title: Process boundaries of irreversible scCO2 -assisted phase separation in biphasic whole-cell biocatalysis.
abstract: The formation of stable emulsions in biphasic biotransformations catalyzed by microbial cells turned out to be a major hurdle for industrial implementation. Recently, a cost-effective and efficient downstream processing approach, using supercritical carbon dioxide (scCO2 ) for both irreversible emulsion destabilization (enabling complete phase separation within minutes of emulsion treatment) and product purification via extraction has been proposed by Brandenbusch et al. (2010). One of the key factors for a further development and scale-up of the approach is the understanding of the mechanism underlying scCO2 -assisted phase separation. A systematic approach was applied within this work to investigate the various factors influencing phase separation during scCO2 treatment (that is pressure, exposure of the cells to CO2 , and changes of cell surface properties). It was shown that cell toxification and cell disrupture are not responsible for emulsion destabilization. Proteins from the aqueous phase partially adsorb to cells present at the aqueous-organic interface, causing hydrophobic cell surface characteristics, and thus contribute to emulsion stabilization. By investigating the change in cell-surface hydrophobicity of these cells during CO2 treatment, it was found that a combination of catastrophic phase inversion and desorption of proteins from the cell surface is responsible for irreversible scCO2 mediated phase separation. These findings are essential for the definition of process windows for scCO2 -assisted phase separation in biphasic whole-cell biocatalysis.
authors.affiliation: Laboratory of Thermodynamics, Emil-Figge-Str. 70, 44227 Dortmund, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Brandenbusch
authors.affiliation: Laboratory of Thermodynamics, Emil-Figge-Str. 70, 44227 Dortmund, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Glonke
authors.affiliation: Laboratory of Chemical Biotechnology, TU Dortmund University, Dortmund, Germany.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Collins
authors.affiliation: Institute of Cell Culture Technology, Bielefeld University, Bielefeld, Germany.
authors.forename: Raimund
authors.initials: R
authors.lastname: Hoffrogge
authors.affiliation: Institute of Cell Culture Technology, Bielefeld University, Bielefeld, Germany.
authors.forename: Klaudia
authors.initials: K
authors.lastname: Grunwald
authors.affiliation: Laboratory of Chemical Biotechnology, TU Dortmund University, Dortmund, Germany.
authors.forename: Bruno
authors.initials: B
authors.lastname: Bühler
authors.affiliation: Laboratory of Chemical Biotechnology, TU Dortmund University, Dortmund, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schmid
authors.affiliation: Laboratory of Thermodynamics, Emil-Figge-Str. 70, 44227 Dortmund, Germany. g.sadowski@bci.tu-dortmund.de.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Sadowski
mesh_terms: D000327:Adsorption; D055162:Biocatalysis; D001709:Biotechnology / Q000379:methods*; D002245:Carbon Dioxide; D025924:Chromatography, Supercritical Fluid / Q000379:methods*; D004655:Emulsions / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*
chemical_list: D004655:Emulsions; D008565:Membrane Proteins; D002245:Carbon Dioxide
keywords: Pickering-type emulsion; phase separation; supercritical carbon dioxide; two-liquid phase system; whole-cell biocatalysis