一些乳酸菌能够产生胞外多糖,基于本地化,可以在游离和荚膜或细胞结合的胞外多糖(CPS)中区分。到目前为止,前者是当前研究的重点,主要是因为它们在发酵乳制品上表现出的技术功能优势。另一方面,CPS会影响细菌细胞的表面特性,从而影响发酵食品的质地特性,但是数据非常稀缺。由于细胞表面特性强烈依赖于应变,我们提出了一种新的方法来研究CPS对细胞表面疏水性和水分负荷的影响。对CPS阳性和阴性的嗜热链球菌和cybariaWeissella进行超声处理,以分离CPS而不会造成细胞损伤。通过扫描电子显微镜和光学显微镜以及培养实验验证了该方法的成功。在使用CPS表现出增加的亲水性的超声处理细胞之前,增强水分负荷,与CPS去除后的细胞相比,水的吸附速度更快,强调CPS对发酵产品质构特性的重要性。超声处理不改变CPS阴性菌株的细胞表面性质。
Some lactic acid bacteria are able to produce exopolysaccharides that, based on localization, can be distinguished in free and capsular or cell-bound exopolysaccharides (CPS). Up to now, the former were the focus of current research, mainly because of the technofunctional benefits they exhibit on fermented dairy products. On the other hand, CPS affect the surface properties of bacteria cells and thus also the textural properties of fermented foods, but data are very scarce. As the cell surface properties are strongly strain dependent, we present a new approach to investigate the impact of CPS on cell surface hydrophobicity and moisture load. CPS positive and negative Streptococcus thermophilus and Weissella cibaria were subjected to ultrasonication suitable to detach CPS without cell damage. The success of the method was verified by scanning electron and light microscopy as well as by cultivation experiments. Before applying ultrasonication cells with CPS exhibiting an increased hydrophilic character, enhanced moisture load, and faster water adsorption compared to the cells after CPS removal, emphasizing the importance of CPS on the textural properties of fermented products. The ultrasonic treatment did not alter the cell surface properties of the CPS negative strains.