The influence of homogenisation conditions on biomass‐adsorbent interactions during ion‐exchange expanded bed adsorption

Abstract

Expanded bed adsorption (EBA) is an integrative step in downstream processing allowing the direct capture of target proteins from cell-containing feedstocks. Extensive co-adsorption of biomass, however, may hamper the application of this technique. The latter is especially observed at anion exchange processes as cells or cell debris are negatively charged under common anion exchange conditions. The restrictions observed under these conditions are, however, directly related to processing steps prior to fluidised bed application. In this study, it could be shown that the effective surface charge of cell debris obtained during homogenisation is closely related to the debris size and thus to the homogenisation method and conditions. The amount and thus effect of cells binding to the adsorbent could be significantly decreased when optimising the homogenisation step not only towards optimal product release but towards a reduction of debris size and charge. The lower size and charge of the debris results not only in a reduced retention probability but also, in a lower collision probability between debris and adsorbent. The applicability was shown in an example where the homogenisation conditions of E. coli were optimised towards EBA applications. In a previous report (Reichert et al., 2001) studying the suitability of EBA for the capture of formate dehydrogenate from E. coli homogenate the pseudo affinity resin Streamline Red was identified as the only suitable adsorbent. The new approach, however, led to a system where anion exchange as capture step became possible, however, to the cost of binding capacity.

A study of the influence of yeast cell debris on protein and α‐glucosidase adsorption at various zones within the expanded bed using In‐Bed sampling

“…The interactions between biomass and adsorbent during the EBA process have been studied by various researchers Feuser et al, 1999;Gondkar et al, 2001;Hubbuch et al, 2006;Lahore et al, 1999Lahore et al, , 2000Lin et al, 2001Lin et al, , 2002Lin et al, , 2003aLin et al, ,b, 2004Lin et al, , 2007Mei et al, 2005;Vergnault et al, 2004Vergnault et al, , 2007. With an anion exchange adsorbent, electrostatic interactions retain the yeast cells which carry a negative surface charge.…”

“…With an anion exchange adsorbent, electrostatic interactions retain the yeast cells which carry a negative surface charge. Intact cells were found to interfere with the adsorption process to a higher extent than cell debris Hubbuch et al, 2006). The size of the cell debris and the surface charge on the yeast debris has been found to depend on the extent of disruption .…”

Colloid deposition experiments as a diagnostic tool for biomass attachment onto bioproduct adsorbent surfaces

“…18 In this study, both factors are kept constant since only intact yeast cells (8 µm diameter) of spherical shape were utilized as model biomass.…”

Surface modification of chromatography adsorbents by low temperature low pressure plasma

“…Perhaps the greatest technical problem affecting EBA is the physical cross-linking of neighbouring adsorbent particles by biomass or large colloidal molecules (especially nucleic acids) present in crude feedstocks, which leads to gross breakdown/collapse of the structure of the expanded bed and consequent loss of 15 chromatographic performance [18,[25][26][27][28][29][30][31][32][33][34]. Attempts to relieve problems of inter-adsorbent particle cross-linking in EBA systems by chemically or mechanically conditioning the crude feedstock prior to application have been at best only partially successful [26,32,33]. This is not surprising given that the root of the problem is that the outer surfaces of expanded bed adsorbents, like other beaded chromatographic materials, are populated with functional groups 20 capable of binding both the product of interest and large adsorbent cross-linking contaminants present in crude feedstocks.…”

“…Pall's HyperZ adsorbents). Rather than help intensify bioprocesses, both of these actions have in fact resulted in less robust EBA operation with crude feedstocks for 30 which the technique was originally intended [25,32,33]. Very little effort has been invested thus far on redesigning expanded bed supports for 'problem-free' use in crude feedstocks.…”