Hackemann Eva, Hasse Hans
Laboratory of Engineering Thermodynamics (LTD), University of Kaiserslautern, Kaiserslautern, Germany.
Biotechnol Prog. 2018 Sep;34(5):1251-1260. doi: 10.1002/btpr.2683. Epub 2018 Oct 2.
Hydrophobic interaction chromatography (HIC) is often used for purifying proteins. The prediction of the adsorption equilibria in such systems is a difficult task as they depend on the pH value and the influence of the salts, which are added for controlling the solvent properties. This is especially tedious when salt mixtures are used, which can have positive or negative cooperative effects on the adsorption. A mathematical model to describe these complex effects of the salts was recently introduced by our group. In that model, the influence of the salts is described by a Taylor series expansion in the individual ion molarities. However, in our previous work, only the loading of the adsorbent at a given constant protein concentration in the liquid phase c = 0.01 mM was considered and correlated as a function of the salt composition at constant ionic strength. In the present study, that model is extended to other protein concentrations and it is shown that the Taylor series expansion works well for a wide range of c . The model parameters are found to depend on c , but only in a simple way. The dependence of the model parameters on c was correlated using a new three parameter equation. From that correlation, the loading q can be determined for any value of c . Hence, the entire adsorption isotherm is known for any salt composition. The approach is illustrated using experimental data from previous studies of our group on the adsorption of bovine serum albumin, lysozyme, polyethylene glycol, and di-PEGylated lysozyme on the mildly hydrophobic resin Toyopearl PPG-600 M. The pH values are between 4.0 and 7.0. Binary and ternary mixtures of ammonium chloride, sodium chloride, ammonium sulfate, and sodium sulfate as well as the single salts are used at overall ionic strengths between 1,500 and 4,200 mM. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018.
疏水作用色谱法（HIC）常用于蛋白质纯化。预测此类系统中的吸附平衡是一项艰巨的任务，因为它们取决于pH值以及为控制溶剂性质而添加的盐的影响。当使用盐混合物时，这尤其繁琐，因为盐混合物对吸附可能具有正协同效应或负协同效应。我们小组最近引入了一个数学模型来描述盐的这些复杂效应。在该模型中，盐的影响通过单个离子摩尔浓度的泰勒级数展开来描述。然而，在我们之前的工作中，仅考虑了在液相中给定恒定蛋白质浓度c = 0.01 mM时吸附剂的负载量，并将其关联为恒定离子强度下盐组成的函数。在本研究中，该模型扩展到了其他蛋白质浓度，结果表明泰勒级数展开在很宽的c范围内都能很好地适用。发现模型参数取决于c，但方式很简单。使用一个新的三参数方程关联了模型参数对c的依赖性。通过该关联，可以确定任何c值下的负载量q。因此，对于任何盐组成，整个吸附等温线都是已知的。使用我们小组先前关于牛血清白蛋白、溶菌酶、聚乙二醇和二聚乙二醇化溶菌酶在轻度疏水树脂Toyopearl PPG - 600 M上吸附的研究中的实验数据来说明该方法。pH值在4.0至7.0之间。氯化铵、氯化钠、硫酸铵和硫酸钠的二元和三元混合物以及单一盐在总离子强度为1500至4200 mM之间使用。© 2018美国化学工程师学会生物技术进展，2018年。
