Separation of Antioxidant Peptides from Pepsin Hydrolysate of Whey Protein Isolate by ATPS of EOPO Co-polymer (UCON)/Phosphate

Separation, enrichment and cytoprotection of antioxidant peptides from Xuanwei ham using aqueous two-phase extraction

An ethanol/(NH4)2SO4 biphasic (aqueous two-phase) system was designed to effectively separate antioxidant peptides from Xuanwei ham, and its potential to prevent ultraviolet A-induced damage to skin cells was explored. Optimization via single factor experiments and response surface methodology revealed that under 20 % ethanol aqueous solution (w/w), 25.5 % (NH4)2SO4 aqueous solution (w/w), and pH 8.80 conditions, the optimal extraction ratio was 59.0 ± 1.73 %. In vitro antioxidant activity and cellular assays showed that the peptide purified in the upper phase exhibited strong antioxidant activity, increasing the viability of HaCat cells damaged by UVA irradiation from 56.14 ± 1.05 % to 66.3 ± 1.76 %. We used an in silico peptide screening strategy and identified 10 with potential antioxidant activity, emphasizing the important role of amino acids Pro, Gly, and Ala in antioxidant activity.

Evaluation of the Biological Activities of Peptides from Epidermal Mucus of Marine Fish Species from Chilean Aquaculture

The skin of fish is a physicochemical barrier that is characterized by being formed by cells that secrete molecules responsible for the first defense against pathogenic organisms. In this study, the biological activity of peptides from mucus of Seriola lalandi and Seriolella violacea were identified and characterized. To this purpose, peptide extraction was carried out from epidermal mucus samples of juveniles of both species, using chromatographic strategies for purification. Then, the peptide extracts were characterized to obtain the amino acid sequence by mass spectrometry. Using bioinformatics tools for predicting antimicrobial and antioxidant activity, 12 peptides were selected that were chemically produced by simultaneous synthesis using the Fmoc-Tbu strategy. The results revealed that the synthetic peptides presented a random coil or extended secondary structure. The analysis of antimicrobial activity allowed it to be discriminated that four peptides, named by their synthesis code 5065, 5069, 5070, and 5076, had the ability to inhibit the growth of Vibrio anguillarum and affected the copepodite stage of C. rogercresseyi. On the other hand, peptides 5066, 5067, 5070, and 5077 had the highest antioxidant capacity. Finally, peptides 5067, 5069, 5070, and 5076 were the most effective for inducing respiratory burst in fish leukocytes. The analysis of association between composition and biological function revealed that the antimicrobial activity depended on the presence of basic and aromatic amino acids, while the presence of cysteine residues increased the antioxidant activity of the peptides. Additionally, it was observed that those peptides that presented the highest antimicrobial capacity were those that also stimulated respiratory burst in leukocytes. This is the first work that demonstrates the presence of functional peptides in the epidermal mucus of Chilean marine fish, which provide different biological properties when the fish face opportunistic pathogens.

Response surface optimization of enzymatic hydrolysis and ROS scavenging activity of silk sericin hydrolysates

CONTEXT

Sericin, a protein found in wastewater from the silk industry, was shown to contain a variety of biological activities, including antioxidant. The enzymatic conditions have been continuously modified to improve antioxidant effect and scavenging capacity against various free radicals of silk sericin protein.

OBJECTIVE

Variables in enzymatic reactions, including pH, temperature and enzyme/substrate ratio were analysed to discover the optimum conditions for antioxidant activity of sericin hydrolysates.

MATERIALS AND METHODS

Hydrolysis reaction catalysed by Alcalase^® was optimized through response surface methodology (RSM) in order to generate sericin hydrolysates possessing potency for % inhibition on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, ferric-reducing power and peroxyl scavenging capacity. Flow cytometry was performed to evaluate cellular ROS level in human HaCaT keratinocytes and melanin-generating MNT1 cells pre-treated either with 20 mg/mL RSM-optimized sericin hydrolysates or 5 mM N-acetyl cysteine (NAC) for 60 min prior exposure with 1 mM hydrogen peroxide (H₂O₂).

RESULTS

Among these three variables, response surface plots demonstrate the major role of temperature on scavenging capacity of sericin hydrolysates. Sericin hydrolysates prepared by using Alcalase^® at RSM-optimized condition (enzyme/substrate ratio: 1.5, pH: 7.5, temperature: 70 °C) possessed % inhibition against H₂O₂ at 99.11 ± 0.54% and 73.25 ± 8.32% in HaCaT and MNT1 cells, respectively, while pre-treatment with NAC indicated the % inhibition only at 30.26 ± 7.62% in HaCaT and 51.05 ± 7.14% in MNT1 cells.

DISCUSSION AND CONCLUSIONS

The acquired RSM information would be of benefit for further developing antioxidant peptide from diverse resources, especially the recycling of waste products from silk industry.

Exploring the DPP-IV Inhibitory, Antioxidant and Antibacterial Potential of Ovine "Scotta" Hydrolysates

The aim of this work was to valorize the by-product derived from the ricotta cheese process (scotta). In this study, ovine scotta was concentrated by ultrafiltration and then subjected to enzymatic hydrolyses using proteases of both vegetable (4% E:S, 4 h, 50 °C) and animal origin (4% E:S, 4 h, 40 °C). The DPP-IV inhibitory, antioxidant, and antibacterial activities of hydrolysates from bromelain (BSPH) and pancreatin (PSPH) were measured in vitro. Both the obtained hydrolysates showed a significantly higher DPP-IV inhibitory activity compared to the control. In particular, BSPH proved to be more effective than PSPH (IC₅₀ 8.5 ± 0.2 vs. 13 ± 1 mg mL⁻¹). Moreover, BSPH showed the best antioxidant power, while PSPH was more able to produce low-MW peptides. BSPH and PSPH hydrolysates showed a variable but slightly inhibitory effect depending on the species or strain of bacteria tested. BSPH and PSPH samples were separated by gel permeation chromatography (GPC). LC-MS/MS analysis of selected GPC fractions allowed identification of differential peptides. Among the peptides 388 were more abundant in BSPH than in the CTRL groups, 667 were more abundant in the PSPH group compared to CTRL, and 97 and 75 of them contained sequences with a reported biological activity, respectively.

Direct separation and purification of α-lactalbumin from cow milk whey by aqueous two-phase flotation of thermo-sensitive polymer/phosphate

BACKGROUND

α-lactalbumin (α-La) is of great interest to the industry as a result of its excellent functional properties and nutritional value. Aqueous two-phase flotation (ATPF) of thermo-sensitive polymer poly (ethylene glycol-ran-propylene glycol) monobutyl ether (UCON) and KH₂ PO₄ was applied to directly separate and purify α-La from milk whey, which was purposed to simplify the production process and reduced cost of production.

RESULTS

The effect of ATPF composition and operating parameters on the flotation efficiency (E) and purity of α-La were investigated. The optimal conditions included 2 min of premixing time, 30 mL min^-1 flow velocity and 20 min of flotation time, whereas the composition conditions comprised 35.0 mL 0.18 g mL^-1 phosphate solution (containing 10% (cow milk whey/salt solution, v/v) cow milk whey, 50 ppm defoamer and 2 g NaCl) and 5.0 mL of 40% (w/w) UCON solution. Under the optimal conditions, E of α-La was 95.67 ± 1.04% and purity of α-La was 98.78 ± 1.19%. UCON was recovered by a thermally-induced phase separation and reused in next ATPF process without reducing E of α-La. Purified α-La was characterized by several key technologies. The results indicated that α-La in cow milk whey could be directly separated and purified by the ATPF and the purity was satisfactory. Moreover, it was suggested there was no obvious structure difference between the α-La separated by ATPF and the α-La standard.

CONCLUSION

The present study enabled the recycling of UCON, providing an effective, economically viable and environmentally friendly approach for the separation and purification of protein. © 2021 Society of Chemical Industry.

A Review on Health-Promoting, Biological, and Functional Aspects of Bioactive Peptides in Food Applications

Food-derived bioactive peptides are being used as important functional ingredients for health-promoting foods and nutraceuticals in recent times in order to prevent and manage several diseases thanks to their biological activities. Bioactive peptides are specific protein fractions, which show broad applications in cosmetics, food additives, nutraceuticals, and pharmaceuticals as antimicrobial, antioxidant, antithrombotic, and angiotensin-I-converting enzyme (ACE)-inhibitory ingredients. These peptides can preserve consumer health by retarding chronic diseases owing to modulation or improvement of the physiological functions of human body. They can also affect functional characteristics of different foods such as dairy products, fermented beverages, and plant and marine proteins. This manuscript reviews different aspects of bioactive peptides concerning their biological (antihypertensive, antioxidative, antiobesity, and hypocholesterolemic) and functional (water holding capacity, solubility, emulsifying, and foaming) properties. Moreover, the properties of several bioactive peptides extracted from different foods as potential ingredients to formulate health promoting foods are described. Thus, multifunctional properties of bioactive peptides provide the possibility to formulate or develop novel healthy food products.

Antioxidant properties of peptides obtained from the split gill mushroom (Schizophyllum commune)

This study sought to assess the ideal conditions under which hydrolysate can be produced from the split gill mushroom proteins through the microbial protease, Alcalase. The research employed a central composite design and response surface methodology. Three specific parameters were varied for the purposes of the experimental process, while a fixed pH value of 8 was used in all cases. The variables were hydrolysis temperature (set as 45 °C, 50 °C, or 55 °C), hydrolysis time (set as 60 min, 120 min, or 180 min), and the ratio of enzyme to substrate (set as 2%, 4%, or 6% w/v). The variables under investigation exert a significant influence upon degree of hydrolysis (DH) in addition to 2,2'-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity (p < 0.05). Fractionation of the hydrolysate was accomplished using molecular weight (MW) cut-off membranes, while the greatest radical-scavenging capability was observed in the < 0.65 kDa fraction. The MW < 0.65 kDa fraction underwent separation through RP-HPLC in order to create five sub-fractions. Among these, the greatest ABTS radical-scavenging capability was observed in the F₅ sub-fraction, which was therefore chosen to undergo additional examination using quadrupole-time-of-flight-electron spin induction-mass spectrometry-based de novo peptide sequencing. Via this process it was possible to determine five antioxidant peptides. Furthermore, the MW < 0.65 kDa fraction was able to demonstrating cellular antioxidant activity in the context of a human intestinal cancer cell line (HT-29). The extent of this activity was shown to depend upon the concentration levels of the peptide.

Separation and Enrichment of Antioxidant Peptides from Whey Protein Isolate Hydrolysate by Aqueous Two-Phase Extraction and Aqueous Two-Phase Flotation

At present, peptides are separated by molecular exclusion chromatography and liquid chromatography. A separation method is needed in any case, which can be scaled up for industrial scale. In this study, aqueous two-phase extraction (ATPE) and aqueous two-phase flotation (ATPF) were applied to separate and enrich antioxidant peptides from trypsin hydrolysates of whey protein isolates (WPI). The best experimental conditions were investigated, and the results were evaluated using the 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radical scavenging activity of the peptides-per-unit concentration and the recovery rate (Y) of peptides in the top phase of both ATPE and ATPF. Under optimal conditions, the Y and ABTS free radical scavenging activity per unit concentration in top phase of ATPE could reach 38.75% and 12.94%, respectively, and in ATPF could reach 11.71% and 29.18%, respectively. The purified peptides were characterized by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and reversed-phase high-performance liquid chromatography (RP-HPLC). PeptideCutter and PeptideMass were applied to analyze and calculate the peptide sequencing. KILDKVGINYWLAHK, VGINYWLAHKALCSEK, and TPEVDDEALEKFDKALK sequences having antioxidant activity were detected in the top phase of ATPE, and VGINYWLAHKALCSEK, KILLDKVGINYWLAHK, ILLDKVGINYWLAHK, IIAEKTKIPAVFK, KIIAEKTKIPAVFK, and VYVEELKPTPEGDLEILLQK sequences having antioxidant activity were detected in the top phase of ATPF. In conclusion, antioxidant peptides were successfully separated from the WPI hydrolysate by ATPE and ATPF; compared with ATPE, ATPF has superior specificity in separating antioxidant peptides.

Recently isolated antidiabetic hydrolysates and peptides from multiple food sources: a review

Diabetes, a metabolic syndrome of global importance has been on a progressive rise in recent years. Several pharmacological approaches have been made, which have proved effective, but with underlying side effects. Bioactive hydrolysates (BHs) and peptides (BPs) from food sources, however, have shown the relative advantage of imparting less adverse effects. Furthermore, BHs and BPs from food have been discovered to impart their antidiabetic potentials through one or more mechanisms such as inhibition of digestive enzymes, inhibition of the antigenic enzyme - Dipeptyl peptidase IV (DPP-IV), decrease in blood glucose levels and increase in insulin uptake. Several plants and animal sources have been used as protein sources for the isolation of antidiabetic hydrolysates and peptides through different mechanisms and analytical techniques. This review integrates recent research information about several popular and unconventional food sources of BHs and BPs, their isolation techniques, antidiabetic effects and protein profiles. In addition, the fractionation technique(s) employed in each study and inhibition potentials of BHs and BPs are reviewed. This article is intended to supplement accessible scholarly literature and intellectual awareness on the subject of food-oriented approach for the management of diabetes.