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

Abstract

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 and structural characteristics of corn gluten meal

“…It is reported that the water solubility of zein can be increased by enzymatic modification [2], and this can increase its utilization. Nevertheless, the traditional enzymolysis has many disadvantages such as low utilization rate of the enzyme, low conversion rate of the substrate, long enzymolysis time, and energy-extensive consumption [3,4]. This is largely due to the unsuitable conformation of protein, which makes it difficult for the enzyme to attack the cleavage sites.…”

“…Recently, the power ultrasound (20-100 kHz) is widely employed in protein enzymolysis to produce bioactive peptides [16][17][18][19], improvement of the functional properties of proteins [20][21][22][23] and synthesis of lysozyme microspheres [24]. It is reported that power ultrasound pretreatment can improve the reaction rate of enzymolysis, and the conversion rate of substrate proteins, and the bioactivity of target products significantly [4,25,26]. Moreover, ultrasound treatment can lead to changes in the secondary structure [18,27] as well as in the microstructure of protein, resulting in the exposure of more hydrolysis sites to be accessible to protease [28,29].…”

Impact of ultrasound on egg white proteins as a pretreatment for functional hydrolysates production

“…Similarly, in a related study where milk protein concentrate was treated with ultrasound at 800 W [26], an improvement in the protein hydrolysis by several proteases up to 184.9 % after pretreatment was reported, depending on the enzyme used and the pretreatment time. Likewise, an ultrasonic treatment of DWGP at 600 W and 20 °C for 10 min with the probetype sonicator and cleaning bath has shown to significantly decrease the energy barrier required for the hydrolytic reaction, improving the reaction rate [25]. SFU and fixed frequency ultrasound pretreatment at 40 ± 2 kHz have also reported to increase the degree of zein hydrolysis by approximately 11.5 % over the control, by altering the second structure of zein and rupturing the smooth surface of protein [23].…”

“…Although the potential of heat pretreatment to improve enzymatic hydrolysis of EWPs has been explored widely in the last decade [24], such method leads to destruction of some functional properties of egg white, such as gelling and foaming, which are often desirable for food manufacture [13]. Ultrasound pretreatment has also been used to improve the hydrolysis of several proteins [25] and in turn improve the production of angiotensin-converting enzyme (ACE) inhibitory peptides, by causing unfolding of protein chains and thus release possible peptides that are responsible for ACE-inhibitory activity [26]. Despite the promising effects of sonication alone or in combination with heat or pressure on a laboratory scale, there is limited information on the hydrolysis of EWPs from different ultrasound treatments and proteolytic enzyme systems.…”

“…On the other hand, Ren et al [23] reported that the sweeping frequency ultrasound (SFU) treatment at 40 ± 2 kHz can remarkably raise the degree of zein hydrolysis and ACE-inhibitory activity of the hydrolysates. Similarly, Qu et al [25] reported that ultrasound significantly promoted the reaction rate of defatted wheat germ protein (DWGP) hydrolysis at various temperatures using a probe-type sonicator and an ultrasonic cleaning bath. On the contrary, the ultrasonic pretreatment reported to promote the release of ACE-inhibitory peptides from DWGP, whereas the overall DH did not significantly alter at different power intensities and at different times using both ultrasonic horn reactor and ultrasonic bath operating with single fixed and sweep frequencies (24-68 kHz) modes [29].…”