Effect of ion form of the ion-exchange resin on ϵ-poly-l-lysine purification from microbial fermentation broth

Abstract

ϵ-Poly-l-lysine (ϵ-PL) is an added-value natural product with widespread application in the fields of food, pharmaceuticals and biopolymer materials. However, the high production cost reduces its application. To improve the efficiency of ϵ-PL purification for decreasing the cost of downstream processes, the ion form of the ion-exchange resin, which is widely used for ϵ-PL purification, was investigated systematically in this study. Among eleven cation-exchange resins tested, the Amberlite IRC-50 resin offered the best adsorption capability and the highest desorption ratio. The adsorption kinetics of IRC-50 resin with H+, Na+ and NH4+ ion forms followed a pseudo-second-order model. The dynamic adsorption and desorption parameters of ϵ-PL were optimized with a column packed with IRC-50 resin with Na+ and NH4+. It is suggested that NH4+ is the optimal ion form of IRC-50 resin for ϵ-PL extraction. Under optimal conditions, the IRC-50 resin with NH4+ achieved the highest ϵ-PL adsorption capability, purity and recovery ratio of 307.96 mg g-1, 76.52% and 96.2%, respectively. After further purification, a final ϵ-PL purity of 97.10% was achieved with a total recovery ratio of 66.01%. This is the first report on improving the ϵ-PL purification efficiency through optimizing the ion form of the ion-exchange resin. Moreover, it would offer guidance for other natural product recovery processes by ion-exchange chromatography.