Ultrasound and enzyme treatments on morphology, structures, and adsorption properties of cassava starch

Porous starch materials are environmentally friendly and renewable and exhibit high adsorption performances. Ultrasound and compound enzyme (α-amylase and glucoamylase) treatments were applied to prepare modified cassava starch. The granules, crystal morphology, crystal structure, and molecular structure of starch were investigated. The hydrolysis degree, solubility, swelling, and adsorption properties of cassava starch were analyzed. After the cassava starch was modified by ultrasound and enzyme treatments, the granule size of the starch decreased, and the surfaces were eroded to form pits, grooves and cavity structure. The starch spherulites weakened or even disappeared. The functional groups of starch did not change significantly, but the degree of crystal order decreased. The double-helix structure was reduced, and the crystal structure was composed of A + V-type crystals, with a decrease in crystallinity. The gelatinization temperature and thermal degradation temperatures enhanced. The enzymatic hydrolysis degree and solubility of the modified cassava starch increased. The swelling degree decreased, and oil adsorption, water adsorption improved. MB adsorption behavior of modified cassava starch closely followed a pseudo-second-order kinetics model and the Langmuir isotherm equation. These findings could help to understand the relationship between the structure and properties of modified starch, and guide its application in the field of adsorption.

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.

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.

Structural and biochemical characterization of SmoPG1, an exo-polygalacturonase from Selaginella moellendorffii

Polygalacturonases (PGs) can modulate chemistry and mechanical properties of the plant cell wall through the degradation of pectins, one of its major constituents. PGs are largely used in food, beverage, textile, and paper industries to increase processes' performances. To improve the use of PGs, knowledge of their biochemical, structural and functional features is of prime importance. Our study aims at characterizing SmoPG1, a polygalacturonase from Selaginella moellendorffii, that belongs to the lycophytes. Transcription data showed that SmoPG1 was mainly expressed in S. moellendorffii shoots while phylogenetic analyses suggested that SmoPG1 is an exo-PG, which was confirmed by the biochemical characterization following its expression in heterologous system. Indeed, LC-MS/MS oligoprofiling using various pectic substrates identified galacturonic acid (GalA) as the main hydrolysis product. We found that SmoPG1 was most active on polygalacturonic acid (PGA) at pH 5, and that its activity could be modulated by different cations (Ca2+, Cu2+, Fe2+, Mg2+, Mn2+, Na2+, Zn2+). In addition, SmoPG1 was inhibited by green tea catechins, including (-)-epigallocatechin-3-gallate (EGCG). Docking analyses and MD simulations showed in detail amino acids responsible for the SmoPG1-EGCG interaction. Considering its expression yield and activity, SmoPG1 appears as a prime candidate for the industrial production of GalA.

Mechanically Controlled Enzymatic Polymerization and Remodeling

In nature, proteins possess the remarkable ability to sense and respond to mechanical forces, thereby triggering various biological events, such as bone remodeling and muscle regeneration. However, in synthetic systems, harnessing the mechanical force to induce material growth still remains a challenge. In this study, we aimed to utilize low-frequency ultrasound (US) to activate horseradish peroxidase (HRP) and catalyze free radical polymerization. Our findings demonstrate the efficacy of this mechano-enzymatic chemistry in rapidly remodeling the properties of materials through cross-linking polymerization and surface coating. The resulting samples exhibited a significant enhancement in tensile strength, elongation, and Young's modulus. Moreover, the hydrophobicity of the surface could be completely switched within just 30 min of US treatment. This work presents a novel approach for incorporating mechanical sensing and rapid remodeling capabilities into materials.

Structure-based modification of a-amylase by conventional and emerging technologies: Comparative study on the secondary structure, activity, thermal stability and amylolysis efficiency

α-Amylase is an endo-enzyme that catalyzes the hydrolysis of starch into shorter oligosaccharides. α-Amylase plays a crucial role in various industries. Manipulated α-amylases are of particular interest due to their remarkable amylolysis efficiency and thermostability for large-scale biotechnological processes. The retained catalytic activity of enzymes is decreased according to extreme pH, temperature, pressure, and chemical reagents. Broad industrial applications of α-amylases need special properties such as stability against temperature, pH, and chelators, and also attain reusability, desirable enzymatic activity, efficiency, and selectivity. Considering the biotechnological importance of α-amylase, its high stability is the most critical challenge for its economic viability. Therefore, improving its functionality and stability recently gained much interest. To achieve this purpose, various emerging technologies in combination with conventional methods on α-Amylases with different sources have been conducted. The present review is an attempt to summarize the effect of various conventional methods and emerging technologies employed to date on α-amylase secondary structure, thermal stability, and performance.

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.

Regulation mechanism of magnetic field on pectinase and its preliminary application in postharvest sapodilla (Manilkara zapota)

In this study, regulation mechanism of magnetic field on pectinase was investigated and it was preliminarily applied in postharvest sapodilla. Results indicated pectinase activity decreased by 44 % when treated by magnetic field (3 mT, 0.5 h) with kinetic parameters V_max/K_m decreasing from 0.799 to 0.366 min. The optimal temperature (48 °C) and pH (4.8) of pectinase was not altered by magnetic field but Ca²⁺ at 0.05 mol/L strengthened its regulation effect. Ultraviolet and fluorescence spectra suggested tyrosine and tryptophan residues in treated pectinase became more hydrophobic while opposite in phenylalanine. CO, CNH, COO^- groups in pectinase were also influenced, resulting in decreased β-sheet (from 53 % to 49 %), increased random coil (from 20 % to 22 %) and β-turn content (from 27 % to 29 %). More importantly, the firmness of treated sapodilla remained 45 % of maximum at 12 days' storage. Our findings provided new insights to illustrate the role of magnetic field in fruit preservation.

Toward gentle chokeberry juice production by ultrasound-assisted enzymatic maceration

Sustainable processes accompanied by high extraction yields and minimized amounts of by-products are a major goal of current fruit juice production. Controlled degradation of cell wall polysaccharides, in particular pectin, may contribute to reduced emergence of side streams. Possible strategies for the optimization are the selection of enzyme preparations based on comprehensive studies of their activities, the adjustment of maceration temperature toward more gentle conditions, and the application of alternative technologies such as ultrasound (US) during maceration. The present study provides insights into the effects of ultrasound-assisted enzymatic maceration (UAEM) on pectin degradation, total anthocyanin content, thermal and storage stability, and juice yield during chokeberry juice production on pilot-plant scale. The two enzyme preparations applied predominantly possessed polygalacturonase or pectin lyase activity. Cell wall polysaccharide degradation was improved by US and resulted in a 3% increase in juice yield by UAEM using an enzyme preparation that shows mostly polygalacturonase activity. Thermostability of anthocyanins was improved in juices produced using pectin lyase and applying US and matched the stability of anthocyanins in juices produced using polygalacturonase. Storage stability of anthocyanins was improved in juice produced using polygalacturonase during UAEM. UAEM also resulted in lower yields of pomace making the production more resource-efficient. Overall, the use of polygalacturonase has promising potential to advance conventional chokeberry juice production by applying US at gentle conditions.

Applications of ultrasonication on food enzyme inactivation- recent review report (2017-2022)

Ultrasound processing has been widely applied in food sector for various applications such as decontamination and structural and functional components modifications in food. Enzymes are proteinaceous in nature and are widely used due to its catalytic activity. To mitigate the undesirable effects caused by the enzymes various technologies have been utilized to inactive the enzymes and improve the enzyme efficiency. Ultrasound is an emerging technology that produces acoustic waves which causes rapid formation and collapse of bubbles. It has the capacity to break the hydrogen bonds and interact with the polypeptide chains due to Vander Waals forces leading to the alteration of the secondary and tertiary structure of the enzymes thereby leading to loss in their biological activity. US effectively inactivates various dairy-related enzymes, including alkaline phosphatase (ALP), lactoperoxidase (LPO), and γ-glutamyl transpeptidase (GGTP) with increased US intensity and time without affecting the natural dairy flavors. The review also demonstrates that inactivation of enzymes presents in fruit and vegetables such as polyphenol oxidase (PPO), polygalacturonase (PG), Pectin methyl esterase (PME), and peroxidase. The presence of the enzymes causes detrimental effects causes off-flavors, off-colors, cloudiness, reduction in viscosity of juices, therefore the formation of high-energy free molecules during sonication affects the catalytic function of enzymes and thereby causing inactivation. Therefore this manuscript elucidates the recent advances made in the inactivation of common, enzymes infruits, vegetables and dairy products by the application of ultrasound and also explains the enzyme inactivation kinetics associated. Further this manuscript also discusses the ultrasound with other combined technologies, mechanisms, and its effects on the enzyme inactivation.

Effect of ultrasound on Pseudoneochloris marina and Chlorella zofingiensis growth

The present work evaluated the ultrasound (US) effects on the growth of Pseudoneochloris marina and Chlorella zofingiensis. For P. marina, US treatment did not increase cell proliferation and reduced cell density when used for 60 min (exponential phase, for 5 days), indicating a possible occurrence of cell damage. For C. zofingiensis, the application of discontinuous US for 10 min resulted in an increase of 65 % in biomass concentration compared to the control. These distinct behaviors indicate that microalgae species react differently to physical stimuli. After US treatment, a reduction of carotenoid, chlorophyll, lipid and protein concentrations was observed, which may be related to changes in the metabolic pathways to produce these compounds. Overall, the results of the present study show the potential of discontinuous US to enhance microalgae cell proliferation.

Sono-activation of food enzymes: From principles to practice

Over the last decade, sono-activation of enzymes as an emerging research area has received considerable attention from food researchers. This kind of relatively new application of ultrasound has demonstrated promising potential in facilitating the modern food industry by broadening the application of various food enzymes, improving relevant industrial unit operation and productivity, as well as increasing the yield of target products. This review aims to provide insight into the fundamental principles and possible industrialization strategies of the sono-activation of food enzymes to facilitate its commercialization. This review first provides an overview of ultrasound application in the activation of food protease, carbohydrase, and lipase. Then, the recent development on ultrasound activation of food enzymes is discussed on aspects including mechanisms, influencing factors, modification effects, and its applications in real food systems for free and immobilized enzymes. Despite the far fewer studies on sono-activation of immobilized enzymes compared with those on free enzymes, we endeavored to summarize the relevant aspects in three stages: ultrasound pretreatment of free enzyme/carrier, assistance in immobilization process, and modification of the already immobilized enzyme. Lastly, challenges for the scalability of ultrasound in these target areas are discussed and future research prospects are proposed.

Transcriptomic and physiological analysis reveals the possible mechanism of ultrasound inhibiting strawberry (Fragaria × ananassa Duch.) postharvest softening

Ultrasound effectively inhibited strawberry softening but the mechanism was not clear. In this study, physical data including firmness, soluble pectin (SP) contents, pectin esterase (PE), polygalacturonase (PG) activity and transcriptome sequencing data were analyzed to explore the mechanism of strawberry response to ultrasonic treatment. After 24 days storage, the firmness reduction rate and soluble contents (SP) increased rate of the strawberry treated with ultrasound (25 kHz, 0.15 W/cm2) for 3 min decreased 41.70 and 63.12% compared with the control, respectively. While the PG and PE enzyme activities of ultrasound-treated strawberries were significantly lower than control after storage for 18 days. A total of 1,905 diferentially expressed genes (DEGs) were identified between ultrasound-treated and control, with 714 genes upregulated and 1,254 genes downregulated, including 56 genes in reactive oxygen species (ROS), auxin (AUX), ethylene (ETH) and jasmonic acid (JA) signaling pathways. At 0 h, 15 genes including LOX, JMT, ARP, SKP, SAUR, IAA, ARF, and LAX were significantly upregulated compared with the control group, which means reactive oxygen specie, auxin, ethylene and jasmonic acid-mediated signaling pathway respond to ultrasound immediately. ERF109, ERF110, and ACS1_2_6 downregulated before 2 days storage indicated ethylene signaling pathway was inhibited, while after 2 days, 9 genes including ERF027, ERF109, and ERF110 were significantly upregulated indicating that the response of the ethylene signaling pathway was lagging. Therefore, in strawberry ultrasound enhanced ROS scavenging and activated JA biosynthesis, which acts as a signal for delaying the activation of ET signaling pathway, thus suppressing the activity of pectin-degrading enzymes PE and PG, and ultimately inhibiting postharvest softening.

Ultrasound enhanced butyric acid-lauric acid designer lipid synthesis: Based on artificial neural network and changes in enzymatic structure

Ultrasound is a green technology for intensifying enzymatic reactions. In this study, an ultrasonic water bath with equipment parameters of 28 kHz, 1750.1 W/m², 60% duty cycle was used to assist the synthesis of butyric acid-lauric acid designer lipid (BLDL), which was catalyzed by Lipozyme 435. A convincing three-layer feed-forward artificial neural network (ANN) model was established (R² = 0.949, RMSE = 4.759, ADD = 7.329) to accurately predict the optimal parameters combination, which was described as 13.72 mL reaction volume, 15.49% enzyme loading, 0.253 substrate molar ratio (tributyrin/lauric acid), 56.58 °C reaction temperature and 120 min reaction time. The ultrasonic assistance increased actual butyric acid conversion rate by 11.38%, and also enhanced the consumption rate of tributyrin and lauric acid during the reaction. Meanwhile, the esterification activity of Lipozyme 435 was enhanced and its effectiveness up to 6 cycles. Structurally, ultrasound assistance significantly disrupted the secondary structure of the Lipozyme 435: reduced the content of α-helices, increased the content of β-sheet and β-turn. In addition, sonication caused an increase in crevice and micro-damage on the surface of the immobilized enzyme. In conclusion, low-intensity ultrasound at 28 kHz improved the synthesis efficiency of BLDL, which was scientifically predicted by ANN model, and the change of enzyme structure may be the vital reason for ultrasound enhanced reaction. However, the effect of ultrasound on immobilized enzymes' activity needs to be further explored.

Evaluation of ultrasound waves for the production of chitinase and β-1,3 glucanase by Trichoderma harzianum through SSF

Cell wall degrading enzymes (chitinase and β-1,3-glucanase) were produced by solid-state fermentation (SSF) using the fungus Trichoderma harzianum and different agro-industrial products, mainly residues. The influence of temperature (25-35 °C), initial moisture content (50-90% w/w), nutrient solution (1-2% v/w), and yeast extract (1-2% w/w) on enzyme activity was evaluated. The application of ultrasound during fermentation for different times (0-6 h/day) was also studied. White rice was the substrate that showed the highest chitinase and β-1,3-glucanase activities, which were 31.31 U/g for chitinase and 23.83 U/g for β-1,3-glucanase after 10 days of fermentation. Application of ultrasound waves during fermentation positively affected (p < 0.05) the enzyme activities. The best results for chitinase (51.88 U/g) and β-1,3-glucanase (39.22 U/g) were obtained with a 50% (w/w) moisture content and 4 h/day ultrasound application for 10 days of fermentation. Increases of 3.6-fold (from 14.37 to 51.88 U/g) and 3.8-fold (from 10.22 to 39.22 U/g) in activities for chitinase and β-1,3-glucanase, respectively, compared to non-sonicated fermentation, were obtained. Ultrasound technique associated with the SSF process was a promising alternative to increase the production activity of cell wall degrading enzymes: chitinase and β-1,3-glucanase.

Current Strategies for Real-Time Enzyme Activation

Enzyme activation is a powerful means of achieving biotransformation function, aiming to intensify the reaction processes with a higher yield of product in a short time, and can be exploited for diverse applications. However, conventional activation strategies such as genetic engineering and chemical modification are generally irreversible for enzyme activity, and they also have many limitations, including complex processes and unpredictable results. Recently, near-infrared (NIR), alternating magnetic field (AMF), microwave and ultrasound irradiation, as real-time and precise activation strategies for enzyme analysis, can address many limitations due to their deep penetrability, sustainability, low invasiveness, and sustainability and have been applied in many fields, such as biomedical and industrial applications and chemical synthesis. These spatiotemporal and controllable activation strategies can transfer light, electromagnetic, or ultrasound energy to enzymes, leading to favorable conformational changes and improving the thermal stability, stereoselectivity, and kinetics of enzymes. Furthermore, the different mechanisms of activation strategies have determined the type of applicable enzymes and manipulated protocol designs that either immobilize enzymes on nanomaterials responsive to light or magnetic fields or directly influence enzymatic properties. To employ these effects to finely and efficiently activate enzyme activity, the physicochemical features of nanomaterials and parameters, including the frequency and intensity of activation methods, must be optimized. Therefore, this review offers a comprehensive overview related to emerging technologies for achieving real-time enzyme activation and summarizes their characteristics and advanced applications.

The promoted hydrolysis effect of cellulase with ultrasound treatment is reflected on the sonicated rather than native brown rice

Brown rice is nutritionally superior to polished white rice, as it maintains a large content of external bran that involves a series of bioactive compounds. However, the presence of bran also restricts water diffusion and results in adverse quality of brown rice. In this work, ultrasound conditions were optimized for cellulase to improve its hydrolysis effect on rice bran, and combinations of enzymatic and ultrasound treatment in different manners were conducted on brown rice, to improve the textural attributes. The results showed significant improvements in the catalytic activity and efficiency of cellulase after ultrasonication at the optimal intensity of 1.67 W cm-3 and duration of 30 min, with the conformational variation of cellulase observed from the fluorescence spectra and circular dichroism (CD). Despite the enhanced activity of ultrasonicated cellulase, it leaded to a similar rice surface morphology and a comparable amount of released glucose, and equivalent textural parameters of brown rice treated by native cellulase. However, for the pre-sonicated brown rice, the ultrasonicated cellulase showed a significantly higher hydrolysis capacity than the untreated enzyme, suggesting the important influence of ruptured bran surface on amplifying the hydrolysis effect of cellulase. Compared to the successive ultrasound stimulation on both cellulase and brown rice, ultrasound-assisted cellulase treatment on brown rice produced less glucose from rice bran, but induced similar textural properties of brown rice, possibly resulting from the simultaneously promoting effect of ultrasonication on cellulase and water diffusion. Ultimately, this study highlighted that the mild rice surface rupture is a crucial factor to display the promoted hydrolysis effect of ultrasonicated cellulase on brown rice. Ultrasound-assisted cellulase treatment potentially provides an effective strategy to improve the edible quality of brown rice.

A parameter study of ultrasound assisted enzymatic esterification

This work is focused on the study of the esterification parameters for the ultrasound assisted synthesis of isoamyl acetate catalyzed by lipase Lipozyme 435 in a continuous loop reactor. Investigating the influence of different parameters shows that a higher concentration of ester (462 mg/g mixture) can be obtained at a temperature of 50 °C, flow rate 0.16 mL/min. The best ultrasonication conditions are: sonication applied continuously for a short time (20 min), ultrasound power 32 mW and amplitude 20%. The enzyme can be successfully reused tree times without loss of enzyme activity. Reaction kinetics for isoamyl acetate ultrasound assisted production showed that satisfactory reaction concentration (close to the equilibrium concentrations) could be reached in short reaction times (2 h). Ultrasound assisted enzymatic esterification is consequently a cleaner and a faster process.

Optimization of ultrasound-assisted enzymatic pretreatment for enhanced extraction of baicalein and wogonin from Scutellaria baicalensis roots

It is of great theoretical interest and industrial significance to improve the extraction efficiency of baicalein and wogonin from Scutellaria baicalensis roots because of their high pharmacological activities. The present study was aimed to establish the optimized ultrasound-assisted enzymatic pretreatment (UAEP) process by which ultrasound irradiation and the exogenous enzyme were simultaneously applied to efficiently transform baicalin and wogonoside into baicalein and wogonin, enhancing their extraction efficiency. Single-factor experiment and Box-Behnken design were used to optimize the main UAEP conditions to maximize the total extraction yield of baicalein and wogonin. The optimized UAEP conditions were cellulase concentration of 1.1%, pH of 5.5, UAEP temperature of 56.5 °C, UAEP time of 39.4 min, and ultrasonic power of 200 W with the total extraction yield of 82.51 ± 0.85 mg/g DW. The comparison of the established technique with the reference method based on the enzymatic pretreatment revealed that the productive efficiency was significantly improved with the transformation rates nearly doubled. These results suggest that the optimized UAEP process has the potential to be applied for the green, simple, and efficient extraction of baicalein and wogonin in the pharmaceutical and food industry.

Effects of ultrasound on the enzymatic degradation of pectin

Ultrasound-assisted enzymatic maceration (UAEM) has gained considerable interest in the fruit juice industry, owing to its potential to increase juice yield and content of polyphenols while simultaneously saving time and energy. In this study, the effects of UAEM (ultrasonic probe, 20 kHz, 21 W*cm^-2 and 33 W*cm^-2) on pectin degradation in a continuous circulation system were investigated over 60 and 90 min. Main pectinolytic enzymes activities of (polygalacturonase, pectin lyase and pectin methylesterase) of a commercial enzyme preparation were examined for individual synergistic effects with US. Pectin hydrolysis by UAEM differed significantly compared to treatment with ultrasound or enzymes alone regarding the profile of degradation products compared to treatment with ultrasound or enzymes alone. Ultrasound fragmented pectin to less branched oligomers of medium molecular weight (Mp approx. 150 kDa), which were further degraded by pectinolytic activities. The low molecular weight fraction (<30 kDa), which is known to be beneficial for juice-quality by adding nutritional value and stabilizing polyphenols, was enriched in small oligomers of homogalacturonan-derived, rhamnogalacturonan I-derived, and rhamnogalacturonan II-derived residues. Synergistic effects of ultrasound application enhanced the effective activities of polygalacturonase and pectin lyase and even prolonged their performance over 90 min, whereas the effective activity of pectin methylesterase was not affected. Final marker concentrations determined by each enzyme assay revealed a considerable higher total process output after UAEM treatment at reduced temperature (30 °C) comparable to the output after conventional batch maceration at 50 °C. The obtained results demonstrate the high potential of UAEM to produce high-quality juice by controlling pectin degradation while reducing process temperature and equally highlight the matrix and enzyme specific effects of a simultaneous US treatment.

Ultrasound for pectinase modification: an investigation into potential mechanisms

BACKGROUND

Today, ultrasound is increasingly utilized in enzyme modification. Strongly dependent on the specific operational conditions, the modification effect brought by ultrasound can be activation and inactivation of enzymes. This work aims to study the ultrasound mechanisms under different conditions, to investigate the respective roles of free radical effect and mechanical effect in pectinase activation and inactivation, and to reveal the influence of pectinase concentration on the ultrasound-modification effect.

RESULTS

When ultrasound was introduced to a liquid system, generation of free radicals was positively correlated with ultrasound intensity and treatment duration, but negatively correlated with temperature. Thiourea with a concentration of 4 mmol L^-1 was selected as a free radical scavenger to effectively shield ultrasound free radicals. The highest enzyme activity of pectinase solutions at 0.1, 1.0, and 10.0 mg mL^-1 was obtained at the same ultrasound intensity of 4.50 W mL^-1 and time of 15 min, where the enzyme activity was increased by 68.24%, 20.98% and 18.83%, respectively. Furthermore, the addition of thiourea enhanced the enzyme activity at each tested ultrasound intensity and time, especially those exceeding the best conditions; it also eliminated the redshift phenomenon that was previously presented in the fluorescence spectra of pectinase samples.

CONCLUSION

Pectinase concentrations did not change the optimum ultrasound conditions for enzyme modification, but pectinase with a low concentration was more vulnerable to ultrasound treatment. During modification, ultrasound mechanical effects dominated in the pectinase activation, while free radical effects dominated in the inactivation process. © 2020 Society of Chemical Industry.

Effects of high power ultrasound on the enzymolysis and structures of sweet potato starch

BACKGROUND

The general enzymatic method for producing reducing sugar is liquefaction followed by saccharification of starch. This method results in lower yields, consuming high energy and time. Therefore, the present study evaluated a new approach for producing reducing sugar from sweet potato starch (SPS), including simultaneous liquefaction (by α-amylase) and saccharification (by glucoamylase) of SPS pretreated with high power ultrasound. The effects of ultrasound parameters on the conversion rate of SPS and mechanism were investigated.

RESULTS

The optimum ultrasound pretreatment conditions were a frequency of 20 kHz, SPS concentration of 125 g L^-1 , temperature of 30 °C, pulsed on-time of 3 s, pulsed off-time of 5 s, power density of 8 W mL^-1 and sonication time of 15 min. The ultrasound assisted enzymolysis resulted in a SPS conversion rate of 59.10%, which was improved by 56.35% compared to the control. The results of pasting properties and thermal analysis showed that ultrasound pretreatment decreased the peak viscosity, breakdown temperature, setback viscosity, gelatinization range (T_C  - T_O ) and enthalpy of gelatinization (ΔH) of SPS significantly (P < 0.05) by 12.1%, 7.6%, 6.6%, 18.8% and 44.4%, respectively. Fourier-transform infrared spectroscopy indicated that ultrasound damaged the ordered structures and crystallization zone. This was confirmed by X-ray diffraction analysis, which showed that the relative crystallinity was reduced by 15.0%. Scanning electron microscopy showed that ultrasound destroyed the surfaces and the linkages between starch granules.

CONCLUSION

Prior to simultaneous liquefaction and saccharification of SPS, high power ultrasound pretreatment is a promising method for improving the conversion rate of starch. © 2020 Society of Chemical Industry.

Influence of vacuum soaking on the brewing properties of japonica rice and the quality of Chinese rice wine

Soaking is an important process in Chinese rice wine brewing. In this study, the influence of vacuum soaking on Chinese rice wine production was investigated. Rice subjected to a 1-h vacuum soaking process or a traditional 2-days soaking process was steamed and fermented. Our results showed that vacuum soaking led to similar absorbed water but less leached solids compared with traditional soaking and showed limited influence on the physiochemical characteristics of steamed rice. Monitoring of the fermentation process suggested that the content of amino acid nitrogen in the vacuum-soaked group was significantly higher than that of the traditional-soaked group, while the other indexes were similar. The detection of flavor substances in the rice wine indicated that the contents of organic acids and free amino acids were higher in the vacuum-soaked group, and the main kinds of volatile flavor compounds from the two groups were similar. Additionally, sensory evaluation reflected that the rice wine brewed with rice subjected to either of the two different soaking treatments had similar sensory performances. Our research indicated that vacuum soaking could effectively shorten the soaking time of rice in Chinese rice wine production, thus shortening the brewing cycle without sacrificing the quality of the rice wine.

Study on the mechanism of ultrasound-accelerated enzymatic hydrolysis of starch: Analysis of ultrasound effect on different objects

Enzymatic hydrolysis of starch is an important process in the food industry. In the present work, ultrasound was introduced in glucoamylase pretreatment, starch pretreatment and mixed reaction system treatment to enhance starch hydrolysis efficiency. These different processes were studied to explore the mechanism of ultrasound in promoting enzymatic reactions. The hydrolysis degree of starch was determined via measuring the reducing sugar yield. Ultrasound caused enzyme inactivation under high temperatures, high ultrasonic power and long-time treatment, especially at high temperatures exceeding 65 °C. Ultrasound pretreatment of starch before enzymolysis led to the furtherance of starch hydrolysis degree. Meanwhile, sonicating the mixed enzymatic reaction system below 65 °C promoted starch hydrolysis significantly, inducing more than five- fold growth in the degree of starch hydrolysis as much as the ultrasound pretreatment caused. Molecular weights analysis conducted by the MALLS system reflected the enormous damage of starch molecules caused by ultrasound. The amylose contents and chain length distributions of samples were separately analyzed by iodine binding method and size exclusion chromatography. The results of the two experiments illustrate that ultrasound could promote the enzymatic hydrolysis of amylopectin, which is harder for glucoamylase to hydrolyze compared to amylose.

Enhancement of chitin suspension hydrolysis by a combination of ultrasound and chitinase

This study evaluated the degradation kinetics and structural characteristics of chitin suspension (CS) with a combination of ultrasound and chitinase. Compared with the enzymolysis, the degradation degree of sonoenzymolysis was enhanced to the maximum by 27.93 % at an intensity of 25 W/mL for 20 min. According to degradation kinetics, ultrasound intensified molecular collision rate between chitinase and substrate, thereby increasing the degradation degree. What's more, combined with chitinase, ultrasound intensified the rate of the breakage of glycosidic bond and viscosity-average molecular weight (M_v) decrease, but no obvious change in acetylation degree (DA). Additionally, the intra- or inter-hydrogen bindings were weakened by ultrasound during sonoenzymolysis, leading to a slight decrease in crystalline index and a more ordered structure, which increased the accessibility of the substrate to enzyme. In conclusion, combination of chitinase and ultrasound could enhance the hydrolysis of CS while without changing its primary structure.

Effects of power ultrasound on the activity and structure of β-D-glucosidase with potentially aroma-enhancing capability

β-d-glucosidase can release aroma precursors to improve the flavor of plant food, but the hydrolysis efficiency of the enzyme is low; the purpose of this study was to improve the enzyme activity using ultrasound. The effects of ultrasound parameters on β-d-glucosidase activity were investigated, and the respective structures of enzyme activated and enzyme inhibited were further analyzed. Low temperature (20-45°C), low ultrasonic intensity (<181.53 W/cm2), and short treatment time (<15 min) led to the activation of β-d-glucosidase, whereas high temperature (45-60°C), high ultrasonic intensity (>181.53 W/cm2), and long treatment time (>15 min) led to its inhibition. Application of ultrasound lowered the optimum temperature for β-d-glucosidase activity from 50 to 40°C. Ultrasound did not change the primary structures of the enzyme, but changed the secondary structures. When ultrasound activated β-d-glucosidase, the α-helix contents were increased, the β-fold and irregular coil content were reduced. When ultrasound inhibited β-d-glucosidase, the contents of β-folds were increased, the α-helix and irregular coil contents were reduced.. In summary, activation or inhibition of β-d-glucosidase under ultrasound was determined by the ultrasound conditions. This study suggests that ultrasound combined with β-D-glucosidase can be used in aroma-enhancing.

Activation and conformational changes of chitinase induced by ultrasound

This study investigated the effect of ultrasound on chitinase activity and conformational changes. Results revealed that ultrasound activated chitinase with a maximum enhancement of 19.17% compared with the untreated chitinase. Furthermore, an increase of V_max and a decrease of K_m after sonication were obtained, illustrating that the affinity between chitinase and substrate was intensified. No obvious effect on the tolerance to most metal ions was exhibited whether sonicated or not (p > 0.05). The conformational changes of chitinase were analyzed by circular dichroism (CD), Fourier transform infrared (FTIR), Raman and fluorescence spectroscopy. Results indicated that the activation of chitinase induced by ultrasound was presumably due to the decrease of tryptophan on the chitinase surface and the increase of β-sheet and random coil in chitinase secondary conformation. In brief, ultrasound is a possible way to activate chitinase to increase its application in food industry.

Degradation of carboxymethylcellulose using ultrasound and β-glucanase: Pathways, kinetics and hydrolysates' properties

In order to provide an efficient way to degrade carboxymethylcellulose (CMC), three pathways were investigated: enzymolysis, combination of ultrasound pretreatment and enzymolysis, and sonoenzymolysis. Effects of these treatments on enzymatic kinetics, degradation kinetics and properties of degraded CMC were investigated. The degradation degree of CMC was increased by 18.90% and 35.73% with ultrasound pretreatment (at an intensity of 24 W/mL for 30 min) and sonoenzymolysis (at an intensity of 9 W/mL for 50 min), compared with that obtained under the traditional enzymolysis. Analysis of kinetics demonstrated that ultrasound, both pretreatment and combined with β-glucanase, could accelerate CMC degradation. Measurements of rheological properties, molecular weight and structures of CMC hydrolysates revealed that ultrasound broke the glycosidic bond of CMC chains without changing its primary structure. The sonoenzymolysis process was the most efficient method to degrade CMC, with potential to provide a way to obtain CMC with lowest molecular weight or viscosity.

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

With the extensive application of enzyme-catalyzed reactions in numerous fields, improving enzymatic efficiency has attracted wide attention for reducing operating costs and increasing output. There are three targets throughout enzymatic reactions: the enzyme, substrate, and mixed reaction system. Ultrasound has been known to accelerate enzymatic reactions by acting on different targets. It can modify both enzyme and substrate macromolecules, which is helpful for enhancing enzyme activity and product yields. The synergistic effect of ultrasound and enzymes is widely reported to increase catalytic rates. The present review discusses the positive effect induced by ultrasound throughout the enzymatic process, including ultrasonic modification of enzymes, ultrasound assisted immobilization, ultrasonic pretreatment of substrates, and ultrasound assisted enzymatic reactions.

Comparison of selected clean and green extraction technologies for biomolecules from apple pomace

Apple pomace has been considered as a sustainable source for antioxidant phenolic compounds. Previous reports show extraction of total phenolic contents (TPC) by following various conventional and non-conventional techniques; however, a comparative study has not been reported. In the present work, conventional extraction was compared with several non-conventional extraction methods including ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), high-speed homogenization (HH). Moreover, efficacy of combined treatments, including high-speed homogenization coupled with MAE and ultrasound-assisted enzymatic extraction (UAEE) was evaluated for the recovery of TPC. The results revealed that UAEE results in the highest TPC (4.62 mg GAE/g), moreover, it simultaneously enabled the recovery of low methoxy pectins with the degree of methylation ranging from 14.03- 28.85%. The LC-Q-Tof analysis revealed the presence of various phenolic acids and flavonoids. The DPPH radical scavenging assay showed that the phenolic rich extracts had IC50 values ranging from 27.1 to 54.6, depending on the extraction parameters. This article is protected by copyright. All rights reserved.

Ultrasound assisted intensification of enzyme activity and its properties: a mini-review

Over the last decade, ultrasound technique has emerged as the potential technology which shows large applications in food and biotechnology processes. Earlier, ultrasound has been employed as a method of enzyme inactivation but recently, it has been found that ultrasound does not inactivate all enzymes, particularly, under mild conditions. It has been shown that the use of ultrasonic treatment at appropriate frequencies and intensity levels can lead to enhanced enzyme activity due to favourable conformational changes in protein molecules without altering its structural integrity. The present review article gives an overview of influence of ultrasound irradiation parameters (intensity, duty cycle and frequency) and enzyme related factors (enzyme concentration, temperature and pH) on the catalytic activity of enzyme during ultrasound treatment. Also, it includes the effect of ultrasound on thermal kinetic parameters and Michaelis-Menten kinetic parameters (k_m and V_max) of enzymes. Further, in this review, the physical and chemical effects of ultrasound on enzyme have been correlated with thermodynamic parameters (enthalpy and entropy). Various techniques used for investigating the conformation changes in enzyme after sonication have been highlighted. At the end, different techniques of immobilization for ultrasound treated enzyme have been summarized.

Ultrasound assisted enzymatic hydrolysis of starch catalyzed by glucoamylase: Investigation on starch properties and degradation kinetics

The present work investigates the synergistic impact of glucoamylase and ultrasound on starch hydrolysis. The extent of starch hydrolysis at different reaction parameters (ultrasonic intensity, temperature, reaction time) was analyzed. The hydrolysis extent increased with the reaction time and reached a maximum value under ultrasonic intensity of 7.20W/mL at 10min. Ultrasound did not alter the optimum enzymatic temperature but speeded up the thermal inactivation of glucoamylase. The evaluation of enzymatic kinetics and starch degradation kinetics indicated a promotion of the reaction rate and enzyme-substrate affinity. According to the thermodynamic results, sonoenzymolysis reactions require less energy than enzymolysis reactions. The measurement of molecular weight, solubility, thermal properties, and structures of the substrates revealed that sonoenzymolysis reaction generated greater impacts on starch properties. The molecular weight and radii of gyration decreased by 80.19% and 90.05% respectively while the starch solubility improved by 136.50%.

Characteristics of pectinase treated with ultrasound both during and after the immobilization process

In this study, ultrasound was applied both during and after the immobilization process and characteristics of different immobilized pectinase samples were studied. When introduced during the immobilization process, ultrasound at an intensity of 9WmL^-1 for 20min increased the immobilization yield 92.28% more than the control. When introduced to the already immobilized pectinase, ultrasound at an intensity of 4.5WmL^-1 for 10min increased the pectinase activity by 30.05%. Results of scanning electron microscope demonstrated that ultrasound increased surface area and loosened structures of immobilized enzymes. Higher V_max and lower K_m were obtained after ultrasound treatment, indicating the increased catalytic efficiency and enhanced affinity of immobilized pectinase. Furthermore, the optimum temperature and pH for free and immobilized pectinase remained unchanged at 50°C and pH 4. Thermostability, reaction stability and reusability of two ultrasound-treated pectinase enzymes slightly decreased due to structural matrix changes.