Jaros Doris, Mende Susann, Häffele Florian, Nachtigall Carsten, Nirschl Hermann, Rohm Harald
Chair of Food Engineering Technische Universität Dresden Dresden Germany.
Institute of Mechanical Process Engineering and Mechanics Karlsruhe Institute of Technology Karlsruhe Germany.
Eng Life Sci. 2017 Nov 2;18(1):62-69. doi: 10.1002/elsc.201700121. eCollection 2018 Jan.
A central step in the production of starter cultures is the separation of the cells from the fermentation medium, which is usually achieved by disk centrifuges. In case of microorganisms which produce exopolysaccharides (e.g., various strains of lactic acid bacteria), the properties of the respective exopolysaccharides may interfere with this separation step. By using six strains of the hypothesis was tested that a shear treatment of the fermented culture medium improves subsequent cell separation markedly. Depending on the type of exopolysaccharides (freely present in the medium, or as capsules around the cells) an energy input of up to 2.5 kJ/mL generated with an Ultra-Turrax affected cell chain length of the strains and viscosity of fermentation medium differently. For bacteria producing capsular exopolysaccharides, space- and time-resolved centrifugation experiments revealed an increase of sedimentation velocity after shear treatment. In general, viability of the microorganisms, detected by flow cytometry measurements and fermentation experiments, was not affected by the shearing procedure. The results therefore indicate that strain-targeted shearing is helpful to improve the separability of cells from the fermented media.
生产发酵剂的一个核心步骤是将细胞与发酵培养基分离，这通常通过碟式离心机来实现。对于产生胞外多糖的微生物（如各种乳酸菌菌株），相应胞外多糖的特性可能会干扰这一分离步骤。通过使用六种菌株，测试了以下假设：对发酵培养基进行剪切处理可显著改善后续的细胞分离。根据胞外多糖的类型（自由存在于培养基中，或作为细胞周围的荚膜），使用Ultra-Turrax产生高达2.5 kJ/mL的能量输入，对菌株的细胞链长度和发酵培养基的粘度有不同影响。对于产生荚膜胞外多糖的细菌，空间和时间分辨的离心实验表明，剪切处理后沉降速度增加。一般来说，通过流式细胞术测量和发酵实验检测到的微生物活力不受剪切过程的影响。因此，结果表明，针对菌株的剪切有助于提高细胞从发酵培养基中的可分离性。
