeast.