Dynamic simulation of simulated moving-bed chromatographic processes for the optimization of chiral separations

Evaluation of Continuous Membrane Chromatography Concepts with an Enhanced Process Simulation Approach

Modern biopharmaceutical products strive for small-scale, low-cost production. Continuous chromatography has shown to be a promising technology because it assures high-capacity utilization, purity and yield increases, and lower facility footprint. Membrane chromatography is a fully disposable low-cost alternative to bead-based chromatography with minor drawbacks in terms of capacity. Hence, continuous membrane chromatography should have a high potential. The evaluation of continuous processes goes often along with process modeling. Only few experiments with small feed demand need to be conducted to estimate the model parameters. Afterwards, a variety of different process setups and working points can be analyzed in a very short time, making the approach very efficient. Since the available modeling approaches for membrane chromatography modules did not fit the used design, a new modeling approach is shown. This combines the general rate model with an advanced fluid dynamic distribution. Model parameter determination and model validation were done with industrial cell cultures containing Immunoglobulin G (IgG). The validated model was used to evaluate the feasibility of the integrated Counter Current Chromatography (iCCC) concept and the sequential chromatography concept for membrane adsorber modules, starting with a laboratory-type module used for sample preparation. A case study representing a fed-batch reactor with a capacity from 20 to 2000 L was performed. Compared to batch runs, a 71% higher capacity, 48.5% higher productivity, and 38% lower eluent consumption could be achieved.

Modeling of the separation of two enantiomers using a microbore column

A microbore column packed with Chiralcel OB (cellulose tribenzoate coated silica) was used for the measurement of the single and competitive equilibrium-isotherm data of the 1-indanol enantiomers by frontal analysis. The amount of sample needed for the isotherm data acquisition was about 20 times less than that required with a conventional column. The data obtained were fitted to different single and competitive isotherm models. Both the single and the competitive data sets fitted best to the same Bilangmuir (BL) isotherm model with small differences in the numerical values of the parameters. The best fitted Bilangmuir single and competitive isotherm models were used to predict the overloaded experimental profiles of both pure enantiomers, of the racemic mixture, and of different enantiomeric mixtures. All the calculated profiles were in excellent agreement with the experimental ones. This agreement confirms that in many chiral separations, the competitive isotherms can be derived from data acquired from the mere racemic mixture with a sufficient accuracy for a correct prediction of the band profiles of all kinds of enantiomer mixtures, making possible the computer-assisted optimization of the experimental conditions.

Optimal design of batch and simulated moving bed chromatographic separation processes

Preparative chromatography, especially simulated moving bed (SMB) chromatography, is a key technology for the separation of fine chemicals on a production scale. Most of the design methods for batch and SMB processes proposed in the open literature deal with the optimisation of the operating conditions for a given chromatographic unit only. Therefore, a comparison of the process economy may lead to incorrect results. In this contribution, an effective strategy for the optimal choice of all process parameters (operation and design parameters) is proposed. The main idea of this strategy is to apply a detailed and experimentally validated process model and to reduce the number of influencing parameters by introducing and optimising dimensionless process parameters. It is shown that there is an infinite choice of design and operating parameters to achieve maximum productivity or minimum separation costs and not at the maximum pressure drop only. The detailed design of the chromatographic unit and the selection of the operating conditions can be adjusted by considering the availability of columns and packing materials. As the model system, the separation of a racemic mixture (EMD53986) on Chiralpak AD was investigated. After complete optimisation of a batch and a SMB unit, a real comparison of the process economy can be achieved. Finally, the influences of two different objective functions, productivity and specific separation cost, are analysed.

Preparative enantioseparation by simulated moving bed chromatography

Simulated moving bed (SMB) chromatography was invented in the 1960s in the petrochemical industry and has since then been widely used to produce petrochemicals and sugars at the multi-ton scale. In the early 1990s its principle could be successfully adapted to chromatographic enantioseparation, due to developments in system design, chiral stationary phase synthesis and improvements in modelling and simulation of non-linear chromatographic behaviour. Since then a lot of separation systems have been brought into production, which are reviewed. In addition new developments are outlined in the field of system design and stationary phase development.

Enantioselective chromatography as a powerful alternative for the preparation of drug enantiomers

The preparative separation of enantiomers by chromatography on chiral stationary phases (CSPs) has been recognized as being a useful alternative to the more conventional approaches such as enantioselective synthesis and enzymatically catalyzed transformations. The possible contribution of enantioselective chromatography with respect to the preparation of enantiomerically pure compounds is reviewed in the context of the competitive approaches and depending on the application scale, with a special emphasis on the recent progresses achieved in this particular field of separation.

Optimization of throughput and desorbent consumption in simulated moving-bed chromatography for paclitaxel purification

In simulated moving-bed (SMB) applications, throughput and desorbent consumption are two key factors that control process cost. For a given adsorbent volume and product purity requirements, throughput and desorbent consumption depend on desorbent composition, column configuration, column length to diameter ratio, and adsorbent particle size. In this study, these design parameters are systematically examined for paclitaxel purification. The results show that if adsorbent particle size, column dimensions and column configuration are fixed, the higher the product purity required, the lower the throughput. If product purity and yield are fixed, the larger the solute migration speed ratio, the higher the throughput, and the lower the desorbent consumption. If total bed volume and product purities are fixed, the longer the separation zones, the higher the throughput, but the higher the desorbent flow-rate. An intermediate configuration gives the minimum desorbent consumption. If there are no limits on pressure drop or zone flow-rate, the larger the column length to diameter ratio, the smaller the adsorbent particle size, the higher the throughput, and the lower the desorbent consumption. If the maximum zone flow-rate is controlled by the pressure drop limit and not by the standing waves requirement, the longer the columns, the lower the zone flow-rates and the lower the throughput. For 150 microns adsorbent particles and a maximum zone flow-rate of 300 ml/min, a design with optimal throughput and desorbent consumption is found for paclitaxel purification.