Fermentation of Saccharomyces cerevisiae in a 7.5 L ultrasound-enhanced fermenter: Effect of sonication conditions on ethanol production,intracellular Ca2+ concentration and key regulating enzyme activity in glycolysis

In this study, the effect of sonication on the fermentation process of a single-celled fungus was examined. During the experiment, Saccharomyces cerevisiae (S. cerevisiae) was used as the starting strain for ethanol fermentation (batch fermentation) in a 7.5 L automated fermentation tank. The fermentation tank connected with a six-frequency ultrasonic equipment. Non-sonication treatment was set up as the control. Sonication treatment with power density of 280 W/L and 48 h of treatment time were set up as trial groups for investigating the influence of different ultrasound frequency including 20, 23, 25, 28, 33 and 40 kHz on the changes in dry cell-weight, glucose consumption rate, and ethanol yield. The results showed that the dry cell-weight, glucose consumption rate, and ethanol content reached the best results under the ultrasonic condition of 28 kHz ultrasound frequency in comparison with other ultrasound frequency. The dry cell-weight and ethanol content of the 28 kHz ultrasonic treatment group increased by 17.30% and 30.79%, respectively in comparison with the control group The residual sugar content dropped to a lower level within 24 h, which was consistent with the change in ethanol production. Besides, the results found that the glucose consumption rate increased compared to the control. It indicated that ultrasound accelerated glucose consumption contributed to increase the rate of ethanol output. In order to explore the mechanism of sonication enhanced the content of ethanol output by S. cerevisiae, the morphology, permeability of S. cerevisiae and key enzyme activities of ethanol synthesis were investigated before and after sonication treatment. The results showed that after sonication treatment, the extracellular nucleic acid protein content and intracellular Ca²⁺ concentration increased significantly. The morphology of S. cerevisiae was observed by SEM and found that the surface of the strain had wrinkles and depressions after ultrasonic treatment. furthermore after sonication treatment, the activities of three key enzymes which catalyze three irreversible reactions in glycolysis metabolism, namely, hexokinase, phosphofructokinase and pyruvate kinase increased by 59.02%, 109.05% and 87.27%, respectively. In a word, low-intensity ultrasound enhance the rate of ethanol output by S. cerevisiae might due to enhancing the growth and cell permeability of strains, and increasing the activities of three key enzymes of ethanol biosynthesis.     

Effects of fine fuel droplets on a laminar flame stabilized in a partially prevaporized spray stream

A partially prevaporized spray burner was developed to investigate the interaction between fuel droplets and a flame. Monodispersed partially prevaporized ethanol sprays with narrow diameter distribution were generated by the condensation method using rapid pressure reduction of a saturated ethanol vapor–air mixture. A tilted flat flame was stabilized at the nozzle exit using a hot wire. Particle tracking velocimetry (PTV) was applied to measurements of the droplet velocity; the laminar burning velocity was obtained from gas velocity derived from the droplet velocity. Observations were made of flames in partially prevaporized spray streams with mean droplet diameters of 7 μm and the liquid equivalence ratios of 0.2; the total equivalence ratio was varied. In all cases, a sharp vaporization plane was observed in front of the blue flame. Flame oscillation was observed on the fuel-rich side. At strain rates under 50 s⁻¹, the change in the burning velocity with the strain rate is small in fuel-lean spray streams. In spray streams of 0.7 and 0.8 in the total equivalence ratio, burning velocity increases with strain rates of greater than 50 s⁻¹. However, in spray streams with 0.9 and 1.0 in the total equivalence ratio, burning velocity decreases as the strain rate increases. At strain rates greater than 80 s⁻¹, burning velocity decreases with an increased gas equivalence ratio. The effect of mean droplet diameter, and the entry length of droplets into a flame on the laminar burning velocity, were also investigated to interpret the effect of the strain rate on the laminar burning velocity of partially prevaporized sprays.     

Concentration dependence of steady-state fluorescence behavior of a liquid crystal molecule E7 in ethanol

The fluorescence excitation and emission spectra of a liquid crystal E7 in ethanol have been explored at a variety of concentrations from very dilute solutions (<1.0×10⁻⁷ mol/L) to concentrated solutions (>1.0×10⁻² mol/L) and also for neat E7. The result showed a strong dependence of the steady-state fluorescence behavior on E7 concentration in ethanol. The photophysical behavior has been interpreted in terms of short-range and long-range intermolecular interactions and ground-state molecular association as well as spectral changes of the fluorescence excitation and emission. The short-range intermolecular interaction characterized by the fluorescence emission band with the maximum between 376 and 385 nm gradually increases with increasing E7 concentration. On the other hand, the long-range intermolecular interaction characterized by the emission band with the maximum between 347 and 362 nm gradually decreases with increasing E7 concentration. Consequently, with increasing E7 concentration in ethanol the long-range interaction effect is reduced, whereas the short-range effect is enhanced and the monomer emission completely disappears at concentrations greater than 2.83×10⁻⁵ mol/L.     

Pulsed spark-discharge assisted synthesis of colloidal gold nanoparticles in ethanol

A green method, using pulsed spark-discharge (PSD) to synthesize gold nanoparticles (AuNPs) in ethanol, is studied in this article. Unlike conventional methods for metal nanoparticles synthesis, the PSD method does not require the addition of chemical surfactants and stabilizers. The size of PSD–AuNPs is examined by transmission electron microscopy, with a range 5–50 nm. The chemical compounds, crystal structure, and surface plasmon resonance of PSD–AuNPs are studied using energy dispersive X-ray spectroscopy, X-ray diffraction, and UV–Visible spectroscopy, respectively. Zeta potential analysis shows that a negative charge (−40 mV) on the surface of the PSD–AuNPs may be contributing to the stability of the suspension. During the gold electrodes discharge in the ethanol, under an intensive electric field and thermal energy, bulk metallic gold and ethanol may produce AuNPs and varieties of chemical derivatives, which are also studied by GC/MS and FTIR to investigate the suspension mechanism. The analysis results show that there is an oxidation reaction of ethanol occurring during the PSD process to produce ethanol derivatives, such as acetaldehyde, acetic acid, and ethyl acetate, which may modify the surface of AuNPs by coordination of oxygen atoms. However, only acetic acid can form a negative charge by the deprotonation of the carboxylic group of surface in ethanol, resulting in the creation of a repulsion force between the particles to form the stable colloid system. The experimental results indicate that PSD is an alternative green process to synthesize gold nanoparticles suspension in ethanol. Moreover, with a gold rod consumption rate of 15 mg/L, concentrations of gold nanoparticles ~9 ppm have been observed; therefore, the net production rate is around 60%.     

Ultrasound-assisted fermentation for cider production from Lebanese apples

The present work studies the impact of low-intensity ultrasound (US) on Hanseniaspora sp. yeast fermentations. The effect of pulse duration and growth phase on US application was first evaluated using a synthetic medium. The optimal conditions were then applied to apple juice US-assisted fermentation. An US treatment chamber was first designed to allow the recycling of the culture medium. The optimal US pulse duration on the yeast growth rate was of 0.5 s followed by 6 s rest period, and during 6 h of both Lag and Log phases. These US parameters led to a faster consumption of glucose in the medium during the fermentation, compared to the untreated culture. The impact of US was also depending on the growth phase, showing higher sensitivity of the yeast to US during the Lag phase rather than the Log phase. US-assisted fermentation of apple juice showed a significant increase in biomass growth and glucose consumption, along with a significant decrease in the ethanol yield. The fastest growth kinetic (by 52%), and the highest ethanol reduction (by 0.55% (v, v)) were obtained for the treatment during the first 12 h of fermentation, thereby, the stationary phase was reached faster, and the maximum biomass growth rate was 10 folds higher compared to the untreated culture. The results obtained in this study demonstrated the promising efficiency of US-assisted fermentation in stimulating the biomass growth and reducing the ethanol content in alcoholic beverages.     

Quinoline formation via a modified Combes reaction: examination of kinetics,substituent effects,and mechanistic pathways

This is the first reported investigation of the Combes condensation employing 19F NMR spectroscopy to monitor intermediate consumption and product formation rates. The reaction was found to be first order in both the diketone and aniline. Product regioselectivity and reaction rates were found to be influenced by substituents on the diketones and anilines with rates varying as much as five fold. The consumption rate of key imine and enamine intermediates mirrored quinoline formation rates, in accord with rate determining annulation. A ρ of ?0.32 was determined for this cyclization. While the sign of the reaction constant is consistent with rate limiting electrophilic aromatic substitution (EAS), the magnitude is likely a composite value, resulting from opposing substituent effects in the nucleophilic addition and EAS steps. Mechanistic details and reaction pathways supporting these findings are proposed. Copyright © 2008 John Wiley & Sons, Ltd.     

Lack of the neighboring group rate effect in solvolytic reactions that proceed via participation

In order to investigate the influence of solvent polarity on the rate effect of double bonds in reactions that proceed via an extended π‐participation mechanism, the solvolysis rates (k_U) of the benzyl chloride derivative 1 and tertiary chloride 2 that have doubly unsaturated side chains were measured in absolute ethanol, 80% v/v. aq. ethanol and 97% wt. aq. trifluoroethanol. The rates of the corresponding saturated analogs 1S and 2S (k_S) were measured in 80% aq. ethanol and 97% wt. aq. trifluoroethanol, while those in pure ethanol were calculated according to LFER equation log k = s_f (E_f + N_f). In solvents with moderate ionizing power (ethanol and 80% aq. ethanol) the expected rate effects were obtained (k_U/k_S>1), while in solvent with high ionizing power (2,2,2‐trifluoroethanol) absence of the rate effect was observed (k_U/k_S≈1), indicating that in the k_S process the solvation of the transition state is very important, while in k_Δ process the breaking of the C? Cl bond is not appreciably developed in the transition state and the solvent effect is marginal. Copyright © 2007 John Wiley & Sons, Ltd.     

AB-8大孔树脂对豆腐柴根提取物中总黄酮的吸附性能

研究了AB-8大孔树脂对豆腐柴根提取物中总黄酮静态和动态的吸附性能。利用分光光度法测定样品中黄酮含量,考察提取液浓度、pH值、乙醇洗脱体积分数、上样液流速等实验条件对吸附结果的影响。结果表明,AB-8大孔树脂对豆腐柴根中总黄酮具有较好的吸附性能。静态吸附最佳条件:上样液浓度为0.0275mg/mL、pH 7、70%乙醇洗脱,总回收率为65.45%;动态吸附的最佳条件:浓度为0.0275mg/mL、pH为5、流速为1mL/min,90%的乙醇洗脱条件下,总回收率为47.27%。     

乙醇在TiO2(110)表面光催化解离的动力学和超快电子动态学 (cited: 2)

采用实时双光子光电子能谱和时间分辨双光子光电子能谱技术分别研究了乙醇在该表面光催化解离的动力学和超快电子动态学过程. 通过测量与乙醇光催化解离相关的电子激发态随时间的演化,发现这个反应满足分型动力学. 乙醇在还原性TiO₂(110)上的光催化解离比在氧化性表面快,这归结于缺陷的存在降低了反应能垒. 这样一个反应的加速过程很可能是与缺陷电子相关的. 通过干涉双脉冲相关的测量,得到了乙醇-TiO₂界面电子激发态的超快动态学. 与甲醇的情况类似,这个电子激发态的寿命为24 fs. 激发态的出现为TiO₂和它周围环境的电子转移提供了一个通道.     

Enhancing carrot convective drying by combining ethanol and ultrasound as pre-treatments: Effect on product structure,quality, energy consumption,drying and rehydration kinetics

Ultrasound was combined with ethanol to improve different aspects of carrot convective drying, evaluating both processing and product quality. The ultrasound in water treatment resulted in cellular swelling and small impact on texture. Differently, the ultrasound in ethanol and ethanol treatments modified both carrot microstructure (cell wall modifications of parenchymatic tissue) and macrostructure (shrinkage and resistance to perforation). Pre-treatments with ultrasound in ethanol and ethanol improved the drying kinetics, reducing the processing time (~50%) and the energy consumption (42–62%). These pre-treatments also enhanced rehydration, whose initial rate and water retention were higher than the control. In addition, the carotenoid content was preserved after drying, for all the treatments. Any impact on shrinkage was observed. A mechanistic discussion, based on structural modification (microstructure and macrostructure) and physical properties of water and ethanol, was provided. As conclusion, this work not only described positive aspects of combining the technologies of ultrasound and ethanol as pre-treatments to convective drying, but also proposed mechanisms to explain the phenomena.     

Kinetic sonication effects in light of molecular dynamics simulation of the reaction medium

Molecular dynamics (MD) simulation of the structure of ethyl acetate solutions in two water–ethanol mixtures was performed at 280 and 330 K. The MD simulations revealed that ethyl acetate was preferentially solvated by ethanol, water being mainly located in the next solvation layer. With increasing temperature ethanol was gradually replaced by water in the first solvation shell. These findings explain the decrease in the rate of ester hydrolysis with increasing molar ratio of ethanol in the solution as the reaction rate was linearly dependent on the relative ethanol content in the first solvation shell of the ester. Predominance of ethanol results in decreased polarity and water activity in the shell and accordingly in a decreased reaction rate. Based on the results of the MD simulations, the principal conclusion of this work is that ultrasound enhances the kinetic energy (the effective temperature) of species in the solution and, in this way, evokes shifts in the solvation equilibria thus affecting the reaction rate. It appears that ultrasound does not completely break down the solvent shells or clusters in the solution as previously believed. Phenomena of thermo-solvatochromism and reaction rate levelling by ultrasound in binary solvents are described.     

Measuring radon exhalation rate by tracing the radon concentration of ventilation-type accumulation chamber

Radon exhalation rate is crucial in the estimation of radiation risk from various materials. RAD7 only focus on the count of the ²¹⁸Po in sniff mode, and is well suited to measure radon exhalation rates. This paper presents a fast method for measuring radon exhalation from medium surface with a ventilation-type accumulation chamber by the RAD7 while making the effects of leakage and back diffusion negligible. The radon exhalation rate can be obtained from the measured values before radioactive equilibrium between Radon and progeny occurs. This method is based on the principle for tracing radon concentration changes by deriving ²²²Rn concentrations through ²¹⁸Po measurements. Several radon exhalation rate measurements of medium surface have been performed in the Radon Laboratory of the University of South China. The radon exhalation rates obtained by verification experiments are within the accepted values for the reference value.     

Kinetics of ultrasound-assisted extraction of antioxidant polyphenols from food by-products: Extraction and energy consumption optimization

Ultrasound-assisted extraction (UAE) of antioxidant polyphenols from chicory grounds was studied in order to propose a suitable valorization of this food industry by-product. The main parameters influencing the extraction process were identified. A new mathematical model for multi-criteria optimization of UAE was proposed. This kinetic model permitted the following and the prediction of the yield of extracted polyphenols, the antioxidant activity of the obtained extracts and the energy consumption during the extraction process in wide ranges of temperature (20–60 °C), ethanol content in the solvent (0–60% (vol.) in ethanol–water mixtures) and ultrasound power (0–100 W). After experimental validation of the model, several simulations at different technological restrictions were performed to illustrate the potentiality of the model to find the optimal conditions for obtaining a given yield within minimal process duration or with minimal energy consumption. The advantage of ultrasound assistance was clearly demonstrated both for the reduction of extraction duration and for the reduction of energy consumption.     

Quantifying the effect of CO2 gasification on pulverized coal char oxy-fuel combustion

Previous research has provided strong evidence that CO₂ and H₂O gasification reactions can provide non-negligible contributions to the consumption rates of pulverized coal (pc) char during combustion, particularly in oxy-fuel environments. Fully quantifying the contribution of these gasification reactions has proven to be difficult, due to the dearth of knowledge of gasification rates at the elevated particle temperatures associated with typical pc char combustion processes, as well as the complex interaction of oxidation and gasification reactions. Gasification reactions tend to become more important at higher char particle temperatures (because of their high activation energy) and they tend to reduce pc oxidation due to their endothermicity (i.e. cooling effect). The work reported here attempts to quantify the influence of the gasification reaction of CO₂ in a rigorous manner by combining experimental measurements of the particle temperatures and consumption rates of size-classified pc char particles in tailored oxy-fuel environments with simulations from a detailed reacting porous particle model. The results demonstrate that a specific gasification reaction rate relative to the oxidation rate (within an accuracy of approximately +/- 20% of the pre-exponential value), is consistent with the experimentally measured char particle temperatures and burnout rates in oxy-fuel combustion environments. Conversely, the results also show, in agreement with past calculations, that it is extremely difficult to construct a set of kinetics that does not substantially overpredict particle temperature increase in strongly oxygen-enriched N₂ environments. This latter result is believed to result from deficiencies in standard oxidation mechanisms that fail to account for falloff in char oxidation rates at high temperatures.     

Effects of ultrasound on adsorption-desorption of p-chlorophenol on granular activated carbon

The aim of this work is the evaluation of the effects of ultrasound on p-chlorophenol adsorption-desorption on granular activated carbon. Adsorption equilibrium experiments and batch kinetics studies were carried out in the presence and the absence of ultrasound at 21 kHz. Results indicate that the adsorption of p-chlorophenol determined in the presence of ultrasound is lower than the adsorption observed in the absence of ultrasound. Desorption of p-chlorophenol from activated carbon with and without the application of ultrasound was studied. The desorption rates were favoured by increased ultrasound intensity. This rise is more noticeable as temperature increases. The addition of ethanol or NaOH to the system causes an enhancement of the amount of p-chlorophenol desorbed, especially in the presence of ultrasound. A synergetic enhancement of the desorption rate was observed when ultrasonic irradiation was coupled with ethanol chemical regeneration.     

Dependence of cooperative emission spectra of complex organic molecules on exciting photon energy

The dependences of cooperative emission, superfluorescence, and lasing spectra on the wavelength of pumping radiation were studied for highly concentrated ethanol solutions of organic dye molecules. The relative intensity of cooperative emission was found to decrease, while the intensities of superfluorescence and lasing were found to increase with the energy of exciting photons. The increase in the dephasing rate of quantum states is supposed to be primarily responsible for the change in proportion between these intensities. On increasing the dephasing rate, with all other factors being the same, the concentration of the excited molecules with the phased quantum states decreases, while that with the dephased states increases. The ratio between the cooperative emission and dephasing rates determines the proportion between the intensities of cooperative emission, superfluorescence, and lasing. The onset of lasing at high concentrations (above >10¹⁹ cm^?3) in the case of pumping by high-energy photons occurs due to the high dephasing rates of quantum states resulting from a more rapid redistribution of vibrational energy.     

Study on successively preparation of nano-TiO2 ethanol colloids by pulsed laser ablation and fluorescence property

Nano-TiO₂ colloids have been successively prepared by focused, pulsed laser ablation (PLA) at the interface of solid titanium dioxide and flowing liquid. Three factors influenced the luminescence of the nano-TiO₂ colloids. The first factor was the flowing rates of the flowing liquid. The second factor was the pulsed laser output power. The third factor was the age of the colloids. The nano-TiO₂ colloids products were characterized by transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV-vis) and fluorescence spectroscopy. The results revealed that anhydrous ethanol was the best flowing liquid, and cyclohexane or water was found to be not suitable for this system; under the conditions of the lowest flowing rates of the flowing liquids in the range of 0.017-0.15 mL/s, the highest pulsed laser output power in the range of 100-250 mJ/pulse and with the proper aging time of the colloids, nano-TiO₂ ethanol colloids with strong fluorescence emission intensity at about 414 nm can be obtained.     

Further consideration of the correlation of the rates of solvolytic displacement of chloride ion from phosphorus (V)

Specific rates of solvolysis of diphenyl ( 1 ) and bis(2,4‐dichlorophenyl) ( 3 ) phosphorochloridate (chlorophosphate) have been determined by a conductivity technique. The available specific rates together with those determined earlier for bis(4‐chlorophenyl) phosphorochloridate ( 2 ) have been analyzed in terms of the extended (two‐term) Grunwald–Winstein equation. It is found that rather poor overall correlations found earlier for 1 and 2 and now for 3 are considerably improved when data points for 2,2,2‐trifluoroethanol–ethanol and acetone–water mixtures are excluded. The large sensitivities toward changes in solvent nucleophilicity are consistent with a bimolecular process. The differences in nucleophilicity of an acetone–water mixture for attack at carbon or at phosphorus are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Molecular dynamics study of size and cooling rate effects on physical properties of Niobium nanoclusters

Using Molecular Dynamics (MD) Simulations, based on the embedded atomic method (EAM), we have investigated the effect of cooling rate and nanocluster size on thermophysics properties of supercooled liquid niobium. Simulations of Nb nanoclusters with sizes 125, 343, 1000, 1728 and 2744 nm³ have been carried out at various cooling rates. Thermophysical properties of Nb system, during quenching process, have been quantifying in terms of radial distribution function, thermal capacity and self-diffusion coefficients. Simulations results show that the crystallization of supercooled liquid Nb occurred at a critical cooling rate of about 7 × 10¹² K/s for all nanocluster sizes. Moreover, our results show that for Nb nanocluster sizes equal or higher than 1000 nm³, the transition temperature increases as the cooling rate decreases. Finally, it is found that the pre-exponential factor and activation energy for self-diffusion in niobium are in good agreement with previous work.     

Performance of a SOFC powered with external ethanol steam reforming

In the present study, a solid oxide fuel cell (SOFC) system was considered being fed by the equilibrium products of the steam reforming of ethanol. The thermodynamic analysis of ethanol steam reforming was undertaken at total pressure of 1 bar in the temperature range between 800–1200 K assuming different steam/ethanol molar feed ratios in the range of 1–5. The possibility of carbon deposition in the equilibrium mixture was examined and all conditions of SOFC operation were selected appropriately so that this deposition to be thermodynamically impossible. The equilibrium mixture of reforming obtainable in each case was mathematically calculated using the method of the direct minimization of Gibbs free energy. The distribution of the molar fraction of the species in thermodynamic equilibrium was obtained in the examined range of conditions, and optimum conditions of SOFC operation were recognized in terms of its thermodynamic efficiency for generation of electrical power. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.