Effect of pectin on epsilon-polylysine purification: Study on preparation, physicochemical property, and bioactivity of pectin-epsilon-polylysine complex

Epsilon-polylysine (ε-PL) is a typical antibacterial peptide with a wide spectrum and high safety. Pectin could form electrostatic complex with ε-PL and affects the antibacterial performance. However, the potential application of pectin on ε-PL purification has not been discussed. In this study, a novel process for preparation antibacterial complex pectin-ε-PL was carried out by adding pectin to the ε-PL fermentation broth and further processing. The results showed that ε-PL could be completely collected when the mass ratio of pectin to ε-PL was 8. After further removing pectin by ethanol precipitation, pectin-ε-PL complex was obtained. The content of ε-PL in pectin-ε-PL complex was 30.59% ± 1.21%, and the recovery rate of ε-PL was 62.63% ± 0.63%. In addition, the physicochemical properties of pectin-ε-PL complex were discussed. The Zeta-potential analysis suggested that the intrinsic pK of pectin-ε-PL complex was 7.74. Furthermore, the cytotoxicity test showed that for Raw264.7 cells pectin-ε-PL was a more compatible and safer product than ε-PL alone. At last, the minimal inhibitory concentration (MIC) of pectin-ε-PL for B. subtilis, and E. coli were 0.25 mg/mL and 0.1 mg/mL respectively, which presented the same activity as high purity ε-PL. Therefore, the separation of ε-PL from fermentation broth by pectin is a novel promising technological process, and the obtained pectin-ε-PL complex is an outstanding product with high stability and antibacterial performance.