Ronghai He

Effect of energy-gathered ultrasound on Alcalase

This research was to explore the mechanism of ultrasonic impact on protease activity. The effects of energy-gathered ultrasound on the activity, kinetics, thermodynamics and molecular structure of Alcalase were investigated with the aid of the chemical reaction kinetics model, Arrhenius equation, Eyring transition state theory, fluorescence spectroscopy and circular dichroism (CD) spectroscopy. Results showed that ultrasound had effect on the activity of Alcalase. The highest Alcalase activity was achieved when the sample was treated with energy-gathered ultrasound at 80 W for 4 min, under which the enzyme activity was increased by 5.8% over the control. After the treatment, thermodynamics parameters Ea, ΔH, ΔS and ΔG were reduced by 70.0%, 75.8%, 34.0% and 1.3%, respectively. Besides, fluorescence and CD spectra revealed that the ultrasonic treatment had increased the number of tryptophan on Alcalase surface slightly, increased number of α-helix by 5.2%, and reduced the number of random coil by 13.6%.

Enzymolysis kinetics and activities of ACE inhibitory peptides from wheat germ protein prepared with SFP ultrasound-assisted processing

There is a great demand for developing efficient enzymolysis methods in order to increase the enzymolysis efficiencies and activities of angiotensin converting enzyme (ACE) inhibitory peptides from wheat germ protein. The enzymolysis kinetics, ACE inhibitory activity of peptide and conversion rate of protein were studied using sweep frequency and pulsed (SFP) ultrasound-assisted enzymolysis and the results were compared with traditional enzymolysis. The studied factors were enzymolysis time and substrate concentration. By considering the activity of ACE inhibitory peptide and operation cost, the recommended conditions of SFP ultrasound-assisted enzymolysis were enzymolysis time of 120 min and substrate concentration of 24.0 g/L, which gave high conversion rates of protein (60.7%) and ACE inhibitory activity of peptide (65.9%). Compared to traditional enzymolysis, SFP ultrasound-assisted enzymolysis significantly increased the initial reaction rate (V) by 60.0% at substrate concentration of 24.0 g/L, increased the apparent breakdown rate constant (k(A)) by 66.7%, decreased the apparent constant (K(M)) by 6.9%, and raised the conversion rate of protein by 35.5% and ACE inhibitory activity of peptides by 35.6% under the recommended conditions. It has been concluded that SFP ultrasound can remarkably raise the enzymolysis efficiency and activity of ACE inhibitory peptides from wheat germ protein.

Effects of multi-frequency power ultrasound on the enzymolysis and structural characteristics of corn gluten meal

The aim of this study was to investigate the effect of multi-frequency power ultrasound (sweeping frequency and pulsed ultrasound (SFPU) and sequential dual frequency ultrasound (SDFU)) on the enzymolysis of corn gluten meal (CGM) and on the structures of the major protein fractions (zein, glutelin) of CGM. The results showed that multi-frequency power ultrasound pretreatments improved significantly (P<0.05) the degree of hydrolysis and conversion rate of CGM. The changes in UV-Vis spectra, fluorescence emission spectra, surface hydrophobicity (H0), and the content of SH and SS groups indicated unfolding of zein and glutelin by ultrasound. The circular dichroism analysis showed that both pretreatments decreased α-helix and increased β-sheet of glutelin. The SFPU pretreatment had little impact on the secondary structure of zein, while the SDFU increased the α-helix and decreased the β-sheet remarkably. Scanning electron microscope indicated that both pretreatments destroyed the microstructures of glutelin and CGM, reduced the particle size of zein despite that the SDFU induced aggregation was observed. In conclusion, multi-frequency power ultrasound pretreatment is an efficient method in protein proteolysis due to its sonochemistry effect on the molecular conformation as well as on the microstructure of protein.

Effects of ultrasound and ultrasound assisted alkaline pretreatments on the enzymolysis and structural characteristics of rice protein.

The objectives of this study were to investigate the effects of multi-frequency energy-gathered ultrasound (MFEGU) and MFEGU assisted alkaline pretreatments on the enzymolysis and the mechanism of two pretreatments accelerating the rice protein (RP) proteolysis process. The results showed that MFEGU and MFEGU assisted alkaline pretreatments improved significantly (P<0.05) the degree of hydrolysis (DH) and the protein elution amount of RP. Furthermore under the same DH conditions, ultrasound and ultrasound assisted alkaline pretreatments were more save the enzymolysis time than the unpretreatment. The changes in UV-vis spectra, fluorescence emission spectra indicated unfolding and destruction of RP by MFEGU and MFEGU assisted alkaline pretreatments. The circular dichroism analysis showed that both pretreatments decreased α-helix but increased β-sheet and random coil of RP. Amino acid composition revealed that MFEGU and MFEGU assisted alkaline pretreatments could increase the protein elution amount and the ratio of hydrophobic amino acids. Atomic force microscopy (AFM) indicated that both pretreatments destroyed the microstructures and reduced the particle size of RP. Therefore, MFEGU and MFEGU assisted alkaline pretreatments are beneficial to improving the degree of hydrolysis due to its sonochemistry effect on the molecular conformation as well as on the microstructure of protein.

Modeling the QSAR of ACE-Inhibitory Peptides with ANN and Its Applied Illustration.

A quantitative structure-activity relationship (QSAR) model of angiotensin-converting enzyme- (ACE-) inhibitory peptides was built with an artificial neural network (ANN) approach based on structural or activity data of 58 dipeptides (including peptide activity, hydrophilic amino acids content, three-dimensional shape, size, and electrical parameters), the overall correlation coefficient of the predicted versus actual data points is R = 0.928, and the model was applied in ACE-inhibitory peptides preparation from defatted wheat germ protein (DWGP). According to the QSAR model, the C-terminal of the peptide was found to have principal importance on ACE-inhibitory activity, that is, if the C-terminal is hydrophobic amino acid, the peptides ACE-inhibitory activity will be high, and proteins which contain abundant hydrophobic amino acids are suitable to produce ACE-inhibitory peptides. According to the model, DWGP is a good protein material to produce ACE-inhibitory peptides because it contains 42.84% of hydrophobic amino acids, and structural information analysis from the QSAR model showed that proteases of Alcalase and Neutrase were suitable candidates for ACE-inhibitory peptides preparation from DWGP. Considering higher DH and similar ACE-inhibitory activity of hydrolysate compared with Neutrase, Alcalase was finally selected through experimental study.

Effects of ultrasound on microbial growth and enzyme activity

Nowadays, ultrasound is widely used in many aspects. In the last few years, many papers have concentrated on the applications of ultrasound in engineering, chemistry, medicine, physics and biology, but few in biological effects such as the acceleration effects on proliferation of microbial cells, the inactivation effects on microorganisms and the influences on the activities of enzyme. Thus, the objective of this review is to investigate the biological effects of ultrasound on these aspects.

Enzymolysis reaction kinetics and thermodynamics of defatted wheat germ protein with ultrasonic pretreatment.

This research explores the mechanism of ultrasonic pretreatment on enzymolysis of defatted wheat germ protein (DWGP). The enzymolysis reaction kinetics and thermodynamics were studied after ultrasonic pretreatments using a probe-type sonicator and an ultrasonic cleaning bath, and the results were compared with traditional enzymolysis. The results showed that both the traditional and ultrasonic pretreated enzymolysis fit well to first-order kinetics. Both the temperature and ultrasound had a positive effect on the enzymolysis of DWGP, with temperature playing a dominant role. Under the optimized conditions of DWGP concentration of 1% (w/v), Alcalase concentration of 2000 U/g, time of 10 min and temperature of 50 °C, both the probe and cleaning bath ultrasonic pretreated enzymolysis showed high polypeptide concentrations (231.019 and 231.320 μg/mL) and low energy requirements. In comparison with traditional enzymolysis, these methods significantly increased the reaction rate constant (k) by 166.7% and 144.4%, 92.9% and 85.7%, 28.0% and 28.0%, 16.1% and 12.9% at 20, 30, 40 and 50 °C, and decreased the activation energy (Ea), enthalpy of activation (ΔH), Gibbs free energy of activation (ΔG) and entropy of activation (ΔS) by 68.6% and 62.4%, 74.1% and 67.5%, 34.3% and 31.2%, 1.4% and 1.3%. It can be concluded that ultrasonic pretreatment of DWGP can remarkably improve the enzymolysis efficiency and consequently leads to the production of higher polypeptide yield.

Effects of multi-frequency power ultrasound on the enzymolysis of corn gluten meal: Kinetics and thermodynamics study.

The effects of multi-frequency power ultrasound (MPU) pretreatment on the kinetics and thermodynamics of corn gluten meal (CGM) were investigated in this research. The apparent constant (KM), apparent break-down rate constant (kA), reaction rate constants (k), energy of activation (Ea), enthalpy of activation (ΔH), entropy of activation (ΔS) and Gibbs free energy of activation (ΔG) were determined by means of the Michaelis-Menten equation, first-order kinetics model, Arrhenius equation and transition state theory, respectively. The results showed that MPU pretreatment can accelerate the enzymolysis of CGM under different enzymolysis conditions, viz. substrate concentration, enzyme concentration, pH, and temperature. Kinetics analysis revealed that MPU pretreatment decreased the KM value by 26.1% and increased the kA value by 7.3%, indicating ultrasound pretreatment increased the affinity between enzyme and substrate. In addition, the values of k for ultrasound pretreatment were increased by 84.8%, 41.9%, 28.9%, and 18.8% at the temperature of 293, 303, 313 and 323 K, respectively. For the thermodynamic parameters, ultrasound decreased Ea, ΔH and ΔS by 23.0%, 24.3% and 25.3%, respectively, but ultrasound had little change in ΔG value in the temperature range of 293-323 K. In conclusion, MPU pretreatment could remarkably enhance the enzymolysis of CGM, and this method can be applied to protein proteolysis industry to produce peptides.

Effects and mechanism of dual-frequency power ultrasound on the molecular weight distribution of corn gluten meal hydrolysates.

The impact of dual-frequency power ultrasound (DPU) on the molecular weight distribution (MWD) of corn gluten meal (CGM) hydrolysates and its mechanism were investigated in the present study. The mechanism was studied from aspects of structural and nano-mechanical characteristics of the major protein fractions of CGM, viz. zein and glutelin. The results of molecular weight distribution indicated that DPU pretreatment of CGM was beneficial to the preparation of peptides with molecular weights of 200-1000Da. Moreover, FTIR spectral analysis and atomic force microscopy characterization showed that the DPU pretreatment changed the contents of secondary structure of proteins, decreased the particle height and surface roughness of glutelin, reduced the Youngs modulus and stiffness of zein while increased its adhesion force. In conclusion, DPU pretreatment of proteins before proteolysis is an efficient alternative method to produce short-chain peptides because of its positive effects originating from acoustic cavitation on the molecular conformation, nano-structures and nano-mechanical properties of proteins as well.

Effect of Ultrasonic Degradation on In Vitro Antioxidant Activity of Polysaccharides from Porphyra yezoensis (Rhodophyta)

This article aims to study the effect of ultrasonic degradation on antioxidant activity of polysaccharides from Porphyra yezoensis (Rhodophyta) (PSPY), and to look for the relationship between molecular structure of fractions (F1, F2, and F3) from ultrasonic-degraded PSPY (UDPSPY) and their activities of scavenging hydroxyl and superoxide anion radicals, chelating ability of iron ion and reducing power. Results of antioxidant assays indicated that the UDPSPY had higher antioxidant activity of scavenging superoxide anion radical and hydroxyl radical than that of the PSPY. As antioxidant activities of the fractions are concerned, this result might suggest that decreasing molecular weight and increasing sulfate group content in the molecule were vital and necessary factors for improving antioxidant activity of PSPY. Decrease of molecular weight was the dominant reason for increasing activities of scavenging non-site and site specific hydroxyl radical and reducing power of F1, F2, and F3, and increase of sulfate group content in the molecule was the dominant reason for increasing activities of scavenging superoxide anion radical and chelating ferrous ions of F1, F2, and F3. It was possible that ultrasonic treatment could be a new and effective method for enhancing PSPYs antioxidant activity.