Localized enzymolysis and sonochemically modified sunflower protein: Physical,functional and structure attributes

Impacts of localized enzymolysis and sonication on physical, techno-functional, and structure attributes of sunflower meal protein (SMP) and its hydrolysate (SMPH) were studied. SMP was subjected to enzymolysis (using alcalase) to prepare SMPH with various degrees of hydrolysis (6–24% DH). Enzymolysis decreased colour lightness, turbidity, and particle size of unsonicated and sonicated SMP, while it increased the absolute values of zeta potential (P < 0.05). Sonication improved oil absorption capacity and dispersibility over unsonicated samples. Contrarily, sonicated preparations showed a decrease in water holding capacity. Intrinsic fluorescence and FTIR spectral analyses suggested that SMPH had more movable/flexible secondary structures than SMP. Moreover, the changes in sulfhydryl clusters and disulfide linkages following sonication demonstrated limited unfolding of SMP and SMPH structure and decrease in intermolecular interactions. SDS-PAGE profile exhibited significant reduction in molecular weight (MW) of sonicated SMP, whereas did not display differences between unsonicated and sonicated SMPH. From further MW analysis, SMPH was categorized with high proportion of small-sized peptides ≤ 3 kDa fractions, which increased from 78.64 to 93.01% (control) and from 82.3 to 93.88% (sonication) with enzymolysis (6–24DH). Localized enzymolysis and sonication can be utilised to modify the physical and conformational attributes of SMP and SMPH, which could enhance their functionalities and broaden the utilisation area in food industry.     

Ultrasound pre-fractured casein and in-situ formation of high internal phase emulsions

Traditional preparation of protein particles is usually complex and tedious, which is a major issue in the development of Pickering high internal phase emulsions (HIPEs). In this study, a facile and in-situ method for the preparation of food-grade Pickering HIPEs was developed using ultrasound pre-fractured casein flocs. The ultrasonic-treated casein protein and resulting Pickering HIPEs were characterised using particle size distribution, confocal laser scanning microscopy (CLSM), cryo-SEM, and rheological measurement. The results indicated that pH values of casein and ultrasonic power level were key parameters for casein protein dispersion into nanoparticles to form o/w Pickering HIPEs. In optimal conditions, the hexagons of emulsion droplets were close together, and the emulsions formed with ultrasonic caseins exhibited gel-like behaviour. Additionally, ultrasonic microscale-sized caseins (about 25 μm) disappeared upon the use of high speed homogenisation during the formation of HIPEs, while the chemical distribution revealed by confocal laser scanning microscopy indicated that the dispersive nanoparticles from casein proteins were evidently absorbed on the interface of HIPEs (cryo-SEM). These findings prove that ultrasound is an effective tool to loosen casein flocs to induce the in-situ formation of stabilised Pickering HIPEs. Overall, this work provides a green and facile route to convert edible oil into a soft solid, which has great potential for applications in biomedical materials, 3D printing technology, and various cosmetics.     

Ultrasonication-promoted synthesis of Ni/mayenite for catalytic reforming of biomass tar

Ultrasound-assisted approach was successfully applied for the synthesis of mayenite from calcium and aluminum hydroxides and then subsequently impregnated with Ni by the wet impregnation method. The synthesis was performed with a 13 mm probe-type ultrasound, operating under an acoustic power of 30.5 W and a frequency of 20 kHz. Ultrasound application was studied in detail from a 3^k experimental design, where the variables studied were ultrasound time (10–50 min) and calcination temperature (900–1200 °C). Ultrasound promoted an effective dispersion of the precursors in a short time of 10 min leading to a high conversion to mayenite after calcination at 1200 °C. Ultrasound treatment also had a positive effect on Ni impregnation, increasing the dispersion of the metal in the support and leading to a stronger interaction of nickel-containing species with mayenite support. The use of ultrasound application has proved to be attractive both for catalyst properties and for facilitating catalyst synthesis.     

Inactivation of foodborne pathogens based on synergistic effects of ultrasound and natural compounds during fresh produce washing

Ultrasound has potential to be used for disinfection, and its antimicrobial effectiveness can be enhanced in presence of natural compounds. In this study, we compared the antimicrobial effects of ultrasound at 20 kHz (US 20 kHz) or 1 MHz (US 1 MHz) in combination with carvacrol, citral, cinnamic acid, geraniol, gallic acid, lactic acid, or limonene against E. coli K12 and Listeria innocua at a constant power density in water. Compared to the cumulative effect of the individual treatments, the combined treatment of US 1 MHz and 10 mM citral generated >1.5 log CFU/mL additional inactivation of E. coli K12. Similarly, combined treatments of US 1 MHz and 2 mM carvacrol (30 min), US 20 kHz and 2 mM carvacrol, 10 mM citral, or 5 mM geraniol (15 min) generated >0.5–2.0 log CFU/mL additional inactivation in L. innocua. The synergistic effect of citral, as a presentative compound, and US 20 kHz treatment was determined to be a result of enhanced dispersion of insoluble citral droplets in combination with physical impact on bacterial membrane structures, whereas the inactivation by US 1 MHz was likely due to generation of oxidative stress within the bacteria. Combined ultrasound and citral treatments improved the bacterial inactivation in simulated wash water in presence of organic matter or during washing of inoculated blueberries but only additive antimicrobial effects were observed. Findings in this study will be useful to enhance fresh produce safety and shelf-life and design other alternative ultrasound based sanitation processes.     

Modeling the drying of ultrasound and glucose pretreated sweet potatoes: The impact on phytochemical and functional groups

The influence of ultrasonic frequency (20 kHz) and glucose pretreatments either alone or in combination on the drying of sweet potato slices (3 mm) using a hot-air dryer at 60 °C was tested to study the kinetics modeling, phytochemicals, antioxidant activities, and functional and textural changes of the final dried product. The results indicated that total phenolic content and total flavonoid content were significantly higher in glucose-pretreated samples while antioxidant activities were higher in ultrasound- and glucose-pretreated samples. For vitamin C, much degradation occurred in the glucose-pretreated samples when compared with the other pretreated samples apart from the control. Enzymatic browning made a minor contribution to the ultrasound/glucose-pretreated samples, while no significant differences were noted in the glucose-pretreated samples. A modified Henderson and Pabis (MHP) model, followed by the two-term and Hii models, fitted best among the 15 selected mathematical models. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the presence of glucose, phenols, and flavonols in all samples. Microstructural analysis confirmed the hardness (N) in the final glucose-pretreated samples due to glucose layers and less cell damage.     

One injection for one-week controlled release: In vitro and in vivo assessment of ultrasound-triggered drug release from injectable thermoresponsive biocompatible hydrogels

Episodic release of bioactive compounds is often necessary for appropriate biological effects under specific physiological conditions. Here, we aimed to develop an injectable, biocompatible, and thermosensitive hydrogel system for ultrasound (US)-triggered drug release. An mPEG-PLGA-BOX block copolymer hydrogel was synthesized. The viscosity of 15 wt% hydrogel is 0.03 Pa*s at 25 °C (liquid form) and 34.37 Pa*s at 37 °C (gel form). Baseline and US-responsive in vitro release profile of a small molecule (doxorubicin) and that of a large molecule (FITC-dextran), from the hydrogel, was tested. A constant baseline release was observed in vitro for 7 d. When triggered by US (1 MHz, continuous, 0.4 W/cm²), the release rate increased by approximately 70 times. Without US, the release rate returned to baseline. Baseline and US-responsive in vivo release profile of doxorubicin was tested by subcutaneous injection in the back of mice and rats. Following injection into the subcutaneous layer, in vivo results also suggested that the hydrogels remained in situ and provided a steady release for at least 7 d; in the presence of the US-trigger, in vivo release from the hydrogel increased by approximately 10 times. Therefore, the mPEG-PLGA-BOX block copolymer hydrogel may serve as an injectable, biocompatible, and thermosensitive hydrogel system that is applicable for US-triggered drug release.     

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.     

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.     

Investigation of acoustic and geometric effects on the sonoreactor performance

In this work, three design configurations of a sonoreactor are considered under various operating conditions, and the acoustic characteristics during water sonication are investigated while using an immersed-type ultrasonic flat transducer probe in a sonoreactor model. Numerical models are also developed to simulate the sonication process, and they are successfully validated and compared with available data in the literature. Several sets of numerical investigations are conducted using the finite-element method and solved by the computational acoustics module in the COMSOL Multiphysics. The effects of the acoustical and geometrical parameters are investigated, analyzed, and reported, including the ultrasonic frequency, acoustic intensity, and scaling-up the reactor. The present study includes a parametric investigation examining the change of the ultrasonic frequency, intensity, and probe immersion depth on the performance. The results of the parametric study show that the highest cavitation energy corresponds to the maximum magnitude of negative pressure that takes place in the range of 60–80 kHz. The cavitation energy analyses are conducted under the conditions of 20 kHz of frequency and at 36 W input power. It is found that the cavitation energy of 15.87 W could produce 2.98 × 10⁻¹⁰ mol/J of sonochemical efficiency. In addition, the effect of altering the transducer probe depth changes the acoustic pressure field insignificantly. Furthermore, a recommendation is made to improve the sonochemical efficiency by introducing more considerable ultrasound input power while operating the sonoreactor at an ultrasonic frequency lower than 60 kHz. The results presented in this paper provide a comprehensive assessment of different sonoreactors and the feasibility of scaling-up their production rate.     

Ultrasound-assisted regeneration of zeolite/water adsorption pair

The use of ultrasound to enhance the regeneration of zeolite 13X for efficient utilization of thermal energy was investigated as a substitute to conventional heating methods. The effects of ultrasonic power and frequency on the desorption of water from zeolite 13X were analyzed to optimize the desorption efficiency. To determine and justify the effectiveness of incorporating ultrasound from an energy-savings point of view, an approach of constant overall input power of 20 or 25 W was adopted. To measure the extent of the effectiveness of using ultrasound, the ultrasonic-power-to-total power ratios of 0.2, 0.25, 0.4 and 0.5 were investigated and the results compared with those of no-ultrasound (heat only) at the same total power. To analyze the effect of ultrasonic frequency, identical experiments were performed at three nominal ultrasonic frequencies of ~28, 40 and 80 kHz. The experimental results showed that using ultrasound enhances the regeneration of zeolite 13X at all the aforementioned power ratios and frequencies without increasing the total input power. With regard to energy consumption, the highest energy-savings power ratio (0.25) resulted in a 24% reduction in required input energy and with an increase in ultrasonic power, i.e. an increase in acoustic-to-total power ratio, the effectiveness of applying ultrasound decreased drastically. At a power ratio of 0.2, the time required for regeneration was reduced by 23.8% compared to the heat-only process under the same experimental conditions. In terms of ultrasonic frequency, lower frequencies resulted in higher efficiency and energy savings, and it was concluded that the effect of ultrasonic radiation becomes more significant at lower ultrasonic frequencies. The observed inverse proportionality between the frequency and ultrasound-assisted desorption enhancement suggests that acoustic dissipation is not a significant mechanism to enhance mass transfer, but rather other mechanisms must be considered.