Oxidative processes during enzymatic hydrolysis of cod protein and their influence on antioxidant and immunomodulating ability

Jellyfish Peptide as an Alternative Source of Antioxidant

Jellyfish is a valuable biological resource in marine ecosystems, and blooms been observed in numerous coastal regions. However, their utility is limited by their high water content. Recent research has focused on extracting antioxidants from marine sources. In this study, we obtained jellyfish peptides (JPHT-2) through enzymatic hydrolysis of lyophilized jellyfish powder under optimal conditions and measured their antioxidant activity. Our findings indicate that JPHT-2 possesses significant radical-scavenging activity and reducing power. At a concentration of 0.74 mg/mL, JPHT-2 exhibited a remarkable ability to scavenge hydroxyl radicals, with a rate of up to 50%. The EC₅₀ values for scavenging superoxide anion and DPPH radical were 1.55 mg/mL and 1.99 mg/mL, respectively. At the cellular level, JPHT-2 was able to protect HaCaT cells from H₂O₂-induced oxidative damage by increasing the level of superoxide dismutase (SOD) in cells. In conclusion, jellyfish peptides with low molecular weight can be easily obtained through hydrolysis with three enzymes and exhibit excellent antioxidant activity and safety. Jellyfish can serve as a promising source of antioxidants.

Formation of Oxidative Compounds during Enzymatic Hydrolysis of Byproducts of the Seafood Industry

There is a significant potential to increase the sustainability of the fishing and aquaculture industries through the maximization of the processing of byproducts. Enzymatic hydrolysis provides an opportunity to valorize downstream fish industry byproducts for the production of protein hydrolysates (FPH) as a source of bioactive peptides (BAP) with health benefits. Deteriorative oxidative reactions may occur during the enzymatic hydrolysis of byproducts, influencing the safety or bioactivities of the end product. Lipid oxidation, autolysis mediated by endogenous enzymes in viscera, protein degradation, and formation of low-molecular-weight metabolites are the main reactions that are expected to occur during hydrolysis and need to be controlled. These depend on the freshness, proper handling, and the type of byproducts used. Viscera, frames, trimmings, and heads are the byproducts most available for enzymatic hydrolysis. They differ in their composition, and, thus, require standardization of both the hydrolysis procedures and the testing methods for each source. Hydrolysis conditions (e.g., enzyme type and concentration, temperature, and time) also have a significant role in producing FPH with specific structures, stability, and bioactivity. Protein hydrolysates with good safety and quality should have many applications in foods, nutraceuticals, and pharmaceuticals. This review discusses the oxidative reactions during the enzymatic hydrolysis of byproducts from different fish industry sectors and possible ways to reduce oxidation.

Protein Characteristics and Bioactivity of Fish Protein Hydrolysates from Tra Catfish (Pangasius hypophthalmus) Side Stream Isolates

Enzymatic hydrolysis is a novel method to recover highly potent bioactive fish protein hydrolysates (FPHs) from fish processing side-streams. The common way of producing FPHs directly from fish side-streams may be inappropriate due to the excess of lipids and pro-oxidants, especially in lipid-rich streams, as obtained from Tra catfish. This study aimed to optimise the hydrolysis conditions for a commercial enzyme (Alcalase® 2.4 L) (enzyme concentrate, temperature, and time) in FPH production from the fish protein isolate obtained from Tra catfish dark muscle (DM-FPI) using the pH-shift method. The degree of hydrolysis (DH), protein recovery (PR), and antioxidant properties, including DPPH radical scavenging activity (DPPH-RSA) and total reducing power capacity (TRPC), were measured to evaluate the effects of the hydrolysis conditions on the FPHs. Optimal hydrolysis was obtained at an enzyme/substrate protein ratio of 3% (v/w) and a hydrolysis temperature of 50 °C for 3 h. The FPHs obtained from different substrates, including DM-FPI, abdominal cut-off (ACO) FPI, and head and backbone blend (HBB) FPI, had similar DHs under these optimum conditions, ranging from 22.5% to 24.0%. However, the FPH obtained from abdominal cut-off isolate (ACO-FPH) showed the highest PR of 81.5 ± 4.3% and the highest antioxidant properties, with a DPPH-RSA of 86.1 ± 1.6% and a TRPC of 6.4 ± 0.4 equivalent mg vitamin C/g protein. The resulting FPHs present a natural source of antioxidants with great potential for food applications, especially the ACO-FPH. In addition, all FPHs had excellent amino acid profiles, indicating strong potential for their use as supplements. Tra catfish protein-rich side-streams can thus be processed into high-value bioactive FPHs using Alcalase for human consumption.

Reduction in flavor-intense components in fish protein hydrolysates by membrane filtration

Enzymatic protein hydrolysates based on side stream materials from the fish-filleting industry are increasingly explored as food ingredients. However, intense sensory properties, and high salt contents, are often a limiting factor. Most of the sensory attributes, such as fish flavor and salty taste, can be ascribed to low-molecular-weight, water-soluble components, whereas bitterness is associated with small hydrophobic peptides. In this study, protein hydrolysates based on head and backbone residuals from Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua) were produced using two different enzymes. The effects of micro- and nanofiltration on the chemical composition, protein recovery, and sensory properties of the final products were investigated. The choice of raw material and enzyme had negligible effects, whereas nanofiltration caused a considerable reduction in metabolites, ash, and the intensity of several sensory attributes. The intensity of bitterness increased after nanofiltration, indicating that small peptides associated with bitter taste were retained by the membrane. Total protein yield after microfiltration was 24%-29%, whereas 19%-24% were recovered in the nanofiltration retentate. PRACTICAL APPLICATION: Enzymatic protein hydrolysates can be included in food products to increase the protein content, and as a nutritional supplement and/or functional ingredient; however, unpalatable and intense flavors limit applications. This study investigated the use of membrane filtration to improve flavor quality and reduce salt content in fish protein hydrolysates. Although some protein loss is unavoidable in micro- and nanofiltration, this study demonstrates the production of fish protein hydrolysates with >90% protein and peptide content, which is suitable for inclusion in foods.

Induced oxidation and addition of antioxidant before enzymatic hydrolysis of heads of rainbow trout (Oncorhynchus mykiss) - effect on the resulting oil and protein fraction

The effect of freshness of heads of rainbow trout (Onchorhynchus mykiss) for hydrolysing fish protein was investigated. To simulate storage and transportation, hydrogen peroxide and iron was added to minced heads to induce oxidation in the raw material prior to one week of storage. The effect of antioxidant in retarding oxidative changes during hydrolysis or to the raw material was investigated by adding butylated hydroxy toluene (BHT) prior to hydrolysis or storage. Enzymatic hydrolysis was carried out using bromelain and papain. The oil fraction was separated from the water soluble proteins, and the soluble phase was freeze dried. Both the oil fraction and protein fraction from enzymatic hydrolysis was affected by oxidative state of raw material. FFA was significantly higher in those FPH made from raw material added pro-oxidants, addition of antioxidant did not affect the level of FFA. The solubility of proteins in dried fish protein hydrolysates (FPH) decreased significantly when using oxidized raw material. Although addition of antioxidant improved the solubility, it was still significantly lower compared to those FPHs not added pro-oxidants. The FPH with decreased solubility also had higher levels of carbonyl groups which indicate protein oxidation. However, the oxidative state of raw material did not affect fatty acid composition in oil fraction or the amino acid composition in the FPH.

Therapeutic Potential of Tuna Backbone Peptide and Its Analogs: An In Vitro and In Silico Study

Tuna backbone peptide (TBP) has been reported to exert potent inhibitory activity against lipid peroxidation in vitro. Since this bears relevant physiological implications, this study was undertaken to assess the impact of peptide modifications on its bioactivity and other therapeutic potential using in vitro and in silico approach. Some TBP analogs, despite lower purity than the parent peptide, exerted promising antioxidant activities in vitro demonstrated by ABTS radical scavenging assay and cellular antioxidant activity assay. In silico digestion of the peptides resulted in the generation of antioxidant, angiotensin-converting enzyme (ACE), and dipeptidyl peptidase-IV (DPPIV) inhibitory dipeptides. Using bioinformatics platforms, we found five stable TBP analogs that hold therapeutic potential with their predicted multifunctionality, stability, non-toxicity, and low bitterness intensity. This work shows how screening and prospecting for bioactive peptides can be improved with the use of in vitro and in silico approaches.

Ultrasound microwave-assisted enzymatic production and characterisation of antioxidant peptides from sweet potato protein

Herein, we investigated the effects of ultrasound microwave (UM)-assisted hydrolysis using Alcalase (ALC), Flavourzyme (FLA), and their combination (ALC + FLA), on the production of sweet potato protein hydrolysates (SPPH). UM-assisted enzymatic hydrolysis significantly increased the degree of hydrolysis of SPPH compared with untreated (UN) samples. Fractions with differences in molecular weight (MW) of >10, 3-10, and < 3 kDa in SPPH from UM-assisted ALC, FLA, and ALC + FLA hydrolysis displayed higher antioxidant activities than those from UN samples. MW < 3 kDa fractions of SPPH from UM-assisted ALC and ALC + FLA hydrolysis treatments presented much stronger Fe²⁺-chelating activity (98.48% and 98.59%), ·OH scavenging activity (67.11% and 60.06%), and higher ORAC values (110.32 and 106.32 µg TE/mL), from which diverse peptides with potential antioxidant activities were obtained by semi-preparative HPLC and LC-MS/MS. All identified peptide sequences exhibited at least three potential antioxidant amino acids. Additionally, changes in peptide conformational structure and antioxidant amino acid composition were revealed by structure-activity relationship analysis. Thus, ultrasound microwave treatment has great potential in antioxidant peptides production.

High stability of bilayer nano-emulsions fabricated by Tween 20 and specific interfacial peptides

To ensure emulsions to be continuously stable, the hydrolysates recovered from cod bones by papain acted as a natural surfactant to synthesize high-stability bilayer nano-emulsions. As assisted by Tween 20, the average diameter of synthesized nano-emulsion with enzymatic hydrolysate could exhibit stability between 300-400 nm under a broad range of pH (4-8), temperatures (30-90 °C) and salt concentration (25-250 mM). With the addition of the hydrolysates, the rate of increase of the TBARS value in the emulsion decreased. Moreover, the bilayer structure of the nano-emulsion was characterized under an atomic force microscopy and a cryo-scanning electron microscopy. Nano-LC-Q-TOF-MS was adopted to primarily identify peptides that contained hydrophobic and hydrophilic amino acids at the emulsion interface. Besides, the absorbed peptides on the interface of emulsion enhanced the stability of emulsion lipid oxidation.

Anticancer and immunomodulatory activity of egg proteins and peptides: a review

Eggs are widely recognized as a highly nutritious food source that offer specific health benefits for humans. Eggs contain all of the proteins, lipids, vitamins, minerals, and growth factors necessary for embryonic development. In particular, egg white and yolk proteins are considered functional food substances because they possess biological activities such as antimicrobial, antioxidant, metal-chelating, antihypertensive, anticancer, and immunomodulatory activities. Peptides produced via processes such as enzymatic hydrolysis, fermentation by microorganisms, and some chemical and physical treatments of egg proteins have been shown to enhance the functional properties and solubility of these peptides. Peptide activity is strongly related to amino acid sequence, composition, and length. At present, cancer remains among the leading causes of mortality worldwide, and therefore research aimed at developing new treatments for cancer immunotherapy is of great interest. The present review focuses primarily on the anticancer and immunomodulatory activities of egg proteins and their peptides and provides some insight into their underlying mechanisms of action. A number of egg proteins and peptides have been reported to induce apoptosis in cancer cells, protect against DNA damage, decrease the invasion ability of cancer cells, and exhibit cytotoxic and antimutagenic activity in various cancer cell lines. Furthermore, egg proteins and peptides can stimulate or suppress pro- or anti-inflammatory cytokines, as well as affect the production of inflammatory mediators in a variety of cell lines. In addition, the composition of eggs and the processes of egg proteins and peptides production will be discussed.

Effects of dietary protein level on growth performance, digestive enzyme activity, and gene expressions of the TOR signaling pathway in fingerling Pelteobagrus fulvidraco

An 8-week feeding trial was conducted to investigate effects of dietary protein levels (37, 40, and 43%) on the growth performance, feed utilization, digestive enzyme activity, and gene expressions of target of rapamycin (TOR) signaling pathway in fingerling yellow catfish. One hundred and eighty fingerlings (average weight 0.77 ± 0.03 g) were equally distributed across four replicate tanks for each of the three treatments, with 15 fish per tank. No difference (P > 0.05) was observed in initial body weight, survival rate (SR), hepatosomatic index (HSI), viscera index (VSI), dressing percentage (DP), and condition factor (CF) among all the treatments. The diet containing 40% protein increased significantly (P < 0.05) final body weight, weight gain rate (WGR), specific growth rate (SGR), protein efficiency ratio (PER), nitrogen retention (NRE), and energy retention (ERE) in fish. The highest protease activity in the stomach and intestine was observed in the P40 group (P < 0.05), while amylase and lipase were not significantly different (P > 0.05). The transcriptional levels of IGF-1, IGF-1R, and Akt were significantly (P < 0.05) higher in fish fed P40 or P43 than those of fish fed P37. TOR and S6K1 mRNA expressions were significantly (P < 0.05) increased in the P40 groups. Hence, the diet containing 40% protein would be suitable for the optimum growth and effective protein utilization of fingerling Pelteobagrus fulvidraco. In vitro, the transcriptional levels of IGF-1, IGF-1R, Akt, TOR, and S6K1 in hepatocyte supplemented with a 40-μM mixed amino acids were significantly (P < 0.05) higher compared to other treatments. No difference (P > 0.05) was observed in eukaryotic translation initiation factor 4E-binding protein 1 in vivo and in vitro among all the treatments. Effects of dietary protein level on growth performance likely are involved in the activation of TOR signaling pathway in fingerling Pelteobagrus fulvidraco.

Relationship between enzyme, peptides, amino acids, ion composition, and bitterness of the hydrolysates of Alaska pollock frame

Alaska pollock frame is a kind of byproduct that was rich in protein, amino acids, and mineral elements. However, the unfavorite bitterness may probably be produced in enzymatic processes. In this study, the bitterness accounted from the hydrolysates prepared by neutral proteases, alkaline proteases, papain, flavourzyme, and animal proteases, was investigated. The hydrolysis conditions, amino acids composition, metal ion composition, molecular weight distribution, and peptide composition of the hydrolysates were detected to figure out the relationship between bitterness and compositions of the hydrolysates. The hydrolysate digested by alkaline protease has the highest bitterness intensity, and that amino acids composition, peptide composition, and molecular weight distribution had a significant influence on the bitterness degree. Hydrophobic amino acids and alkaline amino acids, such as leucine, isoleucine, lysine, and so on are likely to contribute to the bitterness and molecular weight distribution of peptides that affect bitterness is mainly lower than 3,000 Da. PRACTICAL APPLICATIONS: Fish bones would produce a bitter taste when reusing them by hydrolysis. Bitterness is one of unfavorable flavor as to consumers. The results of this study are of great significance for the further utilization of Alaska pollock frame. For products obtained from the hydrolysate of Alaska pollock frame, such as condiments and health care product the results of this study provide the processing technology of the lowest bitter hydrolysate, which can effectively improve the flavor and acceptability of the products.

Enzymatic Processes in Marine Biotechnology

In previous review articles the attention of the biocatalytically oriented scientific community towards the marine environment as a source of biocatalysts focused on the habitat-related properties of marine enzymes. Updates have already appeared in the literature, including marine examples of oxidoreductases, hydrolases, transferases, isomerases, ligases, and lyases ready for food and pharmaceutical applications. Here a new approach for searching the literature and presenting a more refined analysis is adopted with respect to previous surveys, centering the attention on the enzymatic process rather than on a single novel activity. Fields of applications are easily individuated: (i) the biorefinery value-chain, where the provision of biomass is one of the most important aspects, with aquaculture as the prominent sector; (ii) the food industry, where the interest in the marine domain is similarly developed to deal with the enzymatic procedures adopted in food manipulation; (iii) the selective and easy extraction/modification of structurally complex marine molecules, where enzymatic treatments are a recognized tool to improve efficiency and selectivity; and (iv) marine biomarkers and derived applications (bioremediation) in pollution monitoring are also included in that these studies could be of high significance for the appreciation of marine bioprocesses.

Valorisation of tuna processing waste biomass for recovery of functional and antioxidant peptides using enzymatic hydrolysis and membrane fractionation process

The enzymatic hydrolysis using Prolyve BS coupled to membrane process (Ultrafiltration (UF) and nanofiltration (NF)) is a means of biotransformation of tuna protein waste to Tuna protein hydrolysate (TPH) with higher added values. This method could be an effective solution for the production of bioactive compounds used in various biotechnological applications and minimizing the pollution problems generated by the seafood processing industries. The amino acid composition, functional and antioxidant properties of produced TPH were evaluated. The results show that the glutamic acid, aspartic acid, glycine, alaline, valine and leucine were the major amino acids detected in the TPH profile. After membrane fractionation process, those major amino acids were concentrated in the NF retentate (NFR). The NFR and NF permeate (NFP) have a higher protein solubility (>95 %) when compared to TPH (80 %). Higher oil and water binding capacity were observed in TPH and higher emulsifying and foam stability was found in UF retentate. The NFP showed the highest DPPH radical scavenging activity (65 %). The NFR contained antioxidant amino acid (30.3 %) showed the highest superoxide radical and reducing power activities. The TPH showed the highest iron chelating activity (75 %) compared to other peptide fractions. The effect of the membrane fractionation on the molecular weight distribution of the peptide and their bioactivities was underlined. We concluded that the TPH is a valuable source of bioactive peptides and their peptide fractions may serve as useful ingredients for application in food industry and formulation of nutritional products.

Effect of in vitro digested cod liver oil of different quality on oxidative, proteomic and inflammatory responses in the yeast Saccharomyces cerevisiae and human monocyte-derived dendritic cells

BACKGROUND

Upon oxidation of the polyunsaturated fatty acids in fish oil, either before ingestion or, as recently shown, during the gastro-intestinal passage, a cascade of potentially cytotoxic peroxidation products, such as malondialdehyde and 4-hydroxy-2-hexenal, can form. In this study, we digested fresh and oxidised cod liver oils in vitro, monitored the levels of lipid peroxidation products and evaluated oxidative, proteomic and inflammatory responses to the two types of digests in the yeast Saccharomyces cerevisiae and human monocyte-derived dendritic cells.

RESULTS

Digests of cod liver oil with 22-53 µmol L(-1) malondialdehyde and 0.26-3.7 µmol L(-1) 4-hydroxy-2-hexenal increased intracellular oxidation and cell energy metabolic activity compared to a digested blank in yeast cells and the influence of digests on mitochondrial protein expression was more pronounced for oxidised cod liver oil than fresh cod liver oil. The four differentially expressed and identified proteins were related to energy metabolism and oxidative stress response. Maturation of dendritic cells was affected in the presence of digested fresh cod liver oil compared to the digested blank, measured as lower CD86 expression. The ratio of secreted cytokines, IL-12p40/IL-10, suggested a pro-inflammatory effect of the digested oils in relation to the blank (1.47-1.67 vs. 1.07).

CONCLUSION

Gastro-intestinal digestion of cod liver oil increases the amount of oxidation products and resulting digests affect oxidation in yeast and immunomodulation of dendritic cells.

Preventive effect of Nile tilapia hydrolysate against oxidative damage of HepG2 cells and DNA mediated by H2O2 and AAPH

Antioxidant activities of protein hydrolysate prepared from Nile tilapia protein isolate using Alcalase (HA), Alcalase followed by papain (HAPa) and their Sephadex G-25 fractions (FHA and FHAPa) were investigated in both chemical and cellular based models. Amongst all samples, FHAPa showed the highest chemical antioxidant activities, however it had no metal chelation activity. Cellular antioxidant ability of HA, HAPa and their fractions against H2O2 and AAPH induced oxidative damage of HepG2 cell and DNA were tested. When cells were pretreated with all hydrolysates or fractions at different concentrations (0.5-2 mg/mL) in the absence and presence of 50 μM Trolox, cell viability was in the range of 91.10-111.40 %. However, no difference in cell viability was observed among samples having various concentrations (P > 0.05). Cell reactive oxygen species (ROS) generation as mediated by H2O2 and AAPH decreased with treatment of hydrolysates or their fractions, especially in combination with 50 μM Trolox. FHAPa effectively inhibited H2O2 and peroxyl radical induced DNA scission in a dose dependent manner. Therefore, Nile tilapia protein hydrolysates could serve as a functional food ingredient.