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.

Improving the performance of nadolol stereoisomers' preparative separation using Chiralpak IA by SMB chromatography.

The pseudobinary preparative separation of nadolol stereoisomers is performed by simulated moving bed chromatography (SMB). Using the Chiralpak IA adsorbent, a new 25:75:0.1 (v/v/v) methanol-acetonitrile-diethylamine solvent composition was selected to perform the experimental SMB separation and compare it with the previous results obtained using pure methanol. Using a 2 g L-1 total feed concentration of an equimolar mixture of the four stereoisomers of nadolol, the more retained component was fully recovered (100% purity and 100% recovery), with a system productivity of 0.77 g L-1  hour-1 and a solvent consumption of 9.62 L g-1 . Comparing these results with the ones previously reported using 100:0.1 methanol-diethylamine solvent composition, this work shows that the 25:75:0.1 methanol-acetonitrile-diethylamine is a better alternative for the preparative separation of nadolol stereoisomers by SMB chromatography. These results are confirmed by simulation of the SMB operation for higher feed concentrations, by comparing the performances of the two solvent compositions using the data obtained experimentally through the measurement of the adsorption equilibrium isotherms and the kinetic data obtained for both solvents. The new experimental and simulation results stress out that the performance of the preparative separation can be improved by a careful selection of the solvent composition.

Continuous downstream processing for high value biological products: A Review.

There is growing interest in the possibility of developing truly continuous processes for the large-scale production of high value biological products. Continuous processing has the potential to provide significant reductions in cost and facility size while improving product quality and facilitating the design of flexible multi-product manufacturing facilities. This paper reviews the current state-of-the-art in separations technology suitable for continuous downstream bioprocessing, focusing on unit operations that would be most appropriate for the production of secreted proteins like monoclonal antibodies. This includes cell separation/recycle from the perfusion bioreactor, initial product recovery (capture), product purification (polishing), and formulation. Of particular importance are the available options, and alternatives, for continuous chromatographic separations. Although there are still significant challenges in developing integrated continuous bioprocesses, recent technological advances have provided process developers with a number of attractive options for development of truly continuous bioprocessing operations.

New Trends and Technological Challenges in the Industrial Production and Purification of Fructo-oligosaccharides.

An increased commercial interest in fructo-oligosaccharides (FOS) has emerged in the last decade due to their prebiotic activity. At large scale, the FOS are produced by microbial enzymes from sucrose. A mixture of FOS and other saccharides is obtained in this process. The presence of such saccharides reduces the prebiotic, caloric, and cariogenic value of the final product. Therefore, many efforts have been conducted to obtain a product with increased FOS purity. This review comprises the most important technological and physicochemical aspects including FOS production and recovery processes; safety, dose and health claims concerning its intake; and commercially available FOS.

Evaluation of tertiary pyridine resin for the separation of lanthanides by simulated moving-bed chromatography.

Lanthanide separation by simulated moving-bed chromatography was studied as a model system for separating lanthanide fission products and minor actinides from used nuclear fuels. The simulated moving-bed system was modeled for a tertiary pyridine anion-exchange resin supported on silica particles as the stationary phase and a mixture of methanol and 1 M nitric acid as the mobile phase. Pulse injection tests using a single packed column were used to obtain chromatographic parameters for mathematical modeling of the simulated moving-bed system. Higher concentrations of methanol improved the separation, but the chromatograms showed evidence of nonlinearity of the isotherms. The mathematical model of the simulated moving-bed process predicted a production rate of purified samarium and neodymium at 118 g solute/L resin/day and a purity of 99.5%. The optimal methanol ratio for the production rate for various product purities was determined from the model. The excellent separation of Nd and Sm suggests that the simulated moving-bed system could be applied to the separation of minor actinides such as americium and curium.

Experimental evaluation of the effect of a modified port-location mode on the performance of a three-zone simulated moving-bed process for the separation of valine and isoleucine.

The removal of isoleucine from valine has been a key issue in the stage of valine crystallization, which is the final step in the valine production process in industry. To address this issue, a three-zone simulated moving-bed (SMB) process for the separation of valine and isoleucine has been developed previously. However, the previous process, which was based on a classical port-location mode, had some limitations in throughput and valine product concentration. In this study, a three-zone SMB process based on a modified port-location mode was applied to the separation of valine and isoleucine for the purpose of making a marked improvement in throughput and valine product concentration. Computer simulations and a lab-scale process experiment showed that the modified three-zone SMB for valine separation led to >65% higher throughput and >160% higher valine concentration compared to the previous three-zone SMB for the same separation.

UV-based dynamic control improves the robustness of multicolumn countercurrent solvent gradient purification of oligonucleotides.

Therapeutic oligonucleotides (ONs) have great potential to treat many diseases due to their ability to regulate gene expression. However, the inefficiency of standard purification techniques to separate the target sequence from molecularly similar variants is hindering development of large scale ON manufacturing at a reasonable cost. Multicolumn Countercurrent Solvent Gradient Purification (MCSGP) is a valuable process able to bypass the purity-yield tradeoff typical of single-column operations, and hence to make the ON production more sustainable from both an economic and environmental point of view. However, operating close to the optimum of MCSGP can be challenging, resulting in unstable process performance and in a drift in product quality, especially when running a continuous process for extended periods where process parameters such as temperature are prone to variation. In this work, we demonstrate how greater process robustness is introduced in the design and execution of MCSGP for the purification of a 20mer single-stranded DNA sequence through the implementation of UV-based dynamic control. With this novel approach, the cyclic steady state was reached already in the third cycle and disturbances coming from fluctuations in the feed quality, loading amount and temperature were effectively compensated allowing a stable operation close to the optimum. In response to the perturbations, the controlled process kept the standard deviation on product recovery below 3.4%, while for the non-controlled process it increased up to 27.5%.

Three-zone simulated moving bed for the separation of chlorogenic acid and caffeine fractions in the liquid extract of spent coffee grounds.

Spent Coffee Grounds (SCG) is an agricultural residue obtained in a large quantity from local cafes in Thailand. In order to handle this waste effectively, the valorization of SCG is essential. SCG consists of beneficial phenolic compounds with antioxidative properties and caffeine, which can be recovered through extraction followed by separation and purification processes. In this work, water extraction of SCG was carried out. The volumetric composition of the liquid extract of SCG was then adjusted with an organic solvent, and the obtained mixture was used as the feed for subsequent separation. For the separation method of the SCG extract, a single chromatographic column was employed to separate a group of phenolic compounds (represented by chlorogenic acid) and a group of contaminants (represented by caffeine). The volumetric composition of the mobile phase was varied to determine the condition suitable for the separation of chlorogenic acid and caffeine in a C18 column. Adsorption parameters were determined and used to formulate the mathematical models describing the adsorption dynamics of those two bioactive compounds in the experimental breakthrough curves of standard solutions and the liquid extract of SCG. Furthermore, the three-zone simulated moving bed system (TZ-SMB) was designed to continuously separate fractions of chlorogenic acid and caffeine in the liquid extract of SCG. The adsorption parameters were employed in the optimization of TZ-SMB operating conditions using triangle theory, conducted via computer simulation. The experimental result of water extraction revealed that the yields of chlorogenic acid and caffeine were 0.292 and 0.583 mg/g dried SCG, respectively, using solid-to-liquid ratio of 1 g: 30 mL and temperature of 75 °C. The separation result in a single chromatographic column showed that the mobile phase consisting of acetonitrile, water, and formic acid (10: 90: 1.5 vol%) provided the linear adsorption isotherms for both chlorogenic acid and caffeine, and the chromatographic peaks of all compounds in the liquid extract of SCG were well separated. The simulated results of TZ-SMB at the optimal point revealed that the flow rates of desorbent, feed, extract product, and raffinate product were 0.626, 0.115, 0.081, and 0.593 mL/min, respectively, with the switching time of 20 min. At this point, the relative purities of caffeine in the extract product and chlorogenic acid in the raffinate product were 99.45 % and 98.88 %, respectively, with the maximum productivity of 0.045 mg/mL⋅h. In addition, for demonstration purposes, the lab-scale TZ-SMB experiment was conducted to show the separation of chlorogenic acid and caffeine in the liquid extract of SCG. The operating point from the triangle separation region was chosen based on the sensitivity of flow rate that ensured the criteria of purity. The experimental results showed that the relative purities of caffeine in extract product and chlorogenic acid in raffinate product were both 100 %, verifying the successful separation.

Magnetic/flow controlled continuous size fractionation of magnetic nanoparticles using simulated moving bed chromatography.

The use of magnetic nanoparticles shows a steadily increasing technical importance. Particularly in medical technology disciplines such as cancer treatment, the potential of these special particles is increasing rapidly. Magnetic nanoparticles are particles with a submicron size, and consist mostly of magnetite-containing composites. An important quality parameter of such particles is a particle size distribution as narrow as possible, which can only be obtained to a certain degree by synthesis. Apart from ultracentrifugation, there are so far only methods on an analytical scale to narrow the size distribution as a post-processing step. We present a method based on magnetic chromatography, by which high separation efficiencies at yields of up to 99.9% are achieved. The novel technique is based on a competition between the magnetic interaction of the nanoparticles and the separation matrix, as well as the hydrodynamic forces. Furthermore, the method is extended using a continuous mode, namely simulated moving bed chromatography, to obtain potent space-time yields of up to 2.94 g/(L*h). For those reasons, this novel continuous magnetic chromatography method offers high potential for large-scale refinement of magnetic nanoparticles while fulfilling sophisticated quality criteria for high-technology applications.

Design and optimization of the continuous separation process for lignin and alkali by 'Extended Separation Volume' method.

This work is to design and optimize the 4column-simulated moving bed unit to separate and recovery alkali and lignin from black liquor. Since both alkali lignin and NaOH are the main products, we proposed the 'extended separation volume' methodology to construct a four-dimensional separation region (QI×QII×QIII×QIV) to design the operating conditions. Special attention was paid to investigate the influence of flow-rates in each zone on the performance parameters of these two products. The results show besides QII and QIII, QI and QIV can affect the concentrations and productivities significantly and have to be taken into account. Afterwards, the Response Surface Methodology, conducted by Design-Expert® was chosen to deal with the multi-objective optimization problem. The unique optimal operating conditions were finally obtained with the concentration of 74.7% and 48.1% of feed solution, and the productivity of 3.9 and 0.7 g/(L·h)-1 for alkali lignin and NaOH. Considering the actual operation, the productivity of 2.5 and 0.446 g/(L·h)-1 were obtained by experiment of internal actual operation point.

Separation of p-xylene and m-xylene by simulated moving bed chromatography with MIL-53(Fe) as stationary phase.

The separation of p-xylene (PX) and m-xylene (MX) isomers with near boiling points is a worldwide problem. The metal-organic framework material is an ideal stationary phase for chromatographic separation because of its high porosity, homogeneous pore diameter and good chemical stability. In this paper, a simulated moving bed (SMB) chromatography system with MIL-53(Fe) as the stationary phase and petroleum ether-dichloromethane as the mobile phase was designed to separate PX and MX at ambient temperature. Firstly, according to the elution curves of a single column, nonlinear competitive Langmuir adsorption isotherm equation was confirmed by equilibrium dispersive chromatography model. Then, the SMB separation zone was determined based on triangle theory, and the SMB operating conditions were optimized. Finally, the purity, recovery and productivity of PX reached 100.0%, 99.1% and 93.1 g/L/h, respectively; the purity, recovery and productivity of MX reached 96.4%, 100.0% and 23.5 g/L/h, respectively; the solvent consumption was 0.42 L/g.

Effect of radial distribution of injected flow on simulated moving bed performance.

In the modeling of a simulated moving bed, several assumptions are considered, the key assumption is there are no radial concentration gradients based on perfect mixing. However, it is difficult to achieve perfect mixing because the injected flowrate of the bed is periodically changed in the process. In this study, the performance of the simulated moving bed process was analyzed when the injected flow such as the feed or desorbent stream was unevenly distributed. To this end, the distribution function of the injected flow was calculated and applied to the model. Two types of distribution functions were obtained using the experimental results of a previous study, and the simulation results were compared with classical modeling assuming perfect mixing. In the base case simulation, the purity was similar in all cases, the productivity was higher more than 5% in the even distribution case compared to the most uneven distribution case. The effect of distribution was analyzed through sensitivity analysis by changing the overall flow rate, switching time, bed length, and flow rate of sections 2 and 3. As a result, regardless of the distribution applied, the trends of the performance parameters were the same. However, the more uneven the distribution, the greater the difference in productivity, recovery, and desorbent consumption compared to the even distribution case. It was confirmed that the design that distributes the injected flow more evenly has a better performance.

Dual switch simulated moving bed chromatography: An optimal two-fraction yielding separation process.

Conventional Simulated Moving Bed Chromatography (C-SMBC) characterized by a single operating point comprising of the internal flow rates and switching period, yields a single fraction of the extract and raffinate, at cyclic steady state. In the current work, we deal with two-fraction yielding Dual Switch SMBC (DS-SMBC) characterized by two operating points implemented during alternate switches. The higher degrees of freedom in Dual Switch SMBC give it the potential of obtaining a higher average extract purity, for one of its two fractions, compared to conventional SMBC, at a certain minimum feed flow rate and minimum average extract recovery. This becomes possible with a trade-off in the average purity of the other extract fraction of Dual Switch SMBC, without any addition to the conventional SMBC equipment. We solve a multi-objective optimization problem wherein we maximize the average purity of one of the extract fractions of Dual Switch SMBC, with the requirement of certain minimum feed flow rate, minimum average extract recovery and minimum average purity of the non-objective extract fraction. One of the aims of the current work is deduction of the working principle of Dual Switch SMBC, that facilitates superior average extract purity. Next, we analyze the trade-offs due to the said process bounds on the objective i.e. average purity of objective extract fraction of Dual Switch SMBC. This has been done for the two case studies of separation: 1) linear isotherm based separation of fructose-glucose in deionized water on cation exchange resin 2) non-linear isotherm based separation of enantiomers of Tröger's base in ethanol on microcrystalline cellulose triacetate. The findings from the trade-offs in the multi-objective optimization problem, further corroborate our understanding of the working principle.

Automatic control of simulated moving bed process with deep Q-network.

Optimal control of a simulated moving bed (SMB) process is challenging because the system dynamics is represented as nonlinear partial differential-algebraic equations combined with discrete events. In addition, product purity constraints are active at the optimal operating condition, which implies that these constraints can be easily violated by disturbance. Recently, artificial intelligence techniques have received significant attention for their ability to address complex problems, involving a large number of state variables. In this study, a data-based deep Q-network, which is a model-free reinforcement learning method, is applied to the SMB process to train a near-optimal control policy. Using a deep Q-network, the control policy of a complex dynamic system can be trained off-line as long as a sufficient number of data is provided. These data can be efficiently generated by performing numerical simulations in parallel on multiple machines. The on-line computation of the control input using a trained Q-network is fast enough to satisfy the computational time limit for the SMB process. However, because the Q-network does not predict the future state, it is not possible to explicitly impose state constraints. Instead, the state constraints are indirectly imposed by providing a relatively large penalty (negative reward) when the constraints are violate. Furthermore, logic-based switching control is utilized to limit the ranges of the extract and raffinate purities, which helps to satisfy the state constraints and reduce the regions in the state space for reinforcement learning to explore. The simulation results demonstrate the advantages of applying deep reinforcement learning to control the SMB process.

Optimal performance comparison of the simulated moving bed process variants based on the modulation of the length of zones and the feed concentration.

The VariCol and ModiCon processes are two variants of the simulated moving bed (SMB) process, characterized by the modulation of the length of zones of the chromatographic column train and the feed concentration. These features give more flexibility than the conventional operation, leading to essential improvements in the separation and purification of mixtures. The optimal performance comparison of these two variants, the hybrid formed by their combination, and the conventional SMB process are scarce in the literature. This comparison helps discover new characteristics of each single and combined operation mode and creates guidelines to select the appropriate operation mode for possible real applications. In this work, the performance comparison of the ModiCon, VariCol, ModiCon+VariCol, and SMB processes is carried out in terms of maximal throughput for specific product purity values. Particular emphasis is placed on both the ModiCon and the hybrid ModiCon+VariCol processes characteristics. A strategy for combining and optimizing the ModiCon and the VariCol processes was determined. As a case study, the enantioseparation of guaifenesin was considered. In the ModiCon process, more than two modulation subintervals did not improve the performance in the separation. The optimal pattern, based on two subintervals, has zero feed concentration in the first subinterval and the maximal concentration in the second one. The best result for the hybrid operation (ModiCon+VariCol) was reached when the feed port moves simultaneously as the SMB process switching period. The optimal throughput of the ModiCon and the ModiCon+VariCol processes was almost doubled than that of the SMB process. These performances were based on larger zones I and II and not in zones II and III as occur with the SMB and VariCol process. The throughput in the hybrid operation increases more significantly than the ModiCon process when 5 columns were considered instead of 6. The hybrid operation could be more attractive for a system with a few numbers of columns.

Efficient conversion of hemicellulose sugars from spent sulfite liquor into optically pure L-lactic acid by Enterococcus mundtii.

Spent sulfite liquor (SSL), a waste stream from wood pulp production, has great potential as carbon source for future industrial fermentations. In the present study, SSL was separated into a hemicellulose derived sugar syrup (HDSS) and a lignosulfonic fraction by simulated moving bed chromatography. The recovery of SSL sugars in the HDSS was 89% and the fermentation inhibitors furfural, 5-hydroxymethylfurfural and acetic acid were removed by 98.7%, 60.5% and 75.5%, respectively. The obtained sugars have been converted to L-lactic acid, a building block for bioplastics, by fermentation with the lactic acid bacterium Enterococcus mundtii DSM4838. Batch fermentations on HDSS produced up to 56.3 g/L L-lactic acid. Simultaneous conversion of pentose and hexose sugars during fed-batch fermentation of wildtype E. mundtii led to 87.9 g/L optically pure (>99%) L-lactic acid, with maximum productivities of 3.25 g/L.h and yields approaching 1.00 g/g during feeding phase from HDSS as carbon source.

Sample Displacement Batch Chromatography of Proteins.

In downstream processing, large-scale chromatography plays an important role. For its development, screening experiments followed by pilot-plant chromatography are mandatory steps. Here we describe fast, simple, and inexpensive methods for establishing a preparative chromatography for the separation of complex protein mixtures, based on sample displacement batch chromatography. The methods are demonstrated by anion-exchange chromatography of a human plasma protein fraction (Cohn IV-4), including the screening step and upscaling of the chromatography by a factor of one hundred. The results of the screening experiments and the preparative chromatography are monitored by SDS-PAGE electrophoresis. In summary, we provide a protocol, which should be easily adaptable for the chromatographic large-scale purification of other proteins, in the laboratory as well as in the manufacturing of biopharmaceuticals. These protocols cover the initial piloting steps for establishing a large-scale sample batch chromatography. The results from the piloting steps may also be applied for packed columns for performing simulated-moving-bed (SMB) chromatography rather than batch chromatography.

Bovine serum albumin and myoglobin separation by size exclusion SMB.

The separation of the proteins Bovine Serum Albumin (BSA) and Myoglobin (Mb) was achieved by Size-Exclusion Simulated Moving Bed (SE-SMB) and performed experimentally in the FlexSMB® unit, an SMB unit designed and built in the Laboratory of Separation and Reaction Engineering. Before accomplishing the separation experiments in the mentioned unit, separation regions were computed by simulation based on a phenomenological mathematical model to determine appropriate operating conditions. The developed model was validated in advance, against fixed-bed dynamic adsorption experimental results, for pure component and binary mixtures. Then the SMB experiments were carried out, and purities of the Mb on the extract and BSA on the raffinate streams were 98% and 96%, respectively. The achieved recoveries were 80% of Mb on the extract and 94% of BSA on the raffinate. Lastly, productivities of 6.4 gprotein⋅lads-1⋅day-1 for the extract and 28.8 gprotein⋅lads-1⋅day-1 for the raffinate were obtained.

Separation of eicosapentaenoic acid and docosahexaenoic acid by three-zone simulated moving bed chromatography.

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are essential fatty acids for human body, which are widely used in the field of healthy food and medicine. Meanwhile, there are some differences in their physiological functions, such as "scavenger for blood vessel" of EPA and "brain protector" of DHA. In order to make full use of EPA and DHA, it is necessary to prepare their high-purity component. In this paper, EPA and DHA were separated and purified by three-zone simulated moving bed (SMB) chromatography with C18 used as stationary phase and ethanol-water as mobile phase. For the single column experiment, a separation unit of SMB, the effects of the ratio of ethanol to water, pH value and temperature on the separation were investigated. The equilibrium dispersion (ED) model was used to obtain the adsorption parameters of EPA and DHA by inverse method and genetic algorithm, and the accuracy of the adsorption parameters was verified by fitting the overloaded elution curves under different conditions. Based on the acquired nonlinear adsorption isotherms the complete separation region was found according to triangle theory. The effects of sample concentration, flow ratios of adsorption zone and rectification zone, and column distribution mode of SMB on the separation were investigated. Under the optimized SMB conditions, the experimental result was that without regard to the other components, the chromatographic purity and recovery values of EPA and DHA exceeded 99% with the productivity of 4.15 g/L/h, and the solvent consumption of 1.11 L/g.

One-step optimization strategy in the simulated moving bed process with asynchronous movement of ports: A VariCol case study.

The VariCol process is a variant of the conventional simulated moving bed (SMB) process, distinguished by the asynchronous shifting of the inlet and outlet ports of the chromatographic column train. This feature allows for a more flexible operation in column utilization and can also achieve higher separation performances. However, to take full benefit out of it, the operating parameters, such as the strategy for port switching, must be optimal. in this paper, a novel methodology for optimizing those parameters, based on a single NLP (non-linear programming), is proposed. The main advantage of this approach is that it significantly reduces the complexity of the original MINLP (mixed-integer non-linear programming) formulation currently discussed in the literature. The proposed optimization problem is built, considering that the average column configuration of three zones provides the necessary and sufficient information to describe the VariCol process. Several optimization scenarios for the enantioseparation of 1,1´-bi-2-naphthol and aminoglutethimide were considered to evaluate the proposed methodology and to compare the performance of VariCol and SMB processes. The results have shown that with the single NLP approach, it is possible to explore the optimal solution in all the VariCol process domains with less computational effort than other optimization strategies reported in the literature. That is a great advantage, especially in the context of real-time applications.