Efficient purification of the antimicrobial peptide ε-poly-L-lysine from microbial culture medium with continuous ion-exchange chromatography

ε-Poly-L-lysine (ε-PL) is an added-value biopolymer for wide potential applications in food, pharmaceutical, biomaterial, and other industries, which is primarily manufactured through ion-exchange chromatography adsorption from a microbial culture medium. However, the high production cost in the ε-PL downstream limits its application. In this study, the strong acid cation resin SQD-04 was first developed to recover ε-PL from a clarified microbial culture medium. Subsequently, efficient sequential four-column chromatography (SFCC) rather than batch (single-column) chromatography was developed to purify ε-PL. During SFCC adsorption, specific optimal adsorption conditions (ε-PL concentration of 35 g/L, flow rate of 1 BV/h, and ε-PL breakthrough percentage of 60%) were optimized through orthogonal experiments. Finally, the constructed SFCC process achieved 75.11% purity with 94.25% recovery for separating ε-PL from clarified microbial culture medium and offered several advantages, including higher inlet ε-PL concentration (35 g/L), higher adsorption capacity (244.34 mg/g), higher resin utilization (84.69%), lower water consumption (51.60% saving), and lower alkali consumption (58.86% saving) over batch ion-exchange chromatography. After further purification through decoloration and ultrafiltration, a final ε-PL purity of 96.57% was attained with a total recovery ratio of 73.10%. The study demonstrated that continuous ion-exchange chromatography could provide great industrial benefits for ε-PL and other biological products.