Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, and‡College of Biotechnology, Tianjin University of Science and Technology , Tianjin 300457, People's Republic of China.
J Agric Food Chem. 2014 May 14;62(19):4454-65. doi: 10.1021/jf500505n. Epub 2014 May 2.
ε-Poly-L-lysine (ε-PL), a naturally occurring amino acid homopolymer, has been widely used as a food preservative. However, its antimicrobial mechanism has not been fully understood. This study investigated the antimicrobial mode of action of ε-PL on a yeast, Saccharomyces cerevisiae. When treated with ε-PL at the concentration of 500 μg/mL, cell mortality was close to 100% and the phospholipid bilayer curvature, pores, and micelles on the surface of S. cerevisiae were clearly observed by scanning electron microscopy (SEM). At the level of 200 μg/mL, ε-PL significantly inhibited the cell growth of S. cerevisiae. When treated with 50 μg/mL ε-PL, the yeast cell was able to grow but the cell cycle was prolonged. A significant increase in cell membrane permeability was induced by ε-PL at higher concentrations. Metabolomics analysis revealed that the ε-PL stress led to the inhibition of primary metabolic pathways through the suppression of the tricarboxylic acid cycle and glycolysis. It is therefore proposed that the microbiostatic effect of ε-PL at lower levels on S. cerevisiae is achieved by inducing intracellular metabolic imbalance via disruption of cell membrane functions. Moreover, the results suggested that the antimicrobial mechanism of ε-PL on S. cerevisiae can in fact change from microbiostatic to microbicidal when the concentration of ε-PL increased, and the mechanisms of these two modes of action were completely different.
ε-聚赖氨酸（ε-PL）是一种天然存在的氨基酸均聚物，已被广泛用作食品防腐剂。然而，其抗菌机制尚未完全阐明。本研究探讨了ε-PL 对酵母酿酒酵母的抗菌作用方式。当用 500μg/mL 的ε-PL 处理时，细胞死亡率接近 100%，扫描电子显微镜（SEM）清楚地观察到酿酒酵母表面的磷脂双层曲率、孔和胶束。在 200μg/mL 的浓度下，ε-PL 显著抑制了酿酒酵母的细胞生长。当用 50μg/mL 的ε-PL 处理时，酵母细胞能够生长，但细胞周期延长。ε-PL 在较高浓度下会引起细胞膜通透性的显著增加。代谢组学分析表明，ε-PL 应激通过抑制三羧酸循环和糖酵解来抑制主要代谢途径。因此，提出ε-PL 在较低水平对酿酒酵母的抑菌作用是通过破坏细胞膜功能引起细胞内代谢失衡来实现的。此外，结果表明，当ε-PL 的浓度增加时，ε-PL 对酿酒酵母的抗菌机制实际上可以从抑菌变为杀菌，这两种作用方式的机制完全不同。
