Biotechnology Journal DOI 10.1002/biot.201000380 Biotechnol. J. 2011, 6, 392–395 392 © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim eCG is a placental hormone secreted by the en- dometrial cups of pregnant mares. eCG is a 60 kDa glycoprotein hormone composed of two non-cova- lently bound subunits. The average molecular weights of the α and β subunits are 16.96 and 43.72 kDa,respectively.The total carbohydrate con- tent of eCG is 45%, of which 10% correspond to sial- ic acid. This contributes to the very low pI of 1.8 of the hormone [1]. eCG can be detected in mare sera between days 40 and 130 of gestation [2–4], with its highest level of about 60–80 IU/mL in a bioassay in the early state of pregnancy [5]. The classical procedure for the purification of eCG is a multi-step precipitation process, followed by chromatographic steps. The first step is a frac- tionation with 0.5 M metaphosphoric acid at pH 3.0 and the discarding of the resulting precipitate. Af- ter the adjustment of the pH of the supernatant to 4.5, followed by the addition of one volume of cold (-20°C) ethanol, the solution is allowed to precipi- tate for 2 h at 4°C. Subsequently, after discarding the precipitate again, the ethanol fraction in the su- pernatant is raised up to 75% v/v.The resulting pre- cipitate is collected after 20 h at 4°C, dialyzed or di- afiltrated, and lyophilized [6]. The final cleaning consists of two fixed-bed chromatographic steps, including ion exchange and gel filtration. In contrast to this complex procedure, we devel- oped two simplified processes for the purification of eCG based on the application of magnetic mi- croadsorbents. The first process comprises only two precipitation steps, followed by an ultra-/di- afiltration step and a final purification step using magnetic anion exchange (AIX) microadsorbents synthesized by a reaction of carboxylated magnet- ic polyvinyl beads (M-PVA) with N,N-diethyl-am- monium as functional groups. Due to of the high salt and protein contents, direct application of the magnetic AIX adsorbents in untreated serum is im- possible. Nevertheless, the process described is less time-consuming and requires only 1/3 of sol- Short Communication Gonadotropin purification from horse serum applying magnetic beads Christine Müller 1 , Andrea Preußer-Kunze 2 , Kerstin Wagner 3 and Matthias Franzreb 1 1 Karlsruhe Institute of Technology, Institute of Functional Interfaces, Germany 2 fzmb GmbH Institute for Medical Technology and Biotechnology, Germany 3 INNOVENT e.V., Biomaterials Department, Germany The glycoprotein hormone equine chorionic gonadotropin (eCG) is a commercial product used in animal breeding as well as in veterinary medicine. The current state of the art for the purification of eCG from serum is pH fractionation with metaphosphoric acid, two ethanol precipitation steps as well as dialysis followed by fixed-bed chromatography. Two simplified processes, including the use of magnetic microsorbents for the purification of eCG have been developed. The processes reduce or even omit the use of organic solvents and the required solid–liquid separation steps, thus making them potential candidates for a first commercial application of magnetic beads in bioprocessing. Keywords: Equine chorionic gonadotropin · Magnetic adsorbents · Purification · Serum Correspondence: Professor Matthias Franzreb, Karlsruhe Institute of Technology, Institute of Functional Interfaces, Hermann-von-Helmholtz- Platz, 176344 Eggenstein Leopoldshafen, Germany Fax: +49-7247-823478 E-mail: matthias.franzreb@kit.edu Abbreviations: AIX, anion exchange; eCG, equine chorionic gonadotropin; HGMF, high-gradient magnetic fishing Received 29 October 2010 Revised 7 December 2010 Accepted 9 December 2010