Chromatographic Process Research Articles

New models involving quantum chemical parameters for assessing the chromatographic retention process

Knowledge about the theoretical relationship between the analyte properties and the critical chromatographic parameters is mandatory for a better interpretation of the separation mechanism and a more leisurely development of quantitative studies. In a preliminary stage of this work, we introduce the Gumbel distribution, the extreme value distribution type-I widely used in other fields, as a novel tool for modelling the chromatographic peak shape. Further, we develop mathematical models to evaluate the effect of the experimental variables and various quantum parameters on the chromatographic indices, such as the retention time, capacity factor, asymmetry factor, tailing factor and number of theoretical plates. Finally, we propose a mechanistic behaviour for the chromatographic separation process based on the structure-retention relationship of fifteen selected drugs involving several molecular quantum parameters.

Mixed-integer optimal control for multimodal chromatography

Multimodal chromatography is a powerful tool in the downstream processing of biopharmaceuticals. To fully benefit from this technology, an efficient process strategy must be determined beforehand. To facilitate this task, we employ a recent mechanistic model for multimodal chromatography, which takes salt concentration and pH into account, and we present a mathematical framework for the optimization of chromatographic processes. This framework also includes the use of discrete process controls in order to cover a wider range of chromatographic applications. We describe a procedure to numerically solve the resulting nonlinear mixed-integer optimal control problems. We discuss results of computational experiments, covering the cases where one wants to optimize the yield of the product or the batch-cycle time under specified purity requirements. The results indicate that a good separation can be achieved in a two-component system and that both salt concentration and discrete pH play an important role within the purification process.

Determination of New IR and UV/VIS Spectroscopic Parameters of the C84-D2:22 Isomer for Its Quantitative Assessment, Identification and Possible Applications

The stable isomers of the higher fullerenes C76-D2 and C84-D2:22, as well as fullerenes C60 and C70 were isolated from carbon soot by the new and improved extraction and chromatographic methods and processes. Characterizations of the C84-D2:22 isomer in this study were performed by infrared and electronic absorption spectroscopy. All of the experimentally observed IR and UV/VIS bands were in excellent agreement with the semi-empirical, DFT and TB potential theoretical calculations for this molecule. The molar extinction coefficients and the integrated molar extinction coefficients of the observed larger number of completely separated infrared absorption maxima and shoulders of fullerene C84-D2:22, as well as of its main convoluted maxima, in different and new relevant entire integration ranges, including neighboring, and all surrounding absorption shoulders were determined and their relative intensities compared. In addition, the molar absorptivity of the electronic absorption bands of this carbon cluster was found. The new IR and UV/VIS spectroscopic parameters that are significant for the quantitative determination, identification and numerous possible applications of C84-D2:22 are obtained and their changes compared to C76-D2 observed. Isolated and characterized C84-D2:22, as well as other fullerenes from this research can be used in electronic, optical, chemical and biomedical devices, superconductors, semiconductors, batteries, catalysts, polymers, sensors, solar cells, nanophotonic lenses with better optical transmission, refraction and wettability, diagnostic and therapeutic pharmaceutical substances, such as those against diabetes, cancer, neurodegenerative disorders, free radical scavenging, radio nuclear, antibacterial and antiviral agents that can inhibit HIV 1, HSV, COVID-19, influenza, malaria and so forth.

Evaluation of Chiral Liquid Chromatographic Method for Separation and Quantification of Isomers of Brivaracetam.

A selective, sensitive and robust chiral analytical method was developed for the quantification of Brivaracetam (BRV) and its three isomers. Systematic chiral chromatographic elution process was executed in different modes on chiral columns of polysaccharide based to attain the finest condition. The analytical method was developed by utilizing immobilized polysaccharide chiral column (CHIRALPAK IG-U) with reversed phase under isocratic condition containing acetonitrile and 10 mM ammonium bicarbonate in the proportion of 40:60 (v/v). The mobile phase flow rate and column temperature were monitored at 0.3 mLmin-1 and 25°C with a resolution of more than 2.0. The eluted components from the column were processed at 212 nm UV detection. The limit of detection and limit of quantification values of BRV, 2R, 4S-Isomer, 2R, 4R-Isomer and 2S, 4S-Isomers were found to be 0.0066/0.02, 0.0035/0.0107, 0.0036/0.0109 and 0.005/0.0152 µgml-1 respectively. Precision, linearity, accuracy and robustness were conducted according to ICH guidelines and the findings were within the acceptable limits. The proposed analytical method was found to be precise, accurate and specific for the quantification of enantiomer and its diastereomers for drug product and drug substance of BRV.

Development and validation of a rapid high-performance thin-layer chromatographic method for quantification of gallic acid, cinnamic acid, piperine, eugenol, and glycyrrhizin in Divya-Swasari-Vati, an ayurvedic medicine for respiratory ailments.

Divya-Swasari-Vati is a calcium containing polyherbal ayurvedic medicine prescribed for the lung-related ailments observed in the current pandemic of Severe Acute Respiratory Syndrome Coronavirus 2 infections. The formulation is a unique quintessential blend of nine herbs cited in Ayurvedic texts for chronic cough and lung infection. Analytical standardization of herbal medicines is the pressing need of the hour to ascertain the quality compliance. This persuaded us to develop a simple, rapid, and selective high-performance thin-layer chromatographic method for Divya-Swasari-Vati quality standardization. The developed method was validated for the quantification of marker components, gallic acid, cinnamic acid, piperine, eugenol and glycyrrhizin, against reference standards in five different batches of Divya-Swasari-Vati. The analytes were identified by visualization at 254nm, and by matching their retention factor with authentic standards. The developed method was validated as per the guidelines recommended by the International Council for Harmonization for parameters like, linearity, limit of detection, limit of quantification, accuracy, and precision. Therefore, the developed novel high-performance thin-layer chromatographic process could be employed for rapid standardization of Divya-Swasari-Vati and other related herbal formulation, which would aid in quality manufacturing and product development.

Simultaneous analysis of oxytetracycline hydrochloride, lidocaine, and bromhexine hydrochloride in the presence of many interfering excipients.

A gradient elution high-performance liquid chromatographic method with a diode array detector is introduced for the first time for the simultaneous estimation of three drugs, namely, oxytetracycline hydrochloride (OXT), lidocaine (LDC), and bromhexine hydrochloride (BRH), in a veterinary formulation (OxyClear® solution) that contains many interfering additives. The method used a C-8 column. The chromatographic eluting solution included acidified water (0.1% trifluoroacetic acid in water) and acetonitrile at a 1-ml/min flow rate and 254 nm as a nominated detection wavelength. The chromatographic process was assessed in terms of linearity, precision, accuracy, LOD, and LOQ. OXT, LDC, and BRH were linear in the range of 1-60, 5-100, and 1-60 μg/ml, respectively. The three drugs were determined successfully without the interference of three excipients having UV absorbances. Furthermore, the purities of the peaks of the three drugs were confirmed by comparing the UV spectra of investigated peaks to the UV reference spectra in Clarke's Analysis of Drugs and Poisons. The greenness value of the method was 0.69 with a faint green-colored pictogram using the AGREE tool. These merits recommend the application of the planned method in QC laboratories for purity testing and concentration assays for the pure drugs and commercial formulations.

Characterization of an Immobilized Amino Acid Racemase for Potential Application in Enantioselective Chromatographic Resolution Processes

Enantioselective resolution processes can be improved by integration of racemization. Applying environmentally friendly enzymatic racemization under mild conditions is in particular attractive. Owing to the variety of enzymes and the progress in enzyme engineering, suitable racemases can be found for many chiral systems. An amino acid racemase (AAR) from P. putida KT2440 is capable of processing a broad spectrum of amino acids at fast conversion rates. The focus of this study is the evaluation of the potential of integrating AAR immobilized on Purolite ECR 8309 to racemize L- or D-methionine (Met) within an enantioselective chromatographic resolution process. Racemization rates were studied for different temperatures, pH values, and fractions of organic co-solvents. The long-term stability of the immobilized enzyme at operating and storage conditions was found to be excellent and recyclability using water with up to 5 vol% ethanol at 20 °C could be demonstrated. Packed as an enzymatic fixed bed reactor, the immobilized AAR can be coupled with different resolution processes; for instance, with chromatography or with preferential crystallization. The performance of coupling it with enantioselective chromatography is estimated quantitatively, exploiting parametrized sub-models. To indicate the large potential of the AAR, racemization rates are finally given for lysine, arginine, serine, glutamine, and asparagine.

Adsorption/desorption characteristics and chromatographic purification of polyphenols from Vernonia patula (Dryand.) Merr. using macroporous adsorption resin

Vernonia patula (Dryand.) Merr. has long been used as a traditional medicine in some parts of Asia and is a promising source of bioactive polyphenols. In this work, the adsorption/desorption characteristics and chromatographic purification of total polyphenols from V. patula (VPTP) by macroporous adsorption resin (MAR) were investigated. Static adsorption/desorption tests revealed that NKA-II resin was most suitable for purifying VPTP with the adsorption capacity of 92.54 ± 0.85 mg/g and desorption capacity of 71.03 ± 1.83 mg/g, that the Langmuir model afforded the best fit to the isotherm data, that the pseudo-second order model afforded the best fit to kinetics data, and that adsorption was a favourable, spontaneous, exothermic and physical reaction. Additionally, an efficient chromatographic purification process was developed. After purification by scale-up column chromatography (CC) on NKA-II resin under optimum conditions (for adsorption: 6 BV of aqueous solution of VPTP extract with an initial total polyphenols concentration of 3.84 mg/mL was loaded onto the column at 1.5 BV/h; for desorption: the column was eluted using 5.5 BV of 60 % EtOH at 3 BV/h), the content of VPTP improved 2.36-fold from 21.36 %–50.33 % with a satisfactory recovery of 83.45 %. Furthermore, high-performance liquid chromatography (HPLC) analysis showed that compared with the crude extract, the contents of chlorogenic acid and caffeic acid in VPTP-enriched extracts were obviously increased. The results indicated that this work provides a reliable basis for the industrial purification of VPTP using MAR.

Purification of a peptide tagged protein via an affinity chromatographic process with underivatized silica.

Silica is widely used for chromatography resins due to its high mechanical strength, column efficiency, easy manufacturing (i.e. controlled size and porosity), and low‐cost. Despite these positive attributes to silica, it is currently used as a backbone for chromatographic resins in biotechnological downstream processing. The aim of this study is to show how the octapeptide (RH)4 can be used as peptide tag for high‐purity protein purification on bare silica. The tag possesses a high affinity to deprotonated silanol groups because the tag's arginine groups interact with the surface via an ion pairing mechanism. A chromatographic workflow to purify GFP fused with (RH)4 could be implemented. Purities were determined by SDS‐PAGE and RP‐HPLC. The equilibrium binding capacity of the fusion protein GFP‐(RH)4 on silica is 450 mg/g and the dynamic binding capacity around 3 mg/mL. One‐step purification from clarified lysate achieved a purity of 93% and a recovery of 94%. Overloading the column enhances the purity to >95%. Static experiments with different buffers showed variability of the method making the system independent from buffer choice. Our designed peptide tag allows bare silica to be utilized in preparative chromatography for downstream bioprocessing; thus, providing a cost saving factor regarding expensive surface functionalization. Underivatized silica in combination with our (RH)4 peptide tag allows the purification of proteins, in all scales, without relying on complex resins.

(Invited) The Varying Packing Behaviors of Tb@C82 (I, II) Isomers in Their Cocrystals with Ni(OEP)

Carbon soot containing terbium endohedral fullerenes was prepared by vaporizing a graphite rod doped with Tb4O7 in an electric arc-discharge chamber. After Soxhlet extraction with 1,2,4-trichlorobenzene and rotary evaporation, the obtained residue was ultrasonically dissolved in toluene and then subjected to a three-stage high-pressure liquid chromatographic (HPLC) isolation process to collect the Tb@C82 (I, II) isomers. The molecular structures of Tb@C82 (I, II) are unambiguously characterized as Tb@C 2v(9)-C82 and Tb@C s(6)-C82, respectively, in line with single-crystal X-ray diffraction. Moreover, Tb@C82 (I, II) isomers demonstrated different packing behaviors in their cocrystals with Ni(OEP). Tb@C82 (I) forms 1:1 cocrystal with Ni(OEP), whereas Tb@C82 (II) forms 2:2 cocrystal with Ni(OEP). Tb@C s(6)-C82 forms a centrosymmetric dimer in 2[Tb@C s(6)-C82]∙2[Ni(OEP)]∙2(C6H6)∙(CS2), and the two C s(6)-C82 cages are connected by a new C-C bond with a bond length of 1.618(4) Å. Density functional theory calculations show that the dominant unpaired spin exists on a particular C atom of Tb@C s(6)-C82, leading to regionally selective dimerization.

Development of Theoretical Approaches to Determination of the Main Groups of Biologically Active Substances of Medicinal Plant Raw Materials by TLC Method

Introduction. As is known, the selection of optimal conditions for the analysis of extracts from medicinal plant raw materials (MPМ), as well as medicinal herbal preparations and pharmaceutical substances of plant origin, characterized by a complex variable composition of biologically active substances (BAS) by TLC, presents certain difficulties. For the design of mobile phases for the separation of mixtures of BAS of plant origin, in a thin layer of sorbent, the following approaches are used: literary sources; standard mobile phases; spot elution method; the scheme proposed by the firm Camag (Switzerland); model "PRISMA"; variocameras and others. In foreign literature, there are publications on the generalization of the available experimental data on the determination of various natural groups of BAS in objects of plant origin. However, such reviews did not reveal the regularities of the chromatographic behavior of individual BAS in a thin layer, as well as the influence of various factors on the reproducibility of Rf values. The study of the possibility of a theoretical approach to the choice of optimal conditions for chromatography of groups of BAS of different polarity, allowing them to separate, identify and quantify by TLC is a relevant and poorly developed area of chromatography in general.Aim. The aim of this work was to develop a theoretical approach to the choice of optimal conditions for the chromatographic separation of various groups of BAS of plant origin in a thin layer of sorbent.Materials and methods. To study the regularities of chromatographic behavior in a thin layer of representatives of the main classes of BAS present in MPМ (amino acids, flavonoids, tannins, simple sugars, ascorbic acid, fat-soluble vitamins), the value of the main factor affecting the parameters of the efficiency of the chromatographic process, the polarity of the eluent, was studied. As objects of research, we used ready-made chopped raw material of nettle leaves, produced by a domestic manufacturer, that meets the requirements of regulatory documents, as well as sea buckthorn fruits collected on the territory of the Voronezh region, according to the rules for harvesting MPМ of various morphological groups in fresh and dried form.Results and discussion. The regularities of elution and mathematical models describing the chromatographic behavior of plant BAS in a thin layer of sorbent have been established. Based on the totality of the results obtained, from the standpoint of the efficiency of the chromatographic process, the optimal conditions for their TLC analysis were selected and theoretically substantiated. To study the qualitative composition of BAS and to achieve a clear separation of zones on chromatograms, TLC methods were developed and tested on the studied MPМ using simple, frontal or two-dimensional chromatography.Conclusion. It is shown that the determination and separation in a thin layer of the sorbent of hydrophilic and lipophilic BAS of MPМ in the presence of a joint requires different approaches and techniques. The paper proposes an algorithm for the selection of the mobile phase and methods of chromatography of BAS of medicinal products. The revealed mathematical models describing the chromatographic behavior of BAS will make it possible to select the conditions under which it is possible to determine the individual components of multicomponent mixtures without preliminary separation. The developed methods for the determination of BAS can also be used for standardization and quality assessment of other types of MPМ, phytopreparations and pharmaceutical substances of plant origin.

Hybrid Models for the simulation and prediction of chromatographic processes for protein capture

The biopharmaceutical industries are continuously faced with the pressure to reduce the development costs and accelerate development time scales. The traditional approach of heuristic-based or platform process-based optimization is soon getting obsolete, and more generalized tools for process development and optimization are required to keep pace with the emerging trends. Thus, advanced model-based methods that can reduce the can ensure accelerated development of robust processes with minimal experiments are necessary. Though mechanistic models for chromatography are quite popular, their success is limited by the need to have accurate knowledge of adsorption isotherms and mass transfer kinetics. As an alternative, in this work, a hybrid modeling approach is proposed. Thereby, the chromatographic unit behavior is learned by a combination of neural network and mechanistic model while fitting suitable experimental breakthrough curves. Since this approach does not require identifying suitable mechanistic assumptions for all the phenomena, it can be developed with lower effort. Thus, allowing the scientists to concentrate their focus on process development. The performance of the hybrid model is compared with the mechanistic Lumped kinetic Model for in-silico data and experiments conducted on a system of industrial relevance. The flexibility of the hybrid modeling approach results in about three times higher accuracies compared to Lumped Kinetic Model. This is validated for five different isotherm models used to simulate data, with the hybrid model showing about two to three times lower prediction errors in all the cases. Not only in prediction, but we could also show that the hybrid model is more robust in extrapolating across process conditions with about three times lower error than the LKM. Additionally, it could be demonstrated that an appropriately tailored formulation of the hybrid model can be used to generate representations for the underlying principles such as adsorption equilibria and mass transfer kinetics.

Dihydroxyacetone Production: From Glycerol Catalytic Oxidation with Commercial Catalysts to Chromatographic Separation

A process for catalytic production of dihydroxyacetone through glycerol oxidation and dihydroxyacetone purification by chromatographic processes is herein presented. Glycerol oxidation over commercial Pt/AC and Pt–Bi/AC catalysts was performed on a batch reactor operating under base-free conditions, using water as a solvent and oxygen as the oxidant agent. The highest dihydroxyacetone yield obtained was 36%, using the Pt5%-Bi1.5%/AC catalyst, whereas the monometallic Pt/AC catalyst was selective to glyceric acid. It is herein reported for the first time dihydroxyacetone separation from unreacted glycerol and reaction byproducts (organic acids). Two commercial polystyrene-divinylbenzene ion-exchange resins were used as a stationary phase, one in the hydrogen form and the other in the calcium form, and water was used as the mobile phase. Adsorption equilibrium data for the species present in the reaction mixture were determined in both resins through single-component adsorption breakthrough experiments. A continuous chromatographic separation process was designed based on the simulated moving bed (SMB) technology and simulated using the gPROMS model builder software. A two SMB cascade was then considered, performing the pseudobinary mixture separation on the first SMB. The extract stream from the first SMB containing dihydroxyacetone and glycerol was fed to the second SMB, obtaining dihydroxyacetone with a purity of 97%. Considering the overall unit, a dihydroxyacetone productivity of 64 kgDHA (LAds day)−1 was obtained with an eluent consumption of 1218 LDes kgDHA–1.

Rapid optimization of processes for the integrated purification of biopharmaceuticals.

Straight‐through chromatography, wherein the eluate from one column passes directly onto another column without adjustment, is one strategy to integrate and intensify manufacturing processes for biologics. Development and optimization of such straight‐through chromatographic processes is a challenge, however. Conventional high‐throughput screening methods optimize each chromatographic step independently, with limited consideration for the connectivity of steps. Here, we demonstrate a method for the development and optimization of fully integrated, multi‐column processes for straight‐through purification. Selection of resins was performed using an in silico tool for the prediction of processes for straight‐through purification based on a one‐time characterization of host‐cell proteins combined with the chromatographic behavior of the product. A two‐step optimization was then conducted to determine the buffer conditions that maximized yield while minimizing process‐ and product‐related impurities. This optimization of buffer conditions included a series of range‐finding experiments on each individual column, similar to conventional screening, followed by the development of a statistical model for the fully integrated, multi‐column process using design of experiments. We used this methodology to develop and optimize integrated purification processes for a single‐domain antibody and a cytokine, obtaining yields of 88% and 86%, respectively, with process‐ and product‐related variants reduced to phase‐appropriate levels for nonclinical material.

Method Development and Validation of RP-HPLC method for Saxagliptin and Sitagliptin in Pharmaceutical Dosage Form - A Review

The study's goal was to develop a plain, quick, and responsive RP-HPLC method for determining the concentrations of Saxagliptin and Sitagliptin in pharmaceutical bulk dosage form (bulk powders). Isocratic elution with Cosmosil C18 (250nm 4.6nm, 5m particle size) and UV detection at 212nm for Saxagliptin and Develosil ODS HG-5 RP-C18 (15cm 4.6mm, 5m particle size) and UV detection at 255nm for Sitagliptin were used in this chromatographic process. Methanol and water (70:30) in a mobile solution with a flow rate of 0.8ml/min for Saxagliptin and (0.05m) phosphate buffer: methanol and water (70:30) in a mobile solution with a flow rate of 0.8ml/min for Saxagliptin and (0.05m) phosphate buffer: These protocols have been put through their paces in accordance with ICH guidelines. The normal curves for Saxagliptin and Sitagliptin were observed to have a linear relationship across the analytical ranges of 10-50 g/ml and 30-70 g/ml, respectively. The accuracy, precision, limit of identification, the limit of quantification, and robustness of the system were all calculated. Various analytical methods such as UPLC (Ultra performance liquid chromatography), UV spectroscopy, LC-UV methods have performed to the quantitative determination of Saxagliptin and Sitagliptin drugs.

Autoregressive modelling of chromatographic signals from urine samples for prostate cancer diagnosis

This article evaluates autoregressive modeling as a feature extraction method in a database of chromatographic signals from urine samples for non-invasive diagnostic support of prostate cancer in response to the research question: Can chromatographic signals from urine be characterized and used as a non-invasive method for cancer diagnosis? For this purpose, a database of 18 patients, 9 diagnosed with prostate cancer and 9 control patients, is consolidated, statistical methods are implemented to generate autoregressive coefficients from the data signals, and finally, the principal component analysis technique is applied for cross-class classification. As a result, a correct classification was obtained in the total number of samples validating the autoregressive modelling as a feature extraction method in contrast to the conventional methodology usually followed in chromatographic signal processing.

Unexpected effects of mobile phase solvents and additives on retention and resolution of N-acyl-D,L-leucine applying Cinchonane-based chiral ion exchangers

Chiral ion exchangers based on quinine (QN) and quinidine (QD), namely Chiralpak QN-AX and QD-AX as anionic and ZWIX(+) and ZWIX(-) as zwitterionic ion exchanger chiral stationary phases (CSPs) have been investigated with respect to their retention and chiral resolution characteristics. For the evaluation of the effects of the composition of the polar organic bulk solvents of the mobile phase (MP) and those of the organic acid and base additives acting as displacers necessary for a liquid chromatographic ion-exchange process, racemic N-(3,5-dinitrobenzoyl)leucine and other related analytes were applied. The main aim was to evaluate the impact of the MP variations on the observed, and thus the apparent enantioselectivity (αapp), and the retention factor. Significant differences were found using either polar protic methanol (MeOH) or polar non-protic acetonitrile (MeCN) solvents in combination with the acid and base additives as counter- and co-ions. It became clear, that the charged sites of both the chiral selectors of the CSPs and the analytes get specifically solvated, accompanied by the adsorption of all MP components on the CSP, thereby building a stagnant “stationary phase layer” with a composition different from the bulk MP. Via a systematic change of the MP composition, trends of resulting αapp and retention factors have been identified and discussed.In a detailed set of experiments, the effect of the concentration of the acid component in the MP containing MeOH or MeCN was specifically investigated, with the acid considered to be a displacer in anion-exchange type chromatographic systems.Surprisingly, all four chiral columns retained and resolved the tested N-acyl-Leu analytes with αapp values up to 21 within a retention factor window of 0.03 and 10 with pure MeOH as eluent. However, using pure MeCN as eluent, an almost infinite-long retention of the acidic analyte was noticed in all cases. We suggest that the rather different thickness of the solvation shells generated by MeOH or MeCN around the charged/chargeable sites of the chiral selector determines eventually the strength of the electrostatic selector–selectand interactions.As a control experiment we included the non-chiral N-acylglycine derivatives as analyte in all cases to support the interpretations with respect to the contribution of the enantioselective and non-enantioselective retention factor increments as a part of the observed αapp.

Identification of Compounds with Potential Therapeutic Uses from Sweet Pepper (Capsicum annuum L.) Fruits and Their Modulation by Nitric Oxide (NO).

Plant species are precursors of a wide variety of secondary metabolites that, besides being useful for themselves, can also be used by humans for their consumption and economic benefit. Pepper (Capsicum annuum L.) fruit is not only a common food and spice source, it also stands out for containing high amounts of antioxidants (such as vitamins C and A), polyphenols and capsaicinoids. Particular attention has been paid to capsaicin, whose anti-inflammatory, antiproliferative and analgesic activities have been reported in the literature. Due to the potential interest in pepper metabolites for human use, in this project, we carried out an investigation to identify new bioactive compounds of this crop. To achieve this, we applied a metabolomic approach, using an HPLC (high-performance liquid chromatography) separative technique coupled to metabolite identification by high resolution mass spectrometry (HRMS). After chromatographic analysis and data processing against metabolic databases, 12 differential bioactive compounds were identified in sweet pepper fruits, including quercetin and its derivatives, L-tryptophan, phytosphingosin, FAD, gingerglycolipid A, tetrahydropentoxylin, blumenol C glucoside, colnelenic acid and capsoside A. The abundance of these metabolites varied depending on the ripening stage of the fruits, either immature green or ripe red. We also studied the variation of these 12 metabolites upon treatment with exogenous nitric oxide (NO), a free radical gas involved in a good number of physiological processes in higher plants such as germination, growth, flowering, senescence, and fruit ripening, among others. Overall, it was found that the content of the analyzed metabolites depended on the ripening stage and on the presence of NO. The metabolic pattern followed by quercetin and its derivatives, as a consequence of the ripening stage and NO treatment, was also corroborated by transcriptomic analysis of genes involved in the synthesis of these compounds. This opens new research perspectives on the pepper fruit’s bioactive compounds with nutraceutical potentiality, where biotechnological strategies can be applied for optimizing the level of these beneficial compounds.

Simulated-moving-bed technology for purification of the prebiotics galacto-oligosaccharides

A commercial galacto-oligosaccharide (GOS) syrup with prebiotic properties was purified with simulated moving bed (SMB) chromatography to separate undesired side products induced by synthesis reaction mechanism. A promising polystyrene-divinylbenzene resin stationary phase has been characterized with regard to its selective adsorption behavior. The chosen chromatographic system allows a pseudo binary separation of the multi-component GOS syrup mixture exploiting a multi-column continuous chromatographic process. Suitable SMB operation parameters were estimated by means of the equilibrium (triangle) theory, further optimized by modelling the separation in more detail and finally validated experimentally. Changes of temperature, concentration of the feed as well as in the instrumental configuration (open loop, closed loop and 3 zones) were examined with a classical SMB plant in lab scale size. Highly purified GOS products could be obtained with purities up to >99% in the extract and raffinate fractions. A quantitative description of the transfer from batch chromatography to the continuous separation process via SMB technology is provided, indicated significant potential for a scale-up.

Analysis and optimal design of batch and two-column continuous chromatographic frontal processes for monoclonal antibody purification.

The increasing demand for efficient and robust processes in the purification of monoclonal antibodies (mAbs) has recently brought frontal chromatography to the forefront. Applied during the polishing step, it enables the removal of high molecular weight aggregates from the target product, achieving high purities. Typically, this process is operated in batch using a single column, which makes it intrinsically subjected to a purity-yield tradeoff. This means that high purities can only be achieved at the cost of lowering the product yield and vice versa. Recently, a two-column continuous implementation of frontal chromatography, referred to as Flow2, was developed. Despite being able of alleviating the purity-yield tradeoff typical of batch operations, the increase in the number of process parameters complicates its optimal design, with the risk of not exploiting its full potential. In this study, we developed an ad hoc design procedure (DP) suitable for the optimization of both batch frontal chromatography and Flow2 in terms of purity, yield, and productivity. This procedure provided similar results as a multiobjective optimization based on genetic algorithm but with lower computational effort. Then, batch and Flow2 operated at their optimal conditions were compared. Besides showing a more favorable Pareto front of yield and productivity at a specified purity, the Flow2 process demonstrated improved robustness compared to the batch process with respect to modifications in the loading linear velocity, washing buffer ionic strength and loading time, thus providing an appealing operation for integrated processes.