Cellular and chemical antioxidant activities of chicken blood hydrolysates as affected by in vitro gastrointestinal digestion

Enzymatic processing of animal by-products: production of antioxidant hydrolysates with Bacillus sp. CL18 crude protease

Protein hydrolysates might display diverse bioactivities with potential relevance to human and animal health and food technology. Enzymatic hydrolysis of agro-industrial by-products is increasingly focused. In this study, a crude protease from Bacillus sp. CL18 was applied to obtain antioxidant protein hydrolysates from porcine, bovine, poultry, and fish by-products. The crude enzyme hydrolyzed all the twelve investigated by-products, as detected by increased soluble protein contents after 4 h of proteolysis. Hydrolysates exhibited higher radical-scavenging, Fe2+-chelating and reducing power capacities than non-hydrolyzed by-products. Hydrolysis times (0-8 h) and enzyme-to-substrate (E/S) ratios (384, 860, and 1,400 U/g) were assessed to produce antioxidant bovine lung hydrolysates. The highest E/S ratio accelerated both hydrolysis and increases in antioxidant activities; however, it did not result in bioactivities higher than hydrolysates obtained with the intermediate E/S ratio. Optimal antioxidant activities could be reached after 6 h of hydrolysis using 860 U/g. Animal by-products are interesting sources of bioactive protein hydrolysates, which could be produced with a non-commercial bacterial protease. This might represent a promising strategy for the valorization of animal by-products generated in large amounts by the agri-food sector.

Antioxidant peptides generated from chicken feet protein hydrolysates

BACKGROUND

As major industrial poultry by-products, chicken feet are considered as notable sources of several bioactive molecules. The current work covers the processing of chicken feet proteins as substrates to be hydrolysed by combinations of three commercial enzymes (Alcalase®, Flavourzyme® and Protana® Prime) during different hydrolysis periods and the evaluation of the identified peptides having antioxidant activity after simulated gastrointestinal digestion.

RESULTS

Enzymatic hydrolysis with Alcalase® and Protana® Prime combination for 4 h resulted in the highest activities. Reversed-phase high-performance liquid chromatographic separation of the purified hydrolysate yielded three active fractions that were further identified by nano-liquid chromatography-tandem mass spectrometry. The bioactivities of over 230 identified peptide sequences were estimated after simulated gastrointestinal digestion, and those peptides with the highest chance of exerting antioxidant activity were selected to be further synthesised and tested. In this sense, the synthesised dipeptides CF and GY showed the highest antioxidant capacity. CF presented IC50 values of 69.63 and 145.41 μmol L-1 in 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and oxygen radical absorbance capacity (ORAC) assays, respectively. In contrast, GY IC50 values were 15.27 and 10.06 μmol L-1 in ABTS and ORAC assays, respectively. Significant differences (P < 0.05) were registered between peptides in the same antioxidant assays.

CONCLUSION

Overall, the findings emphasised the favourable impact of enzymatic hydrolysis with the obtaining of antioxidant peptides from poultry by-products that could be evaluated as a safe and economical source to retard oxidation in food systems. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Toward the high-efficient utilization of poultry blood: Insights into functionality, bioactivity and functional components

A large amount of poultry blood is annually generated, and currently underutilized or largely disposed of as waste, resulting in environmental pollution and waste of protein resources. As one of the main by-products during the poultry slaughter process, the produced poultry blood can serve as a promising food ingredient due to its excellent functional properties and abundant source of essential amino acids, bioactive peptides and functional components. This work provides a comprehensive summary of recent research progress in the composition, functional and bioactive properties, as well as the functional components of poultry blood. Furthermore, the main preparation methods of poultry blood-derived peptides and their bioactivities were reviewed. In addition, their potential applications in the food industry were discussed. Overall, poultry blood is characterized by excellent functionalities, including solubility, gelation, foaming, and emulsifying properties. The major preparation methods for poultry blood-derived peptides include enzymatic hydrolysis, ultrasound-assisted enzymatic methods, macroporous adsorbent resins, and subcritical water hydrolysis. Poultry blood-derived peptides exhibit diverse bioactivities. Their metallic off-flavors and bitterness can be improved by exopeptidase treatment, Maillard reaction, and plastein reaction. In addition, poultry blood is also abundant in functional components such as hemoglobin, superoxide dismutase, immunoglobulin, and thrombin.

Molecular Insights into the Mode of Action of Antibacterial Peptides Derived from Chicken Plasma Hydrolysates

Due to the overuse and abuse of antibiotics, several antibiotic resistant bacteria have emerged. Antimicrobial peptides (AMPs) have gained attention as alternative antimicrobial agents because of their unique mode of action that impedes bacterial resistance. Two novel antibacterial peptides were isolated from Alcalase-hydrolyzed chicken plasma by size exclusion and reverse-phase chromatography. They were identified by LC-MS/MS to be VSDH and CCCPKAF, which showed effective antibacterial activity toward Bacillus cereus DMST 5040, with varied modes of action. The peptide CCCPKAF caused cell membrane disintegration, as evidenced by propidium iodide (PI) uptake. In contrast, the peptide VSDH targeted intracellular molecules, including proteins and nucleic acids, as revealed by Synchrotron-based Fourier Transform Infrared (SR-FTIR). The secondary structure of intracellular proteins increased to a β-sheet structure concomitant with a decrease in the α-helix structure when exposed to 0.5 mM VSDH. Molecular docking analysis revealed that VSDH showed high binding affinity for the active sites of the various enzymes involved in DNA synthesis. In addition, it showed good affinity for a chaperone protein (Dnak), resulting in the misfolding of intracellular proteins. Nuclear magnetic resonance (NMR) and molecular dynamics simulations also indicated that VSDH chelated well with Mg2+, which could partly contribute to its antibacterial activity.

Production of Protein Hydrolysate Containing Antioxidant and Angiotensin -I-Converting Enzyme (ACE) Inhibitory Activities from Tuna (Katsuwonus pelamis) Blood

Tuna blood (TB) was subjected to enzymatic hydrolysis. The effects of the relationship of hydrolysis time (30–180 min) and enzyme concentration (0.5–3.0% w/w protein) on the degree of hydrolysis (DH), yield, antioxidant and angiotensin-I-converting enzyme (ACE) inhibitory activities were determined. The response surface methodology (RSM) showed that TB hydrolysis’s optimum conditions were hydrolysis for 180 min and Alcalase, Neutrase or Flavourzyme at 2.81%, 2.89% or 2.87% w/w protein, respectively. The hydrolysates with good DH (40–46%), yield (3.5–4.6%), the IC50 of DPPH (0.8–1.6 mg/mL) and ABTS (1.0–1.4 mg/mL) radical scavenging activity, ferric reducing antioxidant power (FRAP) value (0.28–0.65 mmol FeSO4/g) and IC50 of ACE inhibitory activity (0.15–0.28 mg/mL) were obtained with those conditions. The TB hydrolysate using Neutrase (TBHN) was selected for characterization in terms of amino acid composition, peptide fractions and sensory properties. The essential, hydrophobic and hydrophilic amino acids in TBHN were ~40%, 60% and 20% of total amino acids, respectively. The fraction of molecular weight <1 kDa showed the highest antioxidant and ACE inhibitory activities. Fishiness and bitterness were the main sensory properties of TBHN. Fortification of TBHN in mango jelly at ≤ 0.5% (w/w) was accepted by consumers as like moderately to like slightly, while mango jelly showed strong antioxidant and ACE inhibitory activities. TBHN could be developed for natural antioxidants and antihypertensive peptides in food and functional products.

The antioxidant potential of peptides obtained from the spotted babylon snail (Babylonia areolata) in treating human colon adenocarcinoma (Caco-2) cells

This research study investigated the free radical-scavenging activities of peptides which were obtained from the protein hydrolysates of the spotted babylon snail using a combination of pepsin and pancreatin proteolysis which can replicate the conditions of gastrointestinal digestion. In this study, spotted babylon protein hydrolysate (SPH) derived from a sequential 3 hour digestion, first with pepsin and then with pancreatin, was examined. SPH was fractionated using molecular weight cut-off membranes for 10 kDa, 5 kDa, 3 kDa, and 0.65 kDa. It was found that the MW < 0.65 kDa fraction provided the greatest levels of 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazl (DPPH), and nitric oxide (NO) radical scavenging activity. Three subfractions of the MW < 0.65 kDa fraction were then generated via RP-HPLC. The subfraction which subsequently demonstrated the greatest free radical scavenging activity was F₃, which was accordingly chosen for further investigation commencing with quadrupole-time-of-flight-electron spin induction-mass spectrometry-based de novo peptide sequencing. This resulted in the identification of a pair of novel peptides: His–Thr–Tyr–His–Glu–Val–Thr–Lys–His (HTYHEVTKH), and Trp–Pro–Val–Leu–Ala–Tyr–His–Phe–Thr (WPVLAYHF). The WPVLAYHF peptide exhibited greater antioxidant activity. The study also confirmed that the F₃ sub-fraction was able to prevent hydroxyl radicals from causing DNA damage by conducting tests which involved the pKS, pUC19, and pBR322 plasmids using the Fenton reaction. In addition, cellular antioxidant activity was demonstrated by two synthetic peptides toward the human adenocarcinoma colon (Caco-2) cell line, with the potency of the activity dependent upon the peptide concentration.

The isolation and subsequent identification of the two novel antioxidant peptides, HTYHEVTKH, and WPVLAYHF from the spotted babylon snail was achieved. In the Caco-2 cell line, two synthetic peptides produced a dose-dependent response on antioxidant activity.