Purification of ε-polylysine from fermentation broth by a new method of metal ion complexation

Abstract

ε-Polylysine (ε-PL), an efficient and safe natural biological preservative, has shown a promising development. However, the downstream purification of ε-PL remains a bottleneck due to high costs and low yields. This study aimed to develop a new approach of metal ion complexation for the purification of ε-PL from fermentation broth. The purification procedure was optimized and the effect of Ni2+ and Zn2+ on the purification of ε-PL was investigated. The results indicated that the optimal conditions for ε-PL purification included complexation with 130 mM metal ion at pH 9.5, acid dissolution at pH 2, decolorization with 1 % (w/v) activated carbon, and precipitation with 80 % ethanol. Compared with Zn2+, Ni2+ as complexing agent had a better purification effect on ε-PL. The final purity and recovery of ε-PL sample obtained by Ni2+ could reach 98.16 % and 81.27 %, while also meeting the requirement of antimicrobial. Furthermore, infrared spectroscopy and molecular docking were used to analyze the coordination regions of ε-PL and metal ions. The results showed that the coordination regions of ε-PL were amino, carbonyl and carboxyl groups, and molecular docking provided a theoretical basis for the reasonable application of different metal ions in the purification process of ε-PL.