# Relationship between shear energy input and sedimentation properties of exopolysaccharide-producing $Streptococcus$ $thermophilus$ strains

Häffele, Florian; Mende, Susann; Jaros, Doris; Rohm, Harald; Nirschl, Hermann

Abstract:
separation of the bacteria cells. This separation is most commonly carried out with disc stack separators and needs to be adjusted to the respective strain to obtain a high cell recovery rate. Exopolysaccharides (EPS) produced by several starter cultures, however, have a large negative impact on the separation properties of the cells. These EPS can be divided into cell-bound capsular EPS or free EPS that are released into the surrounding fermentation medium. To improve the separation step, shear forces were applied after fermentation with a gear ring disperser to simulate the impact of a homogenizer and the influence on the separation properties of six Streptococcus thermophilus strains was examined. In case of capsular EPS, the sedimentation velocity of the bacteria increased due to shearing off the capsular EPS layer. Shearing media with free EPS resulted in a viscosity decrease and, hence, in a higher sedimentation velocity, as was determined using a disc centrifuge and a LUMiSizer. Sediment compression as measured with the LUMiSizer was also affected by the shearing step. The results of this study suggest that a defined shear tr ... mehr

 Zugehörige Institution(en) am KIT Institut für Mechanische Verfahrenstechnik und Mechanik (MVM) Publikationstyp Zeitschriftenaufsatz Jahr 2018 Sprache Englisch Identifikator ISSN: 1383-5866, 1873-3794 urn:nbn:de:swb:90-814813 KITopen-ID: 1000081481 Erschienen in Separation and purification technology Band 202 Seiten 21-26 Vorab online veröffentlicht am 16.03.2018 Schlagworte Analytical centrifugation, Sedimentation behavior, Starter cultures, Exopolysaccharides, Shear forces Nachgewiesen in Web of ScienceScopus
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