Cerium (IV) initiated graft-from polymerization reactions were employed to convert M-PVA magnetic particles into polyacrylic acid-fimbriated magnetic cation exchange supports displaying ultra-high binding capacity for basic target proteins. The modifications, which were performed at 25mg and 2.5g scales, delivered maximum binding capacities (Qmax) for hen egg white lysozyme in excess of 320mgg1, combined with sub-micromolar dissociation constants (0.450.69 mu m) and tightness of binding values greater than 49Lg1. Two batches of polyacrylic acid-fimbriated magnetic cation exchangers were combined to form a 5g pooled batch exhibiting Qmax values for lysozyme, lactoferrin, and lactoperoxidase of 404, 585, and 685mgg1, respectively. These magnetic cation exchangers were subsequently employed together with a newly designed rotorstator type HGMF rig, in five sequential cycles of recovery of lactoferrin and lactoperoxidase from 2L batches of a crude sweet bovine whey feedstock. Lactoferrin purification performance was observed to remain relatively constant from one HGMF cycle to the next over the five operating cycles, with yields between 40% and 49% combined with purification and concentration factors of 37- to 46-fold and 1.3- to 1.6-fold, respectively. The far superior multi-cycle HGMF performance seen here compared to that observed in our earlier studies can be directly attributed to the combined use of improved high capacity adsorbents and superior particle resuspension afforded by the new rotorstator HGMS design. Biotechnol. Bioeng. 2013; 110: 17141725. (c) 2013 Wiley Periodicals, Inc.