BACKGROUND High-density cultures require operating below the critical threshold of shear stress, in order to avoid reducing the specific growth rate of the cells. When determining this threshold, direct inspection of the cells in flow provides insight into the conditions of shearing. OBJECTIVE Aim of this study was using a novel rheo-optical setup for the observation of cells in laminar shear flow and the determination of the critical shear stress required to damage them in their natural environment. METHODS Dunaliella salina cells were sheared and observed in flow for shear stresses of up to 90 Pa, at ambient temperature, without adding thickeners. The critical shear stress was determined by fitting a hydrodynamics-based criterion to the experimental data on the percentage of deformed cells after shearing. RESULTS Single cells, clusters and strings of cells were visible in shear flow. The strings formed at maximum shear stresses of 10 Pa or higher. Cells lost motility for maximum shear stresses higher than 15 Pa, and more than 80% of the cells were deformed at maximum shear stresses higher than 60 Pa. The estimated critical shear stress was 18 Pa. CONCLUSIONS Shear stresses higher than 18 Pa should be avoided when cultivating D. salina.

中文翻译：

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在不使用增稠剂的情况下，杜氏盐藻在高剪切速率下的变形和破裂。

背景技术高密度培养物需要在剪切应力的临界阈值以下操作，以避免降低细胞的比生长速率。确定此阈值时，直接检查流动中的孔可洞悉剪切条件。目的本研究的目的是使用新型流变光学装置观察层流剪切流中的细胞，并确定破坏其自然环境所需的临界剪切应力。方法在环境温度下，不添加增稠剂的情况下，剪切杜氏盐藻细胞并在流动中观察到高达90 Pa的剪切应力。临界剪切应力是通过将基于流体力学的准则拟合到有关剪切后变形单元百分比的实验数据来确定的。结果单细胞 在剪切流中可见细胞簇和串。弦在最大剪切应力为10 Pa或更高时形成。当最大剪切应力高于15 Pa时，细胞失去动力，并且在最大剪切应力高于60 Pa时，超过80％的细胞发生变形。估计的临界剪切应力为18 Pa。结论应避免高于18 Pa的剪切应力在培养D. salina时。