Besides fermentation, the production of bacterial starter cultures includes another crucial step, namely, the 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 treatment of EPS producing bacterial starter cultures leads to improved separation properties and, hence, higher bacteria yields. We assume that both EPS types affect separation efficiency of the bacteria cells, free EPS because of increased media viscosity and capsular EPS because they act like a friction pad.

除发酵外，细菌发酵剂培养物的生产还包括另一个关键步骤，即分离细菌细胞。这种分离最通常是用圆盘叠层分离器进行的，需要调整到相应的应变以获得高的细胞回收率。然而，由几种起始培养物产生的胞外多糖（EPS）对细胞的分离特性有很大的负面影响。这些EPS可以分为释放到周围发酵培养基中的细胞结合荚膜EPS或游离EPS。为了改进分离步骤，发酵后使用齿轮环分散器施加剪切力，以模拟均质器的影响以及对六个嗜热链球菌的分离特性的影响。检查了菌株。在荚膜EPS的情况下，由于切下荚膜EPS层，细菌的沉降速度增加。如使用圆盘离心机和LUMiSizer所确定的，具有游离EPS的剪切介质会导致粘度降低，并因此导致更高的沉降速度。用LUMiSizer测量的泥沙压缩也受到剪切步骤的影响。这项研究的结果表明，对产生EPS的细菌发酵剂培养物进行明确的剪切处理可提高分离性能，从而提高细菌产量。我们假设这两种EPS类型都会影响细菌细胞的分离效率，由于增加的介质粘度会影响游离EPS，并且会影响胶囊细胞EPS，因为它们起着摩擦垫的作用。