Purification of lactoferrin through a sequential filtration and magnetic separation process: A processing example for acid whey valorization

In the quest for possibilities to valorize the dairy by-product acid whey, we developed a sequential process comprising filtration and magnetic separation to isolate the valuable protein lactoferrin thereof. In the first step, we clarified whey by microfiltration, followed by selective lactoferrin enrichment through ultrafiltration. This process raises the initially low lactoferrin concentration (<0.2 g L^–1) to 2.8 g L^–1, increasing efficiency in the subsequent magnetic lactoferrin isolation step in the commercial rotor-stator magnetic separator. The up to 23-fold volume reduction in the combined micro- and ultrafiltration had a lactoferrin yield of 90 % and helped to reduce the processing time of the subsequent magnetic separation substantially. During magnetic separation, lactoferrin binds to affordable unfunctionalized magnetic iron oxide particles and is thereafter magnetically captured and selectively eluted from its magnetic carrier. We purified 1.55 g lactoferrin with a yield of 60 % and a purity of 78 % from 1.3 L acid whey retentate, corresponding to an original volume of 21 L. The combined process outperforms previously published magnetic separation processes in purity and productivity, pushing the technology toward an industrial application.