Steroid extraction in a microchannel system--mathematical modelling and experiments

Advances in modeling techniques for the production and purification of biomolecules: A comprehensive review

In response to the growing demand for therapeutic biomolecules, there is a need for continuous and cost-effective bio-separation techniques to enhance extraction yield and efficiency. Aqueous biphasic extractive fermentation has emerged as an integrated downstream processing technique, offering selective partitioning, high productivity, and preservation of biomolecule integrity. However, the dynamic nature of this technique requires a comprehensive understanding of the underlying separation mechanisms. Unfortunately, the analysis of parameters influencing this dynamic behavior can be challenging due to limited resources and time. To address this, mathematical modeling approaches can be employed to minimize the tedious trial-and-error experimentation process. This review article presents mathematical modeling approaches for both upstream and downstream processing techniques, focusing on the production of biomolecules which can be used in pharmaceutical industries in a cost-effective manner. By leveraging mathematical models, researchers can optimize the production and purification processes, leading to improved efficiency and processing cost reduction in biomolecule production.

Stable Formation of Aqueous/Organic Parallel Two-phase Flow in Nanochannels with Partial Surface Modification

In microfluidics, various chemical processes can be integrated utilizing parallel multiphase flows. Our group has extended this research to nanofluidics, and recently performed the extraction of lipids using parallel two-phase flow in nanochannels. Although this was achieved in surface-modified nanochannels, a stable condition of parallel two-phase flow remains unknown due to difficulties in device fabrication, for a suitable method of bonding surface-modified substrates is lacking. Therefore, research on parallel two-phase flow in nanochannels has been limited. Herein, a new bonding method which improves the wash process for the substrates and increases the bonding rate to ∼100% is described. The conditions to achieve parallel organic/aqueous two-phase flow were then studied. It was revealed that in nanochannels, higher capillary numbers for the organic phase flow were required compared to that in microchannels. The newly developed fabrication process and flow regimes will contribute to realize integrated nanofluidic devices capable of analyzing single molecules/cells.

Continuous and automated slug flow nanoextraction for rapid partition coefficient measurement

Octanol-water partition coefficients (log Kow) are widely used in pharmaceutical and environmental chemistry to assess the lipophilicity of compounds. Traditionally log Kow is determined using a shake-flask method that uses milliliters of sample and solvent and requires hours for preparation, extraction, and analysis. Here, we report an automated system for rapid log Kow determination for an array of compounds using slug flow nanoextraction (SFNE) enabled by a microfluidic chip. In the method, an autosampler is used to introduce 1 μL of sample into a microfluidic device that segments the injected volume into a series of 4 nL slugs that are each paired to an adjacent octanol slug. Each octanol-water phase pair is compartmentalized by an immiscible fluorous carrier fluid. During flow, rapid extraction occurs at each octanol-water interface. The resulting linear array of slugs flows into an online UV absorbance detector that is used to determine concentrations in the phases, allowing the log Kow to be measured. The microfluidic device allows toggling between two-phase "aqueous plug" generation (aqueous sample separated by fluorous carrier fluid) and three-phase "phase pair" generation. In this way, online calibration for detection in the aqueous phase can be achieved. The method is applied to determining log Kow for a panel of seven pharmaceutical compounds, including complete calibration curves, at three different pHs in under 2 h using 5 μL of extraction standard and 2.9 μL of octanol per extraction standard analyzed.

Exploring New Horizons in Liquid Compartmentalization via Microfluidics

Spatial organization of cellular processes is crucial to efficiently regulate life's essential reactions. Nature does this by compartmentalization, either using membranes, such as the cell and nuclear membrane, or by liquid-like droplets formed by aqueous liquid-liquid phase separation. Aqueous liquid-liquid phase separation can be divided in two different phenomena, associative and segregative phase separation, of which both are studied for their membraneless compartmentalization abilities. For centuries, segregative phase separation has been used for the extraction and purification of biomolecules. With the emergence of microfluidic techniques, further exciting possibilities were explored because of their ability to fine-tune phase separation within emulsions of various compositions and morphologies and achieve one of the simplest forms of compartmentalization. Lately, interest in aqueous liquid-liquid phase separation has been revived due to the discovery of membraneless phases within the cell. In this Perspective we focus on segregative aqueous phase separation, discuss the theory of this interesting phenomenon, and give an overview of the evolution of aqueous phase separation in microfluidics.

Microfluidic Chip-Based Induced Phase Separation Extraction as a Fast and Efficient Miniaturized Sample Preparation Method

Induced phase separation extraction (IPSE) is an efficient sample clean-up technique that can replace liquid-liquid extraction (LLE). The purpose of this study was to miniaturize IPSE by carrying it out in a microfluidic chip. An IPSE chip was designed and evaluated for its ability to separate and purify samples on a microscale. The 5 × 2 cm chip was fed with a solution of polar to non-polar model compounds in acetonitrile-water (1:1). In the 100 µm wide and 40 µm deep microchannels, the sample solution was efficiently separated into two immiscible phases by adding a hydrophobic solvent as inducer. Analytes present in the sample solution each migrated to their own favorable phase upon phase separation. After optimization, extraction and fractionation were easily and efficiently achieved. The behavior of analytes with a pH-dependent partitioning could be influenced by adjusting the pH of the sample solution. Scutellaria baicalensis extract, used in Traditional Chinese Medicine (TCM), was successfully separated in aglycones and glycosides. In this microscale system, the sample and solvent consumption is reduced to microliters, while the time needed for the sample pretreatment is less than one minute. Additionally, the extraction efficiency can reach up to 98.8%, and emulsion formation is avoided.

Kinetic Parameter Estimation and Mathematical Modelling of Lipase Catalysed Biodiesel Synthesis in a Microreactor

Development of green, clean, and sustainable processes presents new challenges in today’s science. Production of fuel is no exception. Considering the utilisation of various renewable sources, the synthesis of biodiesel, characterised as more environmentally-friendly then fossil fuel, has drawn significant attention. Even though the process based on chemical transesterification in a batch reactor still presents the most used method for its production, enzyme catalysed synthesis of biodiesel in a microreactor could be a new approach for going green. In this research, edible sunflower oil and methanol were used as substrates and lipase from Thermomyces lanuginosus (Lipolase L100) was used as catalyst for biodiesel synthesis. Experiments were performed in a polytetrafluoroethylene (PTFE) microreactor with three inlets and in glass microreactors with two and three inlets. For a residence time of 32 min, the fatty acids methyl esters (FAME) yield was 30% higher than the yield obtained for the glass microreactor with three inlets. In comparison, when the reaction was performed in a batch reactor (V = 500 mL), the same FAME yield was achieved after 1.5 h. In order to enhance the productivity of the process, we used proposed reaction kinetics, estimated kinetic parameters, and a mathematical model we developed. After validation using independent experimental data, a proposed model was used for process optimization in order to obtain the highest FAME yield for the shortest residence time.

Co-production of 11α-hydroxyprogesterone and ethanol using recombinant yeast expressing fungal steroid hydroxylases

BACKGROUND

Bioethanol production from sustainable sources of biomass that limit effect on food production are needed and in a biorefinery approach co-products are desirable, obtained from both the plant material and from the microbial biomass. Fungal biotransformation of steroids was among the first industrial biotransformations allowing corticosteroid production. In this work, the potential of yeast to produce intermediates needed in corticosteroid production is demonstrated at laboratory scale following bioethanol production from perennial ryegrass juice.

RESULTS

Genes encoding the 11α-steroid hydroxylase enzymes from Aspergillus ochraceus (11α-SH^Aoch) and Rhizopus oryzae (CYP509C12) transformed into Saccharomyces cerevisiae for heterologous constitutive expression in p425TEF. Both recombinant yeasts (AH22:p11α-SH^Aoch and AH22:p509C12) exhibited efficient progesterone bioconversion (on glucose minimal medial containing 300 µM progesterone) producing either 11α-hydroxyprogesterone as the sole metabolite (AH22:p11α-SH^Aoch) or a 7:1 mixture of 11α-hydroxyprogesterone and 6β-hydroxyprogesterone (AH22:p509C12). Ethanol yields for AH22:p11α-SH^Aoch and AH22:p509C12 were comparable resulting in ≥75% conversion of glucose to alcohol. Co-production of bioethanol together with efficient production of the 11-OH intermediate for corticosteroid manufacture was then demonstrated using perennial ryegrass juice. Integration of the 11α-SH^Aoch gene into the yeast genome (AH22:11α-SHAoch+K) resulted in a 36% reduction in yield of 11α-hydroxyprogesterone to 174 µmol/L using 300 µM progesterone. However, increasing progesterone concentration to 955 µM and optimizing growth conditions increased 11α-hydroxyprogesterone production to 592 µmol/L product formed.

CONCLUSIONS

The progesterone 11α-steroid hydroxylases from A. ochraceus and R. oryzae, both monooxygenase enzymes of the cytochrome P450 superfamily, have been functionally expressed in S. cerevisiae. It appears that these activities in fungi are not associated with a conserved family of cytochromes P450. The activity of the A. ochraceous enzyme was important as the specificity of the biotransformation yielded just the 11-OH product needed for corticosteroid production. The data presented demonstrate how recombinant yeast could find application in rural biorefinery processes where co-production of value-added products (11α-hydroxyprogesterone and ethanol) from novel feedstocks is an emergent and attractive possibility.

Safety assessment in development and operation of modular continuous-flow processes

Improved safety is one of the main drivers for microreactor application in chemical process development and small-scale production.

Interfacial Phenomena and Fluid Control in Micro/Nanofluidics

Fundamental aspects of rapidly advancing micro/nanofluidic devices are reviewed from the perspective of liquid interface chemistry and physics, including the influence of capillary pressure in microfluidic two-phase flows and phase transitions related to capillary condensation.

The enhancement of liquid–liquid extraction with high phase ratio by microfluidic-based hollow droplet

We developed a novel method to enhance the liquid–liquid extraction by a microfluidic-based hollow droplet structure. A one-step microfluidic device is used for the generation of gas-in-oil-in-water double emulsions.

Effects of non-Newtonian power law rheology on mass transport of a neutral solute for electro-osmotic flow in a porous microtube

Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed.

Solvent Extraction of Uranium by Laminar Flow in Microfluidic Chips

The system of uranyl nitrate aqueous solution and tributylphosphate (TBP) dissolved in kerosene is widely used all around the world, no matter in nuclear fuel cycle or analysis of impurities in uranium. The extraction process is mature, but the amount of consumption of organic reagent and generation of radioactive waste solution is huge, that is not environment friendly. Microfluidic is very popular nowadays, and one of its many applications is extraction. Here in this paper, we studied the flow situation of water and 20%TBP-kerosene, find the relationship between width ratio and flow rate ratio. And we used chemical modification to get a good separated outlet, and we observed the stability of OTS modified glass, that is stable in our circumstance. Finally we use the modified channels to achieve the extraction process, and find the extraction ratio is increases by contact time increases, and has no relationship of initial concentration.

Design optimization of liquid-phase flow patterns for microfabricated lung on a chip

Microreactors experience significant deviations from plug flow due to the no-slip boundary condition at the walls of the chamber. The development of stagnation zones leads to widening of the residence time distribution at the outlet of the reactor. A hybrid design optimization process that combines modeling and experiments has been utilized to minimize the width of the residence time distribution in a microreactor. The process was used to optimize the design of a microfluidic system for an in vitro model of the lung alveolus. Circular chambers to accommodate commercial membrane supported cell constructs are a particularly challenging geometry in which to achieve a uniform residence time distribution. Iterative computational fluid dynamics (CFD) simulations were performed to optimize the microfluidic structures for two different types of chambers. The residence time distributions of the optimized chambers were significantly narrower than those of non-optimized chambers, indicating that the final chambers better approximate plug flow. Qualitative and quantitative visualization experiments with dye indicators demonstrated that the CFD results accurately predicted the residence time distributions within the bioreactors. The results demonstrate that such a hybrid optimization process can be used to design microreactors that approximate plug flow for in vitro tissue engineered systems. This technique has broad application for optimization of microfluidic body-on-a-chip systems for drug and toxin studies.

Continuous steroid biotransformations in microchannel reactors

The use of microchannel reactor based technologies within the scope of bioprocesses as process intensification and production platforms is gaining momentum. Such trend can be ascribed a particular set of characteristics of microchannel reactors, namely the enhanced mass and heat transfer, combined with easier handling and smaller volumes required, as compared to traditional reactors. In the present work, a continuous production process of 4-cholesten-3-one by the enzymatic oxidation of cholesterol without the formation of any by-product was assessed. The production was carried out within Y-shaped microchannel reactors in an aqueous-organic two-phase system. Substrate was delivered from the organic phase to aqueous phase containing cholesterol oxidase and the product formed partitions back to the organic phase. The aqueous phase was then forced through a plug-flow reactor, containing immobilized catalase. This step aimed at the reduction of hydrogen peroxide formed as a by-product during cholesterol oxidation, to avoid cholesterol oxidase deactivation due to said by-product. This setup was compared with traditional reactors and modes of operation. The results showed that microchannel reactor geometry outperformed traditional stirred tank and plug-flow reactors reaching similar conversion yields at reduced residence time. Coupling the plug-flow reactor containing catalase enabled aqueous phase reuse with maintenance of 30% catalytic activity of cholesterol oxidase while eliminating hydrogen peroxide. A final production of 36 m of cholestenone was reached after 300 hours of operation.

Microfluidic devices: useful tools for bioprocess intensification

The dawn of the new millennium saw a trend towards the dedicated use of microfluidic devices for process intensification in biotechnology. As the last decade went by, it became evident that this pattern was not a short-lived fad, since the deliverables related to this field of research have been consistently piling-up. The application of process intensification in biotechnology is therefore seemingly catching up with the trend already observed in the chemical engineering area, where the use of microfluidic devices has already been upgraded to production scale. The goal of the present work is therefore to provide an updated overview of the developments centered on the use of microfluidic devices for process intensification in biotechnology. Within such scope, particular focus will be given to different designs, configurations and modes of operation of microreactors, but reference to similar features regarding microfluidic devices in downstream processing will not be overlooked. Engineering considerations and fluid dynamics issues, namely related to the characterization of flow in microchannels, promotion of micromixing and predictive tools, will also be addressed, as well as reflection on the analytics required to take full advantage of the possibilities provided by microfluidic devices in process intensification. Strategies developed to ease the implementation of experimental set-ups anchored in the use of microfluidic devices will be briefly tackled. Finally, realistic considerations on the current advantages and limitation on the use of microfluidic devices for process intensification, as well as prospective near future developments in the field, will be presented.

Analysis of polychlorinated biphenyls in transformer oil by using liquid-liquid partitioning in a microfluidic device

Polychlorinated biphenyls (PCBs) that are present in transformer oil are a common global problem because of their toxicity and environmental persistence. The development of a rapid, low-cost method for measurement of PCBs in oil has been a matter of priority because of the large number of PCB-contaminated transformers still in service. Although one of the rapid, low-cost methods involves an immunoassay, which uses multilayer column separation, hexane evaporation, dimethyl sulfoxide (DMSO) partitioning, antigen-antibody reaction, and a measurement system, there is a demand for more cost-effective and simpler procedures. In this paper, we report a DMSO partitioning method that utilizes a microfluidic device with microrecesses along the microchannel. In this method, PCBs are extracted and enriched into the DMSO confined in the microrecesses under the oil flow condition. The enrichment factor was estimated to be 2.69, which agreed well with the anticipated value. The half-maximal inhibitory concentration of PCBs in oil was found to be 0.38 mg/kg, which satisfies the much stricter criterion of 0.5 mg/kg in Japan. The developed method can realize the pretreatment of oil without the use of centrifugation for phase separation. Furthermore, the amount of expensive reagents required can be reduced considerably. Therefore, our method can serve as a powerful tool for achieving a simpler, low-cost procedure and an on-site analysis system.

Miniaturization in biocatalysis

The use of biocatalysts for the production of both consumer goods and building blocks for chemical synthesis is consistently gaining relevance. A significant contribution for recent advances towards further implementation of enzymes and whole cells is related to the developments in miniature reactor technology and insights into flow behavior. Due to the high level of parallelization and reduced requirements of chemicals, intensive screening of biocatalysts and process variables has become more feasible and reproducibility of the bioconversion processes has been substantially improved. The present work aims to provide an overview of the applications of miniaturized reactors in bioconversion processes, considering multi-well plates and microfluidic devices, update information on the engineering characterization of the hardware used, and present perspective developments in this area of research.

Lipase-catalyzed synthesis of isoamyl acetate in an ionic liquid/n-heptane two-phase system at the microreactor scale

A continuously operated psi-shaped microreactor was used for lipase-catalyzed synthesis of isoamyl acetate in the 1-butyl-3-methylpyridinium dicyanamide/n-heptane two-phase system. The chosen solvent system with dissolved Candida antarctica lipase B, which was attached to the ionic liquid/n-heptane interfacial area due to its amphiphilic properties, was shown to be highly efficient and enabled simultaneous esterification and product removal. At preliminarily selected conditions regarding the type of acyl donor, its molar ratio to alcohol and enzyme concentration, 48.4 g m(-3) s(-1) of isoamyl acetate was produced, which was almost three-fold better as compared to the intensely mixed batch process. This was mainly a consequence of efficient reaction-diffusion dynamics in the microchannel system, where the developed flow pattern comprising of intense emulsification provided a large interfacial area for the reaction and simultaneous product extraction.