Synthetic biology is the engineering approach to edit or write the genome aiming to design the biological devices (promoters, transcription factors, TFBS, terminators etc.) of an organism to achieve the improved properties, while, metabolic engineering aiming to engineer the microbes to produce metabolites on industrial scale through recombinant DNA technologies. Recently, both synthetic biology and metabolic engineering fields are growing quickly and are used to produce metabolites of interest. The main theme of Synthetic Biology – Metabolic Engineering book is to review the tools and techniques used in synthetic biology and metabolic engineering to design and engineer the microbes to produce value-added metabolites and its application in industrial biotechnology. The book is written by the world-renowned metabolic engineers and synthetic biologists in series of Advances in Biochemical Engineering/Biotechnology and primarily elaborates the synergy between metabolic engineering and synthetic biology.
The manuscript describes a computational study that provides molecular-level insight into shale gas adsorption and transport in shale rocks, which are composed of organic and inorganic matter. Atomistic simulations were used to generate realistic models of the organic matter structures with both micro- and mesoporosity, and correspond to mature and overmature type-II kerogens. These porous material models are unique to most other previous kerogen models since they contain other components (asphaltene/resin, hydrocarbons and carbon dioxide/water fractions) that are typically not modeled. The inclusion of these additional components significantly influences the resulting porous structure characteristics. The adsorption and diffusion behavior of methane (as a shale gas proxy) and methane/carbon dioxide mixtures were simulated in the model structures. Several key industrial-relevant findings are described in the manuscript.
In this investigation, CO2 capture performance of zeolite 13X monoliths with 600 and 800 cpsi in presence of SO2/NO impurities under dry and humid conditions were evaluated and compared with that of 13X beads. Dynamic breakthrough tests demonstrated a drastic reduction in CO2 capture capacity and deterioration of kinetics under dry-clean conditions, whereas, upon switching the feed from a clean gas to contaminated gas which contained SO2 and NO, different adsorption performance was observed. Specifically, in dry-contaminated mode, the adsorbents retained their capture capacities with comparable kinetics to that of dry-clean feed conditions, however, in humid-contaminated mode, the adsorbents experienced improved CO2 uptake and CO2/N2 selectivity, albeit at the expense of deteriorated kinetics. These findings indicate that the presence of SO2 and NO contaminants, especially SO2 contaminants, lead to dramatic changes in the adsorption performance of zeolite 13X monoliths, indicating the importance of evaluating adsorbent materials under realistic conditions.
In Rodriguez et al.1 an analytical expression was deduced to predict the slip ratio in dispersed oil-water flow. Although the quantitative agreement was quite good, the expression systematically underestimated the slip ratio. New experimental data of similar flows were collected in two different experimental facilities in pipes of different materials and diameters (26 mm and 82.8 mm i.d.). Oil-water flow data collected within a range of mixture Reynolds numbers from 1∙10^5 to 20∙10^6 in glass, acrylic and steel pipes with oil viscosities varying from 7 to 220 mPa.s were used to deduce a more generic correlation for slip ratio as a function of the mixture Froud number (5 < Fr < 70). The underestimation of the slip ratio was corrected. The new slip-ratio correlation can be used to significantly improve the prediction of volumetric fraction in flow situations where turbulent dispersion of oil in water occurs.
We introduce a straightforward method for the preparation of novel starch-based ultramicroporous carbons (SCs) that demonstrate high CH4 uptake and excellent CH4/N2 selectivity. These SCs are derived from a combination of starch and 1-6 wt. % of acrylic acid, and the resulting materials are amenable to surface cation exchangeability as demonstrated by the formation of highly dispersed K+ in carbon precursors. Following activation, these SCs contain ultramicropores with narrow pore-size distributions of <0.7 nm, leading to porous carbon-rich materials that exhibit CH4 uptake values as high as 1.86 mmol/g at 100 kPa and 298 K, the highest uptake value for CH4 to date, with the IAST-predicted CH4/N2 selectivity up to 5.7. Both the potential mechanism for the formation of narrow pores and the origin of the favorable CH4 adsorption properties are discussed and examined. This work may potentially guide future designs for carbon-rich materials with excellent gas adsorption properties.
Synthesis of adipic acid (AA) through the oxidation of cyclohexanol and cyclohexanone (K/A oil) with nitric acid was conducted in a capillary microreactor system. Effects of the temperature, the nitric acid concentration, the volumetric flow rate ratio of nitric acid to K/A oil, and the capillary length on the selectivity and the product yield were investigated systematically to achieve optimal reaction conditions. Notably, a high yield of adipic acid (i.e., 90%) was achieved just in 6 seconds at 85℃ with the use of 55 wt% nitric acid. Gas components produced in this oxidation process and its total volumetric flow rate were determined under various operating conditions, which was beneficial for reaction mechanism characterization and process optimization. Finally, a kinetic model was established, which was of crucial theoretical significance and practical value for optimizing the reactor design and better understanding such fast and highly exothermic multiphase processes with abundant gas production.
We study the evaporation dynamics of multiple water droplets deposited in ordered arrays or randomly distributed (sprayed) on superhydrophobic substrates (SHP) and smooth silicone wafers (SW). The evaluation of mass of the droplets as a function of time shows a power-law behavior with exponent 3/2, and from the prefactor of the power-law an evaporation rate can be determined. We find that the evaporation rate on a SHP surface is slower than a normal surface for both single droplet and collection of droplets. By dividing a large droplet into more smaller ones, the evaporation rate increases and the difference between the evaporation rates on SHP and SW surfaces becomes higher. The evaporation rates depend also on the distance between the droplets and increase with increasing this distance.
Charged clay surfaces can impact the storage and mobility of hydrocarbon and water mixtures. Here, we use equilibrium molecular dynamics (MD) and nonequilibrium MD simulations to investigate hydrocarbon-water mixtures and their transport in slit-shaped illite nanopores. We construct two illite pore models with different surface chemistries: potassium-hydroxyl (PH) and hydroxyl-hydroxyl (HH) structures. In HH nanopore, we observe water adsorption on the clay surfaces. In PH nanopores, however, we observe the formation of water bridges because of the existence of a local, long-range electric field. Our NEMD simulations demonstrate that the velocity profiles across the pore depends strongly on water concentration, pore width and the presence or absence of the water bridge. This fundamental study provides a theoretical basis for understanding nanofluidics with charged surfaces and can be applied in such as biological processes, chemical and physical fields, and the oil and gas extraction in clay-rich formations.
Enzyme immobilization enhances the catalytic activity and stability of the enzyme, and also improves reusability. Metal organic frameworks (MOFs), which possess diversified structures and porosity, have been used as excellent carriers for enzyme immobilization. Pseudomonas fluorescens lipase (PFL) has been successfully immobilized onto MOFs by covalent cross-linking to obtain a series of immobilized lipase (PFL@MOFs). PFL@MOFs are used for catalytic enantioselective hydrolysis of 2-(4-hydroxyphenyl) propionic acid ethyl ester enantiomers (2-HPPAEE) in aqueous medium and transesterification of 4-methoxymandelic acid enantiomers (4-MMA) in organic medium. The experimental results indicated that PFL@Uio-66(Zr) exhibits excellent enzymatic catalysis performances and high enantioselectives. In addition, to increase catalytic activity and reusability, PFL is modified by the polyethylene glycol (PEG) to prepare PEG-modified lipase (PFL-PEG), then PFL-PEG is immobilized onto Uio-66(Zr) to prepare PFL-PEG@Uio-66(Zr), demonstrating better reusability and catalytic activity compared with PFL@Uio-66(Zr).
Interfacial tension is an essential physical property in two phase flow and it changes due to the mass transfer. The measurement of dynamic interfacial tension (DIFT) in such condition is a difficult problem. In previous study (Zhou at al., Chem Eng Sci. 2019; 197:172-183), we presented the quantitative relation between the droplet breakup frequency function (DBFF) and interfacial tension. It is found that the DBFF is highly depends on interfacial tension. Therefore the DBFF is a suitable parameter to quantitatively characterize the interfacial tension. Based on this concept, the DIFT in the column is determined by regression method after the DBFF under mass transfer condition is measured. It is found that the DIFT is smaller than the static interfacial tension. This result indicates that interphase mass transfer leads to decreasing of the interfacial tension. The decreasing extent of the DIFT has a positive correlation with the mass transfer flux.
In this letter, we investigate the rebound dynamics of two equally sized droplets simultaneously impacting a superhydrophobic surface via lattice Boltzmann method (LBM) simulations. We discover three rebound regimes depending on the droplet distance: a complete-coalescence-rebound (CCR) regime, a partial-coalescence-rebound (PCR) regime, and a no-coalescence-rebound (NCR) regime. We demonstrate that the rebound regime is closely associated with dynamic behaviors of the formed liquid ridge or bridge between two droplets. We also present the contact time in the three regimes. Intriguingly, although partial coalescence takes places, the contact time is still dramatically shortened in the PCR regime, which is even smaller than that of a single droplet impact. These findings provide new insights into the contact time of multiple droplets impact, and thereby offering useful guidance for some application such as anti-icing, self-cleaning, and so forth.
Bubble formation from a downward-pointing capillary nozzle was investigated in this study. The experiments were conducted at gas flow rate of 40-5400 mL/h and inner nozzle radius of 0.030-0.255 mm. Experimental results show that microbubbles were formed continuously at moderate Weber number, which was not reported in pervious investigations with injecting gas through an upward-pointing capillary nozzle. High-speed visualization indicates that the formation of microbubbles arises from the convergence of the capillary waves induced by the partial coalescence of larger bubbles. A bubbling regime map is given to identify the critical conditions for the formation of microbubbles. In the present air-water experiments, the generated microbubbles are 20-170 μm in diameter. From experimental data, a scaling law for microbubble size is proposed as a function of Weber and Bond numbers.
Particle-laden flows in a vertical channel were simulated using an Eulerian–Eulerian, Anisotropic-Gaussian (EE-AG) model. Two sets of cases varying the overall mass loading were done using particle sizes corresponding to either a large or small Stokes number. Primary and turbulent statistics were extracted from these results and compared with counterparts collected from Eulerian–Lagrangian (EL) simulations. The statistics collected from the small Stokes number particle cases correspond well between the two models, with the EE-AG model replicating the transition observed using the EL model from shear-induced turbulence to relaminarization to cluster-induced turbulence as the mass loading increased. The EE-AG model was able to capture the behavior of the EL simulations only at the largest particle concentrations using the large Stokes particles. This is due to the limitations involved with employing a particle-phase Eulerian model (as opposed to a Lagrangian representation) for a spatially intermittent system that has a low particle number concentration.
We investigated the flow characteristics in a tank of H/T=1.5 stirred by a novel multi-blade combined agitator (MBC) by using time-resolved PIV and LES approach. The predictions were assessed by Y+ values and power spectrum analysis, as well as experimental validation of velocity distributions. Results demonstrate that the MBC agitator can load the energy into the system effectively with a power number of 12.5 in a turbulent regime, resulting in improved axial and radial mass exchange. The upper and lower short blades produce an axial down-flow in the top half and an axial up-flow in the bottom half, respectively. Part of axial flows change to radial flows by the radial pumping of the long blades, meanwhile, the impingement of two axial flows improves the axial mass exchange. These flow characteristics leads to an obvious improvement in the turbulent kinetic energy distribution uniformity.
Multiple breakdown phenomena may take place when operating dielectric elastomers. Thermal breakdown, which occurs due to Joule heating, becomes of special importance when using multilayered stacks of dielectric elastomers, due to the large volume-to-surface-area-ratio. In this article, a 2D axisymmetric finite-element model of a multilayered stack of dielectric elastomers is set up in \comsol. Both the electro-thermal and electro-mechanical couplings are considered, allowing for determination of the onset of thermal breakdown. Simulation results show that an entrapped particle in the dielectric elastomer drastically reduces the possible number of layers in the stack. Furthermore, the possible number of layers is greatly affected by the ambient temperature and the applied voltage. The performance of three hyperelastic material models for modelling the elastomer deformation are compared, and it is established that the Gent model yields the most restrictive prediction of breakdown point, while the Ogden model yields the least restrictive estimation.
The flow characteristics of the blade unit of a tridimensional rotational flow sieve tray was investigated experimentally in this study. First, the flow patterns are defined under different liquid arrangement methods. They are bilateral film flow, continuous perforated flow, and dispersion-mixing flow in overflow distribution and film and jet flow and jet and mixed flow in spray distribution. Second, the time and frequency domain analysis of the differential pressure pulsation signal in the blade unit is carried out. The influence of perforation and mixing intensity on the flow pattern transition is clarified. Third, the rotational flow ratio of the gas-liquid phase is measured. The influence of the operating conditions on the distribution of the rotational and perforated flow for the gas-liquid phase is investigated. Finally, a prediction model for the rotational flow ratio is proposed. The prediction results agree well with the experimental data.