Structural Changes and Antibacterial Activity of Epsilon-poly-l-lysine in Response to pH and Phase Transition and Their Mechanisms

• Published in: Journal of agricultural and food chemistry Vol. 68; no. 4; pp. 1101 - 1109
• Main Authors: Liu, Jia-Ning, Chang, Sen-Lin, Xu, Peng-Wei, Tan, Ming-Hui, Zhao, Bing, Wang, Xiao-Dong, Zhao, Qing-Sheng
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 29.01.2020
• Subjects: Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - metabolism; Anti-Bacterial Agents - pharmacology; Bacillus subtilis - drug effects; Bacillus subtilis - growth & development; Escherichia coli - drug effects; Escherichia coli - growth & development; Hydrogen-Ion Concentration; Phase Transition; Polylysine - chemistry; Polylysine - metabolism; Polylysine - pharmacology; Staphylococcus aureus - drug effects; Staphylococcus aureus - growth & development; Streptomyces - chemistry; Streptomyces - metabolism; antibacterial activity; β-sheet; conformation; ε-poly- l -lysine; pH responsivity; carbamoylated ε-PL; ε-poly-l-lysine
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/acs.jafc.9b07524

ε-Poly-l-lysine (ε-PL) consists of 25–35 lysine residues which are linked by an isopeptide bond formed by dehydration condensation of α-carboxyl and ε-amino groups and has good antibacterial activity and broad-spectrum inhibition range. However, there is no clear conclusion about the structure and antibacterial mechanism of ε-PL in aqueous solution. Herein, a high purity of ε-PL was prepared using Amberlite IRC-50 ion-exchange resin. Membrane filtration and dynamic light scattering were used to study the variations of ε-PL aggregation in aqueous solution with pH value. The conformational changes and antibacterial activities of ε-PL and carbamoylated ε-PL in different water environments were studied with circular dichroism (CD) and inhibition zone. The structural changes during the spray-drying process were determined by Fourier transform infrared spectroscopy. The results indicated that the side chain amino charge played a decisive role in the ε-PL conformation and aggregation. ε-PL exhibited the properties of a β-sheet during spray drying from acidic liquids to solids. The cation enhanced the antibacterial activity of ε-PL but did not play a key role. Instead, the backbone of ε-PL might determine the mechanism of ε-PL antibacterial.