Ultrasound promotes enzymatic reactions by acting on different targets: Enzymes, substrates and enzymatic reaction systems

Impact of ultrasonic pretreatment on pumpkin seed protein: Effect on protease activities, protein structure, hydrolysis kinetics and functional properties

Adding value to food by-products, such as pumpkin seeds, is an important strategy for the complete utilization of plant foods and advancing sustainability goals. This study aimed to maximize the production of bioactive peptides from pumpkin seed protein (PSP) by combining ultrasonic (US) pretreatment (40 kHz, 23.8 W/L) with enzymatic hydrolysis. The PSP's structure after sonication and its effects on the commercial proteases (Brauzyn®, Flavourzyme®, Neutrase®) activity and degree of hydrolysis were studied. The hydrolysis consequences regarding solubility and antioxidant activity of the resulting peptides were also evaluated. Sonication of PSP increased enzymatic activity by up to 21.3 % for Brauzyn®, 24.8 % for Flavourzyme® and 19.2 % for Neutrase®. Consequently, there was an increase in the degree of hydrolysis (up to 89 %) using sonicated PSP, particularly at 60 min/40 °C. These effects can be attributed to ultrasound-induced protein conformation changes, including increased intrinsic fluorescence intensity (<22 %), shifts in UV spectra, and alterations in FTIR amide bands, especially a decrease in β-sheet content (<7.14 %). Additionally, ultrasonic pretreatment reduced particle size (<43.9 %) and polydispersity index (<58 %), enhancing enzyme accessibility by fragmenting protein aggregates, as observed via scanning electron microscopy. As a result, the peptides obtained from the hydrolysis of sonicated PSP exhibited higher protein solubility (12 % to 49 % at pH 6.0) and improved antioxidant activity (5.6 % to 77 %). Overall, sonication of PSP for 60 min at 40 °C followed by hydrolysis with Neutrase® proved to be the most effective strategy for producing highly soluble peptides with enhanced antioxidant properties, highlighting the potential of ultrasound as a valuable tool for optimizing bioactive peptide production. Based on these results, the developed process is ready for scale-up by the food industry, aiming to obtain protein hydrolysates with improved functional and/or nutritional properties from a low-cost raw material. In parallel, further researches can focus on the potential application of these hydrolysates as ingredients in bakery, meet or dairy products.

Evaluation of the Impact of HIFU on Peptide Bond Formation: A Study Using SPE-LC-MS/MS Methodology

High-intensity focused ultrasound (HIFU) is a noninvasive soft tissue ablation technique, which utilizes ultrasound energy to induce thermal coagulation necrosis in targeted tissues. Whether this high energy causes side effects in vivo, such as the formation of peptide bonds, has not been fully investigated. Glycylglycine is the simplest dipeptide and hence is often used as a model compound for peptide studies. In this study, we developed and validated a sensitive quantification method based on ion-exchange solid-phase extraction, liquid chromatography, and tandem mass spectrometry (SPE-LC-MS/MS) for the analysis of glycylglycine without derivatization, and then used it to evaluate whether HIFU promoted peptide bond formation in aqueous solution (without enzymes) and plasma (with enzymes). The results showed that strong cation exchange SPE significantly reduced the matrix effect and improved the sensitivity of the LC-MS/MS method. No formation of glycylglycine in the aqueous solution or plasma was observed following HIFU irradiation.

Advancements in Acoustic Cavitation Modelling: Progress, Challenges, and Future Directions in Sonochemical Reactor Design

This review provides a comprehensive overview of ultrasonic wave propagation, with a primary focus on high-power ultrasound systems where cavitation bubbles are likely to occur. The review is structured to guide readers through the historical development of cavitation models, from early works such as the Rayleigh-Plesset equation to more advanced numerical approaches. It explores the dynamics of cavitation bubbles, their physical effects, and the key factors influencing bubble formation, growth, and collapse. In addition to bubble-induced cavitation, the review addresses nonlinear wave propagation in the absence of bubbles, highlighting phenomena such as harmonic generation and shock wave formation. A detailed discussion on the numerical modelling of ultrasonic systems follows, covering linear and nonlinear approaches, boundary conditions, and the challenges of accurately simulating cavitating systems. The review concludes with an analysis of recent developments, emerging trends, and future directions in computational modelling for ultrasonic applications. By presenting a structured overview of both the theoretical and practical aspects of ultrasonic wave propagation, this work aims to provide a foundation for future research and design improvements in sonochemical and acoustic systems.

Purification and characterization of a protease produced by submerged fermentation: Ultrasound-enhanced collagenolytic protease from Streptomyces parvulus

Proteases are a large group of enzymes in high demand due to their wide and different biotechnological applications mainly in the biomedical field. Ultrasound (US) has been used successfully in several Bioprocesses in biotechnology, such as in the upregulation of enzymatic hydrolysis (biocatalysis). The objective of this work was to purify an enzyme from Streptomyces parvulus and to characterize it through physic-chemical applications including ultrasound effect. The purified protease has a molecular weight of 78.0 KDa, a yield of 31 % and 11.8-fold, it was stable between pH 4-9, optimum pH at 7.5, temperature of 0-45 °C, and showed optimum temperature at 45 °C, exhibited enhanced activity with Ca2+ and Mg2+, and was inhibited by PMSF. US in the treatment or pre-treatment of enzymatic reactions showed to be favorable and increase the activity around 85 % for the optimum temperature 45 °C. Also, in circular dichroism spectra it was shown a significant change in enzyme structure under US effect enhancing the real activity. Besides, the US improved the enzyme reactions for all assays. The purified enzyme was successfully immobilized in chitosan film. Thus, the present work demonstrated the promising results of a protease with collagenolytic activity in the field of Biotechnology by proving the positive effect induced by ultrasound.

Simultaneous extraction of five heavy metal ions from root vegetables via dual-frequency ultrasound-assisted enzymatic digestion

The dual-frequency ultrasound-assisted enzymatic digestion (DUED) technique was developed for synchronous green extraction of five heavy metal ions in root vegetables. The combination of α-amylase, cellulase, and papain showed significant advantageous in extracting heavy metal ions. Under optimized dual-frequency ultrasonic conditions, the extraction rates of Cr, As, Cd, Pb, and Hg in carrots reached 99.04%, 105.88%, 104.65%, 104.10%, and 103.13% respectively. And the extraction process is highly efficient, completing in just 15 min. Compared to conventional microwave-assisted acid hydrolysis method, this technique eliminates the need for high-temperature concentrated acid, enhancing its environmental sustainability while maintaining mild reaction conditions, making it ideal for biosensors application. Additionally, simultaneous extraction and detection of four heavy metals in lotus roots were successfully achieved by using DUED and a fluorescent paper-based microfluidic chip. The obtained results are consistent with those obtained using conventional methods.

Ultrasonication assisted enzymatic hydrolysis for generation of pulses protein hydrolysate having antioxidant and ACE-inhibitory activity

The main objective of this work was to investigate the impact of ultrasonication assisted enzymatic treatment on the physicochemical and bioactive properties of broad bean (BBP), lentil bean (LBP), and mung bean (MBP) protein isolates. The protein was extracted using alkaline acid precipitation method, ultrasonicated at a frequency of 20 kHz, temperature 20-30 °C and then hydrolysed using alcalase enzyme (1 % w/w, pH 8.5, 30 min, 55 οC). The generated hydrolysates were characterized by degree of hydrolysis (DH), SDS, FTIR, surface hydrophobicity, amino acid composition, antioxidant and antihypertensive properties. Results showed that the degree of hydrolysis was found to increase in ultrasonicated protein hydrolysate (18.9 to 40.71 %) in comparison to non- ultrasonicated protein hydrolysate (11 to 16.3 %). SDS-PAGE results showed significant changes in protein molecular weight profiles (100-11kDa) in comparison to their natives. However, no substantial change was found in ultrasonicated and non-ultrasonicated protein hydrolysates. The FTIR spectrum showed structural alterations in ultrasonicated and non-ultrasonicated protein hydrolysates, suggesting modifications in secondary structure such as amide A, amide I and amide II regions. The essential amino acid content varied in the range of 60.09 mg/g to 73.77 mg/g and 28.73 to 50.26 mg/g in case of ultrasonicated and non-ultrasonicated protein hydrolysates, and non-essential content varied in the range of 49.42 to 65.93 mg/g and 43.12 to 47.12 mg/g. Both antioxidant and antihypertensive activities were found to increase significantly in ultrasonicated and non-ultrasonicated protein hydrolysates in comparison to their native counterparts, highlighting their potential as functional ingredients for management of hypertension. It was concluded that ultrasonication assisted enzymatic hydrolysis is an efficient approach for production of bioactive pulse protein hydrolysates with enhanced nutracutical properties, thus offering promising avenues for their utilization in the food industry and beyond.

Stabilization of Eversa® Transform 2.0 lipase with sorbitol to enhance the efficiency of ultrasound-assisted biodiesel production

Ultrasound technology has emerged as a promising tool for enhancing enzymatic biodiesel production, yet the cavitation effect induced can compromise enzyme stability. This study explored the efficiency of polyols in enhancing lipase stability under ultrasound conditions to further improve biodiesel yield. The incorporation of sorbitol resulted in the highest fatty acid methyl ester (FAME) content in the ultrasound-assisted biodiesel production catalyzed by Eversa® Transform 2.0 among the investigated polyols. Furthermore, sorbitol enhanced the stability of the lipase, allowing it to tolerate up to 100 % ultrasound amplitude, compared to 60 % amplitude in its absence. Enzyme activity assays revealed that sorbitol preserved 99 % of the lipase activity, in contrast to 84 % retention observed without sorbitol under an 80 % ultrasound amplitude. Circular dichroism (CD) and fluorescence spectroscopy analyses confirmed that sorbitol enhanced lipase rigidity and preserved its conformational structure under ultrasound exposure. Furthermore, employing a stepwise methanol addition strategy in ultrasound-assisted reactions with sorbitol achieved an 81.2 wt% FAME content in 8 h with only 0.2 wt% enzyme concentration. This promising result highlights the potential of sorbitol as a stabilizing agent in ultrasound-assisted enzymatic biodiesel production, offering a viable approach for enhancing biodiesel yield and enzyme stability in industrial applications.

Use of ultrasound to improve the activity of cyclodextrin glycosyltransferase in the producing of β-cyclodextrins: Impact on enzyme activity, stability and insights into changes on enzyme macrostructure

This work explored the impact of ultrasound (US) on the activity, stability, and macrostructural conformation of cyclodextrin glycosyltransferase (CGTase) and how these changes could maximize the production of β-cyclodextrins (β-CDs). The results showed that ultrasonic pretreatment (20 kHz and 38 W/L) at pH 6.0 promoted increased enzymatic activity. Specifically, after sonication at 25 °C/30 min, there was a maximum activity increase of 93 % and 68 % when biocatalysis was carried out at 25 and 55 °C, respectively. For activity measured at 80 °C, maximum increase (31 %) was observed after sonication at 25 °C/60 min. Comparatively, US pretreatment at low pH (pH = 4.0) resulted in a lower activity increase (max. 28 %). These activation levels were maintained after 24 h of storage at 8 °C, suggesting that changes on CGTase after ultrasonic pretreatment were not transitory. These pretreatments altered the conformational structure of CGTase, revealed by an up to 11 % increase in intrinsic fluorescence intensity, and resulted in macrostructural modifications, such as a decrease in particle size and polydispersion index (up to 85 % and 45.8 %, respectively). Therefore, the sonication of CGTase under specific conditions of pH, time, and temperature (especially at pH 6.0/ 30 min/ 25 °C) promotes macrostructural changes in CGTase that induce enzyme activation and, consequently, higher production of β-CDs.

Encapsulation of Enzymes into Hydrophilic and Biocompatible Metal Azolate Framework: Improved Functions of Biocatalyst in Cascade Reactions and its Sensing Applications

Multiple enzyme-triggered cascade biocatalytic reactions are vital in vivo or vitro, considering the basic biofunction preservation in living organisms and signals transduction for biosensing platforms. Encapsulation of such enzymes into carrier endows a sheltering effect and can boost catalytic performance, although the selection and preparation of an appropriate carrier is still a concern. Herein, focusing on MAF-7, a category of metal azolate framework (MAF) with superiority against the topologically identical ZIF-8, this enzyme@MAF system can ameliorate the sustainability of encapsulating natural enzymes into carriers. The proposed biocatalyst composite AChE@ChOx@MAF-7/hemin is constructed via one-pot in situ coprecipitation method. Subsequently, MAF-7 is demonstrated to exhibit an excellent capacity of the carrier and protection against external factors in the counterpart of ZIF-8 through encapsulated and free enzymes. In addition, detections for specific substrates or inhibitors with favorable sensitivity are accomplished, indicating that the properties above expectation of different aspects of the established platform are successfully realized. This biofunctional composite based on MAF-7 can definitely provide a potential approach for optimization of cascade reaction and enzyme encapsulation.

Assessing the impact of ultrasound on the rate and extent of early post-mortem glycolysis in bovine Longissimus thoracis et lumborum

The rate of pH decline, early post-mortem, has been identified as a key factor that impacts the tenderness of meat, and manipulating this rate of pH decline is highly relevant to ensure consistent high quality meat. Ultrasound is a potential intervention in early post - mortem muscle that may have an impact on the rate of glycolysis through its ability to alter enzyme activity. Following a variety of different ultrasound treatments frequencies (25 and 45 kHz) and durations (15, 30 and 45 min), it was found, when analysed in muscle, that ultrasound treatment duration, specifically the 30 min treatment, and interaction between treatment duration and frequency, had a significant impact on the rate of pH decline, post - treatment. Frequency did not have a significant effect on the rate of pH decline, post - treatment, in muscle. Ultrasound did not have a significant permanent effect on the activity of glycolytic enzymes present in bovine Longissimus lumborum et thoracis muscle, where no significant differences were observed on the rate of pH decline and rate of change of reducing sugars, glycogen and lactic acid, when analysed in an in vitro glycolytic buffer. It seems that the impact observed in intact muscle is not as a consequence of a permanent change in enzymatic activity, instead indicating an impact on conditions in the muscle which enhanced enzyme activity.

Ultrasound-assisted intensification of Pickering interfacial biocatalysis preparation of vitamin A aliphatic esters

A novel approach to ultrasound-assisted Pickering interfacial biocatalysis (PIB) has been proposed and implemented for the efficient enzymatic transesterification production of vitamin A fatty acid esters. This is the first instance of exploiting the synergistic effect of ultrasound and the bifunctional modification of enzyme supports to accelerate biocatalytic performance in PIB systems. The optimal conditions were determined to be ultrasound power of 70 W, on/off time of 5 s/5 s, substrate molar ratio of 1:1, enzyme addition of 2 %, and a volume ratio of n-hexane to PBS of 3:1, a temperature of 40 °C, and a time of 30 min. The application of ultrasound technology not only improved lipase activity but also allowed for a reduction in emulsion droplet size to enhance interfacial mass transfer.Bifunctional modification of silica-based supports enhanced stability of immobilized enzymes by increasing hydrogen bonding while maintaining the active interface microenvironment. Compared with a non-ultrasound-assisted PIB system stabilized by mono-modified immobilized enzyme particles, the catalytic efficacy (CE) of the novel system reached 8.18 mmol g-1 min-1, which was enhanced by 3.33-fold, while the interfacial area was found to have increased by 17.5-fold. The results facilitated the conversion of vitamin A palmitate (VAP), vitamin A oleate (VAO), vitamin A linoleate (VAL), and vitamin A linolenate (VALn), with conversion rates of approximately 98.2 %, 97.4 %, 96.1 %, and 94.7 %, respectively. This represents the most efficient example that has been reported to our knowledge. Furthermore, the system demonstrated improved reusability, with a conversion rate of 62.1 % maintained even after 10 cycles. The findings presented in this paper provide valuable insights into an efficient and conveniently promising protocol for the development of PIB systems.

Enhancing efficiency of ultrasound-assisted biodiesel production catalyzed by Eversa® Transform 2.0 at low lipase concentration: Enzyme characterization and process optimization

This study focused on the ultrasound-assisted transesterification of simulated low-quality feedstocks using a low-cost liquid lipase Eversa® Transform 2.0 (ET2). Enzyme characterization was also performed to investigate the effect of ultrasound parameters on enzyme structure. The optimal ultrasound parameters, 40 % amplitude, and 5 % duty cycle effectively enhanced the reaction rate compared to the conventional stirring method while retaining 95 % of the enzyme activity. Analysis of circular dichroism (CD) spectra revealed the preservation of the secondary structure of ET2 under the optimal ultrasound intensities, while fluorescence spectra indicated a slight change in its tertiary structure. The implementation of a two-stage methanol dosing strategy in the ultrasound-assisted reaction effectively mitigated lipase inhibition, yielding a remarkable fatty acid methyl ester (FAME) content of 92.2 % achieved within a 12-h reaction time. Notable, this high FAME content was achieved with only a 4:1 methanol-to-oil molar ratio and a 0.5 wt% enzyme concentration. Under these optimized conditions, the ultrasound-assisted reaction also demonstrated a 15 % improvement in the final FAME content compared to the conventional stirring method. These promising results hold significant potential for advancing the field of biodiesel production via ultrasound technology, contributing substantively to sustainable energy sources.

Effects of ultrasound and thermal treatment on the interaction between hyaluronic acid and lactoferrin: Preparation, structures and functionalities

Complexes of polysaccharides and proteins have superior physicochemical and functional properties compared to single proteins or polysaccharides. In this study, lactoferrin-hyaluronic acid (LF-HA) complexes were prepared by both ultrasonic and thermal treatment. Appropriate preparation conditions, including ultrasonic and thermal treatment conditions, have been established. The complexes formed by different methods were structurally characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis, fourier transform infrared spectroscopy, and circular dichroism spectroscopy. Ultrasound formed non-covalent binding, while thermal treatment generated covalent bonding, altering the structure of LF. The LF-HA complexes showed improved heat stability, foaming stability, emulsifying activity and antioxidant capacity, but deceased foaming ability. Iron binding ability could only be improved by HA through thermal treatment. Moreover, the in vitro digestibility of LF-HA complexes decreased to below 80 % compared to LF.

Investigating the impact of ultrasound-assisted cellulase pretreatment on the nutrients, phytic acid, and phenolics bioaccessibility in sprouted brown rice

This study aimed to elucidate the impact of ultrasound-assisted cellulase (UC) pretreatment on nutrients, phytic acid, and the bioavailability of phenolics during brown rice sprouting. It sought to unveil the underlying mechanisms by quantifying the activity of key enzymes implicated in these processes. The sprouted brown rice (SBR) surface structure was harmed by the UC pretreatment, which also increased the amount of γ-oryzanol and antioxidant activity in the SBR. Concurrently, the UC pretreatment boosted the activity of phytase, glutamate decarboxylase, succinate semialdehyde dehydrogenase, Gamma-aminobutyric acid (GABA) transaminase, chalcone isomerase, and phenylalanine ammonia lyase, thereby decreasing the phytic acid content and increasing the GABA, flavonoid, and phenolic content in SBR. In addition, UC-pretreated SBR showed increased phenolic release and bioaccessibility during in vitro digestion when compared to the treated group. These findings might offer theoretical direction for using SBR to maximize value.

Solubilization and structural changes of lignin in naked oat stems during subcritical water autohydrolysis

In this study, the solubilization and structural changes of lignin in naked oat stems were investigated under subcritical water autohydrolysis systems (170-210 °C, 0.68-1.85 MPa). In this system, Hemicellulose was preferentially hydrolyzed in the liquid water at elevated temperatures, leading to the production of acetic acid and glucuronic acid, which acidified the reaction system. Under acidic and high-temperature conditions, lignin primarily underwent degradation and condensation reactions. At autohydrolysis temperatures below 190 °C and autohydrolysis pressures below 1.22 MPa, lignin degradation was predominant, realizing a maximum lignin removal of 47.8 % and breakage of numerous β-O-4 bonds from lignin. At autohydrolysis temperatures above 190 °C and autohydrolysis pressures above 1.22 MPa, lignin condensation dominated, with an increase in the amount of organic acids generated upon hemicellulose degradation, leading to condensation reactions with the degraded low-molecular-weight lignin. The degree of lignin condensation was positively correlated with the temperature of the reaction system. This study provides essential insights into the dynamic changes in the structure of lignin in both the hydrolysis residue and hydrolysis solution during subcritical water autohydrolysis.

The impact of ultrasound treatment on glycolytic enzymes when applied to crude extracts from early post-mortem bovine muscle

The rate of pH decline post - mortem and its interaction with temperature influences the final tenderness of meat, and therefore, the manipulation of the rate of pH decline is a strategy of interest in order to obtain consistent high quality meat. Ultrasound is a potential early post - mortem carcass intervention, which may alter the rate of glycolysis based on its ability to alter enzyme activity. In this study, homogenates (prepared from early post-mortem Longissimus thoracis et lumborum muscle) were subjected to different ultrasound intensities (0 %/60 %/100 % amp) and treatment durations (15/ 30 min). The effect of these treatments on the inherent activity of the glycolytic enzymes was investigated using an in vitro glycolytic buffer model system. It was found that ultrasound treatment intensity and duration had a significant interactive effect on the rate of pH decline, and on reducing sugars and lactic acid concentrations, specifically following the 100 % amp ultrasound for 30 min treatment and between 30 and 240 min incubation. No significant differences in pH or metabolites content were observed between treatments after 1440 min of incubation. No effect of ultrasound intensity or treatment duration was observed on the degradation of glycogen. Under the reported conditions of this trial, it can be concluded that the application of ultrasound has limited potential to have an impact on the glycolytic pathways in bovine muscle.

Ultrasonic-ethanol pretreatment assisted aqueous enzymatic extraction of hemp seed oil with low Δ9-THC

In this study, ultrasonic-ethanol pretreatment combined with AEE was developed for oil extraction from hemp seeds. The oil yield reached a maximum of 23.32 % at 200 W ultrasonic power and 30 min ultrasonic time, at this point, the degradation rate of Δ9-THC was 83.11 %. By determining the composition of hemp seed before and after pretreatment, it was shown that ultrasonic-ethanol pretreatment reduced the protein content of the raw material. An enzyme mixture consisting of pectinase and hemicellulase (1/1/1, w/w/w) was experimentally determined to be used, and the AEE extraction conditions were optimized using the Plackett-Burman design and the Box-Behnken. The optimal conditions were determined to be pH 5, total enzyme activity of 37,800 U/g, liquid-solid ratio of 10.4 mL/g, enzyme digestion temperature of 32 °C, enzymatic time of 189 min, and oil recovery of 88.38 %. The results of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) showed that the emulsion formed during ultrasonic ethanol pretreatment was not uniformly distributed, and the droplets appeared to be aggregated; and the irregular pores of hemp seed increased after pretreatment. The contents of Δ9-THC and CBN in the extracted oil samples were 9.58 mg/kg and 52.45 mg/kg, respectively. Compared with the oil extracted by Soxhlet extraction (SE), the oil extracted by this experimental method was of better quality and similar in fatty acid composition.

Effect of ultrasonic treatment on enzymes: Decoupling the relation between the ultrasonic driven conformational change and enzyme activity

Considering the growing interest in enzyme-based extraction technology as a safe and eco-friendly extraction technique, along with the relatively high cost associated with enzymatic applications, it became necessary to explore novel strategies aimed to improve enzyme activity. In this study, the impact of ultrasonic treatment on commercial cellulase and pectinase was investigated. As this effect may be influenced by various ultrasonic and enzyme-related parameters, changes in enzyme conformation were explored under optimal and non-optimal enzyme conditions. The intrinsic fluorescence spectrum was utilized as a tool for monitoring these changes. Additionally, the enzyme's catalytic potential was also assessed under the same conditions. Results indicated that the impact of ultrasonic treatment on enzyme conformation primarily depends on the total ultrasonic energy delivered to the system, rather than other ultrasonic parameters such as power, sample volume, treatment time, or duty cycle. The maximum relative decrease in intrinsic fluorescence intensity of Pectinex® Ultra Clear (PUC) and Pectinex® Ultra SPL (PUS) after ultrasonic treatment was approximately 51% and 55%, respectively, while the decrease induced by thermal denaturation was 25% and 30% respectively. Furthermore, a blue shift in the fluorescence spectrum of both pectinases was observed upon sonication for all process conditions indicating a change in enzyme conformation. However, ultrasonic treatment did not result in a significant change in enzyme activity, suggesting that these conformational adjustments may occur in regions other than the active sites. Moreover, ultrasonicated pectinases and cellulases did not exhibit any improvement in their catalytic potential under either optimal or non-optimal conditions.

Valorization of protein-rich waste and its application

Energy shortages present significant challenges with the rising population and dramatic urbanization development. The effective utilization of high-value products generated from massive protein-rich waste has emerged as an excellent solution for mitigating the growing energy crisis. However, the traditional disposal and treatment of protein-rich waste, have been proven to be ineffective in resource utilization, which led to high chemical oxygen demand and water eutrophication. To effectively address this issue, hydrolysate and bioconversion products from protein-rich waste have been widely investigated. Herein, we aim to provide an overview of the valorization of protein-rich waste based on a comprehensive analysis of publicly available literature. Firstly, the sources of protein-rich waste with various quantities and qualities are systematically summarized. Then, we scrutinize and analyze the hydrolysis approaches of protein-rich waste and the versatile applications of hydrolyzed products. Moreover, the main factors influencing protein biotransformation and the applications of bioconversion products are covered and extensively discussed. Finally, the potential prospects and future directions for the valorization of protein-rich waste are proposed pertinently.

Ultrasound-Assisted Enzymatic Protein Hydrolysis in Food Processing: Mechanism and Parameters

Ultrasound has been widely used as a green and efficient non-thermal processing technique to assist with enzymatic hydrolysis. Compared with traditional enzymatic hydrolysis, ultrasonic-pretreatment-assisted enzymatic hydrolysis can significantly improve the efficiency of enzymatic hydrolysis and enhance the biological activity of substrates. At present, this technology is mainly used for the extraction of bioactive substances and the degradation of biological macromolecules. This review is focused on the mechanism of enzymatic hydrolysis assisted by ultrasonic pretreatment, including the effects of ultrasonic pretreatment on the enzyme structure, substrate structure, enzymatic hydrolysis kinetics, and thermodynamics and the effects of the ultrasonic conditions on the enzymatic hydrolysis results. The development status of ultrasonic devices and the application of ultrasonic-assisted enzymatic hydrolysis in the food industry are briefly described in this study. In the future, more attention should be paid to research on ultrasound-assisted enzymatic hydrolysis devices to promote the expansion of production and improve production efficiency.

Implementation of an Ultrasensitive Biomolecular Controller for Enzymatic Reaction Processes With Delay Using DNA Strand Displacement

In this article, a set of abstract chemical reactions has been employed to construct a novel nonlinear biomolecular controller, i.e, the Brink controller (BC) with direct positive autoregulation (DPAR) (namely BC-DPAR controller). In comparison to dual rail representation-based controllers such as the quasi sliding mode (QSM) controller, the BC-DPAR controller directly reduces the number of CRNs required for realizing an ultrasensitive input-output response because it does not involve the subtraction module, reducing the complexity of DNA implementations. Then, the action mechanism and steady-state condition constraints of two nonlinear controllers, BC-DPAR controller and QSM controller, are investigated further. Considering the mapping relationship between CRNs and DNA implementation, a CRNs-based enzymatic reaction process with delay is constructed, and a DNA strand displacement (DSD) scheme representing time delay is proposed. The BC-DPAR controller, when compared to the QSM controller, can reduce the number of abstract chemical reactions and DSD reactions required by 33.3% and 31.8%, respectively. Finally, an enzymatic reaction scheme with BC-DPAR controller is designed using DSD reactions. According to the findings, the enzymatic reaction process's output substance can approach the target level at a quasi-steady state in both delay-free and non-zero delay conditions, but the target level can only be achieved during a finite-time period, mainly due to the fuel stand depletion.

Study on the effects and mechanisms of ultrasound on the peptide profile and taste of unsmoked bacon using peptidomics and bioinformatics

The ultrasound-induced impacts on the peptide characteristics and taste of unsmoked bacon have been evaluated through the use of peptidomics and bioinformatics approaches. Furthermore, the effect of such ultrasound-induced changes on the main endogenous proteases responsible for peptide generation was also investigated. In fact, the activity of main endogenous proteases was significantly increased after ultrasonic treatment during the processing of unsmoked bacon, and contributed to an increased number and an enhanced LFQ intensity of peptides. Besides, such increased amount of peptides and LFQ intensity with up to 500 W ultrasonic treatment were beneficial for the taste improvement of the final products as shown by taste prediction analysis. Nevertheless, an excessive ultrasonic power like 750 W hindered protein hydrolysis and further exerted a negative effect on peptide generation. Therefore, ultrasound under controlled conditions could be considered as a promising way to improve the taste of unsmoked bacon.

Environment friendly emerging techniques for the treatment of waste biomass: a focus on microwave and ultrasonication processes

In the recent past, an increasing interest is mostly observed in using microwave and ultrasonic irradiation to aid the biological conversion of waste materials into value-added products. This study is focused on various individual impacts of microwaves and ultrasonic waves for the treatment of biomass before the synthesis of value-added products. Following, a comprehensive review of the mechanisms governing microwaves and ultrasonication as the treatment methods, their effects on biomass disruption, solubilization of organic matter, modification of the crystalline structure, enzymatic hydrolysis and production of reducing sugars was performed. However, based on the lab-scale experiments evaluated, microwaves and ultrasonication were studied to be economically and energetically ineffective despite their beneficial effects on the waste biomass. This article reviews some of the difficulties associated with using microwaves and ultrasonic irradiation for the efficient processing of waste biomasses and identified some potential directions for future study.

Ultrasound-assisted enzymatic synthesis of galacto-oligosaccharides using native whey with two commercial β-galactosidases: Aspergillus oryzae and Kluyveromyces var lactis

Native whey obtained during casein micelle microfiltration was used as a novel source to produce galacto-oligosaccharides (GOS). Since the presence of macromolecules and other interferers reduces biocatalyst performance, this work evaluated the effect of different ultrasound processing conditions on GOS synthesis using concentrated native whey. Ultrasonic intensities (UI) below 11 W/cm² tended to increase the activity in the enzyme from Aspergillus oryzae for several minutes but accelerated the inactivation in that from Kluyveromyces lactis. At 40 °C, 40 % w/w native whey, 70 % wave amplitude, and 0.6 s/s duty-cycle, a UI of 30 W/cm² was achieved, and the increased specific enzyme productivity was similar to the values obtained with pure lactose (∼0.136 g GOS/h/mg_E). This strategy allows for obtaining a product containing prebiotics with the healthy and functional properties of whey proteins, avoiding the required purification steps used in the production of food-grade lactose.

New ultrasonic assisted technology of freezing, cooling and thawing in solid food processing: A review

Solid foods include fish, shrimp, shellfish, and other aquatic products, fruits, and vegetables. These products are commonly used for food freezing, cooling, and thawing. However, traditional freezing, cooling, and thawing of solid food technologies have limitations in quality, such as protein denaturation and water loss in food. Ultrasound-assisted technology has become a useful method in solid food processing due to improved preservation quality of solid food. This paper comprehensively reviews the mechanism and application of ultrasonic in solid food processing technology. Although the application of ultrasound-assisted ultrasound in solid food processing is relatively comprehensive, the energy saving of food cold processing is essential for practical application. This paper analyzes the optimization of ultrasonic in solid food processing, including orthogonal/multi-frequency technology and the combination of ultrasonic and other technologies, which provides new ideas for freezing, cooling, and thawing of solid food processing.

Effects of dual-frequency slit ultrasound on the enzymolysis of high-concentration hydrolyzed feather meal: Biological activities and structural characteristics of hydrolysates

Ultrasound-assisted enzymolysis has been applied to improve conventional enzymolysis, while there are rare reports on the application of ultrasound to high-concentration feather protein enzymolysis. Therefore, the feasibility of dual-frequency slit ultrasound (DFSU) for enzymolysis of high-concentration hydrolyzed feather meal (HFM), as well as the biological activities and structural characteristics of hydrolysates were investigated. The single-factor test was used to optimize the ultrasonic processing parameters: substrate concentration, frequency mode, intermittent ratio, power density, and time. The results showed that protein recovery rate and conversion rate increased by 6.08% and 18.63% under the optimal conditions (200 g/L, 28/80 kHz, 5:2 s/s, 600 W/L, and 3 h) compared with conventional enzymolysis, respectively. The macromolecular proteins in hydrolysates were converted into micromolecular peptides (< 500 Da) when treated by DFSU, and antioxidant activity and angiotensin-I-converting enzyme (ACE) inhibitory activity of hydrolysates were increased. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images illustrated the microstructure changes of feather protein particles in the ultrasound-assisted enzymatic hydrolysates of HFM (UEH), including more porous, smaller, and more uniform. Additionally, the conformation of protein molecules was significantly affected (P < 0.05), including the increase in free sulfhydryl (SH), the decrease in disulfide bond (SS) and surface hydrophobicity (H₀). Fourier transform infrared (FTIR) spectra analysis further showed that the secondary structure of feather proteins was modified with a reduction in α-helix, β-turn, and β-sheet, while an increase in random coil content was observed. These results indicated that DFSU could be a promising method to enhance high-concentration HFM for preparing peptide-rich hydrolysates with high antioxidant activity and ACE inhibitory activity.

A Comparative Study on the Debittering of Kinnow (Citrus reticulate L.) Peels: Microbial, Chemical, and Ultrasound-Assisted Microbial Treatment

Kinnow mandarin (Citrus reticulate L.) peels are a storehouse of well-known bioactive compounds, viz., polyphenols, flavonoids, carotenoids, limonoids, and tocopherol, which exhibit an effective antioxidant capacity. However, naringin is the most predominant bitter flavanone compound found in Kinnow peels that causes their bitterness. It prohibits the effective utilization of peels in food-based products. In the present study, a novel approach for the debittering of Kinnow peels has been established to tackle this problem. A comparative evaluation of the different debittering methods (chemical, microbial, and ultrasound-assisted microbial treatments) used on Kinnow peel naringin and bioactive compounds was conducted. Among the chemical and microbial method; solid-state fermentation with A. niger led to greater extraction of naringin content (7.08 mg/g) from kinnow peels. Moreover, the numerical process optimization of ultrasound-assisted microbial debittering was performed by the Box–Behnken design (BBD) of a response surface methodology to maximize naringin hydrolysis. Among all three debittering methods, ultrasound-assisted microbial debittering led to a greater hydrolysis of naringin content and reduced processing time. The optimum conditions were ultrasound temperature (40 °C), time (30 min), and A. niger koji extract (1.45%) for the maximum extraction rate of naringin (11.91 mg/g). These debittered Kinnow peels can be utilized as raw material to develop therapeutic food products having a high phytochemical composition without any off-flavors or bitterness.

Application of sonodynamic technology and sonosensitizers in food sterilization: a review of developments, trends and challenges

Food safety and food waste have always been hot topics of discussion in recent years. However, the infection of human pathogenic bacteria and the waste of food resources caused by microbial-contaminated food remains common. Although traditional sterilization technology has been very mature, it causes changes in food flavor and excessive energy consumption to a certain extent. Moreover, the widespread bacterial resistance has also sounded a warning for researchers and finding a new alternative to antibiotics is urgently needed. The application of sonodynamic sterilization technology in medical treatment has aroused the interest of researchers. It provides ideas for new food sterilization technology. As a new non-thermal sterilization technology, sonodynamic sterilization technology has strong penetration, safety, less residue and by-products, and will less change the quality of the food itself. Therefore, sonodynamic sterilization technology has great potential applied in food sterilization technology. This review describes the concept of sonodynamic sterilization technology, the sterilization mechanism of sonodynamic sterilization and the inactivation mechanism of various pathogens, the classification and application of sonosensitizers, and the ultrasonic technology in sonodynamic sterilization in the application over the recent years. It provides a scientific reference for the application of sonodynamic sterilization technology in the field of food sterilization.

Effect of Ultrasonic Induction on the Main Physiological and Biochemical Indicators and γ–Aminobutyric Acid Content of Maize during Germination

Research on the nutrient content of cereal grains during germination is becoming a hot topic; however, studies on germinated maize are still scarce. This study aimed to provide a technical reference and theoretical basis for the development of functional maize health foods and to expand the application of ultrasonic technology in the production of germinated grains. In this study, the germination rate of maize was used as the evaluation index, and the ultrasonic frequency, ultrasonic temperature, and induction time were selected as the influencing factors in orthogonal experiments to determine the optimal process parameters for ultrasonic induction of maize germination (ultrasonic frequency of 45 kHz, ultrasonic temperature of 30 °C, and ultrasonic induction time of 30 min). Based on this process, the effects of ultrasonic induction on the main physiological, biochemical, and γ–aminobutyric acid contents of maize during germination were investigated. The results showed that the respiration of the ultrasonic treated maize was significantly enhanced during germination, resulting in a 27% increase in sprout length, as well as a 4.03% higher dry matter consumption rate, and a 2.11% higher starch consumption rate. Furthermore, the reducing sugar content of germinated maize increased by 22.83%, soluble protein content increased by 22.52%, and γ–aminobutyric acid content increased by 30.55% after ultrasonic induction treatment. Throughout the germination process, the glutamate acid decarboxylase activity of the ultrasonically treated maize was higher than that of the control group, indicating that ultrasonication can promote maize germination, accelerate the germination process, and shorten the enrichment time of γ–aminobutyric acid in germinated maize. The results of this study can be applied to the production of γ–aminobutyric acid enrichment in germinated maize.

Ultrasound-assisted enzymatic hydrolysis of yeast β-glucan catalyzed by β-glucanase: Chemical and microstructural analysis

The purpose of this study was to investigate the effect of ultrasound-assisted enzymolysis on modified solubilization of yeast β-glucan and its related mechanism. The depolymerization effects of this system on the physicochemical properties and structural features of the degraded fragments were studied systematically. The structure and physicochemical properties of the samples showed that the solubility of yeast β-glucan achieved 75.35 % after modification; and ultrasonic enzymatic enhanced the degradation efficiency. The yeast β-glucan obtained after solubilization and modification owned better antioxidant activities. The yeast β-glucan particles become obviously smaller, sparsely dispersed in the aqueous solution and the stability was improved. In addition, the hydrogen bonds in yeast β-glucan native triple helix structure were partially broken. Moreover, the disruption of yeast β-glucan's original structure made it decreased thermostability and easier to dissolve in water. The atomic force microscope (AFM) imaging directly verified the branched-chain morphology of yeast β-glucan and the small-strand degradation fragments. Therefore, this research can provide a feasible and effective approach for improving solubility of water-insoluble yeast β-glucan to enlarge its food and biomedical applications.

Nitrate removal under low carbon to nitrogen ratio by modified corn straw bioreactor: Optimization and possible mechanism

ABSTRACTThe removal of nitrate (NO₃^--N) from water bodies under the conditions of poor nutrition and low carbon to nitrogen (C/N) ratio is a widespread problem. In this study, modified corn stalk (CS) was used to immobilize Burkholderia sp. CF6 with cellulose-degrading and denitrifying abilities. The optimal operating parameters of the bioreactor were explored. The results showed that under the hydraulic retention time (HRT) of 3 h and the C/N ratio of 2.0, the maximum nitrate removal efficiency was 96.75%. In addition, the organic substances in the bioreactor under different C/N ratios and HRT were analyzed by three-dimensional fluorescence excitation-emission mass spectrometry (3D-EEM), and it was found that the microorganisms have high metabolic activity. Scanning electron microscope (SEM) showed that the new material has excellent immobilization effects. Fourier transform infrared spectrometer (FTIR) showed that it has potential as a solid carbon source. Through high-throughput sequencing analysis, Burkholderia sp. CF6 was observed as the main bacteria present in the bioreactor. These research results showed that the use of waste corn stalks waste provides a theoretical basis for the advanced treatment of low C/N ratio wastewater.

Trends in "green" and novel methods of pectin modification - A review

Modification of hydrocolloids to alter their functional properties using chemical methods is well documented in the literature. There has been a recent trend of adopting eco-friendly and "green" methods for modification. Pectin, being a very important hydrocolloid finds its use in various food applications due to its gelling, emulsifying, and stabilizing properties. The adoption of various "green" methods can alter the properties of pectin and make it more suitable for incorporation in food products. The novel approaches such as microwave and pulsed electric field can also be utilized for solvent-free modification, making it desirable from the perspective of sustainability, as it reduces the consumption of organic chemicals. Pectic oligosaccharides (POSs) produced via novel approaches are being explored for their biological properties and incorporation in various functional foods. The review can help to set the perspective of potential scale-up and adoption by the food industry for modification of pectin.

Recent Advances in the Application of Enzyme Processing Assisted by Ultrasound in Agri-Foods: A Review

The intensification of processes is essential for the sustainability of the biorefinery concept. Enzyme catalysis assisted by ultrasound (US) may offer interesting opportunities in the agri-food sector because the cavitation effect provided by this technology has been shown to improve the efficiency of the biocatalysts. This review presents the recent advances in this field, focused on three main applications: ultrasound-assisted enzymatic extractions (UAEE), US hydrolysis reactions, and synthesis reactions assisted by US for the manufacturing of agri-food produce and ingredients, enabling the upgrading of agro-industrial waste. Some theoretical and experimental aspects of US that must be considered are also reviewed. Ultrasonic intensity (UI) is the main parameter affecting the catalytic activity of enzymes, but a lack of standardization for its quantification makes it unsuitable to properly compare results. Applications of enzyme catalysis assisted by US in agri-foods have been mostly concentrated in UAEE of bioactive compounds. In second place, US hydrolysis reactions have been applied for juice and beverage manufacturing, with some interesting applications for producing bioactive peptides. In last place, a few efforts have been performed regarding synthesis reactions, mainly through trans and esterification to produce structured lipids and sugar esters, while incipient applications for the synthesis of oligosaccharides show promising results. In most cases, US has improved the reaction yield, but much information is lacking on how different sonication conditions affect kinetic parameters. Future research should be performed under a multidisciplinary approach for better comprehension of a very complex phenomenon that occurs in very short time periods.

Ultrasound aided debittering of bitter variety of citrus fruit juice: Effect on chemical, volatile profile and antioxidative potential

In the present study, sonication assisted debittering of pomelo fruit juice was carried out and the effect of sonication along with resin/enzyme on the chemical, phytochemical and volatile composition of juice was also investigated. The optimum conditions for sonication coupled debittering using resin were 50 kHz, 2 min, and 45 ℃ while 50 kHz, 60 min, and 60 ℃ were obtained for enzyme hydrolysis. Sonication treatment not only reduced the debittering time but also enhanced the adsorption and hydrolysis of naringin by 17% and 20% in resin and enzyme respectively. In addition, enzymatic activity was also improved and weakened C-O bonds in naringin. At the same time, sonication significantly affected the bioactive compounds of juice, chemical composition, and volatile compounds of juice. Flavor compounds including octanal, linalool, citral, and ethyl butyrate were enhanced by sonication-assisted enzymatic treated juice.

Application of multi-frequency power ultrasound in selected food processing using large-scale reactors: A review

Ultrasound as an eco-friendly green technology has been widely studied in food processing. Nevertheless, there is a lack of publications regarding the application of ultrasound in food processing using large-scale reactors. In this paper, the mechanisms and the devices of multi-frequency power ultrasound (MFPU) are described. Moreover, the MFPU applied in enzymolysis of protein, and washing of fruits and vegetables are reviewed. The application of MFPU can improve the enzymolysis of protein through modification on enzyme, modification on substrate materials, and facilitation of the enzymatic hydrolysis process. The ultrasound treatment can enhance the removal of microorganisms, and pesticides on the surface of fruits and vegetables. Furthermore, the reactors of ultrasound-assisted enzymolysis of protein, and washing of fruits and vegetables on the industrial scale are also detailed. This review paper also considers future trends, limitations, drawbacks, and developments of ultrasound application in enzymolysis and washing.

Changes in collagen properties and cathepsin activity of beef M. semitendinosus by the application of ultrasound during post-mortem aging

The effects of ultrasound (0, 300 and 600 W for 20 min at the frequency of 20 kHz) followed by postmortem aging (0, 4 and 8 d aging time) on beef quality were evaluated. Ultrasound treatment, aging time and their interaction all significantly affected the pH and tenderness of beef (p < 0.05). Furthermore, ultrasound improved the cathepsin B + L activities and the solubility of collagen compared with the control without ultrasound treatment (p < 0.05). In terms of microstructure, the perimysium was ruptured by the ultrasound treatment which caused the collagen fibers to be disorderly and loosely arranged. In addition, ultrasound could affect the structural stability of collagen resulting in a significant reduction of thermal denaturation temperature (p < 0.05). The results showed that ultrasound could improve beef tenderness during postmortem aging by changing collagen structure and regulating the activities of cathepsin B + L.