Pearson Carrie R, Heng Meng, Gebert Mark, Glatz Charles E
Department of Chemical Engineering, Iowa State University, Ames, IA 50011, USA.
Biotechnol Bioeng. 2004 Jul 5;87(1):54-60. doi: 10.1002/bit.20097.
Characterization of flocculation for cell removal from fermentation broth via polyelectrolyte addition is commonly based on qualitative methods such as physical appearance of the floc. The use of zeta potential as a quantitative measure of floc character was evaluated as an indicator of optimal polymer addition. Zeta potential was found to increase with increasing cationic polyelectrolyte dosage, but never reached zero regardless of the total amount of polymer added, indicating flocculation occurs at least partially through a bridging type mechanism. Experiments were conducted using various polymer concentrations (25-75 g/L) and dosing methods (batch, incremental and continuous addition) that resulted in variable overall polymer requirements to achieve optimum flocculation. Zeta potential was found to be constant at optimal floc character regardless of the total amount of polymer added, polymer concentration, or method of polymer addition. Experiments with two additional types of fermentation broth also showed characteristic zeta potentials at optimal flocculation. Polymer requirements to achieve a particular floc character can vary greatly, depending on polymer dosing conditions and fermentation batch. The effect of polymer dosing conditions on the polymer requirement to obtain optimal floc character was evaluated. Polymer dosing method and calcium concentration were both found to have a significant effect (P < 0.0001) with continuous polymer addition and high calcium concentration requiring less polymer than did batch polymer addition and low calcium concentration, respectively. Polymer dosing concentration did not significantly affect polymer requirement for optimal flocculation.
通过添加聚电解质从发酵液中去除细胞的絮凝特性通常基于定性方法，如絮凝物的物理外观。评估了使用zeta电位作为絮凝特性的定量指标，以指示最佳聚合物添加量。发现zeta电位随阳离子聚电解质用量的增加而升高，但无论添加的聚合物总量如何，都不会达到零，这表明絮凝至少部分是通过桥连型机制发生的。使用各种聚合物浓度（25 - 75 g/L）和投加方法（分批、增量和连续添加）进行实验，这些方法导致实现最佳絮凝所需的聚合物总量各不相同。发现无论添加的聚合物总量、聚合物浓度或聚合物添加方法如何，在最佳絮凝特性下zeta电位是恒定的。对另外两种类型的发酵液进行的实验也表明，在最佳絮凝时具有特征性的zeta电位。实现特定絮凝特性所需的聚合物量可能因聚合物投加条件和发酵批次而有很大差异。评估了聚合物投加条件对获得最佳絮凝特性所需聚合物量的影响。发现聚合物投加方法和钙浓度都有显著影响（P < 0.0001），连续添加聚合物和高钙浓度分别比分批添加聚合物和低钙浓度所需的聚合物更少。聚合物投加浓度对最佳絮凝所需的聚合物量没有显著影响。
