Fenneteau Frédérique, Aomari Hafida, Chahal Parminder, Legros Robert
Department of Chemical Engineering, Ecole Polytechnique, Montreal, Canada.
Biotechnol Bioeng. 2003 Mar 30;81(7):790-9. doi: 10.1002/bit.10522.
Expanded-bed adsorption (EBA) is a technique for primary recovery of proteins starting from unclarified broths. This process combines centrifugation, concentration, filtration, and initial capturing of the proteins in a single step. An expanded bed (EB) is comparable to a packed bed in terms of separation performance but its hydrodynamics are that of a fluidized bed. Downstream process development involving EBA is normally carried out in small columns to minimize time and costs. Our purpose here is to characterize the hydrodynamics of expanded beds of different diameters, to develop scaling parameters that can be reliably used to predict separation efficiency of larger EBA columns. A hydrodynamic model has been developed which takes into account the radial liquid velocity profile in the column. The scale-down effect can be characterized in terms of apparent axial dispersion, D(axl,app), and plate number, N(EB), adapted for expanded bed. The model is in good agreement with experimental results obtained from 1- and 5-cm column diameters with buffer solutions of different viscosities. The model and the experiments show an increase of apparent axial dispersion with an increase in column diameter. Furthermore, the apparent axial dispersion is affected by an increase in liquid velocity and viscosity. Supported by visual observations and predictions from the model, it was concluded that operating conditions (liquid viscosity and superficial velocity) resulting in a bed-void fraction between 0.7 and 0.75 would provide the optimal separation efficiency in terms of N(EB).
扩张床吸附(EBA)是一种从未澄清发酵液中初步回收蛋白质的技术。该过程将离心、浓缩、过滤以及蛋白质的初步捕获合并为一个步骤。就分离性能而言,扩张床(EB)与填充床相当,但其流体动力学特性与流化床相同。涉及EBA的下游工艺开发通常在小柱中进行,以尽量减少时间和成本。我们在此的目的是表征不同直径扩张床的流体动力学特性,开发可可靠用于预测较大EBA柱分离效率的放大参数。已开发出一种考虑柱中径向液体速度分布的流体动力学模型。可以根据适用于扩张床的表观轴向扩散系数D(axl,app)和塔板数N(EB)来表征缩小效应。该模型与使用不同粘度缓冲溶液、直径为1厘米和5厘米的柱子所获得的实验结果吻合良好。模型和实验均表明,表观轴向扩散系数随柱直径的增加而增大。此外,表观轴向扩散系数受液体速度和粘度增加的影响。在模型的视觉观察和预测支持下,得出结论:就N(EB)而言,使床层空隙率在0.7至0.75之间的操作条件(液体粘度和表观速度)将提供最佳分离效率。