Prediction of mass transfer coefficients in non-Newtonian fermentation media using first-principles methods

Bubble flows in non-Newtonian fluids were analyzed using first-principles methods with the aim to compute and predict mass transfer coefficients in such fermentation media. The method we used is a Direct Numerical Simulation (DNS) of the reactive multiphase flow with deformable boundaries and interfaces. With this method, we are able for the first time to calculate mass transfer coefficients in non-Newtonian liquids of different rheologies without any experimental data. In the current article, shear-thinning fluids are considered. However, the results provide the basis for further investigations, such as the study of viscoelastic fluids.     

Liquid saturation in concurrent gas-liquid downflow through packed beds

The total and dynamic liquid saturation under concurrent gas-liquid downflow through packed beds were experimentally measured for non-foaming, foaming Newtonian and non-Newtonian liquids. The variables include the column diameter, packing size and shape, flow rate of the phases, and physical properties. Correlations were presented in terms of Lockhart-Martinelli parameter, χ for non-foaming Newtonian and non-Newtonian liquids and in terms of modified Lockhart-Martinelli parameter, χ′ for foaming Newtonian liquids.     

High-throughput screening for ionic liquids dissolving (ligno-)cellulose

The recalcitrance of lignocellulosic biomass poses a major challenge for its sustainable and cost-effective utilization. Therefore, an efficient pretreatment is decisive for processes based on lignocellulose. A green and energy-efficient pretreatment could be the dissolution of lignocellulose in ionic liquids. Several ionic liquids were identified earlier which are capable to dissolve (ligno-)cellulose. However, due to their multitude and high costs, a high-throughput screening on small scale is essential for the determination of the most efficient ionic liquid. In this contribution two high-throughput systems are presented based on extinction or scattered light measurements. Quasi-continuous dissolution profiles allow a direct comparison of up to 96 ionic liquids per experiment in terms of their dissolution kinetics. The screening results indicate that among the ionic liquids tested EMIM Ac is the most efficient for dissolving cellulose. Moreover, it was observed that AMIM Cl is the most effective ionic liquid for dissolving wood chips.     

A triple system water-urea-L-α-alanine. Thermodynamic properties and intermolecular interactions

The heat of dissolution of L-α-alanine at 293, 298, 306, and 318 K in aqueous solutions of urea in the concentration range 0–7 mol urea/kg water has been determined by the microcalorimetric method. It was found that the heat of dissolving the amino acid linearly depends on the square root of the molality of the urea solution. It was shown that the enthalpy and entropy of the transfer of L-α-alanine from water into an aqueous solution of urea do not depend on temperature, and the heat capacity of transfer is equal to zero. Almost complete enthalpy-entropy compensation was noted. It was shown that the parameter characterizing the changes in the effective Gibbs energy of dissolving L-α-alanine in water and aqueous urea solutions has negative values due to the dominant entropy component. The system water-urea-L-α-alanine becomes less structured with increasing temperature and more structured as the urea concentration increases.     

Rheometry of fermentation liquids

This article is concerned with the measurements of rheological properties of nonhomogeneous fermentation liquids. In order to determine the flow curves of such liquids, an impeller measuring system of own design was used, and the method of calibration of the system is presented. The experimental verification was carried out using samples of fermentation broth of Aureobasidium pullulans and it has been shown that the applied measuring technique gives internally consistent results. The sensitivity of the technique proves its applicability for monitoring and control purposes in fermentation technology.     

Properties and principles of mycelial flow: a tube rheometer system for fermentation fluids

A tube rheometer system has been constructed for aseptic study of the rheology and fundamental flow properties of mycelial fermentation fluids. The rheometer consists of a U-formed tube circuit starting and ending inside the fermentor. The mash is pumped through the tubes with a lobe rotor pump. The flow is measured by an electromagnetic flow meter. Pressure drops have been measured with a system of differential membrane transducers for different flow rates. The rheometer system was tested with Newtonian and non-Newtonian fluids.     

DPD simulation of non-Newtonian electroosmotic fluid flow in nanochannel

We use the dissipative particle dynamics (DPD) method to simulate the non-Newtonian electroosmotic flow (EOF) through nanochannels. Contrary to a large amount of past computational efforts dedicated to the study of EOF profile, this work pays attention to the EOF of non-Newtonian fluids, which has been rarely touched in past publications. Practically, there are many MEMS/NEMS devices, in which the EOF behaviour should be treated assuming both non-continuum and non-Newtonian conditions. Therefore, our concern in this work is to simulate the EOF through nanochannels considering both non-Newtonian fluid properties and non-continuum flow conditions. We have chosen DPD as our working tool because it provides several important advantages comparing with the classical time consuming molecular dynamics method. Using the DPD method, we explore the effect of a few important fluid properties and nanochannel parameters on the EOF behaviour and the resulting flow rate magnitudes. Our investigation will result in a number of findings, which have not been reported in past research works.     

CD spectra of isoionic DNA solutions

The ion-exchange transition of Na-DNA----H-DNA in concentrated salt-free solutions is accompanied by strong variations in CD spectra. The rotational force of the negative band magnitude of delta epsilon 249 decreases when going to H-DNA by about 4 times, and the value of delta epsilon 279, by 1.2 times. These changes are irreversible to a considerable extent, which is evident because the spectra of Na-DNA obtained by neutralizing isoionic H-DNA solutions with NaOH or by the ion-exchange method significantly differ from those of Na-DNA taken by dissolving solid Na-DNA in deionized water. It has been shown that additions of NaCl to an isoionic solution of DNA leads to variations of spectra, typical for deprotonation processes as well as for an increase in DNA hydration.     

Dynamics of mechanical properties of drying drops of biological liquids as a reflection of the features of self-organization of their components from nano- to microlevel

It has been shown that the dynamics of molecular self-organization of the components of liquids drying in the form of drops on a solid wettable surface contains information about their composition and structure. The physical mechanisms of this phenomenon have been considered. A method of recording this dynamics and retrieving useful information has been suggested. Examples of using this method in medical diagnosis and quality assessment of food products, drugs, and liquids of domestic appliance are given.     

A NEW METHOD FOR THE EXTRACTION OF MACROFOSSILS FROM CALCAREOUS ROCKS USING SULPHURIC ACID

Abstract:  A new method for the extraction of calcified and/or partly pyritized macrofossils has been developed. This method is based upon the differential speeds for the dissolving of microcrystalline and macrocrystalline calcite in 38% sulphuric acid. The effectiveness of the sulphuric acid treatment is also influenced by the volume of clay minerals in the host rock. Therefore, this method is highly applicable for the extraction of macrofossils from marlstones, marly limestones, and other lithified calcareous sediments. The main advantages of this method, when compared with other chemical methods, are (1) the short treatment time, (2) the capability of dissolving the sediment on the fossil's surface, and (3) its efficiency in dissolving calcareous rocks with low porosity. This method has been successfully applied to Upper Cretaceous macrofossils from the Bohemian Cretaceous Basin. The surface of extracted macrofossils remained undamaged, exhibiting minute skeletal details; perhaps even encrusters and bioerosions.     

Modeling of DNAPL-Dissolution, Rate-Limited Sorption and Biodegradation Reactions in Groundwater Systems

This article presents an approach for modeling the dissolution process of single component dense non-aqueous phase liquids (DNAPL), such as tetrachloroethene and trichloroethene, in a biologically reactive porous medium. In the proposed approach, the overall transport processes are conceptualized as three distinct reactions. Firstly, the dissolution (or dissolving) process of a residual DNAPL source zone is conceptualized as a mass-transfer limited reaction. Secondly, the contaminants dissolved from the DNAPL source are allowed to partition between sediment and water phases through a rate-limited sorption reaction. Finally, the contaminants in the solid and liquid phases are allowed to degrade by a set of kinetic-limited biological reactions. Although all of these three reaction processes have been researched in the past, little progress has been made towards understanding the combined effects of these processes. This work provides a rigorous mathematical model for describing the coupled effects of these three fundamental reactive transport mechanisms. The model equations are then solved using the general-purpose reactive transport code RT3D (Clement, 1997).     

Modeling of DNAPL-Dissolution,Rate-Limited Sorption and Biodegradation Reactions in Groundwater Systems

This article presents an approach for modeling the dissolution process of single component dense non-aqueous phase liquids (DNAPL), such as tetrachloroethene and trichloroethene, in a biologically reactive porous medium. In the proposed approach, the overall transport processes are conceptualized as three distinct reactions. Firstly, the dissolution (or dissolving) process of a residual DNAPL source zone is conceptualized as a mass-transfer limited reaction. Secondly, the contaminants dissolved from the DNAPL source are allowed to partition between sediment and water phases through a rate-limited sorption reaction. Finally, the contaminants in the solid and liquid phases are allowed to degrade by a set of kinetic-limited biological reactions. Although all of these three reaction processes have been researched in the past, little progress has been made towards understanding the combined effects of these processes. This work provides a rigorous mathematical model for describing the coupled effects of these three fundamental reactive transport mechanisms. The model equations are then solved using the general-purpose reactive transport code RT3D (Clement, 1997).     

Dynamics of the mechanical properties of drops of biological liquids during drying as a reflection of the features of selfassembly of their components from the nano- to microlevel

It has been shown that the dynamics of the molecular self-assembly of the components of liquids drying in the form of drops on a solid moistened surface contains information about their composition and structure. The physical mechanisms of this phenomenon have been considered. A method of recording this dynamics and retrieving useful information has been suggested. Examples of using this method in medicinal diagnosis and the assessment of the quality of food products, drugs, and liquids of domestic appliance are given.     

A method using solubility to predict dry matter digestibility of cellulosic materials.

A rapid chemical procedure based on the solubility of a holocellulose sample in a system of dimethyl sulfoxide with paraformaldehyde has been developed to provide a laboratory method for predicting dry matter digestibility of cellulose containing samples. The amount of dry matter solubilized by the chemical procedure was closely correlated with anaerobic, in vitro, rumen fluid digestion and with digestibility as measured by aerobic Cellulomonas, sp. bacteria. The quantity of solvent and dissolving time had little effect on solubility over a wide range. The method is rapid, well suited for various cellulosic materials, and may be carried out with simple equipment and facilities.     

Enantioseparation of flurbiprofen enantiomers using chiral ionic liquids by liquid‐liquid extraction

Flurbiprofen is a kind of nonsteroidal anti‐inflammatory drug, which has been widely used in clinic for treatment of rheumatoid arthritis and osteoarthritis. It has been reported that S‐flurbiprofen shows good performance on clinic anti‐inflammatory treatment, while R‐enantiomer almost has no pharmacological activities. It has important practical values to obtain optically pure S‐flurbiprofen. In this work, chiral ionic liquids, which have good structural designability and chiral recognize ability, were selected as the extraction selector by the assistance of quantum chemistry calculations. The distribution behaviors of flurbiprofen enantiomers were investigated in the extraction system, which was composed of organic solvent and aqueous phase containing chiral ionic liquid. The results show that maximum enantioselectivity up to 1.20 was attained at pH 2.0, 25°C using 1,2‐dichloroethane as organic solvent, 1‐butyl‐3‐methylimidazole L‐tryptophan ([Bmim][L‐trp]) as chiral selector. The racemic flurbiprofen initial concentration was 0.2 mmol L^?1, and [Bmim][L‐trp] concentration was 0.02 mol L^?1. Furthermore, the recycle of chiral ionic liquids has been achieved by reverse extraction process of the aqueous phase with chiral selector, which is significant for industrial application of chiral ionic liquids and scale‐up of the extraction process.     

Axial dispersion in packed bed reactors involving viscoinelastic and viscoelastic non-Newtonian fluids

Axial dispersion is an important parameter in the performance of packed bed reactors. A lot of fluids exhibit non-Newtonian behaviour but the effect of rheological parameters on axial dispersion is not available in literature. The effect of rheology on axial dispersion has been analysed for viscoinelastic and viscoelastic non-Newtonian fluids. Aqueous solutions of carboxymethyl cellulose and polyacrylamide have been chosen to represent viscoinelastic and viscoelastic liquid-phases. Axial dispersion has been measured in terms of Bo_L number. The single parameter axial dispersion model has been applied to analyse RTD response curve. The Bo_L numbers were observed to increase with increase in liquid flow rate and consistency index ‘K’ for viscoinelastic as well as viscoelastic fluids. Bodenstein correlation for Newtonian fluids proposed has been modified to account for the effect of fluid rheology. Further, Weissenberg number is introduced to quantify the effect of viscoelasticity.     

Recent advances of enzymatic reactions in ionic liquids

The tremendous potential of room temperature ionic liquids as an alternative to environmentally harmful ordinary organic solvents is well recognized. Ionic liquids, having no measurable vapor pressure, are an interesting class of tunable and designer solvents, and they have been used extensively in a wide range of applications including enzymatic biotransformation. In fact, ionic liquids can be designed with different cation and anion combinations, which allow the possibility of tailoring reaction solvents with specific desired properties, and these unconventional solvent properties of ionic liquids provide the opportunity to carry out many important biocatalytic reactions that are impossible in traditional solvents. As compared to those observed in conventional organic solvents, the use of enzymes in ionic liquids has presented many advantages such as high conversion rates, high enantioselectivity, better enzyme stability, as well as better recoverability and recyclability. To date, a wide range of pronounced approaches have been taken to further improve the performance of enzymes in ionic liquids. This review presents the recent technological developments in which the advantages of ionic liquids as a medium for enzymes have been gradually realized.     

Absorption of oxygen in highly viscous newtonian and non-Newtonian fermentation model media in bubble column bioreactors

Summary Mean relative gas holdup, slip velocity, bubble size distribution, mean specific interfacial area, and volumetric mass transfer coefficient of oxygen were estimated in sparged columns 14 cm in diameter and 380 and/or 390 cm high with two different aerator types (porous plate and injector nozzle) in highly viscous Newtonian (glycerol solutions) and non-Newtonian (CMC solutions) fluids.For the Newtonian liquids the above properties were estimated as function of the viscosity of the liquid. For the non-Newtonian liquids they were determined as function of the fluid consistency index and flow behavior index. Significant differences between Newtonian and non-Newtonian systems appear. In Newtonian medium k_L a drops with increasing viscosity and already approaches a constant value at =40 cP. In pseudoplastic medium k_L a varies with the fluid consistency and flow behavior indexes in the entire investigated range.In both of these systems the primary bubble population changes into two or three populations along the reactor: the medium bubbles gradually disappear and small and large bubbles are formed.     

Rheological behaviour of some antibiotic biosynthesis liquids

This paper prsents the results of teh study of rheological behaviour of antibiotic biosynthesis liquids obtained by submerged aerobic cultivation of microorganisms belonging to the actinomycete and fungi classes, in stirred tank bioreactors with turbine impellers. These liquids have a non-Newtonian behaviour which follows the power-law rhcological model with a correlation index of over 0.95. The studied liquids are pseudoplastic, and alter their rheological properties, such as consistency index, (K), flow index, (n), apparent viscosity, (η_a), maximum Newtonian viscosity (η₀), with the culture age, microrganism strain and batch conditions. Also, these liquids are time dependent, exhibiting thixotropy. The most viscous liquids are produced by Streptomyces aureofaciens and Streptomyces rimosus cultivation, while that produced by Streptomyces griseus is the least viscous. A higher pseudoplasticity appears after 30 hours culture age. Since all these biosynthesis are aerobic, a careful observation of the rhelogical behaviour dynamics is necessary to avoid the oxygen culture supply limitation and the decrease of the bioreactor performance during biosynthesis.     

Rheology of embryonic avian blood

Shear stress, a mechanical force created by blood flow, is known to affect the developing cardiovascular system. Shear stress is a function of both shear rate and viscosity. While established techniques for measuring shear rate in embryos have been developed, the viscosity of embryonic blood has never been known but always assumed to be like adult blood. Blood is a non-Newtonian fluid, where the relationship between shear rate and shear stress is nonlinear. In this work, we analyzed the non-Newtonian behavior of embryonic chicken blood using a microviscometer and present the apparent viscosity at different hematocrits, different shear rates, and at different stages during development from 4 days (Hamburger-Hamilton stage 22) to 8 days (about Hamburger-Hamilton stage 34) of incubation. We chose the chicken embryo since it has become a common animal model for studying hemodynamics in the developing cardiovascular system. We found that the hematocrit increases with the stage of development. The viscosity of embryonic avian blood in all developmental stages studied was shear rate dependent and behaved in a non-Newtonian manner similar to that of adult blood. The range of shear rates and hematocrits at which non-Newtonian behavior was observed is, however, outside the physiological range for the larger vessels of the embryo. Under low shear stress conditions, the spherical nucleated blood cells that make up embryonic blood formed into small aggregates of cells. We found that the apparent blood viscosity decreases at a given hematocrit during embryonic development, not due to changes in protein composition of the plasma but possibly due to the changes in cellular composition of embryonic blood. This decrease in apparent viscosity was only visible at high hematocrit. At physiological values of hematocrit, embryonic blood viscosity did not change significantly with the stage of development.