A scalable biomanufacturing platform for bacterial magnetosomes

Alfred Fernandez-Castane, Hong Li, Moritz Ebeler, Matthias Franzreb, Tim W. Overton, Owen R.T. Thomas

Research output: Contribution to journalArticlepeer-review


An integrated scalable platform for fermentative production and downstream processing of bacterial magnetosome products is advanced. Long magnetosome chains, high cellular magnetism, and low numbers of polyhydroxyalkanoate granules were obtained during the exponential growth phase of a two-stage continuous high cell density fermentation of M. gryphiswaldense MSR-1. Centrifugally concentrated 20% (w/v) suspensions of exponential phase cells were disrupted with high efficiency (~92%) in a single pass through a Constant Systems Cell Disruptor operated at 10 kpsi, releasing ~75% of the cellular iron. Magnetosomes were recovered in partially purified form from crude whole cell disruptates by rotor-stator high-gradient magnetic separation. Further purification/polishing was achieved by magnetically enhanced density separation in an aqueous micellar two-phase system (a new technique developed in this work as a low-cost alternative to sucrose gradient ultracentrifugation). The unoptimised 4-step process delivered highly purified magnetosomes (ca. 50 and 80-fold with respect to polyhydroxyalkanoate and protein) in >50% yield, with no evidence of crystal coat damage, acceptable reduction (~35%) in median magnetosome chain length, and magnetic properties (pot-bellied hysteresis loop, coercivity = 9.8 mT, ‘squareness’ = 0.32) expected of isolated magnetosome chains. Though demonstrated in batch mode, the platform displays potential for end-to-end continuous manufacture of future magnetosome-based products.
Original languageEnglish
Pages (from-to)110-122
Number of pages13
JournalFood and Bioproducts Processing
Early online date17 Jan 2024
Publication statusPublished - Mar 2024

Bibliographical note

© 2024 The Authors. CC BY 4.0


  • Aqueous two-phase systems, ATPS
  • Bioprocess separations
  • Downstream processing, DSP
  • Magnetic nanoparticles, MNP
  • Magnetotactic bacteria, MTB
  • Purification


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