Biochemical Reactors Research Articles

Exploring pNIPAM lyogels: Experimental study on swelling equilibria in various organic solvents and mixtures, supported by COSMO-RS analysis

Stimuli-responsive lyogels are considered to be smart materials due to their capability of undergoing significant macroscopic changes in response to external triggers. Due to their versatile and unique properties, smart lyogels exhibit great potential in various applications such as drug delivery or actuation processes. While Poly-N-isopropylacrylamide (pNIPAM) is widely known as a thermo-responsive material, it also shows significant solvent-responsive swelling behavior. For the systems tested, polar solvents induce strong swelling due to hydrogen bonding with the amide group, nonpolar solvents lead to significant shrinkage of the lyogels. The aim of this study is to investigate and to model this behavior for future application in chemical or biochemical reactors. As a current area of research, incorporating smart lyogel technology into (bio-)chemical reactors facilitates the development of smart reactor systems. Applying thermodynamic modelling with the gE model COSMO-RS on the monomer or oligomers of pNIPAM, the correlation between solvent-polymer interactions and the degree of swelling can be observed. pNIPAM derivatives exhibit low infinite dilution activity coefficients (IDACs) in polar solvents with large degrees of swelling, while displaying an increase of IDACs in nonpolar solvents. Hydrogen bonds dominate the swelling behavior of lyogels not only in pure solvents but also in mixtures of solvents with varying polarity. Even in mixtures containing high amounts of nonpolar solvents, large degrees of swelling were observed due to the uptake of the polar solvent in the lyogel matrix. This effect can be observed in binary solvent mixtures but also in representative mixtures along an esterification reaction with varying carboxylic chain length of alcohol and carboxylic acids.

Protocell Flow Reactors for Enzyme and Whole-Cell Mediated Biocatalysis.

The design and construction of continuous flow biochemical reactors comprising immobilized biocatalysts have generated great interest in the efficient synthesis of value-added chemicals. Living cells use compartmentalization and reaction-diffusion processes for spatiotemporal regulation of biocatalytic reactions, and implementing these strategies into continuous flow reactors can offer new opportunities in reactor design and application. Herein, the fabrication of protocell-based continuous flow reactors for enzyme and whole-cell mediated biocatalysis is demonstrated. Semipermeable membranized coacervate vesicles are employed as model protocells that spontaneously sequester enzymes or accumulate living bacteria to produce embodied microreactors capable of single- or multiple-step catalytic reactions. By packing millions of the enzyme/bacteria-containing coacervate vesicles in a glass column, a facile, cost-effective, and modular methodology capable of performing oxidoreductase, peroxidase and lipolytic reactions, enzyme-mediated L-DOPA synthesis, and whole-cell glycolysis under continuous flow conditions, is demonstrated. It is shown that the protocell-nested enzymes and bacterial cells exhibit enhanced activities and stability under deleterious operating conditions compared with their non-encapsulated counterparts. These results provide a step toward the engineering of continuous flow reactors based on cell-like microscale agents and offer opportunities in the development of green and sustainable industrial bioprocessing.

Effects of different precipitation on the runoff-lake library carbon cycle process in the Three Gorges reservoir

Precipitation significantly affects the carbon cycle of reservoirs. We regarded the reservoir as a biochemical reactor to investigate the impact of precipitation on the external carbon content of the CO2 (CO2–C) load and internal CO2–C cycle. Detailed descriptions of the reservoir carbon-cycle models under different rainfall conditions are provided. The field monitoring data collected literature parameters, and the calculation formulas of each part of the carbon-cycle mass balance model were integrated. Many ecological mathematical models were used in this study, including the thin boundary layer (TBL) equation, the pH sub-model equation system, the two-component exponential model, the algal synthetic carbon fixation equation, and the bacterial respiratory equation. Our study reveals that different rainfall levels in the backwater area of the Three Gorges Reservoir (TGR) would affect the dynamic balance of the reservoir carbon budget. In the discharge period of the reservoir, 10 mm d−1 rainfall is the critical point of the transformation of CO2 source and sink flux at the water-air interface. When the rainfall exceeds 24 mm d−1, the surface runoff begins to disturb the carbon budget. Our research provides a biochemical and physical model of the impact of rainfall events on reservoir CO2 budgets.

CFD simulation for comparative of hydrodynamic effects in biochemical reactors using population balance model with varied inlet gas distribution profiles

Abstract The operational efficiency of the airlift reactors relies significantly on the aeration and mixing provided by the inlet system. The diffused aeration system is the most energy-intensive component affecting the operation of the bioreactor, accounting for 45–75 % of the energy costs. This study presents a coupled CFD-PBM to investigate the collective impacts of multiple bubble diameters, variations in inlet gas distribution types, and flow rates on the hydrodynamic characteristics of bubble columns. The simulation results were validated through comprehensive comparisons with experimental data. The experimental data and simulations of the single bubble size model (SBSM) and multi-bubble size model (MBSM) were compared, proposing an enhanced inlet gas distribution type. The results indicate a close resemblance between the MBSM data and the experimental results, with an error margin not exceeding 5 %. Moreover, different flow rates were found to cause varying sensitivities in the bubble size distribution (BSD) within the column. Furthermore, the simulation results validate the similarity between lift coefficients and critical diameters to experiments and shed light on favorable conditions for reactor design. The key findings of this study encompass: (1) the use of MBSM can accurately predict the tower system characteristics; (2) the column circulation is intensified with small inlet bubble size and high gas velocity, which is favorable for chemical reactions and microbial aggregation to proceed; and (3) the BSD is not sensitive to the inlet gas distribution type at high flow rates.

Bioprocess Intensification of a Continuous-Flow Enzymatic Bioreactor via Productivity Dynamic Optimization under Modeling Uncertainty

In this contribution, a class of observer-based optimal feedback control is designed. The proposed feedback control is based on the Euler–Lagrange theoretical framework, and it is motivated by the productivity intensification from the chemical reactors, which is optimally increased. A Lagrangian is computed by employing the corresponding mass balance equation of a specifically selected biochemical compound. The resulting optimal controller is coupled with a novel uncertainty estimator with bounded feedback to derive an accurate estimation of the unknown terms and functions, mostly related to the reaction rate. Via Lyapunov analysis, it was shown that the proposed observer is asymptotically stable. The estimation of the unknown terms and functions is used by the proposed controller. The proposed methodology is applied to a generic model of an enzymatic biochemical continuous reactor with complex oscillatory dynamic behavior described by mass balance equations, so, in general, the proposed controller may be applied to any continuous stirred tank bioreactor; that is, the controller is independent of the specific kinetic functions. Numerical simulations show a satisfactory performance of the proposed control strategy.

Mixed convective flow of nanofluid across exponential surface: A numerical assessment of the impact of Darcy-Forchheimer and nanoparticle aggregation

Improving heat transmission is a modern difficulty faced in a multitude of areas, incorporating but not limited to electronics, heat exchangers, biochemical reactors, and other similar areas. In their capacity as cutting-edge heat transfer fluids, nanofluids have the promise of becoming a useful instrument in the pursuit of greater energy transfer efficiency. So, the focus of this work is on how it is possible to enhance heat transmission by using nanofluids. Using a stretched exponentially accelerating surface, this analysis investigates the effect that nanoparticle aggregation with thermal radiation has on the nanofluid of mixed convective stagnation point flow through Darcy-Forchheimer porous surfaces. The aggregation of nanoparticles may be assessed using modified Krieger-Dougherty and Maxwell-Bruggeman models. By using the right similarity transformations, the controlling equations of this problem were turned into a numerical model that can be unraveled. Mathematica was used to resolve the issue numerically by using the shooting with Runge-Kutta (RK-IV) procedure. nanoparticles with base fluid under aggregation effect boost heat transfer performance. A diversity of parameter estimates, including the mixed convection, mass suction, solid volume fraction of nanoparticles, thermal radiation, and stretching, were used to provide solutions for heat transfer and lower skin friction coefficients, as well as velocity and temperature curves. In addition to the findings, there were graphs and tables with explanations. The increase in heat transfer rates was 6.7021% when the suction parameters were set between 2.0 to 2.5 with =0.01. When the amount of nanoparticles volume fraction went from 0% to 1% by volume, the ineptitude of heat transfer went by an average of 4.249%. Aggregation models are often favored over non-aggregation models due to their ability to provide more accurate velocity and skin fraction profiles. Because of their superior precision, they are often used in situations where accuracy is paramount.

Bioenergy Production from Tannery Waste via a Single-Chamber Microbial Fuel Cell with Fly Ash Cathodic Electrodes

Microbial Fuel Cells (MFCs) are attracting attention for their application in simultaneous energy production and waste treatment, as innovative biochemical reactors. They usually operate under adiabatic conditions, utilizing microorganisms to treat wastewater compositions using mainly carbon-based electrodes as anodes and cathodes. During the past years, various anodic and cathodic electrodes with plenty of variations were used in MFC configurations. On the anode side metal-based electrodes are used while on the cathode, ceramic electrodes are currently introduced. In this study, a stainless steel anode is used in a single chamber MFC. Ceramic cathodic electrodes are used, coated with Fly Ash (FA). The mixed transition oxides of FA are tested as potential cathodic catalysts in the operation of the MFC. The FA powder was deposited by two methods: an ultrasound-assisted method and a conventional brush coating. Tannery liquid waste is used as the waste/substrate to be treated in the single-chamber MFC. The configuration with ultrasound-assisted Fly-Ash produced cathodic electrodes, led to the highest power output in batch operation modes and a high degree of simultaneous COD decrease of the tannery waste reaching the values of 0.44 mW/gcat and 85.6% COD removal respectively.

Municipal Solid Waste Landfill as a Dangerous Ungovernable Biochemical Reactor

Municipal Solid Waste Landfill as a Dangerous Ungovernable Biochemical Reactor

Cellulose acetate-based smart gating membrane with pH/thermal response for flux control

Inspired by the stomatal opening and closing mechanism of plants, a cellulose acetate-based pH/thermal response smart gating membrane was designed through surface segregation mechanism by embedding stimulation-responsive poly(N- isopropylacrylaminde) (PNIPAM)/poly(acrylic acid) (PAAc) microgels in the membrane pore channels. The water flux of the optimized smart membrane (CAM1.5) is 0.420 L/m2·h at 20 ℃/pH= 11 and changes to 121 L/m2·h at 65 ℃/pH= 1 with the highest gating ratio of 174. Meanwhile, the membrane gating ratio can be further improved to 216 when citric acid is used as coagulation bath. The carboxyl group content in the PAAc side chain is decreased and the interaction between water and microgels is improved under acid environment, which promotes the surface segregation of microgel. In addition, there is significant increase in the wet strength owing to the covalent crosslinking of citric acid. A fluid control system was designed based on the tunable membrane pore structure. According to the change of temperature and pH of the reaction system, the membrane can be opened and closed independently to precisely control the flow of reactants. This smart membrane shows promising applications in micro/nano fluid valves and temperature/pH sensitive biochemical reactors.

Simulation and Dynamic Properties Analysis of the Anaerobic–Anoxic–Oxic Process in a Wastewater Treatment PLANT Based on Koopman Operator and Deep Learning

The accurate simulation of the dynamics of the anaerobic–anoxic–oxic (A2O) process in the biochemical reactions in wastewater treatment plants (WWTPs) is important for system prediction and optimization. Previous studies have used real-time monitoring data of WWTPs to develop data-driven predictive models, but these models cannot be used to provide mathematical analysis of A2O dynamic properties. In this study, we developed a new simulation and analysis method for determining A2O dynamics in biochemical reactions using deep learning and the Koopman operator to address the above problems. This method was validated through data from a real-world WWTP in east China and compared it with the traditional deep learning model. According to the results, the new method achieved high-accuracy prediction. Meanwhile, with the help of the Koopman operator, the new method was able to analyze the asymptotical stability and convergence behavior of the A2O process, which provides a brand-new perspective for the in-depth study of biochemical reactor dynamics.

Hydrodynamics, power consumption and bubble size distribution in gas-liquid stirred tanks

In this work, we present the results collected in a gas-liquid stirred tank by a combination of experimental and computational methods, with the aim of presenting original data on the bubbles size distribution and contributing to the development of fully predictive methods for the design and the scale-up of chemical and biochemical gas-liquid reactors. Basic variables which affect mass transfer and consequently the performances of industrial aerobic fermentations are discussed, with special focus on the bubble size distribution, the gassed power consumption and the gas cavities. The current developments of Two Fluid and Population Balance models for obtaining fully predictive results on gas-liquid mixing in stirred tanks are discussed. The results confirm that the correct prediction of the bubble size in the impeller zone is a crucial prerequisite for obtaining reliable results of the hydrodynamics of aerated stirred tanks.

Experimental mass and heat transfer at a serpentine tube heat exchanger located at the wall of a square stirred tank reactor

• Rates of mass and heat transfer of a serpentine tube heat exchanger were studied. • The serpentine is located at the wall of a square stirred tank reactor. • Variables studied were impeller speed and geometry, tube diameter, and tube pitch. • Dimensionless correlations were developed to design and operate the heat exchanger. • The possibility of using the serpentine tube as a catalyst support was highlighted. Although the study of the heat transfer behavior of stirred tank heat exchangers such as helical coils, vertical tube baffles, and cooling jackets has received much attention, no study has been reported on the heat or mass transfer behavior of serpentine tube heat exchangers, so the present work aims to study rates of mass and heat transfer (by analogy) at the outer surface of a serpentine tube heat exchanger located at the wall of a square stirred tank reactor by the electrochemical technique. Variables studied were impeller rotational speed, impeller geometry, tube diameter, and tube pitch. The mass or heat transfer coefficients were found to increase with increasing impeller speed and decrease with increasing cylinder diameter and pitch. For a given set of conditions, a radial flow turbine produces higher rates of mass transfer than an axial flow turbine. The data were correlated by dimensionless mass transfer correlations which can be used to scale up and operate the heat exchanger. When the mass transfer data at the serpentine tube were compared with those at an active flat wall of equal height, it was found that the mass transfer rate at the serpentine tube is higher than that of the flat wall by an amount ranging from 10% to 210% depending on the operating conditions. The possibility of using the serpentine tube as a catalyst support for conducting diffusion-controlled exothermic immobilized cell biochemical reactions which need rapid cooling to avoid thermal degradation of the biomass was highlighted. The dual-use of the serpentine tubes as a catalyst support and a cooler would reduce the capital and operating costs of immobilized enzyme or cell stirred tank biochemical reactors compared, for instance, with the traditional stirred slurry reactor owing to the elimination of the costly and time-consuming process of separating the final product from the catalyst particles.

Assessment of algae and greenhouse gases in different reservoirs worldwide by reactor model

The increasing concentration of greenhouse gases (GHGs) in the atmosphere is a great challenge to the development of human society. GHGs emissions in reservoirs have been a hot topic of freshwater GHG research for nearly two decades. The factors influencing the emissions of GHGs from reservoirs are intricate. From a hydrological perspective, the fundamental reservoir characteristics, such as water depth, area and perimeter, have an impact on the total GHGs emissions. From a biological perspective, GHGs emissions from the reservoir could be impacted by bacteria, algae, and other microorganisms because of their physiological metabolism. Here, we classified the global reservoirs as continuous stirred tank reactor (CSTR), general reactor (GR), and plug flow reactor (PFR) reservoirs by referring to the simulation graphics and dynamics theory of biochemical reactors. In addition, we examined the connection between algal blooms and GHGs emissions in light of algae degradation and hydrodynamic factors like the water flow rate, water residence time (WRT), and thermal structure of the water column. The results indicated that GHGs emissions have a negative relationship with algae in the GR-reservoirs, while the algae could promote GHGs emissions in the PFR-reservoirs or CSTR-reservoirs. The reactor classification method was introduced into the Three Gorges Reservoir (TGR), and the spatial heterogeneity of algal bloom-GHGs coupling in different tributaries of the TGR was explained, which proved that the reactor classification method is reliable.

Chemical and Biochemical Reactors for Controlled Synthesis of Organic and Inorganic Compounds

Chemical and Biochemical Reactors for Controlled Synthesis of Organic and Inorganic Compounds

Solid‐Liquid Mass Transfer of an Array of Separated Parallel Corrugated Plates

AbstractA vertical array of corrugated copper plates was tested for its ability to conduct diffusion‐controlled liquid‐solid reactions. The mass transfer coefficient was investigated in terms of solution velocity, physical parameters of the solution, equivalent diameter of the channel, and array height. It was found that the mass transfer coefficient increases with increasing solution velocity and channel equivalent diameter while decreasing with increasing array height. Compared with flow through flat plates under the same conditions, flow across corrugated‐plate channels enhanced the mass transfer rate by a factor of 2–2.72. Dimensionless analysis was used to correlate the mass transfer data. The present work finds wide practical applications in enhancing mass transfer in many processes, such as membrane separation processes, electrochemical processes, heterogeneous liquid‐solid catalytic and photocatalytic reactions, and biochemical reactors in which enzymes or microorganisms are immobilized on such corrugated surfaces.

Mass and Heat Transfer at the Bottom of Cylindrical Unbaffled Stirred Tank Reactor and Possible Applications

Liquid-solid mass and heat (by analogy) transfer at the bottom of a cylindrical stirred vessel were studied by using the well-known electrochemical technique. Variables studied included the impeller geometry and its rotational speed. Results revealed that the radial flow impeller is preferable over the axial flow one in terms of mass transfer enhancement, additionally, increasing the impeller rotational speed led to an increase in the mass transfer coefficient. Results were correlated by dimensionless equations. Application of these equations in the design and operation of an improved catalytic biochemical reactor suitable for conducting diffusion-controlled immobilized cell (or enzyme) reactions was highlighted. These equations can serve in predicting the corrosion rate and corrosion allowance required to calculate the bottom thickness of the agitated vessel in its design stage. Furthermore, these equations can be used in estimating the heat lost from the tank bottom, accordingly, design an effective cooling jacket surrounding the agitated vessel bottom in case of exothermic biochemical reactions to avoid thermal degradation of the biomass.

Amyloidogenesis via interfacial shear in a containerless biochemical reactor aboard the International Space Station

Fluid interfaces significantly influence the dynamics of protein solutions, effects that can be isolated by performing experiments in microgravity, greatly reducing the amount of solid boundaries present, allowing air-liquid interfaces to become dominant. This investigation examined the effects of protein concentration on interfacial shear-induced fibrillization of insulin in microgravity within a containerless biochemical reactor, the ring-sheared drop (RSD), aboard the international space station (ISS). Human insulin was used as a model amyloidogenic protein for studying protein kinetics with applications to in situ pharmaceutical production, tissue engineering, and diseases such as Alzheimer’s, Parkinson’s, infectious prions, and type 2 diabetes. Experiments investigated three main stages of amyloidogenesis: nucleation studied by seeding native solutions with fibril aggregates, fibrillization quantified using intrinsic fibrillization rate after fitting measured solution intensity to a sigmoidal function, and gelation observed by detection of solidification fronts. Results demonstrated that in surface-dominated amyloidogenic protein solutions: seeding with fibrils induces fibrillization of native protein, intrinsic fibrillization rate is independent of concentration, and that there is a minimum fibril concentration for gelation with gelation rate and rapidity of onset increasing monotonically with increasing protein concentration. These findings matched well with results of previous studies within ground-based analogs.

Treatment of organic pollutants in coke plant wastewater by micro-nanometer catalytic ozonation, A/A/O and reverse osmosis membrane.

Coking wastewater has a complex and highly concentrated chemical composition which is toxic and does not biodegrade easily. Treating the organic pollutants in this wastewater is very challenging. The toxic substances in this wastewater make traditional biotechnological treatments inefficient. Current wastewater treatment studies are based on unit processes, and no full process studies could be found. This study used the micro-nanometer catalytic ozonation process as a pretreatment unit, and reverse osmosis membrane treatment as a depth processing unit to improve the effect of the coking wastewater degradation. The micro-nanometer catalytic ozonation pretreatment greatly improves the biodegradability of the coking wastewater and promotes the coking wastewater degradation in the anoxia/anaerobic/oxic (A/A/O) system. The integrated coagulation air flotation-micro-nanometer catalytic ozonation-A/A/O-reverse osmosis membrane system can remove 98% of the chemical oxygen demand, which meets the direct emission standard of the new national standard (China). The dominant genera in the A/A/O biochemical reactor were Thioalkalimicrobium, Proteiniphilum, Azoarcu, Bacillus, Fontibacter, and Taibaiella. This work provides a novel approach for the degradation of high-concentration organic wastewater and lays a solid foundation for the restoration of environmental water bodies.

Convex Optimization of Bioprocesses

We optimize a general model of bioprocesses, which is nonconvex due to the microbial growth in the biochemical reactors. We formulate a convex relaxation and give conditions guaranteeing its exactness in both the transient and steady-state cases. When the growth kinetics are modeled by the Contois or, under constant biomass, Monod or Powell functions, the relaxation is a second-order cone program, which can be solved efficiently at large scales. We implement the model on a numerical example based on a wastewater treatment system.

Theoretical and Experimental Analysis of Miniaturization of Conventional Oscillatory Flow Technology

The requirement for any configuration of a chemical or biochemical reactor is the presence of efficient mixing to enhance heat and mass transfer as needed for the application of interest. Furthermore, as an Oscillatory Flow (OF) reactor has a combination of flow oscillation and baffled tube configuration, which has the potential to ensure efficient mixing, heat transfer, and mass transfer. In this way, an efficient mixing in an OF reactor is able to tackle any type of resistance in any chemical process from polymer synthesis to enzyme production. It has been observed that an OF reactor improved both conversion and selectivity of the relevant reaction by efficient mixing and transport properties. However, this technology was not still extended to mini-fluidic configuration via process intensification methods and so far, a novel approach for enhanced mixing at reduced scales was not explored. This work explores the application of OF technology in mini-fluidics. The feasibility analysis of Oscillatory Flow Technology in mini channels has been investigated using theoretical correlations from Conventional Oscillatory flow technology in process equipment. As a preliminary step in the process intensification of OF technology in mini channels, The Nusselt number (Nu) and pressure drop values are predicted from the literature and it has been observed that the transfer operations are also improved when oscillatory flow is applied in mini channels compared to commercial mini contactors such as corning heart shaped reactor. The plot between energy dissipation vs. mixing evaluated from theoretical calculations was drawn and compared with mini-fluidic mixers reported in literature. The most common mini-fluidic mixer is corning heart shaped reactor used for comparison with the proposed minichannel. Because of this analysis, the novel mixing geometries was expected to develop for various chemical processing applications. The OFT experimental set up was developed to create oscillatory flow via either forward rotation or backward rotation of valve. Furthermore, pressure vs. time profile and flow vs. time profile for the given OF mini fluidic arrangement is initially investigated and described. Preliminary experimental results are provided for an OF generator, intended for use in subsequent experiments exploring mini-fluidic mixers with OF technology.