Sonophotocatalytic inactivation of E. coli using ZnO nanofluids and its mechanism

The present study evaluated inactivation efficiency of a sonophotocatalytic process using ZnO nanofluids including ultrasonic parameters such as power density, frequency and time. The result showed that inactivation efficiency was increased by 20% when ultrasonic irradiation was combined with photocatalytic process in the presence of natural light. Comparison of inactivation efficiency in photocatalytic, ultrasonic and sonocatalytic processes using Escherichia coli as a model bacteria identified that inactivation efficiencies are shown in the following order: ultrasonic irradiation < sonocatalysis < photocatalysis < sonophotocatalysis. Furthermore, inactivation mechanism of sonophotocatalysis was proposed. Studies of reactive oxygen species (ROS) and zinc ions (Zn²⁺) release evaluation revealed that ROS play a key role in bacterial inactivation rather than Zn²⁺. Permeability of outer membrane (OM) and inner membrane (IM) of E. coli bacterial cells were studied and exhibited that sonophotocatalysis increased the permeability of OM and IM significantly. The enhanced bacterial inactivation effect in sonophotocatalytic process contributed to acoustic cavitation, sonocatalysis of ZnO and sonoporation phenomenon.     

Effects of multi-frequency ultrasound pretreatment under low power density on the enzymolysis and the structure characterization of defatted wheat germ protein

The effects of ultrasonic frequency mode, power density, pretreatment time and other parameters under low power density on the degree of hydrolysis (DH) of defatted wheat germ protein (DWGP) and angiotensin-I-converting enzyme (ACE) inhibitory activity of DWGP hydrolysate were studied in this research. Ultraviolet–visible (UV–Vis) spectra, free sulfhydryl (SH), disulfide bond (SS), surface hydrophobicity and hydrophobic protein content of ultrasound-pretreated protein and hydrophobic amino acid (HAA) content of alcalase-hydrolysate of DWGP were measured under optimized ultrasonic condition. The ultrasonic frequency mode with dual-fixed frequency combination of 28/40 kHz showed higher ACE inhibitory activity of DWGP hydrolysate compared with that of other ultrasound frequency modes and all the ultrasonic frequency combinations involving in 28 kHz showed higher ACE inhibitory activity. Under the dual-fixed frequency ultrasound mode of 28/40 kHz, ultrasonic power density of 60 W/L, pretreatment time of 70 min, temperature of 60°C and substrate concentration of 60 g/L, the ACE inhibitory activity of DWGP hydrolysate was the highest with its value of 74.75% (increased by 62.30% compared to control). However, all the ultrasonic pretreatment did not increase the DH of DWGP significantly (p > 0.05). The changes in UV–Vis spectra, SH and SS groups, surface hydrophobicity and hydrophobic protein content indicated that the structure of DWGP unfolded after ultrasound pretreatment. The HAA content of hydrolysate from the pretreated DWGP increased significantly (p < 0.05). The results proved that ultrasound pretreatment loosed the protein structure and exposed more HAA residues of protein to be attacked easily by alcalase. This resulted in the increase in the HAA content which related to the ACE inhibitory activity.     

Ultrasound assisted dispersal of a copper nanopowder for electroless copper activation

This paper describes the ultrasound assisted dispersal of a low wt./vol.% copper nanopowder mixture and determines the optimum conditions for de-agglomeration. A commercially available powder was added to propan-2-ol and dispersed using a magnetic stirrer, a high frequency 850 kHz ultrasonic cell, a standard 40 kHz bath and a 20 kHz ultrasonic probe. The particle size of the powder was characterized using dynamic light scattering (DLS). Z-Average diameters (mean cluster size based on the intensity of scattered light) and intensity, volume and number size distributions were monitored as a function of time and energy input. Low frequency ultrasound was found to be more effective than high frequency ultrasound at de-agglomerating the powder and dispersion with a 20 kHz ultrasonic probe was found to be very effective at breaking apart large agglomerates containing weakly bound clusters of nanoparticles. In general, the breakage of nanoclusters was found to be a factor of ultrasonic intensity, the higher the intensity the greater the de-agglomeration and typically micron sized clusters were reduced to sub 100 nm particles in less than 30 min using optimum conditions. However, there came a point at which the forces generated by ultrasonic cavitation were either insufficient to overcome the cohesive bonds between smaller aggregates or at very high intensities decoupling between the tip and solution occurred. Absorption spectroscopy indicated a copper core structure with a thin oxide shell and the catalytic performance of this dispersion was demonstrated by drop coating onto substrates and subsequent electroless copper metallization. This relatively inexpensive catalytic suspension has the potential to replace precious metal based colloids used in electronics manufacturing.     

Enhancing the adhesion strength of micro electroforming layer by ultrasonic agitation method and the application

Micro electroforming is widely used for fabricating micro metal devices in Micro Electro Mechanism System (MEMS). However, there is the problem of poor adhesion strength between micro electroforming layer and substrate. This dramatically influences the dimensional accuracy of the device. To solve this problem, ultrasonic agitation method is applied during the micro electroforming process. To explore the effect of the ultrasonic agitation on the adhesion strength, micro electroforming experiments were carried out under different ultrasonic power (0 W, 100 W, 150 W, 200 W, 250 W) and different ultrasonic frequencies (0 kHz, 40 kHz, 80 kHz, 120 kHz, 200 kHz). The effects of the ultrasonic power and the ultrasonic frequency on the micro electroforming process were investigated by polarization method and alternating current (a.c.) impedance method. The adhesion strength between the electroforming layer and the substrate was measured by scratch test. The compressive stress of the electroforming layer was measured by X-ray Diffraction (XRD) method. The crystallite size of the electroforming layer was measured by Transmission Electron Microscopy (TEM) method. The internal contact surface area of the electroforming layer was measured by cyclic voltammetry (CV) method. The experimental results indicate that the ultrasonic agitation can decrease the polarization overpotential and increase the charge transfer process. Generally, the internal contact surface area is increased and the compressive stress is reduced. And then the adhesion strength is enhanced. Due to the different depolarization effects of the ultrasonic power and the ultrasonic frequency, the effects on strengthening the adhesion strength are different. When the ultrasonic agitation is 200 W and 40 kHz, the effect on strengthening the adhesion strength is the best. In order to prove the effect which the ultrasonic agitation can improve the adhesion strength of the micro devices, micro pillar arrays were fabricated under ultrasonic agitation (200 W, 40 kHz). The experimental results show that the residual rate of the micro pillar arrays is increased about 17% by ultrasonic agitation method. This work contributes to fabricating the electroforming layer with large adhesion strength.     

Ultrasound assisted intensified recovery of lactose from whey based on antisolvent crystallization

The current work deals with understanding the fundamental aspects of intensified recovery of lactose from paneer (cottage cheese) whey using the anti-solvent induced sonocrystallization. Ultrasonic horn (22 kHz) with varying power levels over the range of 40–120 W has been used for initial experiments at 100% duty cycle and two different levels of ultrasonic exposure time as 10 min and 20 min. Similar experiments were also performed using ultrasonic bath for the same time of exposure but with at two ultrasonic frequencies (22 kHz and 33 kHz). It was observed that the lactose recovery as well as purity increased with an increase in ultrasonic power at 100% duty cycle for the case of treatment time as 10 min whereas the lactose recovery and purity increased only till an optimum power for the 20 min treatment. In the case of ultrasonic bath, lactose purity increased with an increase in the ultrasonic frequency from 22 kHz to 33 kHz though the lactose recovery marginally decreased. Overall, it was observed that the maximum lactose recovery was ∼98% obtained using ultrasonic horn while the maximum lactose purity was ∼97%. It was also observed that maximum lactose recovery was ∼94% for the case of ultrasonic bath while the maximum lactose purity was ∼92%. The work has enabled to understand the optimized application of ultrasound so as to maximize both the lactose yield and purity during the recovery from whey.     

Pretreatment of defatted wheat germ proteins (by-products of flour mill industry) using ultrasonic horn and bath reactors: Effect on structure and preparation of ACE-inhibitory peptides

The ultrasonic horn and bath reactors were compared based on production of angiotensin-converting-enzyme (ACE) inhibitory peptides from defatted wheat germ proteins (DWGP). The DWGP was sonicated before hydrolysis by Alcalase. Degree of hydrolysis, ACE-inhibitory activity, surface hydrophobicity, fluorescence intensity, free sulfhydryl (SH), and disulfide bond (SS) were determined. The highest ACE-inhibitory activity of DWGP hydrolysate was obtained at power intensity of 191.1 W/cm² for 10 min in the ultrasonic horn reactor. The fixed frequency of 33 kHz and the sweep frequency of 40 ± 2 kHz resulted in the maximum ACE-inhibitory activity. The combined irradiation of dual fixed frequency (24/68 kHz) produced significant increase in ACE-inhibitory activity compared with single frequency (33 kHz). The ultrasonic probe resulted in significant higher ACE-inhibitory activity compared with ultrasonic bath operating at single or dual fixed and sweep frequencies. The changes in conformation of the DWGP due to sonication were confirmed by the changes in fluorescence intensity, surface hydrophobicity, SH_f and SS contents and they were found in conformity with the ACE-inhibitory activity in case of the ultrasonic horn reactor but not in bath reactor.     

Mapping of an ultrasonic bath for ultrasound assisted extraction of mangiferin from Mangifera indica leaves

The present work deals with the mapping of an ultrasonic bath for the maximum extraction of mangiferin from Mangifera indica leaves. I₃⁻ liberation experiments (chemical transformations) and extraction (physical transformations) were carried out at different locations in an ultrasonic bath and compared. The experimental findings indicated a similar trend in variation in an ultrasonic bath by both these methods. Various parameters such as position and depth of vessel in an ultrasonic bath, diameter and shape of a vessel, frequency and input power which affect the extraction yield have been studied in detail. Maximum yield of mangiferin obtained was approximately 31 mg/g at optimized parameters: distance of 2.54 cm above the bottom of the bath, 7 cm diameter of vessel, flat bottom vessel, 6.35 cm liquid height, 122 W input power and 25 kHz frequency. The present work indicates that the position and depth of vessel in an ultrasonic bath, diameter and shape of a vessel, frequency and input power have significant effect on the extraction yield. This work can be used as a base for all ultrasonic baths to obtain maximum efficiency for ultrasound assisted extraction.     

Inactivation of microorganisms by low-frequency high-power ultrasound: 1. Effect of growth phase and capsule properties of the bacteria

The aim of this study was to determine the effects of high-intensity low-frequency (20 kHz) ultrasound treatment on the viability of bacteria suspension. More specifically, we have investigated the relationship between the deactivation efficiency and the physical (size, hydrophobicity) and biological (gram-status, growth phase) properties of the microbes. Enterobacter aerogenes, Bacillus subtilis, Staphylococcus epidermidis, S. epidermidis SK and Staphylococcus pseudintermedius were chosen for this study owing to their varying physical and biological properties. The survival ratio of the bacteria suspension was measured as a function of the ultrasound power (up to 13 W) for a constant sonication time of 20 min. Transmission electron microscopy was used to evaluate the ultrasound-induced damages to the microbes. Ultrasound treatment resulted in lethal damage to E. aerogenes and B. subtilis (up to 4.5-log reduction), whereas Staphylococcus spp. were not affected noticeably. Further, E. aerogenes suspensions were more sensitive to ultrasonication in exponential growth phase than when they were in stationary phase. The results of this study demonstrate that the main reason for bacterial resistance to ultrasonic deactivation is due to the properties of the bacterial capsule. Microbes with a thicker and “soft” capsule are highly resistant to ultrasonic deactivation process.     

The disinfection effect of a novel continuous-flow water sterilizing system coupling dual-frequency ultrasound with sodium hypochlorite in pilot scale

In this paper, a self-designed novel continuous-flow water disinfection system coupling dual-frequency ultrasound (US) with chemical disinfectant sodium hypochlorite (NaClO) was tested in a pilot scale using a simulated effluent containing Bacillus subtilis (B. subtilis), one of the indicators of water treatment efficiency. A suspension having a B. subtilis concentration of approximately 10⁴ CFU/mL was introduced into the system to (1) investigate disinfection efficiency of US pretreatment with NaClO (US + NaClO) and simultaneous US and NaClO (US/NaClO) disinfection under different single frequencies; (2) further examine the disinfection efficiency of these two processes with dual-frequency US; and (3) identify dosage reduction of chlorine in this disinfection system. The results demonstrated that lower dual-frequency (17 kHz + 33 kHz) US pretreatment with NaClO disinfection and simultaneous higher dual-frequency (70 kHz + 100 kHz) US and NaClO were beneficial to bacterial inactivation in terms of sterilizing efficiency. It has also been observed that US pretreatment with lower combination of 17 + 33 kHz frequencies showed better enhancement in which log reduction reached to 3.82 after 10 min chlorine reaction (chlorine alone was 0.22 log reduction), nearly 1 log reduction higher than single frequencies at the same constant power. Consequently, at equivalent power dissipation levels, US of lower frequencies combination pretreatment with NaClO disinfection performed such a promising process that one-thirds (from 12 mg/L NaClO reduced to 8 mg/L NaClO) of the required NaClO dosage was reduced for the ideal disinfection efficiency of 4 log reduction, namely 100% disinfection. And the utilization efficiency of NaClO was increased from 37.67% to 85.25% in 30 min of treatment time using an optimized combination of pretreatment and chlorination.     

Effects of ultrasonic agitation and surfactant additive on surface roughness of Si (1 1 1) crystal plane in alkaline KOH solution

In the silicon wet etching process, the “pseudo-mask” formed by the hydrogen bubbles generated during the etching process is the reason causing high surface roughness and poor surface quality. Based upon the ultrasonic mechanical effect and wettability enhanced by isopropyl alcohol (IPA), ultrasonic agitation and IPA were used to improve surface quality of Si (1 1 1) crystal plane during silicon wet etching process. The surface roughness R_q is smaller than 15 nm when using ultrasonic agitation and R_q is smaller than 7 nm when using IPA. When the range of IPA concentration (mass fraction, wt%) is 5–20%, the ultrasonic frequency is 100 kHz and the ultrasound intensity is 30–50 W/L, the surface roughness R_q is smaller than 2 nm when combining ultrasonic agitation and IPA. The surface roughness R_q is equal to 1 nm when the mass fraction of IPA, ultrasound intensity and the ultrasonic frequency is 20%, 50 W and 100 kHz respectively. The experimental results indicated that the combination of ultrasonic agitation and IPA could obtain a lower surface roughness of Si (1 1 1) crystal plane in silicon wet etching process.     

Ultrasound-intensified laccase production from Trametes versicolor

An efficient intermittent ultrasonic treatment strategy was developed to improve laccase production from Trametes versicolor mycelia cultures. The optimized strategy consisted of exposing 2-day-old mycelia cultures to 5-min ultrasonic treatments for two times with a 12-h interval at the fixed ultrasonic power and frequency (120 W, 40 kHz). After 5 days of culture, this strategy produced the highest extracellular laccase activity of 588.9 U/L among all treatments tested which was 1.8-fold greater than the control without ultrasound treatment. The ultrasonic treatment resulted in a higher pellet porosity that facilitated the mass transfer of nutrients and metabolites from the pellets to the surrounding liquid. Furthermore, the ultrasonic treatment induced the expression of the laccase gene (lcc), which correlated with a sharp increase in both extracellular and intracellular laccase activity. This is the first study to find positive effects of ultrasound on gene expression in fungal cells. These results provide a basis for understanding the stimulation of metabolite production and process intensification by ultrasonic treatment in filamentous fungal culture.     

Numerical simulation of ultrasonic enhancement on mass transfer in liquid–solid reaction by a new computational model

Mass transfer coefficient is an important parameter in the process of mass transfer. It can reflect the degree of enhancement of mass transfer process in liquid–solid reaction and in non-reactive systems like dissolution and leaching, and further verify the issues by experiments in the reaction process. In the present paper, a new computational model quantitatively solving ultrasonic enhancement on mass transfer coefficient in liquid–solid reaction is established, and the mass transfer coefficient on silicon surface with a transducer at frequencies of 40 kHz, 60 kHz, 80 kHz and 100 kHz has been numerically simulated. The simulation results indicate that mass transfer coefficient increases with the increasing of ultrasound power, and the maximum value of mass transfer coefficient is 1.467 × 10⁻⁴ m/s at 60 kHz and the minimum is 1.310 × 10⁻⁴ m/s at 80 kHz in the condition when ultrasound power is 50 W (the mass transfer coefficient is 2.384 × 10⁻⁵ m/s without ultrasound). The extrinsic factors such as temperature and transducer diameter and distance between reactor and ultrasound source also influence the mass transfer coefficient on silicon surface. Mass transfer coefficient increases with the increasing temperature, with the decreasing distance between silicon and central position, with the decreasing of transducer diameter, and with the decreasing of distance between reactor and ultrasound source at the same ultrasonic power and frequency. The simulation results indicate that the computational model can quantitatively solve the ultrasonic enhancement on mass transfer coefficient.     

Variation of dissolved organic nitrogen concentration during the ultrasonic pretreatment to Microcystis aeruginosa

Algae cells were the main sources of dissolved organic nitrogen (DON) in raw water with plenty of algae, and ultrasonic pretreatment was one of the algae-controlling methods through the damage of algae cells. However, the variation of DON concentration during the ultrasonic treatment process was not confirmed. Variation of DON concentration during the processes of low frequency ultrasound treatment of Microcystis aeruginosa was investigated. In addition, the effect of sonication on the metabolite concentration, algae cellar activity and the subsequent coagulation performance were discussed. The results showed that after a long duration of ultrasonic (60 s), nearly 90% of the algal cells were damaged and the maximum concentration of DON attained more than 3 mg/L. In order to control the leakage extent of DON, the sonication time should be less than 30 s with power intensity of more than 1.0 W/cm³. In the mean time, ultrasonic treatment could inhibit the reactivation and the proliferation of algal, keep the algae cell wall integrity and enhance coagulation effectively under the same condition. However, ultrasound frequency had little effect on DON at the frequency range used in this study (20–150 kHz).     

Effects of low-intensity ultrasound on the growth,cell membrane permeability and ethanol tolerance of Saccharomyces cerevisiae

Effects of low-intensity ultrasound (at different frequency, treatment time and power) on Saccharomyces cerevisiae in different growth phase were evaluated by the biomass in the paper. In addition, the cell membrane permeability and ethanol tolerance of sonicated Saccharomyces cerevisiae were also researched. The results revealed that the biomass of Saccharomyces cerevisiae increased by 127.03% under the optimum ultrasonic conditions such as frequency 28 kHz, power 140 W/L and ultrasonic time 1 h when Saccharomyces cerevisiae cultured to the latent anaphase. And the membrane permeability of Saccharomyces cerevisiae in latent anaphase enhanced by ultrasound, resulting in the augment of extracellular protein, nucleic acid and fructose-1,6-diphosphate (FDP) contents. In addition, sonication could accelerate the damage of high concentration alcohol to Saccharomyces cerevisiae although the ethanol tolerance of Saccharomyces cerevisiae was not affected significantly by ultrasound.     

Effect of amplitude and frequency of ultrasonic irradiation on morphological characteristics control of calcium carbonate

We have previously reported on the morphological control of calcium carbonate by changing synthetic conditions such as temperature, pH and degree of supersaturation in liquid reaction. The present study reports the effect of amplitude and frequency of ultrasonic irradiation on the particle size of calcium carbonate using a horn type ultrasonic apparatus at two different frequencies. The calcium carbonate precipitated by mechanical stirring had a particle size of about 20 μm. By contrast, the particle size of vaterite formed under ultrasonic irradiation was about 2 μm, with a specific surface area of 25–30 m²/g. The major polymorph of calcium carbonate formed by ultrasonic irradiation was vaterite with some calcite present. For 40 kHz ultrasonic irradiation, the specific surface area of the calcium carbonate increased with increasing amplitude. The particle size of vaterite formed at this frequency was about 2 μm, and its distribution was sharper than that obtained at 20 kHz. The mode diameter of the synthesized vaterite was found to decrease with increasing amplitude at 40 kHz.     

Ultrasound stimulated production of a fibrinolytic enzyme

The present study is aimed at enhanced production of a fibrinolytic enzyme from Bacillus sphaericus MTCC 3672 under ultrasonic stimulation. Various process parameters viz; irradiation at different growth phases, ultrasonication power, irradiation duration, duty cycle and multiple irradiation were studied for enhancement of fibrinolytic enzyme productivity. The optimum conditions were found as follows, irradiation of ultrasonic waves to fermentation broth at 12 h of growth phase with 25 kHz frequency, 160 W ultrasound power, 20% duty cycle for 5 min. The productivity of fibrinolytic enzyme was increased 1.82-fold from 110 to 201 U/mL compared with the non sonicated control fermentation. Drop in glucose concentration from 0.41% to 0.12% w/v in ultrasonicated batch implies that, ultrasonication increases the cell permeability, improves substrate intake and progresses metabolism of microbial cell. Microscopic images before and after ultrasonic stimulation clearly signifies the impact of duty cycle on decreasing biomass concentration. However, environmental scanning electron micrograph does not show any cell lysis at optimum ultrasonic irradiation. Offshoots of our results will contribute to fulfill the demand of enhancement of microbial therapeutic enzyme productivity, through ultrasonication stimulation.     

Optimization of ultrasound-assisted extraction of total monomeric anthocyanin (TMA) and total phenolic content (TPC) from eggplant (Solanum melongena L.) peel

The present study describes the extraction of total monomeric anthocyanin (TMA) and total phenolic content (TPC) from eggplant peel using ultrasonic treatments and methanol and 2-propanol as extraction solvents. The extraction yields were optimized by varying the solvent concentration, ultrasonic frequency, temperature and time of ultrasonic treatment. Box–Behnken design was used to investigate the effect of process variables on the ultrasound-assisted extraction. The results showed that for TPC extraction the optimal condition were obtained with a methanol concentration of 76.6%, 33.88 kHz ultrasonic frequency, a temperature of 69.4 °C and 57.5 min extraction time. For TMA the optimal condition were the following: 54.4% methanol concentration, 37 kHz, 55.1 °C and process time of 44.85 min.     

Effect of acoustic frequency and power density on the aqueous ultrasonic-assisted extraction of grape pomace (Vitis vinifera L.) – A response surface approach

Aqueous ultrasound-assisted extraction (UAE) of grape pomace was investigated by Response Surface Methodology (RSM) to evaluate the effect of acoustic frequency (40, 80, 120 kHz), ultrasonic power density (50, 100, 150 W/L) and extraction time (5, 15, 25 min) on total phenolics, total flavonols and antioxidant capacity. All the process variables showed a significant effect on the aqueous UAE of grape pomace (p < 0.05). The Box–Behnken Design (BBD) generated satisfactory mathematical models which accurately explain the behavior of the system; allowing to predict both the extraction yield of phenolic and flavonol compounds, and also the antioxidant capacity of the grape pomace extracts. The optimal UAE conditions for all response factors were a frequency of 40 kHz, a power density of 150 W/L and 25 min of extraction time. Under these conditions, the aqueous UAE would achieve a maximum of 32.31 mg GA/100 g fw for total phenolics and 2.04 mg quercetin/100 g fw for total flavonols. Regarding the antioxidant capacity, the maximum predicted values were 53.47 and 43.66 mg Trolox/100 g fw for CUPRAC and FRAP assays, respectively. When comparing with organic UAE, in the present research, from 12% to 38% of total phenolic bibliographic values were obtained, but using only water as the extraction solvent, and applying lower temperatures and shorter extraction times. To the best of the authors’ knowledge, no studies specifically addressing the optimization of both acoustic frequency and power density during aqueous-UAE of plant materials have been previously published.     

Experimental study on the influence of low-frequency and low-intensity ultrasound on the permeability of the Mycobacterium smegmatis cytoderm and potentiation with levofloxacin

Tuberculosis is an infectious disease caused by the bacterium M. tuberculosis. The aim of this study was to investigate the bactericidal effect and underlying mechanisms of low-frequency and low-intensity ultrasound combined with levofloxacin treatment against M. smegmatis (a surrogate of M. tuberculosis). As part of this study, M. smegmatis was continuously irradiated with low frequency ultrasound (42 kHz) using several different doses whereby both intensity (0.138, 0.190 and 0.329 W/cm²) and exposure time (5, 15 and 20 min) were varied. Flow cytometric analyses revealed that the permeability of M. smegmatis increased following ultrasound exposure. The survival rate, structure and morphology of bacteria in the lower-dose (I_SATA = 0.138 W/cm² for 5 min) ultrasound group displayed no significant differences upon comparison with the untreated group. However, the survival rate of bacteria was significantly reduced and the bacterial structure was damaged in the higher-dose (I_SATA = 0.329 W/cm² for 20 min) ultrasound group. Ultrasound irradiation (0.138 W/cm²) was subsequently applied to M. smegmatis in combination with levofloxacin treatment for 5 min. The results demonstrated that the bactericidal effect of ultrasonic irradiation combined with levofloxacin is higher compared to ultrasound alone or levofloxacin alone.     

Intensification of extraction of curcumin from Curcuma amada using ultrasound assisted approach: Effect of different operating parameters

Curcumin, a dietary phytochemical, has been extracted from rhizomes of Curcuma amada using ultrasound assisted extraction (UAE) and the results compared with the conventional extraction approach to establish the process intensification benefits. The effect of operating parameters such as type of solvent, extraction time, extraction temperature, solid to solvent ratio, particle size and ultrasonic power on the extraction yield have been investigated in details for the approach UAE. The maximum extraction yield as 72% was obtained in 1 h under optimized conditions of 35 °C temperature, solid to solvent ratio of 1:25, particle size of 0.09 mm, ultrasonic power of 250 W and ultrasound frequency of 22 kHz with ethanol as the solvent. The obtained yield was significantly higher as compared to the batch extraction where only about 62% yield was achieved in 8 h of treatment. Peleg’s model was used to describe the kinetics of UAE and the model showed a good agreement with the experimental results. Overall, ultrasound has been established to be a green process for extraction of curcumin with benefits of reduction in time as compared to batch extraction and the operating temperature as compared to Soxhlet extraction.