The Rhobust® Adsorbent

Rhobust® Adsorbents are purpose-designed for EBA processes. The key to making the technology successful at an industrial scale lies with Upfront’s development of a unique, very high-density adsorbent bead that captures soluble proteins efficiently and selectively. The basic Rhobust® Adsorbent consists of spherical beads with an agarose outer shell and a tungsten carbide core. The agarose skin is actually a hydrogel that allows free movement of protein molecules within an open pore structure.

The agarose/tungsten carbide adsorbent beads have a density of 2.5 – 3.5 kg/l and typical diameters within the range of 20 – 300 micrometer. These small, high density beads allow extremely high process flow rates. The expanded bed is exceptionally robust due to the adsorbent’s “inertia”, resisting interference from particulates or air bubbles in the feed stream. The Rhobust® EBA process consistently achieves ‘plug flow’ conditions, meaning that protein capture profiles are highly efficient with minimal consumption of process liquids.


Ligand chemistry

The adsorbent beads are functionalized by linking purpose-designed surface chemistries to the structure of the agarose hydrogel. Proteins can be captured and then released by controlling salinity and pH in the liquids flowing around (and diffusing within) the beads.

Ligands are selected to bind specifically to proteins of interest in the feed stock. Optimal ligands have:

  • high selectivity towards the target protein
  • excellent protein separation capabilities
  • stable in harsh, column regeneration conditions
  • non toxic

Upfront has developed an extensive ligand library that is screened when a customized adsorbent is sought for a particular purpose. The library consists of both conventional ligands, such as ion exchangers and hydrophobic adsorbents, as well as Upfront’s patented mixed mode ligands. These ligands capture the soluble proteins and peptides directly from the raw material feedstock and are selected to provide a high degree of selectivity, even at high salt concentrations.

To design a specific Rhobust® Adsorbent for a customer’s requirement Upfront draw’s on the company’s extensive knowhow to optimise the key parameters:

  • Bead density
  • Bead size distribution
  • Protein binding surface chemistries

Thus Rhobust® Adsorbents are designed specifically for the customer’s process requirements and are essential to achieve the very best performance from the EBA process, both technically and financially.


Close-up of agarose bead with tungsten carbide particles incorporated.















Upfront Chromatography A/S - Oliefabriksvej 51 B, 2770 Kastrup, Copenhagen, DENMARK- Email:

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