Search

Oak bark is a by-product known for its richness in polyphenols, with tanning substances being particularly interesting for their application in different fields. Vegetable tannins are mostly utilized in the leather sector, but are also widely used as adhesives, in cement plasticizers and for medical and agrochemical applications owing to their natural antimicrobial activity. This study aimed to develop a green and efficient pilot-scale technique for extracting polyphenols from oak bark by ultrasound-assisted extraction (UAE) using a modified Dual-Frequency Reactor (DFR). Different parameters, such as extraction time, temperature, and solvent type (water, sodium hydroxide or sodium sulfite and bisulfite solutions) were investigated for their influence on the total phenolic content (TPC) and the quantity of dry extract. Control experiments by conventional methods were also performed. UAE at 50 °C yielded the highest TPC and dry extract (confirmed by ANOVA analysis, p < 0.05) in just 10 min, suggesting that UAE can be considered an energy- and cost-effective alternative to conventional techniques. The most suitable solvent was found to be a 0.5% sodium hydroxide solution. The molecular profile of the extracts was assessed by FTIR-ATR spectroscopy, revealing typical signals of tannins in all extracts. Furthermore, antimicrobial activity tests demonstrated the complete absence of Gram-positive and Gram-negative bacteria in the extracts, ensuring the suitability of the product for different kinds of application. [ABSTRACT FROM AUTHOR]

The move towards environmentally friendly processing has been a driving force for research into green methods for the extraction of bioactive compounds from plant materials. In this study, a green and efficient process for the extraction of β-carotene from sea buckthorn berries through the simultaneous use of ultrasound and microwave, using a novel green solvent, fatty acid ethyl esters (FAEE), is described. For the same extraction time (45 min), the β-carotene content in the extract was significantly increased (according to ANOVA analysis—p < 0.05) by the simultaneous use of ultrasound and microwave, compared with the separate use of these technologies—an increase of 15 and 89% compared with ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE), respectively. The resulting extract can be used directly, without further purification, as a food supplement because the solvent itself is safe for consumption. Furthermore, FAEE contains omega-3 and omega-6 fatty acids which add to the health benefits of the extract. When β-carotene is extracted from the plant matrix, it is subjected to degradation due to oxidation, but the addition of the antioxidant vitamin E (13 mg/mL of extract) to the extract extends its stability to more than 90 days at room temperature even when exposed to light. The addition of vitamin E also enhances the health benefits of the extract. [ABSTRACT FROM AUTHOR]

This work is focused on the study of the esterification parameters for the ultrasound assisted synthesis of isoamyl acetate catalyzed by lipase Lipozyme 435 in a continuous loop reactor. Investigating the influence of different parameters shows that a higher concentration of ester (462 mg/g mixture) can be obtained at a temperature of 50 °C, flow rate 0.16 mL/min. The best ultrasonication conditions are: sonication applied continuously for a short time (20 min), ultrasound power 32 mW and amplitude 20%. The enzyme can be successfully reused tree times without loss of enzyme activity. Reaction kinetics for isoamyl acetate ultrasound assisted production showed that satisfactory reaction concentration (close to the equilibrium concentrations) could be reached in short reaction times (2 h). Ultrasound assisted enzymatic esterification is consequently a cleaner and a faster process. [ABSTRACT FROM AUTHOR]

Bioethanol is the world’s leader biofuel and it is produced by fermentation from glucose feedstocks. The fermentation rate is quite low and any method of increasing the reaction rate is welcome. The main goal of our research is to identify the domain for microwave Specific Absorption Ratio (SAR) which leads to an increase in fermentation rate of Saccharomyces cerevisiae without affecting its viability. For this purpose, an installation was setup which allows for glucose fermentation to be carried out in the presence of microwave, with good control on SAR and on temperature of the fermentative medium. An optimum SAR domain, between 15 and 25 W kg −1 , was determined, in which a significant boost of glucose fermentation manifests, with an increase in fermentation rates of up to 20%. Based on the observations made through electron and optical microscopy on cell growth and viability, we have noticed that microwave irradiation favours ethanol production of the cells, against their growth. [ABSTRACT FROM AUTHOR]

As a renewable and sustainable resource, lignocellulosic biomass serves as a crucial raw material for the production of biofuels, biochemicals, and various value-added products. This paper aims to develop and optimize a mild alkaline treatment of sawdust assisted by ultrasound, along with enzymatic hydrolysis of the pretreated material. The alkaline sonochemical pretreatment emerged as the optimal approach to enhance the susceptibility of cellulose to subsequent enzymatic hydrolysis to improve the yield of reducing sugars. A comparative study was performed using various ultrasonic applicators (horn and bath) and conventional assisted alkaline pretreatment. The ultrasonic-assisted pretreatment revealed a higher delignification of 68% (horn) and 57% (bath) compared with conventional pretreatment. Processes were optimized using a statistical analysis based on a 23 factorial design. The ratios between sawdust and alkaline solution (RSL = 0.5–1.5 g/100 mL), US amplitude (A = 20–60%), and working temperature (t = 30–50 °C) were selected as process factors. The optimal operating conditions to maximize the reducing sugar yield (138.15 mg GE/gsubstrate) were found as follows: a solid/liquid ratio of RSL,opt = 1.25 g/100 mL, US amplitude of Aopt = 60%, and pretreatment temperature of topt = 50 °C. The overall outcomes clearly confirmed the intensification of delignification by ultrasound-assisted alkaline pretreatment. [ABSTRACT FROM AUTHOR]

The extraction of essential oils (EOs) and polyphenols from rosemary and thyme has been done using an integrated process: microwave hydro-diffusion and gravity (MHG) for EOs and microwave-assisted extraction (MAE) for polyphenols. The innovative installation based on the MHG principle allows uniform microwave irradiation field due to a mechanical stirring and experiments done at low pressure. The results of quantitative analysis of the EOs extracted by MHG after 10 min were similar with those obtained by traditional methods (conventional hydro-distillation (CHD) and microwave-assisted hydro-distillation (MHD)) after 150 and 105 min, respectively. The specific energy for MHG was 5-15 times lower compared with these classical methods. The MHG extraction of EOs is also an effective method for plant material pretreatment before polyphenol extraction. Total phenolic content increased from 35 to 55 mg GAE/g DM for rosemary and from 23 to 38 mg GAE/g DM for thyme. [ABSTRACT FROM AUTHOR]

We report a direct comparison of microwave heating and conventional heating in solvent extraction by using exactly the same reaction conditions (including heating rate) in the extraction of polyphenols from dried sea buckthorn leaves. We have for the first time decoupled the effects of bulk heating rate and mixing regime from the fundamental microwave heating mechanism. We show that although microwave selective heating can increase the yield and quality of the polyphenols extracted, if the same bulk heating rate is applied there is no difference in treatment time and therefore theoretical energy requirements of the process. The first implication of these results for process intensification is that if microwave selective heating can be enhanced in scaled up processes through electromagnetic design, the extract yield and quality may be increased further. The second implication is that conventional extraction processes could be designed to provide the same heating rate and hence treatment time as microwave extraction, but any potential energy and space savings would have to be balanced against the increase in capital cost and complexity of the equipment. That said, the very small penetration depth of microwaves into ethanol/water solvent also poses design challenges in the scale up of microwave equipment. [ABSTRACT FROM AUTHOR]

Extraction of polyphenols from sea buckthorn leaves using microwave-assisted extraction (MAE) is described. The influence of different parameters on the extraction process (reactor type, stirring rate, extraction time, temperature, ethanol/water ratio) was studied. The polyphenolic extracts were analyzed in order to determine the total phenolic content (TPC) either by the Folin-Ciocalteu method or by differential pulse voltammetry (DPV), and the concentration of the main polyphenolic compounds by high-performance liquid chromatography (HPLC). The specific microwave energy was also determined. MAE resulted in a shorter extraction time (7.5 versus 30 min for the conventional method). The best results for MAE were obtained at a temperature of 90°C, using a solvent/plant ratio of 20/1 and 50% ethanol in the extraction solvent. The highest values of antioxidant capacity were obtained for polyphenolic extracts resulted from microwave extraction. [ABSTRACT FROM AUTHOR]

Abstract: The Electron Beam Flue Gas Treatment (EBFGT) has been proposed as an efficient method for removal of SO2 and NO x many years ago. However, the industrial application of this procedure is limited to just a few installations. This article analyses the possibility of using medium-power EB accelerators for off-gases purification. By increasing electron energy from 0.7MeV to 1–2MeV it is possible to reduce the energy losses in the windows and in the air gap between them (transformer accelerators can be applied as well in the process). In order to use these mid-energy accelerators it is necessary to reduce their penetration depth through gas and this can be achieved by increasing the density of the reaction medium by means of dispersing a sufficient amount of fine water droplets (FWD). The presence of FWD has a favorable effect on the overall process by increasing the level of liquid phase reactions. A special reactor was designed and built to test the effect of FWD on the treatment of flue gases with a high concentration of SO2 and NO x using high-energy EBs (9MeV). By determining the energy efficiency of the process the favorable effect of using FWD and high-energy EB was demonstrated. [Copyright &y& Elsevier]

- Heterogeneous liquid-phase dechlorination of chlorobenzene over supported palladium-based catalysts to form benzene was examined using microwave and conventional heating methods. The reaction was carried out in a solution of NaOH in 2-propanol at atmospheric pressure and reflux temperature (approx. 83°C). Two types of commercial aluminium-silicate and γ-alumina-supported catalysts have been tested. The results obtained under microwave (MW) and conventional (CH) conditions were compared with respect to the rate enhancement, selectivity and catalyst activity. The sole product of the chlorobenzene dehalogenation was benzene. The effect of the addition of NaOH has been analysed for the neutralisation of HCl. [ABSTRACT FROM AUTHOR]

Ca- and Cu-decorated TiO2 microparticles are titanium dioxide nanoparticles that have been decorated with calcium and copper ions. TiO2, CaO, and CuO are low-cost, non-toxic, and non-hazardous materials. The aim of the present study was the physicochemical characterization of Ca- and Cu-decorated TiO2 microparticles and the evaluation of their antimicrobial activity. Thus, Ca2+ and Cu2+ species were incorporated onto TiO2 surfaces by a two-step wet method. The obtained TiO2-CaO-CuO composites were characterized by several experimental techniques. The electronic structure and charge properties of the composites were investigated by density functional theory calculations. Furthermore, the composites were successfully tested for inhibitory effects on Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans standard strains. The zeta potential data indicate that the physiological condition of investigated microbial strains was strongly affected in presence of a dispersion of 10 μg/L of composites in a saline phosphate buffer also, the recorded SEM images show a damaged microbial cell surface in the presence of composites. [ABSTRACT FROM AUTHOR]

• The synthesis of biodiesel in a continuous laboratory process has been studied. • Ultrasounds or microwaves have been tested for intensifying the process. • For each technique used the conditions were optimized. • The grid energy consumption was measured for each process. • The additional energy consumption due to the intensification method was only 0.08%. At this time biodiesel appears to be a viable proposition as a renewable energy source and an alternative to fossil-based fuels. Following many years of research, the use of process intensification techniques for the production of biodiesel is well documented. This work has focused more on a study of biodiesel production using continuous flow systems assisted by acoustic cavitation (ultrasonic or hydrodynamic) or microwaves. The target end user is the small or medium farm where such equipment could provide sufficient fuel for on-site agricultural machinery using renewable or waste green materials produced on site. [ABSTRACT FROM AUTHOR]

The influence of ultrasound irradiation on the algal biomass productivity as well as its oil content and fatty acids profile, grown in a modified Zarrouk medium, i.e., deproteinized whey waste solution, was investigated. The algal samples (Nannochloris sp. 424-1 microalgae) were grown for 7 days in a thermostated incubator at 28 °C, shaken under continuous light. During this period, the algal biomass was subjected to induced stress by ultrasonic irradiation at different powers and sonication time. The obtained results demonstrate that ultrasound stressing of algae biomass has a positive effect on both the quantity of biomass and the oil obtained, also causing a shift in fatty acid composition by increasing the proportion of C16 and C18 polyunsaturated fatty acids. A low dosage level of exposure to the ultrasound led to algal biomass increase as well as lipid accumulation. For both types of irradiation modes which were investigated, daily and only initial irradiation, the beneficial effect of the ultrasound decreases as the exposure time increases and the excessive sonication becomes detrimental to microalgae growth. [ABSTRACT FROM AUTHOR]

[Display omitted] • applying a method to improving the light fastness of natural curcumin dyes extracted from turmeric by encapsulation in silica matrix. • determining the optimal conditions for extraction of curcumin compounds by conventional (maceration, reflux) and unconventional (microwave-assisted) methods. • encapsulation into a silica matrix by by three different routes in the presence of NaOH, lysine or triethanol amine. • the light fastness of the capsules was investigated by UV–Vis and fluorescence spectroscopy. The study shows the possibility of improving the light fastness of natural curcumin dyes extracted from turmeric by encapsulation in silica matrix. Curcumin extracts were obtained by conventional and microwave assisted extractions. Encapsulation into a silica matrix was performed by using three different routes in the presence of NaOH, lysine or triethanol amine. The curcumin loaded silica particles were characterized by SEM, EDX, FT-IR, UV–Vis and photoluminescence spectroscopy analyses. The light fastness of the curcumin capsules was further investigated by UV–Vis spectroscopy. The color description was performed by employing the CIEL*a*b* system and the color difference was calculated. The stabilization methods lead to high encapsulation efficiencies and a very good light fastness for all samples. [ABSTRACT FROM AUTHOR]

The aim of this study was to establish the best ultrasound assisted extraction (UAE) conditions of saponins from Hedera helix L. leaves and to evaluate the in vitro biocompatibility of the extracts richest in saponins. Different parameters, such as extraction time, temperature, ultrasound power, solvent to plant material ratio, and solvent concentration, were investigated. The most efficient extraction conditions were a temperature of 50 °C, an ultrasound amplitude of 40%, an extraction time of 60 min, a plant material to solvent ratio of 1:20 (w:v), and 80% ethanol as solvent. In vitro cytotoxicity of the extracts richest in saponins and their influence on the DNA content of L929 (NCTC) fibroblasts were tested. Until 200 µg/mL, the studied extracts were cytocompatible with L929 fibroblast cell lines at 48 h of treatment. These in vitro cell culture results provide useful information for further applications of Hedera helix extracts in a pharmaceutical field. [ABSTRACT FROM AUTHOR]

Plasmonic silver film was directly generated on a variety of substrates through a facile and environmentally friendly method, which involves a UV-photoreduction process without any reducing or stabilizing agent and requiring no thermal step. Top-coated films of unprotected silver nanoparticles (3-11 nm) were generated from hydroalcoholic AgNO solution and directly on glass substrates or food packaging plastic wraps, low density polyethylene film, and polyvinyl chloride. The natural antibacterial activity of the material was evaluated. The correlation between silver migration and antimicrobial activity of silver-functionalized substrates against pure strains of gram-negative bacteria ( Escherichia coli) and gram-positive bacteria ( Staphylococcus aureus) was demonstrated. By way of illustration, food plastic wraps top-coated in this way exhibited a high antibacterial activity. The metal nanoparticle film obtained in this way was characterized and the influence of several parameters (fluence, exposure, silver nitrate concentration, and nature of the free radicals generator) on their formation was studied. Moreover, by shaping the actinic beam with an appropriate device, it is very easy to pattern the brown yellow silver nanofilm or to print messages in plain text. [ABSTRACT FROM AUTHOR]

Liquid-phase polymerisation of acrylamide-acrylic acid to form polyelectrolytes used in wastewater cleaning was examined using accelerated electron beam and microwave irradiation methods. Polymerisation was carried out in aqueous solutions at temperatures ∼60 °C. Monomers total concentration was established at 40% (36% acrylamide and 4% acrylic acid). Only using the features of simultaneous radiation–induction and microwave heating can result in the formation of linear polymer chains with good water solubility and low residual monomer concentration. The flocculation capacity of the obtained polymers was tested using two wastewaters, one sampled from a slaughterhouse and the other from a vegetable oil plant. Quality indicators such as total suspended matters (TSM), chemical oxygen demand (COD), biological oxygen demand (BOD) and fat, oils and grease (FOG) were measured before and after the treatment with polymeric flocculants and compared with the results obtained in classical treatment with Al2(SO4)3. It was found that the combined treatment with polymers and Al2(SO4)3 increases the degree of purification of both wastewaters up to 99%. [Copyright &y& Elsevier]

Microwave discharges at 2.45 GHz frequency and accelerated electron beams operated at atmospheric pressure in synthetic gas mixtures containing N2, O2, CO2, SO2, and NOx are investigated experimentally for various gas mixture constituents and operating conditions, with respect to their ability to purify exhaust gases. An original experimental unit easily adaptable for both separate and simultaneous irradiation with microwaves and electron beams was set up. The simultaneous treatment with accelerated electron beams and microwaves was found to increase the removal efficiency of NOx and SO2 and also helped to reduce the total required dose rate with ∼30%. Concomitant removal of NOx (∼80%) and SO2 (>95%) by precipitation with ammonia was achieved. [Copyright &y& Elsevier]

The article discusses results of a systematic study performed on Gaillardia aristata and Gaillardia x grandiflora Burgunder to identify significant volatile compounds of these species. Topics discussed include method employed to identify volativle compounds which includes headspace gas chromatography-mass spectrometry (HS GC-MS), compounds identified in these two species of Gaillardia and their potential therapeutic properties like anti-inflammatory, antimicrobial and antibiotic.

An abstract of the article "Chemical Composition of the Aerial Part and Fruits of Coreopsis tinctoria" by Claudia Corina Crisan, Mihaela Buleandra, Ioan Calinescu, Christina Zalaru, Iulia Gabriela David, and Irinel Adriana Badea is presented.

A solvent free in situ microwave hydro-distillation method for extraction of essential oil from fresh ginger root it presented. Extraction was conducted in a TE10n single-mode microwave cavity and variable power 2 kW generator operating at 2.45GHz. The main extracted components identified by gas chromatography (GC) were Zingiberene, α-Curcumene, β-Sesquiphellandrene and α-Selinene. At energy inputs of 0.40 kWh/kg higher powers and shorter exposure times, crucially did not degrade the highly volatile components (α-Pinene and Camphene) despite providing the highest essential oil yields. Optimum processing conditions were found to be 1000W (0.40kWh/kg) for 5 min, for whole ginger root, where 0.35g oil/100g plant was obtained. This was compared to a yield of 0.2g/100g plant in 150 in using conventional hydro-distillation and 0.3g/100g plant in 90 min using a multi-mode microwave cavity-based hydro-distillation. [ABSTRACT FROM AUTHOR]

The use of dielectric property assessment to gauge the catalytic activity and rate of deactivation of heterogeneous catalysts is reported. Four supported catalysts containing a combination of Fe and Ni active sites and γ-Al2O3, ZSM-5, MCM-41, and SBA-15 supports were synthesized, characterized, and utilized to catalyze a Fischer-Tropsch process over a temperature range of 250-400 °C that was specifically directed toward the production of lower olefins. While the highest conversion was obtained from ZSM-5 and MCM-41 supports containing Fe and Ni as active sites at 350 °C, all these catalysts were observed to be deactivated by the formation of carbon on their surface. The dielectric properties of the fresh, used catalysts and supports were evaluated and correlated with their catalytic activity and structural/textural properties. It was clearly shown that the dielectric property measurement could demonstrate both the presence and magnitude of carbon deposits on the catalyst via the differences in the values of fresh and used catalysts. Furthermore, the ability to differentiate between the levels of the carbon deposition observed was shown to be independent of the morphology exhibited by the carbon deposit demonstrating that this is a method that can be generally applied. [ABSTRACT FROM AUTHOR]

The aim of this study was the obtaining of a modified textile material capable of absorbing the body heat resulting from intense activities and maintaining the optimum human body temperature (36-37 °C). Thus, temperature-sensitive reactive polymer particles were obtained through the use of suspension polymerization of glycidyl methacrylate and paraffin and subsequent grafting on textile material was realized. The materials were characterized in order to determine their morphological, thermal, and comfort parameters. [ABSTRACT FROM AUTHOR]

The present study presents two different methods to obtain hybrid material formed by the poly [styrene (ST)-poly(ethylene glycol) methyl ether methacrylate (PEGMA) 1100] and silver (Ag). The aim has been to cover the polymeric particles with Ag shell. The first method consisted of mixing Ag nanoparticles dispersion with poly (ST-PEGMA 1100) dispersion, while in the second method, the Ag nanoparticles have been generated in situ. The hybrid materials have been characterized by MO, dynamic light scattering, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray energy dispersive spectrometry, and ultraviolet-visible spectrophotometry. The results confirm the obtaining of two types of morphologies. In the first case, the nanoparticles have been arranged in the interspatial zones of the polymer particles, while in the second method, the Ag nanoparticles have covered the polymer particles. Thus, the film obtained using the second method is more suitable for the practical application, as a separation membrane, using the antiseptic properties of Ag. [ABSTRACT FROM AUTHOR]

A new method based on microwave (MW) energy addition to accelerated electron beam (ER) energy for material processing was developed. In order to investigate this method, several specially designed facilities which permit separate, successive, and simultaneous MW and EB irradiation were carried out. These facilities as well as the associated MW and EB injection systems are described. In comparison with separate EB or MW irradiation, the simultaneous EB and MW irradiation of the acrylamide-acrylic acid aqueous solution leads to the highest molecular weight values simultaneously with the smallest Huggins' constant values. Also, the absorbed dose is reduced from 0.8 kGy in the separate EB irradiation case to 0.4 kGy in the simultaneous EB and MW irradiation applied to acrylamide-acrylic acid co-polymerization. Significant higher vulcanization degrees are obtained only for higher EB irradiation doses, especially in terms of the values of the 300% modulus and tensile strength. By using simultaneous EB and MW irradiation, compared to separate EB irradiation, the same maximum value of 300% modulus is obtained for EB absorbed dose and irradiation time of 2.5 times lower at 60-W MW power and five times lower at 100-W MW power. Also, the same maximum value of tensile strength is obtained for EB absorbed dose and irradiation time of four times lower at 60-W MW power and 5.33 times lower at 100-W MW power. The combined EB and MW irradiation applied to the SO2 and NOx removal from the simulated flue gases demonstrated that for the same removal efficiency of 98% for SO2 and 76% for NOx at separate EB irradiation of 40 kGy, the required absorbed dose is about two times smaller for simultaneous EB and MW irradiation. [ABSTRACT FROM AUTHOR]

Preventing and controlling the spread of multidrug-resistant (MDR) bacteria implicated in healthcare-associated infections is the greatest challenge of the health systems. In recent decades, research has shown the need for passive antibacterial protection of surfaces in order to reduce the microbial load and microbial biofilm development, frequently associated with transmission of infections. The aim of the present study is to analyze the efficiency of photocatalytic antimicrobial protection methods of surfaces using the new photocatalytic paint activated by light in the visible spectrum. The new composition is characterized by a wide range of analytical methods, such as UV-VIS spectroscopy, electron microscopy (SEM), X-ray powder diffraction (PXRD) or X-ray photoelectron spectroscopy (XPS). The photocatalytic activity in the UV-A was compared with the one in the visible light spectrum using an internal method developed on the basis of DIN 52980: 2008-10 standard and ISO 10678—2010 standard. Migration of metal ions in the composition was tested based on SR EN1186-3: 2003 standard. The new photocatalytic antimicrobial method uses a type of photocatalytic paint that is active in the visible spectral range and generates reactive oxygen species with inhibitory effect against all tested microbial strains. [ABSTRACT FROM AUTHOR]