Low-intensity Ultrasonication Research Articles

Mechanically Triggered Protein Desulfurization.

The technology of native chemical ligation and postligation desulfurization has greatly expanded the scope of modern chemical protein synthesis. Here, we report that ultrasonic energy can trigger robust and clean protein desulfurization, and we developed an ultrasound-induced desulfurization (USID) strategy that is simple to use and generally applicable to peptides and proteins. The USID strategy involves a simple ultrasonic cleaning bath and an easy-to-use and easy-to-remove sonosensitizer, titanium dioxide. It features mild and convenient reaction conditions and excellent functional group compatibility, e.g., with thiazolidine (Thz) and serotonin, which are sensitive to other desulfurization strategies. The USID strategy is robust: without reoptimizing the reaction conditions, the same USID procedure can be used for the clean desulfurization of a broad range of proteins with one or more sulfhydryl groups, even in multi-hundred-milligram scale reactions. The utility of USID was demonstrated by the one-pot synthesis of bioactive cyclopeptides such as Cycloleonuripeptide E and Segetalin F, as well as convergent chemical synthesis of functionally important proteins such as histone H3.5 using Thz as a temporary protecting group. A mechanistic investigation indicated that USID proceeds via a radical-based mechanism promoted by low-frequency and low-intensity ultrasonication. Overall, our work introduces a mechanically triggered approach with the potential to become a robust desulfurization method for general use in chemical protein synthesis by both academic and industrial laboratories.

Enhancing enzyme activity via low-intensity ultrasound for protein extraction from excess sludge.

Rich protein within excess sludge could be recovered to prepare high value-added products such as liquid fertilizer and foaming agents. Low-intensity ultrasonication was adopted to help extract sludge protein by improving enzyme activity. Alkaline protease was added to the sludge for ultrasonic irradiation, and the maximum enzyme activity at 3500kJ/kg TS was approximately 21% higher than that without ultrasonication. The protein extraction effect, specific resistance of sludge (SRS) and economics of low-intensity ultrasound-assisted enzymatic hydrolysis (LUEH) were compared with those of single enzymatic hydrolysis (EH) and HUEH under optimal conditions. The protein extraction rates of HUEH and LUEH were both higher than that of EH. Although the protein extraction rate of LUEH was 13.6% lower than that of HUEH, the amino acid content was similar because the low-intensity ultrasonic radiation promoted the enzyme activity and thereby enhanced the protein hydrolysis capacity. After hydrolysis, the SRS of LUEH was lower than that of HUEH, indicating that LUEH possessed a better dewatering performance, which was beneficial to the subsequent separation of the protein solution. The amount consumed by LUEH was approximately 20% lower than that consumed by HUEH and 17.3% lower than that consumed by EH. In addition, the enzyme dosage was reduced by approximately 38.5% with LUEH. Therefore, the total cost of LUEH was less than that of EH and HUEH, indicating that LUEH is more economically feasible for the extraction of protein from excess sludge.

Recovery of Iron-Dependent Autotrophic Denitrification Activity from Cell-Iron Mineral Aggregation-Induced Reversible Inhibition by Low-Intensity Ultrasonication.

Iron-dependent autotrophic denitrification (IDAD) has garnered increasing interests as an efficient method for removing nitrogen from wastewater with a low carbon to nitrogen ratio. However, an inevitable deterioration of IDAD performance casts a shadow over its further development. In this work, the hidden cause for such a deterioration is uncovered, and a viable solution to this problem is provided. Batch test results reveal that the aggregation of microbial cells and iron-bearing minerals induced a cumulative and reversible inhibition on the activity of IDAD sludge. Extracellular polymeric substances were found to play a glue-like role in the cell-iron mineral aggregates, where microbial cells were caged, and their metabolisms were suppressed. Adopting low-intensity ultrasound treatment efficiently restored the IDAD activity by disintegrating such aggregates rather than stimulating the microbial metabolism. Moreover, the ultrasonication-assisted IDAD bioreactor exhibited an advantageous nitrogen removal efficiency (with a maximum enhancement of 72.3%) and operational stability compared to the control one, demonstrating a feasible strategy to achieve long-term stability of the IDAD process. Overall, this work provides a better understanding about the mechanism for the performance deterioration and a simple approach to maintain the stability of IDAD.

Graphene Suspension from Modified Electrochemical Exfoliation of Graphite

Graphene has emerged as one of the most exciting materials since its discovery in 2004. Graphene is a term used for one to ten layers of sp2 hybridized carbon atoms arranged in a hexagonal pattern. Monolayer graphene is the building block of all graphitic structures and has high electron mobility, high thermal conductivity, high specific surface area, extremely high resistance to gas permeation and high optical transmittance. These exceptional properties make monolayer graphene attractive for potential applications as a catalyst or catalyst support in direct methanol fuel cells (DMFC), proton exchange membrane fuel cells (PEMFC), electrode in lithium-ion batteries, supercapacitors, as well as in thermally and electrically conductive sensors. AB-stacked bilayer and trilayer graphene have applications in the electronic industry, such as fabrication of field-effect transistors (FEts) and light detectors, due to an induced bandgap in the presence of an applied electric field. In addition, graphene finds major applications in the optoelectronic industry, such as electrode materials in solar cells, supercapacitors and transparent LCDs.Graphene is traditionally synthesized using the simple mechanical exfoliation of graphite, which is not scalable, or from chemical vapour deposition of a carbon source on a suitable substrate, which is both a complex and an expensive method. Hence, a scalable and economic graphene synthesis method is needed to harness the remarkable properties of graphene. The electrochemical exfoliation of graphite provides a promising route for the bulk production of graphene because it provides graphene flakes with the largest size and a smaller defect density than the well-known chemical synthesis methods such as Hummer or modified Hummer processes. The large size flakes resulting from electrochemical exfoliation are suitable for scalable electronic device fabrication methods. Electrochemical exfoliation proceeds via intercalation of the ions present in the electrolyte and is followed by the subsequent expansion and later exfoliation of graphite. However, this strategy produces graphene with a scatter in the layer numbers. A polydisperse suspension of graphene is undesirable because the electronic properties of graphene change with the number of layers. The intermediate graphite intercalation compounds are formed by the insertion of intercalants between the layers of the graphite host material. The intercalants can be atoms, ions or molecules. Graphite intercalation occurs in stages where the stage number indicates the number of graphene layers between the two nearest intercalant layers. In the present study, a modified electrochemical exfoliation route of graphite is explored, which proceeds through the exfoliation of a stage pure graphite intercalation compound followed by low-intensity ultrasonication. The modified electrochemical exfoliation of graphite is capable of providing a monodisperse graphene suspension

Elevated cellular PpIX potentiates sonodynamic therapy in a mouse glioma stem cell-bearing glioma model by downregulating the Akt/NF-\u03baB/MDR1 pathway

Glioblastoma (GBM) has high mortality rates because of extreme therapeutic resistance. During surgical resection for GBM, 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence is conventionally applied to distinguish GBM. However, surgical intervention is insufficient for high invasive GBM. Sonodynamic therapy (SDT) combined with low-intensity ultrasonication (US) and PpIX, as a sonosensitizer, is an emerging and promising approach, although its efficacy is limited. Based on our previous study that down-regulation of multidrug resistant protein (MDR1) in GBM augmented the anti-tumor effects of chemotherapy, we hypothesized that elevation of cellular PpIX levels by down-regulation of MDR1 enhances anti-tumor effects by SDT. In high invasive progeny cells from mouse glioma stem cells (GSCs) and a GSC-bearing mouse glioma model, we assessed the anti-tumor effects of SDT with a COX-2 inhibitor, celecoxib. Down-regulation of MDR1 by celecoxib increased cellular PpIX levels, as well as valspodar, an MDR1 inhibitor, and augmented anti-tumor effects of SDT. MDR1 down-regulation via the Akt/NF-κB pathway by celecoxib was confirmed, using an NF-κB inhibitor, CAPÉ. Thus, elevation of cellar PpIX by down-regulation of MDR1 via the Akt/NF-κB pathway may be crucial to potentiate the efficacy of SDT in a site-directed manner and provide a promising new therapeutic strategy for GBM.

Application of ultrasonication at different microbial growth stages during apple juice fermentation by Lactobacillus plantarum: Investigation on the metabolic response

In this work, low-intensity ultrasonication (58.3 and 93.6 W/L) was performed at lag, logarithmic and stationary growth phases of Lactobacillus plantarum in apple juice fermentation, separately. Microbial responses to sonication, including microbial growth, profiles of organic acids profile, amino acids, phenolics, and antioxidant capacity, were examined. The results revealed that obvious responses were made by Lactobacillus plantarum to ultrasonication at lag and logarithmic phases, whereas sonication at stationary phase had a negligible impact. Sonication at lag and logarithmic phases promoted microbial growth and intensified biotransformation of malic acid to lactic acid. For example, after sonication at lag phase for 0.5 h, microbial count and lactic acid content in the ultrasound-treated samples at 58.3 W/L reached 7.91 ± 0.01 Log CFU/mL and 133.70 ± 7.39 mg/L, which were significantly higher than that in the non-sonicated samples. However, the ultrasonic effect on microbial growth and metabolism of organic acids attenuated with fermentation. Moreover, ultrasonication at lag and logarithmic phases had complex influences on the metabolism of apple phenolics such as chlorogenic acid, caffeic acid, procyanidin B2, catechin and gallic acid. Ultrasound could positively affect the hydrolysis of chlorogenic acid to caffeic acid, the transformation of procyanidin B2 and decarboxylation of gallic acid. The metabolism of organic acids and free amino acids in the sonicated samples was statistically correlated with phenolic metabolism, implying that ultrasound may benefit phenolic derivation by improving the microbial metabolism of organic acids and amino acids.

Bio-stimulation of anaerobic digestion by low intensity ultrasonication.

Low intensity ultrasonication (US) was applied to stimulate the biological activities in anaerobic digestion (AD) process. The enhancement in methane production was used to investigate the sono-biostimulation effects on the process performance. The 32% higher CH4 production was observed over control at best US intensity and irradiation time of 0.0028 W/mL and 120 s, respectively. The sono-biostimulation effects in terms of higher CH4 generation over control lasted for 45 h. The increase in the concentration of NH4 +-N and K+ considered the indication of cell lysis under applied US conditions. At best US intensity and irradiation time, the NH4 +-N and K+ fraction in the medium remained similar as of control, which indicated that no cell lysis occurred. The preliminary findings of the study showed that low intensity US can be a promising solution to enhance the process efficiency in terms of higher methane production with minimal energy requirement.

Preparation and characterization of individual chitin nanofibers with high stability from chitin gels by low-intensity ultrasonication for antibacterial finishing

Individual chitin nanofibers with high stability were feasibly prepared from chitin gel via low-intensity ultrasonication. The morphology of the treated gel could be controlled from nanoparticles to nanofibers by simply adjusting the ultrasonic time. The nanofibers had a nanoscaled width and an average length of 650 nm. Compared with original chitin gel, the chemical structure, α-chitin crystalline structure and thermo stability of chitin nanofibers were well maintained after the treatment. TGA results proved that nanofibers were obtained by hydrogen bonding structure’s reorganization of chitin gel which was driven by ultrasonication. These nanofibers had high suspension stability and were used as finishing agent for cotton fabric. The SEM result showed that chitin nanofibers had good compatibility to cotton fabrics. The finished cotton fabric had a low color difference of 4.88 to raw cotton fabric and an antibacterial activity with 99% bacterial reductions. Our results indicate that this cost-effective and eco-friendly product holds immense potential value in textile industry for antibacterial finishing application.

Exploring the use of Low-intensity Ultrasonics as a Tool for Assessing the Salt Content in Pork Meat Products

Meat industry demands non-destructive techniques for the control of the salting process to achieve a homogeneous final salt content in salted meat products. The feasibility of using low-intensity ultrasound for characterizing the salting process of pork meat products was evaluated. The ultrasonic velocity (V) and time of flight (TF) were measured by through-transmission and pulse-echo methods, respectively, in salted meat products. Salting involved an increase of the V in meat muscles and a decrease of the time of flight in whole hams. Measuring the V before and after salting, the salt content could be estimated. Moreover, online monitoring of the salting process by computing the TF could be considered a reliable tool for quality control purposes.

Extraction and Characterization of Cellulose Nanofibers from Phyllostachys nidularia Munro via a Combination of Acid Treatment and Ultrasonication

In this work, α-cellulose was extracted from Phyllostachys nidularia Munro using an acidified sodium chlorite treatment followed by alkali treatments, and cellulose nanofibers (CNFs) were then extracted from α-cellulose via the combination of sulfuric acid (64 wt%) and low-intensity ultrasonication. The results showed that superior CNFs were successfully extracted and their diameters were in the range of 5 to 20 nm. Fourier transform infrared spectroscopy (FTIR) suggested that a majority of the hemicellulose and lignin were removed from the original material and that the chemical constituents of α-cellulose and CNFs were similar. X-ray diffraction (XRD) analysis indicated that the relative crystallinity of CNFs was significantly increased to approximately 69.32% and all specimens presented a typical cellulose I crystal form. Thermogravimetric analysis (TGA) showed that the thermostability of the CNFs was greatly increased.

Removal of biofilms by intermittent low-intensity ultrasonication triggered bursting of microbubbles

In this study, a chemical-free cleaning method for biofilms removal is presented, which is based on intermittent low-intensity ultrasonication (US) triggered bursting of microbubbles (MB) in such a sequence that MB were continuously introduced into the reaction vessel for 15 min, while US was activated for 2 s after every 2 min of microbubbling. It was found that the fixed biomass, and the extracellular proteins and polysaccharides of 24-h old biofilms grown on a nylon membrane surface were reduced, respectively, by 75, 79 and 72% after treatment by the US + MB method. Fourier transform infrared (FTIR) analysis further revealed that the chemical composition of the biofilms was not altered by the US + MB treatment, suggesting that biofilms were removed through physical forces due to the generation of a shock wave and a high-speed water jet through US-triggered bursting of the MB. The proposed method can be considered a chemical-free technology for biofilm removal.

Sono-biostimulation of aerobic digestion: a novel approach for sludge minimization

BACKGROUND For the first time, low intensity ultrasonication was applied to stimulate biological activities during aerobic digestion of municipal waste activated sludge (AS). Specific oxygen uptake rate (SOUR) analysis was performed to investigate the sono-biostimulation effects on AS activity. RESULTS The greatest improvement of 60% in SOUR was observed at sonication density and irradiation time of 0.2 W mL-1 and 60 s, respectively. A subsequent batch aerobic digestion study showed 74% reduction in total chemical oxygen demand (TCOD) and volatile suspended solids (VSS) after 12 days of aerobic digestion, with 127% and 112% improvement in TCOD and VSS removal, respectively, in comparison with the control reactor. The sono-biostimulation effects on AS lasted 6 h and completely disappeared within 8 h after sonication stopped. CONCLUSIONS The sonication density, irradiation time and volume and frequency of sludge sonication were observed to play important roles in bio-stimulation and the subsequent aerobic digestion process. Intermittent sonication protocol for 60 s every 8 h was the best treatment condition to improve aerobic digestion efficiency. © 2013 Society of Chemical Industry

Ultrasonication-Induced Formation of Silver Nanofibers in Reverse Micelles and Small-Angle X-ray Scattering Studies

The Ag nanorods and nanofibers have been synthesized in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles with the aid of low-intensity ultrasonication. The TEM results show that only spherical silver nanoparticles can be obtained from the reverse micelles in the absence of ultrasonication whereas needle-shaped and wire-shaped silver particles are obtained as ultrasonication is applied. The possibility of ultrasonication to induce the aggregation of nanoparticles dispersed in reverse micelles is also confirmed by UV spectra. Small-angle X-ray scattering (SAXS) is used to obtain information on the microstructure change of the reverse micelles by ultrasonication. It is revealed that by ultrasonication the micelles change from a spherical to an ellipsoidal structure, of which the size can be tuned by the ultrasonication time.

Application of low intensity ultrasonics to cheese manufacturing processes

Ultrasound has been used to non-destructively assess the quality of many foods such as meat, fish, vegetables and dairy products. This paper addresses the applications of low intensity ultrasonics in the cheese manufacturing processes and highlights the areas where ultrasonics could be successfully implemented in the future. The decrease of ultrasonic attenuation during the renneting process can be used to determine the optimum cut time for cheese making. The ultrasonic velocity increases during maturation for those types of cheese that become harder during this manufacturing stage, thus being an indicator of the maturity degree. Moreover, ultrasonic measurements could be linked to sensory parameters. From the ultrasonic velocity measurements at two different temperatures, it is possible to assess cheese composition, thus allowing an improvement in the quality and uniformity of cheese commercialization. In addition, in pulse-echo mode it is possible to detect cracked pieces due to abnormal fermentations and also to assess the distance of the crack from the surface.

Cheese Maturity Assessment Using Ultrasonics

The relationship between Mahon cheese maturity and ultrasonic velocity was examined. Moisture and textural properties were used as maturity indicators. The ultrasonic velocity of the cheese varied between 1630 and 1740 m/s, increasing with the curing time mainly because of loss of water, which also produced an increase of the textural properties. Because of the nature of low-intensity ultrasonics, velocity was better related to those textural parameters that involved small displacements. Ultrasonic velocity decreased with increasing temperature because of the negative temperature coefficient of the ultrasonic velocity of fat and the melting of fat. These results highlight the potential use of ultrasonic velocity measurements to rapidly and nondestructively assess cheese maturity.

Review: Low intensity ultrasonics in food technology / Revisión: Ultrasonidos de baja intensidad en tecnología de alimentos

Ultrasonic applications can be classified into low intensity or high intensity applications. The latter are used to modify a process or product with ultrasonics, while in low intensity applications the process or product modifies the ultrasonic signal, thus providing information about the product. Low inten sity ultrasonics in food technology can be used to monitor a process (liquid level, flowmeters) or to determine the quality of food products. Since ultrasonic techniques are rapid, non-destructive, easy to automate and relatively inexpensive, the number of applications is rapidly growing in this field. Ultrasonics can also be considered for use in laboratory testing devices to determine physical and chemical properties of foods. Ultrasonics has been used to determine texture, composition and physical state in liquid and solid foods. The commonly measured ultrasonic parameters are velocity, attenua tion and frequency spectrum composition. Velocity is the parameter used most since it is the simplest and most reliable measurement. This paper reviews the basic principles of ultrasonics, the most suit able techniques for each type of application, the testing devices needed to make measurements and the most interesting applications.