Phase separation behaviour during direct solvent extraction of Corynebacterium glutamicum fermentation broth – Systematic study of crud suppression

Current Research in Green and Sustainable Chemistry, vol. 10, pp. 100448

Abstract

The economic competitiveness of bio-based production processes is often hindered by the high costs associated with downstream processing, compared to fossil-based methods. Liquid-liquid extraction is a widely used technique for aqueous fermentation systems and offers significant cost-saving potential, especially if extraction could be performed directly from the fermentation broth without prior cell separation. However, this is often hindered by the formation of "crud" — a deposit or emulsion at the interface between two partially settled phases. This study investigates the liquid-liquid phase separation of Corynebacterium glutamicum DM 1933 fermentation broths using five different solvents. We systematically examined the impact of cell surface properties, modified through nutrient concentration, on crud formation. In addition, the variation in salt concentration and pH after fermentation was analysed. Our findings show that the present nutrient concentration influences the cell surface properties and, consequently, crud formation. A more hydrophilic cell surface was present at a lower phosphate concentration, whereas a more hydrophobic cell surface was measured for a lower nitrogen and iron concentration. With a more hydrophobic cell surface, the fermentation broth showed a large crud phase, while a decrease in crud formation could be seen for fermentation broths with a more hydrophilic cell surface. Furthermore, the crud formation is influenced by the pH, cell and salt concentration and strongly by the used solvent. • Nutrient variations impact the cell surface properties of Corynebacterium glutamicum DM 1933. • Influence of solvent, salt and pH on the formation of crud during direct extraction of fermentation broths. • Indications of a correlation between cell surface properties and phase separation behaviour and crud formation. • Study on crud suppression in which factors influencing both upstream and downstream are considered.

Authors 5

1. Jörg Eberz Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Aachener Verfahrenstechnik – Fluid Process Engineering (AVT.FVT), Forckenbeckstr. 51, 52074, Aachen, Germany

2. Lara Strehl Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Aachener Verfahrenstechnik – Biochemical Engineering (AVT.BioVT), Forckenbeckstr. 51, 52074, Aachen, Germany

3. Marcel Mann Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Aachener Verfahrenstechnik – Biochemical Engineering (AVT.BioVT), Forckenbeckstr. 51, 52074, Aachen, Germany

4. Andreas Jupke corresponding Aachen

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Institute for Bio- and Geosciences (IBG-2), Wilhelm-Johnen-Straße, 52428 Jülich, Germany

   RWTH Aachen University, Aachener Verfahrenstechnik – Fluid Process Engineering (AVT.FVT), Forckenbeckstr. 51, 52074, Aachen, Germany

5. Jørgen Barsett Magnus corresponding Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Aachener Verfahrenstechnik – Biochemical Engineering (AVT.BioVT), Forckenbeckstr. 51, 52074, Aachen, Germany