How to design a low-cost pilot scale magnetic bioseparation process for protein separation from complex mixtures using in-line process analytics

Magnetic separation is a powerful tool for the integrated capture and purification of biomolecules and cells directly from complex feed media without the need for prior clarification and without the risk of equipment blockage. In this study, we equipped a commercially available rotor–stator high-gradient magnetic separator (RS-HGMS) with in-line analytics of hygienic design (absorbance, conductivity, pH, and flow) and used it for a systematic characterization of the equipment. By combining particle agglomeration and separation studies with residence time analysis, magnetic filter capacity, and particle retention experiments for bare iron oxide nanoparticles (BIONs), we developed a generic RS-HGMS operation protocol optimized for minimal particle carry-over and efficient buffer exchange. To demonstrate the versatility of our approach, we customized this operation protocol for the challenging task of lactoferrin separation from crude acid whey, which serves as an illustrative example in this paper. The modifications involved simple adjustments of pump speed, step duration, and cycle repetition without altering the fundamental principles of our generic approach. In this proof-of-concept, a BIONs carry-over of less than 0.037 g L^-1 was achieved in the elution fractions, and the in-line sensors enabled continuous monitoring and documentation of the process, providing valuable data for process optimization and validation. This paper demonstrates how a magnetic separation process can be effortlessly tailored for challenging bioseparation tasks, while emphasizing the importance of implementing continuous in-line process monitoring and data logging. We believe this is an essential step toward the wider adoption of this promising technique in the industry.