絮凝颗粒酵母悬浮液流变特性比较分析

絮凝酵母细胞流变特性是影响发酵过程重要的基础数据之一。利用旋转黏度计测定自絮凝颗粒酵母悬浮液和其亲本游离酵母悬浮液的流变特性,分别建立流变本构方程并进行模型比较分析。低质量浓度絮凝酵母悬浮液近似为牛顿性流体,随着菌体质量浓度的增加流动行为指数降低,悬浮液为非牛顿性流体。絮凝酵母悬浮液表观黏度随剪切速率增加而降低,表明剪切使絮凝酵母颗粒聚合力降低从而产生剪切稀化现象。利用柠檬酸对絮凝酵母解絮凝从而改变颗粒聚集分布状态,进一步测定流变行为。结果证明,不同絮凝酵母颗粒聚集状态的分布是决定絮凝酵母流变行为的主要因素。

Comparison and analysis of rheological property of self-flocculation yeast suspension

The rheological property of the self-flocculating yeast is one of the most important data for the fermentation process.The rheological properties of the self-flocculating yeast and its parent strain free yeast were measured by a rotation viscometer,and the rheological constitutive equations were established and comparatively analyzed.When the biomass mass concentration of the self-flocculating yeast is very low,the flow behavior of the suspension is a Newtonian fluid.As the biomass mass concentration increases,the flow index decreases and the flow behavior of the suspension is converted to a non-Newtonian fluid.Moreover,the apparent viscosity of the suspension decreases with the increase of shear rate,indicating a shear thinning phenomenon since the aggregation degree of yeast flocs is reduced by the shear rate.And the studies on the rheological behaviors of the suspensions of de-flocculated yeast flocs with citric acid illustrate that it is the aggregation degree of the yeast flocs rather than the biomass mass concentration that contributes to the rheological property of the self-flocculating yeast suspension.