Ultrasound-assisted Enzymatic Hydrolysis Research Articles

Enhancing the recovery of complex amino acids from excess sludge via low-intensity ultrasound-assisted enzymatic hydrolysis

The recovery of high-value products such as complex amino acids from activated sludge is a crucial alternative for the recycling of excess sludge, although several challenges still need to be addressed, especially in terms of extraction efficiency and product quality. Herein, a promising approach involving low-intensity ultrasound-assisted enzymatic hydrolysis (UEH) was utilized to obtain complex amino acids from sludge protein. Compared with the values obtained for single enzymatic hydrolysis (EH), after a 20-minute pre-treatment at ambient temperature using low-intensity ultrasound (0.15 W/mL), the enzyme activity increased by 28.7 %, and the degree of protein hydrolysis (DH) correspondingly rose by 93.3 %. The application of ultrasound during subsequent EH resulted in a decrease in DH, with the extent of the decrease increasing over time. This suggested that the primary cause was conformational changes of enzymes rather than mass transfer. Moreover, both the Michaelis–Menten model (R2 > 0.99) and protein hydrolysis model (R2 > 0.96) accurately simulated EH and UEH, indicating that UEH exhibits superior enzyme–substrate affinity and a higher rate of protein hydrolysis. Furthermore, after separation and purification, the total content of seven essential amino acids in the dry material exceeded that in traditional feed sources such as soybean meal. Additionally, the safety test and energy consumption analysis demonstrated that UEH has good potential for the extraction of complex amino acids from excess sludge.

Preparation of housefly (Musca domestica) larvae protein hydrolysates: Influence of dual-sweeping-frequency ultrasound-assisted enzymatic hydrolysis on yield, antioxidative activity, functional and structural attributes

Dual-sweeping-frequency ultrasound (DSFU) was utilized in the preparation of polypeptides from housefly (Musca domestica) larvae protein (HLP). Results indicated that ultrasonication (20 ± 2/28 ± 2 kHz, 42 W/L, 25 min) significantly increased peptide yield and DPPH scavenging capacity by 8.25 % and 14.83 %, respectively. Solubility, foaming and emulsification properties of polypeptides were improved by 19.89 %, 33.33 % and 38.74 % over the control; along with notable reduction in particle size and increase in zeta potential. Tertiary structural changes of the sonicated hydrolysates were illustrated by UV and fluorescence spectra. FTIR showed that ultrasonication increased α-helix, β-turn, and random coil by 38.23 %, 46.35 % and 16.36 %, respectively, but decreased β-sheet by 48.03 %, indicating partial unfolding in HLP hydrolysate conformation and reduction in intermolecular interactions. The research results demonstrated that dual-sweeping-frequency ultrasonication has a great prospect in industry application for the purpose of improving enzymolysis efficiency and product quality for housefly larvae protein hydrolysates production.

Optimization of ultrasound-assisted enzymatic hydrolysis of channel catfish (Ictalurus punctatus) frames yield high-calcium and high-amino acid hydrolysates

ABSTRACT In this study, a high-calcium and high-amino acid fish frame hydrolyzate (FFH) was prepared from channel catfish (Ictalurus punetaus) through ultrasound-assisted enzymatic hydrolysis (UAEH). A 4-factor and 3-level Box-Behnken design of response surface methodology was employed to optimize the hydrolysis conditions, where the independent variables were sonication power (W), sonication time (min), enzyme activity (U) and water-substrate ratio (v/w). The degree of hydrolysis (DH) and soluble calcium content (SCC) were used as response factors. The optimal hydrolysis conditions were found to be sonication power (X1) = 492.91 W, sonication time (X2) = 15.01 min, enzyme activity (X3) = 6677.88 U, and water-to-substrate ratio (X4) = 3.56 v/w. Under these conditions, UAEH effectively disintegrated fish frame collagen and converted bound calcium to soluble calcium. Nevertheless, this study investigated the pattern of collagen transformation into short peptides and free amino acids throughout the degradation process. These findings highlight the potential of the FFH from channel catfish to serve as a foundation for creating highly nutritious food additive. The outcomes of this study further enhance the food industry’s ability to capitalize on the nutritional benefits offered by fish frame hydrolyzates. This expansion of health-focused product options and endorsement of the sustainable use of fish by-products harmonizes seamlessly with the industry’s evolving goals of waste reduction and value optimization.

Study on the anti-inflammatory activity of the porcine bone collagen peptides prepared by ultrasound-assisted enzymatic hydrolysis

In this study, the effects of ultrasound-assisted enzymatic hydrolysis on the extraction of anti-inflammatory peptides from porcine bone collagen were investigated. The results showed that ultrasound treatment increased the content of α-helix while decreased β-chain and random coil, promoted generation of small molecular peptides. Ultrasound-assisted enzymatic hydrolysis improved the peptide content, enhanced ABTS+ radical scavenging and ferrous ion chelating ability than non-ultrasound group. At the ultrasonic power of 450 W (20 min), peptides possessed significant anti-inflammatory activity, where the releasing of interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) was all suppressed in lipopolysaccharide (LPS) induced RAW264.7 cells. After the analysis with LC-MS/MS, eight peptides with potential anti-inflammatory activities were selected by the PeptideRanker and molecular docking. In general, the ultrasound-assisted enzymatic hydrolysis was an effective strategy to extract the bioactive peptides from porcine bone, and the inflammatory regulation capacity of bone collagen sourced peptides was firstly demonstrated.

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.

Ultrasound-assisted enzymatic hydrolysis enhances anti-inflammatory and hypoglycemic activities of edible Bird's nest

Edible bird's nest (EBN) is the solidified saliva of swiftlet Aerodramus fuciphagus. It is an expensive premium health food that has long been consumed, especially in China. However, the broken EBN pieces left behind after the cleaning process have low market value due to high contaminants, particularly fine feathers. Thus, EBN hydrolysate (EBNH) is the best downstream product to add value to this low-grade EBN. This study aims to investigate the effects of ultrasound pretreatment on the enzymatic process of EBNH production. Initially, the EBN was treated with ultrasound at different amplitudes (30%, 60%, 90%) and times (15 min, 30 min, 45 min), then hydrolyzed for 1.5 h at 60 °C using papain enzyme (pH 7). The viscosity, degree of hydrolysis (DH), total soluble protein (TSP), anti-lipoxygenase activity and α-amylase inhibition activity of the EBNHs produced were determined. Results suggested that ultrasound amplitude exerted a more prominent effect than time in lowering the viscosity of EBNH. Viscosity of EBNH dropped by 4.4 folds–6.58 ± 0.10 mPa s after 30 min ultrasound at 90% amplitude. Under this condition, the produced EBNH exhibited 61.66 ± 2.89% anti-lipoxygenase activity and 77.40 ± 5.41% α-amylase inhibition activity, which were >100% and 43%, respectively higher than the control. However, ultrasound had exerted no significant effects on DH and TSP. These findings speculate that ultrasound enhances bioactivities of EBNH by modifying intermolecular interactions between glycopeptides and glycoproteins. This study proved that ultrasound is a promising green pretreatment technology in EBNH production. Besides, this study also provides an insight into the importance of pretreatment in bioactive EBNH production.

Comparison of methods for detecting protein extracted from excess activated sludge

The protein contents of hydrolyzed sludge supernatant are commonly determined with the Kjeldahl method, but this method suffers from complicated operations, long process times, and large quantities of chemicals consumed. In this paper, the Lowry, bicinchoninic acid (BCA), and Bradford methods were used to test the precision and spiked recovery of proteins from sludge supernatants hydrolyzed by alkaline-thermal hydrolysis (ATH), enzymatic hydrolysis (EH), and ultrasound-assisted enzymatic hydrolysis (UEH), and the results were compared with those obtained with the Kjeldahl method. For all the hydrolytic processes, the sludge protein values determined with the three tested methods were within 0.05 of each other, which met the experimental requirement for accuracy. Both the Lowry and BCA methods had recovery rates of 95-105%, while the Bradford method showed large deviations and was not highly reliable. The three protein determination methods showed significant differences with the Kjeldahl method (P<0.05). However, the relative deviation between the Kjeldahl and BCA methods was the smallest (3-5%), followed by those between the Kjeldahl and the Lowry (11-21%) and Bradford methods (21-90%), and the causes of the deviations were analyzed based on the protein hydrolysate components and the mechanisms for the different detection methods. On the basis of these results, the BCA method was chosen as the most appropriate quantification method for use with sludge protein extraction, and it was used to analyze the protein contents extracted from residual sludge samples obtained from two sewage treatment plants. The reliability of the method was verified, and this lays a foundation for the extraction and reclamation of sludge proteins.

Optimization of R-Phycoerythrin Extraction by Ultrasound-Assisted Enzymatic Hydrolysis: A Comprehensive Study on the Wet Seaweed Grateloupia turuturu

Enzyme-assisted extraction (EAE) and ultrasound-assisted extraction (UAE) are both recognized as sustainable processes, but little has been done on the combined process known as ultrasound-assisted enzymatic hydrolysis (UAEH), and even less on seaweed. The present study aimed to optimize the UAEH of the red seaweed Grateloupia turuturu for the extraction of R-phycoerythrin (R-PE) directly from the wet biomass by applying a response surface methodology based on a central composite design. Three parameters were studied: the power of ultrasound, the temperature and the flow rate in the experimental system. Data analysis demonstrated that only the temperature had a significant and negative effect on the R-PE extraction yield. Under the optimized conditions, the R-PE kinetic yield reached a plateau between 90 and 210 min, with a yield of 4.28 ± 0.09 mg·g-1 dry weight (dw) at 180 min, corresponding to a yield 2.3 times higher than with the conventional phosphate buffer extraction on freeze-dried G. turuturu. Furthermore, the increased release of R-PE, carbohydrates, carbon and nitrogen can be associated with the degradation of G. turuturu constitutive polysaccharides, as their average molecular weights had been divided by 2.2 in 210 min. Our results thus demonstrated that an optimized UAEH is an efficient method to extract R-PE from wet G. turuturu without the need for expensive pre-treatment steps found in the conventional extraction. UAEH represents a promising and sustainable approach that should be investigated on biomasses where the recovery of added-value compounds needs to be improved.

Structural and physicochemical properties of resistant starch under combined treatments of ultrasound, microwave, and enzyme

The structural characteristics and physicochemical properties of native corn starch (NCS) and resistant starch (RS) prepared by enzymatic hydrolysis (RS-E), microwave-enzymatic hydrolysis (RS-ME), ultrasound assisted enzymatic hydrolysis (RS-UE), and microwave-ultrasound assisted enzymatic hydrolysis (RS-MUE) were investigated. The results showed that the combined treatments of ultrasound, microwave, and enzyme resulted in increases in RS content, amylose content, and solubility with a decrease in swelling power. RS-MUE exhibited the lowest digestibility, with a 41.71 % RS content. Particle-size distribution and scanning electron microscopy analyses demonstrated that RS samples exhibited larger granule sizes and rougher surfaces with irregular shapes. The Fourier transform infrared spectroscopy and X-ray diffraction pattern analysis demonstrated that no new groups were created during the modification processes, the crystal structure of all RS samples changed from A to B + V, and the short-range order and relative crystallinity of RS-E, RS-ME, RS-UE, and RS-MUE increased. RS-MUE exhibited the highest molecular order R1047/1022 value (0.8769) and relative crystallinity (45.54 %). These results suggested that the new technology combining microwave, ultrasound, and enzyme for improving RS content is effective and has potential for application in the production of RS and low glycemic index foods.

Production, identification and characterization of antioxidant peptides from potato protein by energy-divergent and gathered ultrasound assisted enzymatic hydrolysis

Effects of energy divergent ultrasound (EDU, 30, 40 and 50 W/L) and energy gathered ultrasound (EGU)-assisted enzymatic hydrolysis on production, identification and characterization of antioxidant peptides from potato protein hydrolysates (PPH) were investigated. EDU and EGU significantly increased degree of hydrolysis and recovery of PPH compared with conventional (C) enzymatic hydrolysis. PPH by EGU40 showed the highest Fe2+-chelating activity (55.33 µg EDTA/mL), ·OH scavenging activity (230.05 µg Vc/mL) and oxygen radical absorbance capacity (82.24 µg TE/mL). Peptides with molecular weight <1 and 1–2 kDa of PPH by EGU40 displayed higher antioxidant activities than those by C and EDU40, which might be contributed to their more hydrophobic, polar charged and antioxidant amino acids at terminals and/or inside the sequences identified by LC-MS/MS. Additionally, structure–activity relationship was revealed by peptide conformation and position of some specific amino acids. Therefore, EGU has great potential in production of functional peptides with enhanced antioxidant activity.

Ultrasound-assisted enzymatic hydrolysis of tobacco leaf scraps for enhanced utilization of aromatic components

Ultrasound-assisted enzymatic hydrolysis of tobacco leaf scraps for enhanced utilization of aromatic components

Enhancing enzyme activity via low-intensity ultrasound for protein extraction from excess sludge.

Rich protein within excess sludge could be recovered to prepare high value-added products such as liquid fertilizer and foaming agents. Low-intensity ultrasonication was adopted to help extract sludge protein by improving enzyme activity. Alkaline protease was added to the sludge for ultrasonic irradiation, and the maximum enzyme activity at 3500kJ/kg TS was approximately 21% higher than that without ultrasonication. The protein extraction effect, specific resistance of sludge (SRS) and economics of low-intensity ultrasound-assisted enzymatic hydrolysis (LUEH) were compared with those of single enzymatic hydrolysis (EH) and HUEH under optimal conditions. The protein extraction rates of HUEH and LUEH were both higher than that of EH. Although the protein extraction rate of LUEH was 13.6% lower than that of HUEH, the amino acid content was similar because the low-intensity ultrasonic radiation promoted the enzyme activity and thereby enhanced the protein hydrolysis capacity. After hydrolysis, the SRS of LUEH was lower than that of HUEH, indicating that LUEH possessed a better dewatering performance, which was beneficial to the subsequent separation of the protein solution. The amount consumed by LUEH was approximately 20% lower than that consumed by HUEH and 17.3% lower than that consumed by EH. In addition, the enzyme dosage was reduced by approximately 38.5% with LUEH. Therefore, the total cost of LUEH was less than that of EH and HUEH, indicating that LUEH is more economically feasible for the extraction of protein from excess sludge.

Ultrasonication followed by enzymatic hydrolysis as a sample pre-treatment for the determination of Ag nanoparticles in edible seaweed by SP-ICP-MS

Seaweed can bioaccumulate nanomaterials that would be transferred to the trophic chain. This work describes the optimization of a method for the separation of silver nanoparticles (AgNPs) from seaweed using an ultrasound-assisted enzymatic hydrolysis method and ulterior determination by single particle inductively coupled plasma mass spectrometry (SP-ICP-MS).The following parameters affecting the isolation of AgNPs were optimized using a Palmaria palmata (red seaweed) sample previously exposed to AgNPs: type of sonication (bath vs. ultrasonic probe), ultrasound amplitude, sonication time, sonication mode (pulsed vs. continuous sonication), concentration of the enzymes mixture (Macerozyme R-10®), and enzymatic hydrolysis time. The stability of AgNPs during extraction was tested by transmission electron microscopy (TEM) and using a standard of 15 nm of polyvinylpyrrolidone (PVP)-coated AgNPs analyzed by SP-ICP-MS. The analytical performance was evaluated with good results. For total Ag determination, the limits of detection and quantification were 2.2 and 7.7 ng g−1, respectively; and for AgNPs determination, the limits of detection in size and number were 14 nm and 4.34 × 107 part g−1, respectively. Besides, the matrix effect, the repeatability and the analytical recovery were also studied. Finally, the method was applied to the analysis of several red (Palmaria palmata) and green (Ulva sp.) seaweed samples.

Ultrasound-assisted enzymatic hydrolysis of goat milk casein: Effects on hydrolysis kinetics and on the solubility and antioxidant activity of hydrolysates

This study evaluated the ability of ultrasound (US) bath to improve the hydrolysis of goat milk casein (GMC) by three commercial proteases (Alcalase, Brauzyn and Flavourzyme) using assisted reactions at 60 °C for up to 300 min. Process performance was evaluated based on the rate reaction, final hydrolysis degree, solubility, and antioxidant activity of the hydrolysates. For all enzymes, the US-assisted reaction increased the rate of GMC hydrolysis (up to 120%), the hydrolysis degree (23–48%), and the small peptides formed, i.e., those soluble in trichloroacetic acid (TCA) (up to 40%). Consequently, US-assisted GMC hydrolysis improved the solubility of the hydrolyzed product (up to a 35.7% increase after 300 min of reaction) and, compared to conventional hydrolysis, reduced the time to achieve the maximum solubility by up to 10 times. Regarding the in vitro antioxidant activity, especially for Alcalase, the technology promoted a higher scavenging capacity of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (p < 0.05), thus 10-fold accelerating the production of antioxidant peptides, according to ABTS assays (p < 0.05). In conclusion, the US-assisted enzymatic reaction is a promising technology to improve the hydrolysis rate and yield of the process of obtaining hydrolysates from GMC. Moreover, these hydrolysates showed high solubility and good in vitro antioxidant activity, which demonstrates the potential to be used as food ingredient with nutritional and techno-functional appeal.

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.

Green and Simple Extraction of Arsenic Species from Rice Flour Using a Novel Ultrasound-Assisted Enzymatic Hydrolysis Method

It is well established that arsenic (As) has many toxic compounds, and in particular, inorganic As (iAs) has been classified as a type-1 carcinogen. The measuring of As species in rice flour is of great importance since rice is a staple of the diet in many countries and a major contributor to As intake in the Asian diet. In this study, several solvents and techniques for the extraction of As species from rice flour samples prior to their analysis by HPLC-ICP-MS were investigated. The extraction methods were examined for their efficiency in extracting various arsenicals from a rice flour certified reference material, NMIJ-7532a, produced by the National Metrology Institute of Japan. Results show that ultrasound-assisted extraction at 60 °C for 1 h and then heating at 100 °C for 2.5 h in the oven using a thermostable α-amylase aqueous solution was highly effective in liberating the arsenic species. The recoveries of iAs and dimethylarsinic acid (DMA) in NMIJ-7532a were 99.7% ± 1.6% (n = 3) and 98.1% ± 2.3% (n = 3), respectively, in comparison with the certificated values. Thus, the proposed extraction method is a green procedure that does not use any acidic, basic, or organic solvents. Moreover, this extraction method could effectively maintain the integrity of the native arsenic species of As(III), As(V), monomethylarsonate (MMA), DMA, arsenobetaine (AsB) and arsenocholine (AsC). Under the optimum extraction, chromatography and ICP-MS conditions, the limits of detection (LOD) obtained were 0.47 ng g−1, 1.67 ng g−1 and 0.80 ng g−1 for As(III), As(V) and DMA, respectively, while the limits of quantification (LOQ) achieved were 1.51 ng g−1, 5.34 ng g−1 and 2.57 ng g−1 for As(III), As(V) and DMA, respectively. Subsequently, the proposed method was successfully applied to As speciation analysis for several rice flour samples collected from contaminated areas in China.

Ultrasound-assisted enzymatic hydrolysis of broken Riceberry rice for sugar syrup production as a substrate for bacterial cellulose facial mask development

Nanocomposites based on bacterial cellulose in combination with osteogenic growth peptide for bone repair: cytotoxic, genotoxic and mutagenic evaluationsRaquel Mantuaneli Scarel-Caminagaa, Sybele Saskab, Leonardo Pereira Franchic, Raquel A. Santose, Ana Maria Minarelli Gaspara, Ticiana S.O. Capotea, Sidney José Lima Ribeirob, Younés Messaddeqb, Reinaldo Marchetto b, Catarina S. Takahashic d

Caco-2 in vitro model of human gastrointestinal tract for studying the absorption of titanium dioxide and silver nanoparticles from seafood

Titanium dioxide nanoparticles (TiO2 NPs) are widely used in industry as a white pigment (paints, paper industry and toothpastes), photocatalysts (environmental decontamination and photovoltaic cells), inorganic UV filter (sunscreens and personal care products) and as a food additive (E171) and antimicrobial food packaging material. Silver nanoparticles (Ag NPs) are used in photonics, microelectronics, catalysis and medicine due to their catalytic activity, magnetic and optical polarizability, electrical and thermal conductivities and enhanced Raman scattering. They also have antibacterial, antifungal and antiviral activities, as well as anti-inflammatory potential. The huge increase in the use of nano-based products, mainly metallic NPs, implies the presence of nanomaterials in the environment, and hence, the unintentional human ingestion through water or foods (gastrointestinal tract is the main pathway of NPs intake in humans).The presence of TiO2 NPs and Ag NPs in seafood samples was firstly established using an ultrasound assisted enzymatic hydrolysis procedure and sp-ICP-MS analysis. Several clams, cockles, mussels, razor clams, oysters and variegated scallops, which contain TiO2 NPs and Ag NPs, were subjected to an in vitro digestion process simulating human gastrointestinal digestion in the stomach and in the small and large intestine to determine the bioaccessibility of these NPs. Caco-2 cells were selected as model of human intestinal epithelium for transport studies because of the development of membrane transporters that are responsible for the uptake of chemicals. Parameters as transepithelial electrical resistance (TEER) and permeability of Lucifer Yellow were studied for establishing cell monolayer integrity. TiO2 NPs and Ag NPs transport as well as total Ti and Ag concentrations passing through the gastrointestinal epithelial barrier model (0–2 h) were assessed by sp-ICP-MS and ICP-MS in several molluscs.

Comparison of the thermo-oxidative stability of murici oil (Byrsonima crassifolia L. Kunt) obtained by enzymatic hydrolysis assisted by ultrasound and classical method

The extraction of oil from various raw materials by enzymatic process has received great importance for being considered clean technology. In addition, the product obtained by enzymatic action has better yields as well as better chemical quality parameters, also better stability conditions. Thus, the objective of the present work was to optimize the murici pulp oil extraction process by enzymatic hydrolysis and to compare the thermo-oxidative stability of murici oil extracted by ultrasound-assisted enzymatic hydrolysis and the oil obtained by the classic method (Soxhlet). The results obtained showed a dependence on the dependent variable - yield (%) - as a function of the independent variables - enzyme concentration (%) and exposure time on ultrasound (min). From the applied statistical analysis, it was observed that the oil extracted by enzymatic hydrolysis showed greater thermal stability (400 °C) compared to that obtained by the classical method (384 °C). The analysis of oxidative stability showed greater propensity to oxidation the oil obtained by classical method compared to that obtained by enzymatic hydrolysis in 6 hours of induction at 110 °C. Thus, the oil obtained by enzymatic hydrolysis has properties superior to that obtained by the classical method and, thus, with better thermo-oxidative stability.

Optimization of antihypertensive and antioxidant hydrolysate extraction from rice bran proteins using ultrasound assisted enzymatic hydrolysis

In this study, antihypertensive and antioxidant protein extraction by means of ultrasound-assisted enzymatic hydrolysis was optimized in order to increase the added value of rice bran, which is a byproduct of rice milling. For this purpose, ultrasound treatment optimization was carried out with protein yield as response and solid/liquid ratio, time and power as independent factor using the response surface methodology (RSM). However, degree of hydrolysis (DH), ACE inhibitory activity, DPPH radical scavenging activity were selected as responses and solid/liquid ratio together with time as independent factors during alcalase pepsin and trypsin treatments. Three fractions depending on the molecular weight were separated by ultrafiltration. In enzyme treatments; the increase in solid/liquid ratio resulted in an increase in DH. On the other hand the impact of solid/liquid ratio and treatment time on antihypertensive and antioxidant properties varied. Differences of ACE inhibitory activity between ultrafiltrated protein fraction is not significant statistically. However, 5–10 kDa ultrafiltrated fraction is different for DPPH, hydroxy radical scavenging activity and trolox equivalent antioxidant capacity. Furthermore, the highest bioactivity values were obtained from 5–10 kDa ultrafiltrated fraction as 11.10% for DPPH, 6.20% for hydroxy radical scavenging activity and 8.19 µg trolox/mg sample for trolox equivalent antioxidant capacity.