The counterintuitive role of extra-column volume in the determination of column efficiency and scaling of chromatographic processes

Enrichment and purification of trace substances from yew extracum by twin-column recycling chromatography with a step solvent gradient

The concentration and purification of trace substances from natural products represent a bottleneck in current chromatographic separations. In this study, a twin-column recycling chromatography with a step solvent gradient method was proposed and successfully applied in the purification of unknown substances with tiny content in yew extracum. The method consists of two steps. Initially, the target substances were enriched from the yew extracum stock solution, followed by further separation and purification of the enriched substances in the second step. Ultimately, the target substances A and B were obtained with a purity of 99.7 % and 96.6 %, respectively. The proposed method has the potential to be applied in the preparation of trace substances for toxicological evaluation in natural product studies.

Mechanistic Modeling of Preparative Column Chromatography for Biotherapeutics

Chromatography has long been, and remains, the workhorse of downstream processing in the production of biopharmaceuticals. As bioprocessing has matured, there has been a growing trend toward seeking a detailed fundamental understanding of the relevant unit operations, which for some operations include the use of mechanistic modeling in a way similar to its use in the conventional chemical process industries. Mechanistic models of chromatography have been developed for almost a century, but although the essential features are generally understood, the specialization of such models to biopharmaceutical processing includes several areas that require further elucidation. This review outlines the overall approaches used in such modeling and emphasizes current needs, specifically in the context of typical uses of such models; these include selection and improvement of isotherm models and methods to estimate isotherm and transport parameters independently. Further insights are likely to be aided by molecular-level modeling, as well as by the copious amounts of empirical data available for existing processes.

Elevated viscosities in a simulated moving bed for γ-aminobutyric acid recovery

Process streams of agro‐food industries are often large and viscous. In order to fractionate such a stream the viscosity can be reduced by either a high temperature or dilution, the former is not an option in case of temperature sensitive components. Such streams are diluted prior to chromatographic fractionation, resulting in even larger volumes and high energy costs for sub‐sequential water removal. The influence of feed viscosity on the performance of simulated moving bed chromatography has been investigated in a case study of the recovery of a γ‐aminobutyric acid rich fraction from tomato serum. This work addresses the chromatographic system design, evaluates results from a pilot scale operation, and uses these to calculate the productivity and water use at elevated feed concentration. At the two higher feed viscosities (2.5 and 4 mPa·s) water use is lower and productivity higher, compared to the lowest feed viscosity (1 mPa·s). The behavior of the sugars for different feed viscosities can be described well by the model using the ratio of feed to eluent as dilution factor. The behavior of γ‐aminobutyric acid is highly concentration dependent and the recovery could not be accurately predicted.