Synergistic antibacterial effects of ultrasound and thyme essential oils nanoemulsion against Escherichia coli O157:H7

Essential oil nanoemulsions have been proven to have stronger antimicrobial effects compared to the essential oil alone or coarse emulsion. Sonoporation could be the promising candidate to trigger a synergistic effect with thyme essential oil nanoemulsion (TEON) and produce a more effective antibacterial efficacy. Therefore, in this study, the bactericidal effects of ultrasound (US) in combination with TEON treatments against Escherichia coli (E. coli) O157:H7 were investigated. The remarkable synergistic effects of US (20 kHz, 255 W/cm², 9 min) and TEON (0.375 mg/mL) treatments at 22 °C reduced E. coli O157:H7 populations by 7.42 ± 0.27 log CFU/mL.The morphological changes of cells exposed to different treatments were observed by scanning electron microscopy and transmission electron microscopy. The results showed that the synergistic effects of the ultrasound and TEON treatments altered the morphology and interior microstructure of organism cells. Laser scanning confocal microscopy (LSCM) images revealed that the combination treatments of ultrasound and TEON altered the permeability of cell membranes, and this affected the integrity of E. coli O157:H7 cells. This was further indicated by the high amounts of nucleic acids and proteins released from these cells following treatment.The results from this study illustrated the mechanisms of the synergistic effects of sonoporation and TEON treatments and provided valuable information for their potential in food pasteurization.     

Intensified dissolution of uranium from graphite substrate using ultrasound

Decontamination of graphite structural elements and recovery of uranium is crucial for waste minimization and recycle of nuclear fuel elements. Feasibility of intensified dissolution of uranium-impregnated graphite substrate using ultrasound has been studied with objective of establishing the effect of operating parameters and the kinetics of sonocatalytic dissolution of uranium in nitric acid. The effect of operating frequency and acoustic intensity as well as the acid concentration and temperature on the dissolution of metal has been elucidated. It was observed that at lower acid concentrations (6 M–8 M), the dissolution ratio increases by 15% on increasing the bath temperature from 45 to 70 °C. At higher acid concentration (>10 M), the increase was only around 5–7% for a similar change in temperature. With 12 M HNO₃, pitting was also observed on the graphite surface along with erosion due to high local reaction rates in the presence of ultrasound. For higher frequency of applied ultrasound, lower dissolution rate of uranium was observed though it also leads to high rates of erosion of the substrate. It was thus established that suitable optimization of frequency is required based on the nature of the substrate and the choice of recycling it. The dissolution rate was also demonstrated to increase with acoustic intensity till it reaches to the maximum at the observed optimum (1.2 W/cm² at 33 kHz). Comparison with silent conditions revealed that enhanced rate was obtained due to the use of ultrasound under optimum conditions. The work has demonstrated the effective application of ultrasound for intensifying the extent of dissolution of metal.     

Sonochemical approach for synthesis of zinc oxide-poly methyl methacrylate hybrid nanoparticles and its application in corrosion inhibition

Hybrid nanoparticles (HNPs) with zinc oxide and polymethyl metha acrylate (inorganic/ polymer) were synthesized through the exploitation of ultrasound approach. The synthesized HNPs were further characterized employing transmission electron microscopy and x-ray diffraction. ZnO-PMMA based HNPs exhibit excellent protection properties to mild steel from corrosion when gets exposed to acidic condition. Electrochemical impendence spectroscopy (EIS) analysis was accomplished to evaluate the corrosion inhibition performance of MS panel coated with 2 wt% or 4 wt% of HNPs and its comparison with bare panel and that of loaded with only standard epoxy coating., Tafel plot and Nyquist plot analysis depicted that the corrosion current density (I_corr) decreases from 16.7 A/m² for bare material to 0.103 A/m² for 4% coating of HNPs. Applied potential (E_corr) values shifted from negative to positive side. These results were further supported by qualitative analysis. The images taken over a period of time indicated the increase in lifetime of MS panel from 2 to 3 days for bare panel to 10 days for HNPs coated panel, showing that ZnO-PMMA HNPs have potential application in metal protection from corrosion by forming a passive layer.     

A facile and eco-friendly approach for preparation of microkeratin and nanokeratin by ultrasound-assisted enzymatic hydrolysis

Protein is one of the most abundant natural polymeric materials, but only a few studies on nanoproteins have been conducted. In this paper, a novel approach based on ultrasound-assisted enzymatic hydrolysis was employed for the preparation of microkeratin and nanokeratin from wool. The hydrolysis system included a solution containing enzyme (esperase) and reductant (L-cysteine) and treated ultrasonically to remove the scales and amorphous regions within wool. Results showed that the reaction was most effective at 50 °C and pH 7, when incubated for 3 h, followed by sonication for 6 h. The products included spindle-shaped microkeratin (4–7 μm in diameter and 70–120 μm in length) and cone-shaped nanokeratin (50–300 nm in diameter and less than 15 μm in length). Under ultrasonic-assisted conditions, the yields of microkeratin and nanokeratin increased significantly, while the treatment time decreased. Fourier transform infrared spectroscopy (FTIR) showed that the chemical structures of microkeratin and nanokeratin did not change, compared to that of wool. X-ray diffraction (XRD) analysis showed that the microkeratin was mainly composed of α-helical structure, while the β-sheet structure was more prevalent in nanokeratin. The presented method is facile and eco-friendly, thereby paving new pathways for the preparation of microkeratin and nanokeratin.     

Fabrication of high-performance nickel/graphene oxide composite coatings using ultrasonic-assisted electrodeposition

Ultrasonic-assisted electrodeposition was used to fabricate the nickel/graphene oxide composite coatings with high hardness, low friction coefficient, and high wear resistance. In the present study, the effects of ultrasonic power and concentration of graphene oxide on the mechanical and tribological properties of the electrodeposited nickel/graphene oxide composite coatings were systematically studied. X-ray diffraction (XRD) analyses showed that the crystallite size of the nickel decreased with an increase of ultrasonic power (0–50 W, 40 KHz, square wave) and concentration of graphene oxide (0.1–0.4 g/L). Morphologies of the surface and cross-section of the composite coatings observed by Scanning Electron Microscopy (SEM) confirmed the existence of graphene oxide particles in the nickel matrix. The results from microhardness measurement demonstrated that the hardness was increased by 1.8 times using 50 W ultrasonic-assisted electrodeposition with the fixed concentration of graphene oxide (0.1 g/L), compared to the pure nickel coating. The hardness was increased by 4.4 times for the 0.4 g/L graphene oxide with the optimized ultrasonic power of 50 W in comparison to the pure nickel coating. Meanwhile, the friction coefficient decreased gradually with an increase in ultrasonic power and concentration of graphene oxide, respectively, where the effect of the concentration of graphene oxide played a more important role.     

Effects of multi-frequency ultrasound on freezing rates and quality attributes of potatoes

The effects of multi-frequency ultrasound assisted freezing on the freezing rate, microstructure, quality properties (drip loss, firmness, total calcium content, l-ascorbic acid content and total phenol content) of potatoes were studied. The results indicated that the freezing effects of multi-frequency ultrasound was better than those of single-frequency ultrasound. Multi-frequency ultrasound could significantly increase the freezing rate and preserve the quality of frozen samples better. With increase in the number of ultrasonic frequencies, the freezing effect was more obvious. In addition, scan electron microscopy (SEM) images showed that the ice crystals formed by the multi-frequency ultrasonic treatment were fine and uniformly distributed, which caused less damage to the frozen potato samples. From the analysis of the quality attributes, the nutritional values of the samples after multi-frequency ultrasonic treatment was higher, but attention should be paid to the negative influence of the hydroxyl radical generated by the multi-frequency ultrasound.     

Ultrasound irradiation effect on morphological and adsorptive properties of a nanoscale 3D Zn-coordination polymer and derived oxide

In this work, Zn-based coordination polymer [Zn₂(1,3-bdc)bzim₂]_n was successfully synthesized by the sonochemical method using a 13 mm probe-type ultrasound operating at 20 kHz and amplitudes of 30, 40 and 50% corresponding to an acoustic power of 5.5, 8.6, and 10.3 W, respectively. Additionally, a sample was prepared by the slow-diffusion method for comparison. The samples were characterized by FTIR, PXRD, SEM, and BET techniques. The influence of the time and sonication amplitude on the yield of the reaction, crystallite size, and morphology were also studied. It was found that the sonochemical method provided the desired product in 83.9% within 20 min of sonication using the highest level of sonication amplitude. Moreover, this approach resulted in regular, controlled morphology, smaller particles, and higher surface area of the Zn-sample and derived oxide, than the slow diffusion method. The samples prepared by different methodologies were tested for the adsorption of BTEX (benzene, toluene, ethylbenzene, and xylenes) components in six different systems, and the uptakes were quantified by ¹³C NMR spectroscopy. Both samples showed excellent adsorption of benzene, 119.8 mmol/g, and 88.1 mmol/g, for the coordination polymers prepared via the sonochemical and slow-diffusion methods, respectively, corresponding to 63.9%, and 46.9%. These results are in agreement with the non-polar surface of these samples.     

Ultrasound wave assisted removal of Ceftriaxone sodium in aqueous media with novel nano composite g-C3N4/MWCNT/Bi2WO6 based on CCD-RSM model

The aim of this study was ultrasound assisted removal of Ceftriaxone sodium (CS) based on CCD model. Using sonochemical synthesized Bi₂WO₆ implanted on graphitic carbon nitride/Multiwall carbon nanotube (g-C₃N₄/MWCNT/Bi₂WO₆). For this purpose g-C₃N₄/MWCNT/Bi₂WO₆ was synthesized and characterized using diverse approaches including XRD, FE-SEM, XPS, EDS, HRTEM, FT-IR. Then, the contribution of conventional variables including pH, CS concentration, adsorbent dosage and ultrasound contact time were studied by central composite design (CCD) under response surface methodology (RSM). ANOVA was employed to the variable factors, and the most desirable operational conditions mass provided. Drug adsorption yield of 98.85% obtained under these defined conditions. Through conducting five experiments, the proper prediction of the optimum point were examined. The respective results showed that RSD% was lower than 5% while the t-test confirmed the high quality of fitting. Langmuir isotherm equation fits the experimental data best and the removal followed pseudo-second order kinetics. The estimation of the experimentally obtained maximum adsorption capacities was 19.57 mg.g⁻ of g-C₃N₄/MWCNT/Bi₂WO₆ for CS. Boundary layer diffusion explained the mechanism of removal via intraparticle diffusion.     

Analysis in protein profile,antioxidant activity and structure-activity relationship based on ultrasound-assisted liquid-state fermentation of soybean meal with Bacillus subtilis

This study investigated effects of ultrasound on the contents of peptide and soluble protein, antioxidant activity, functionalities and structural characteristics of fermented soybean meal (FSBM) with Bacillus subtilis systematically. The results showed that there were significant effects of ultrasound treatments (frequency, treatment time and power density) on the contents of peptide and soluble protein (p < 0.05). Under the optimum ultrasound conditions (power density of 0.08 W/mL, frequency of 33 kHz and treatment time of 1 h) by single factor experiment, the contents of peptide and soluble protein increased by 31.27% and 18.79% compared to those of the control, respectively. Additionally, the in vitro antioxidant activity (•OH scavenging rate, Fe²⁺ chelating capacity and DPPH radical scavenging rate) and functional properties (emulsifying activity and emulsifying stability) of FSBM were found to be noticeably improved by ultrasound (p < 0.05). The fourier transform infrared (FTIR) spectroscopy revealed that ultrasound caused protein molecules to unfold with a decrease content of α-helix and β-turn and an increase in the proportion of β-sheet and random coil. Besides, atomic force microscope (AFM) results indicated that ultrasonication generally increased the surface roughness of protein and the protein sonicated with higher frequency (≥33 kHz) exhibited a greater height compared to lower frequency ultrasonication. Structure-activity relationship analysis illustrated that there was a good linear relationship between •OH scavenging rate and β-sheet/β-turn with Pearson’s correlation coefficient r of −0.86/0.90. Collectively, the selection of ultrasonic parameters is essential for the preparation of functional protein and bioactive peptide by enhancing fermentation of agroindustrial by-products.     

Sonoelectrochemical hydrogenation of safrole: A reactor design,statistical analysis and computational fluid dynamic approach

In this work, ultrasound-assisted electrocatalytic hydrogenation (US-ECHSA) of safrole was carried out in water medium, using sacrificial anode of nickel. The ultrasonic irradiation was carried out at frequency of 20 kHz ± 500 Hz with a titanium cylindrical horn (MS 73 microtip; Ti-6AI-4V alloy; 3.0 mm diameter). The optimal conditions were analyzed by statistical experimental design (fractional factorial). The influence of the sonoelectrochemical reactor design was also investigated by using computational fluid dynamics as simulation tool. Among the five parameters studied: catalyst type, use of β-cyclodextrin as inverse phase transfer catalyst, sonoelectrochemical reactor design, ultrasound mode and the temperature of the solution, only the last three were significant. The hydrogenation product, dihydrosafrole, reached 94% yield, depending on the experimental conditions applied. Data of computational fluid dynamics showed that a wing shape tube added to the sonoelectrochemical reactor can work as a cooling apparatus, during the electrochemical process. The reactional solution temperature diminishes 14 °C when compared to the four-way-type reactor. Cooper cathode, absence of β-cyclodextrin, four-way-type reactor, ultrasound continuous mode (14 W) and absence of temperature control were the most effective reaction parameters for the safrole hydrogenation using US-ECHSA method. The proposed approach represents an important contribution for understanding the hydrodynamic behavior of sonoelectrochemical reactors designs and, consequently, for the reducing of the experimental costs inherent to the sonoelectrochemical process.