Li Zhao, Zydney Andrew L
Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802.
Biotechnol Prog. 2017 Nov;33(6):1561-1567. doi: 10.1002/btpr.2545. Epub 2017 Sep 4.
There is renewed interest in the possibility of using precipitation for initial capture of high value therapeutic proteins as part of an integrated continuous downstream process. These precipitates can be continuously washed using tangential flow filtration, with long term operation achieved by operating the membrane modules below the critical filtrate flux for fouling. Our hypothesis was that the critical flux for the precipitated protein would be a function of the properties of the precipitate as determined by the precipitation conditions. We evaluated the critical flux using a flux-stepping procedure for model protein precipitates (bovine serum albumin) generated using a combination of a crosslinking agent (zinc chloride) and an excluded volume precipitant (polyethylene glycol [PEG]). The critical flux varied with shear rate to approximately the 1/3 power, consistent with predictions of the classical polarization model. The critical flux increased significantly with increasing zinc chloride concentration, going from 60 L/m /h for a 2 mM ZnCl solution to 200 L/m /h for an 8 mM ZnCl solution. In contrast, the critical flux achieved a maximum value at an intermediate PEG concentration. Independent measurements of the effective size and viscosity of the protein precipitates were used to obtain additional understanding of the effects of ZnCl and PEG on the precipitation and the critical flux. These results provide important insights into the development of effective tangential flow filtration systems for processing large quantities of precipitated protein as would be required for large scale continuous protein purification by precipitation. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1561-1567, 2017.
人们对利用沉淀法初步捕获高价值治疗性蛋白质作为集成连续下游工艺的一部分的可能性重新产生了兴趣。这些沉淀物可以使用切向流过滤进行连续洗涤，通过在低于临界滤液通量的条件下操作膜组件来实现长期运行，以防止膜污染。我们的假设是，沉淀蛋白质的临界通量将是沉淀条件所决定的沉淀物性质的函数。我们使用通量步进程序评估了模型蛋白质沉淀物（牛血清白蛋白）的临界通量，该沉淀物是使用交联剂（氯化锌）和体积排阻沉淀剂（聚乙二醇[PEG]）组合生成的。临界通量随剪切速率变化至约1/3次方，这与经典极化模型的预测一致。随着氯化锌浓度的增加，临界通量显著增加，从2 mM ZnCl溶液的60 L/m²/h增加到8 mM ZnCl溶液的200 L/m²/h。相比之下，临界通量在中间PEG浓度时达到最大值。对蛋白质沉淀物的有效尺寸和粘度进行独立测量，以进一步了解ZnCl和PEG对沉淀和临界通量的影响。这些结果为开发有效的切向流过滤系统提供了重要见解，该系统用于处理大量沉淀蛋白质，这是大规模连续沉淀蛋白质纯化所必需的。© 2017美国化学工程师学会生物技术进展，33:1561 - 1567，2017。
