Purification and antioxidant properties of octapeptide from salmon byproduct protein hydrolysate by gastrointestinal digestion

Preparation of Antioxidant Peptides from Salmon Byproducts with Bacterial Extracellular Proteases

Bacterial extracellular proteases from six strains of marine bacteria and seven strains of terrestrial bacteria were prepared through fermentation. Proteases were analyzed through substrate immersing zymography and used to hydrolyze the collagen and muscle proteins from a salmon skin byproduct, respectively. Collagen could be degraded much more easily than muscle protein, but it commonly showed weaker antioxidant capability. The hydrolysate of muscle proteins was prepared with crude enzymes from Pseudoalteromonas sp. SQN1 displayed the strongest activity of antioxidant in DPPH and hydroxyl radical scavenging assays (74.06% ± 1.14% and 69.71% ± 1.97%), but did not perform well in Fe²⁺ chelating assay. The antioxidant fractions were purified through ultrafiltration, cation exchange chromatography, and size exclusion chromatography gradually, and the final purified fraction U2-S2-I displayed strong activity of antioxidant in DPPH, hydroxyl radical scavenging assays (IC₅₀ = 0.263 ± 0.018 mg/mL and 0.512 ± 0.055 mg/mL), and oxygen radical absorption capability assay (1.960 ± 0.381 mmol·TE/g). The final purified fraction U2-S2-I possessed the capability to protect plasmid DNA against the damage of hydroxyl radical and its effect was similar to that of the original hydrolysis product. It indicated that U2-S2-I might be the major active fraction of the hydrolysate. This study proved that bacterial extracellular proteases could be utilized in hydrolysis of a salmon byproduct. Compared with collagen, muscle proteins was an ideal material used as an enzymatic substrate to prepare antioxidant peptides.

Purification and Characterization of Antioxidant Peptides of Pseudosciaena crocea Protein Hydrolysates

Two peptides with antioxidant activity were isolated from Pseudosciaena crocea proteins. Pseudosciaena crocea muscle was hydrolyzed with neutral protease to obtain Pseudosciaena crocea protein hydrolysates (PCPH). After ultrafiltration through molecular weight cut-off membranes of 10, 5 and 3 kDa and assessment of free radical scavenging ability, the fraction (PCPH-IV) with the highest antioxidant activity was obtained. Several purification steps, i.e., ion exchange chromatography, gel filtration chromatography and reversed phase high performance liquid chromatography, were applied to further purify PCPH-IV. Two antioxidant peptides with the amino acid sequences Ser-Arg-Cys-His-Val and Pro-Glu-His-Trp were finally identified by LC-MS/MS.

Anti-Fatigue Effect by Peptide Fraction from Protein Hydrolysate of Croceine Croaker (Pseudosciaena crocea) Swim Bladder through Inhibiting the Oxidative Reactions including DNA Damage

The swim bladder of the croceine croaker (Pseudosciaena crocea) was believed to have good curative effects in various diseases, including amnesia, insomnia, dizziness, anepithymia, and weakness after giving birth, in traditional Chinese medicine. However, there is no research focusing on the antioxidant and anti-fatigue peptides from croceine croaker swim bladders at present. Therefore, the purpose of this study was to investigate the bioactivities of peptide fractions from the protein hydrolysate of croceine croaker related to antioxidant and anti-fatigue effects. In the study, swim bladder peptide fraction (SBP-III-3) was isolated from the protein hydrolysate of the croceine croaker, and its antioxidant and anti-fatigue activities were measured using in vitro and in vivo methods. The results indicated that SBP-III-3 exhibited good scavenging activities on hydroxyl radicals (HO•) (EC50 (the concentration where a sample caused a 50% decrease of the initial concentration of HO•) = 0.867 mg/mL), 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH•) (EC50 = 0.895 mg/mL), superoxide anion radical ( O 2 - •) (EC50 = 0.871 mg/mL), and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid radical (ABTS⁺•) (EC50 = 0.346 mg/mL). SBP-III-3 also showed protective effects on DNA damage in a concentration-effect manner and prolonged the swimming time to exhaustion of Institute of Cancer Research (ICR) mice by 57.9%-107.5% greater than that of the control. SBP-III-3 could increase the levels of muscle glucose (9.4%-115.2% increase) and liver glycogen (35.7%-157.3%), and decrease the levels of blood urea nitrogen (BUN), lactic acid (LA), and malondialdehyde (MDA) by 16.4%-22.4%, 13.9%-20.1%, and 28.0%-53.6%, respectively. SBP-III-3 also enhanced the activity of lactic dehydrogenase to scavenge excessive LA for slowing the development of fatigue. In addition, SBP-III-3 increased the activities superoxide dismutase, catalase, and glutathione peroxidase to reduce the reactive oxygen species (ROS) damage in mice. In conclusion, SBP-III-3 possessed good anti-fatigue capacities on mice by inhibiting the oxidative reactions and provided an important basis for developing the swim bladder peptide functional food.

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.

Antioxidant properties of salmon (Salmo salar L.) protein fraction hydrolysates revealed following their ex vivo digestion and in vitro hydrolysis

BACKGROUND

Salmon (Salmo salar L.) myofibryllar protein (MP) and sarcoplasmic protein (SP) were digested with human gastric and duodenal juices and hydrolysed in vitro with commercial pepsin and Corolase PP.

RESULTS

The digestion after duodenal juice/Corolase PP caused almost complete breakdown of peptide bonds in MP and SP. The DPPH(•) scavenging activity of proteins decreased during both ex vivo digestion and in vitro hydrolysis. The highest value of DPPH(•) scavenging activity was shown for the gastric digest of SP (8.88 ± 0.87%). The ABTS(+•) scavenging activity of MP and SP increased during digestion/hydrolysis. The duodenal digest of SP was characterised by the highest value of ABTS(+•) scavenging activity (72.7 ± 1.2%). In turn, the highest value of ferric-reducing power was determined for the gastric digest of SP (84.8 ± 0.2%). Salmon antioxidant peptides Phe-Ile-Lys-Lys, His-Leu, Ile-Tyr, Pro-His-Leu, Pro-Trp, Val-Pro-Trp were identified in both ex vivo digested and in vitro hydrolysed MP and SP. An antioxidant peptide, Val-Tyr, was additionally detected in the in vitro hydrolysate of SP.

CONCLUSION

The results indicate the salmon myofibrillar and sarcoplasmic protein fractions as potential sources of antioxidant peptides that could be released in the gastrointestinal tract but their amino acid sequence and quantification vary. © 2015 Society of Chemical Industry.

Preparation of gluten free bread enriched with green mussel (Perna canaliculus) protein hydrolysates and characterization of peptides responsible for mussel flavour

Green mussel protein hydrolysates (GMPH) utilization for the enrichment of gluten-free bread followed by characterization of flavour peptides using chromatography and electronic nose techniques have been done. The degree of hydrolysis was carried out in each protease digest, and the higher degree of hydrolysis was observed in pepsin digestion. Gluten-free (GF) bread was formulated by using buckwheat flour (BWF), rice flour (RF) and chickpea flour (CPF) (70:20:10) and GMPH were added in the range of 0-20% in the GF bread for enrichment with GMPH. Radar plot of the electronic nose analysis showed that the sensors P30/2, T30/1 and T70/2 had a higher response to the GF bread and GMPH. Consequently, the peptide sequence was obtained manually by ESI-MS spectra of GMPH (KGYSSYICDK) and F-II (SSYCIVKICDK). Flavour quality was 97% discriminately comparable to the GMPH and F-II fractions. Mussel flavoured GF bread can be included in the celiac diet.

Valorisation of smooth hound (Mustelus mustelus) waste biomass through recovery of functional, antioxidative and antihypertensive bioactive peptides

Concerns over the environmental and waste disposal problems created by the large amounts of by-products generated from fish processing industries are increasing worldwide. The bioconversion of those marine waste by-products through the enzymatic hydrolysis of their protein content offers the possibility for the development of bioactive peptides for use in various biotechnological applications. The present study aimed to investigate and evaluate the biological and functional properties of smooth hound (Mustelus mustelus) protein hydrolysates (SHPHs) obtained by treatment with intestinal and gastric enzyme preparations from M. mustelus viscera and porcine pancreatin. The results revealed that the SHPHs exhibited different degrees of hydrolysis and antioxidant activity. The hydrolysate produced by the intestinal crude extract presented the highest rate of antioxidative activity, showing an IC50 value of 1.47 ± 0.07 mg/mL in 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assays. The alkaline protease extract from the intestine of M. mustelus produced hydrolysate with the highest angiotensin I-converting enzyme (ACE) inhibitory activity (82 ± 1.52% at 2 mg/mL). All the protein hydrolysates showed excellent solubility and interfacial properties that were governed by pH. The major amino acids detected in SHPHs were glutamic acid/glutamine, aspartic acid/asparagine, histidine and arginine, followed by methionine, phenylalanine, serine, valine and leucine. Overall, the results indicated that smooth hound by-products can be used to generate high value-added products, thus offering a valuable source of bioactive peptides for application in wide range of biotechnological and functional food applications.

Overview of Antioxidant Peptides Derived from Marine Resources: The Sources, Characteristic, Purification, and Evaluation Methods

Marine organisms are rich sources of structurally diverse bioactive nitrogenous components. In recent years, numerous bioactive peptides have been identified in a range of marine protein resources, such as antioxidant peptides. Many studies have approved that marine antioxidant peptides have a positive effect on human health and the food industry. Antioxidant activity of peptides can be attributed to free radicals scavenging, inhibition of lipid peroxidation, and metal ion chelating. Moreover, it has also been verified that peptide structure and its amino acid sequence can mainly affect its antioxidant properties. The aim of this review is to summarize kinds of antioxidant peptides from various marine resources. Additionally, the relationship between structure and antioxidant activities of peptides is discussed in this paper. Finally, current technologies used in the preparation, purification, and evaluation of marine-derived antioxidant peptides are also reviewed.

Production of Chondroitin Sulphate from Head, Skeleton and Fins of Scyliorhinus canicula By-Products by Combination of Enzymatic, Chemical Precipitation and Ultrafiltration Methodologies

This study illustrates the optimisation of the experimental conditions of three sequential steps for chondroitin sulphate (CS) recovery from three cartilaginous materials of Scyliorhinus canicula by-products. Optimum conditions of temperature and pH were first obtained for alcalase proteolysis of head cartilage (58 °C/pH 8.5/0.1% (v/w)/10 h of hydrolysis). Then, similar optimal conditions were observed for skeletons and fin materials. Enzymatic hydrolysates were subsequently treated with a combination of alkaline hydroalcoholic saline solutions in order to improve the protein hydrolysis and the selective precipitation of CS. Ranges of 0.53–0.64 M (NaOH) and 1.14–1.20 volumes (EtOH) were the levels for optimal chemical treatment depending on the cartilage origin. Finally, selective purification and concentration of CS and protein elimination of samples obtained from chemical treatment, was assessed by a combination of ultrafiltration and diafiltration (UF-DF) techniques at 30 kDa.

Two novel antioxidant nonapeptides from protein hydrolysate of skate (Raja porosa) muscle

In the current study, the preparation conditions of neutrase hydrolysate (SMH) from skate (Raja porosa) muscle protein were optimized using orthogonal L9(3)4 tests, and R values indicated that pH was the most important factor affecting HO· scavenging activity of SMH. Under the optimum conditions of pH 7.0, enzymolysis temperature 60 °C, enzyme/substrate ratio (E/S) 2%, and enzymolysis time 5 h, EC50 of SMH on HO· was 2.14 ± 0.17 mg/mL. Using ultrafiltration, gel filtration chromatography, and RP-HPLC, two novel antioxidant nonapeptides (SP-A and SP-B) were isolated from SMH and their amino acid sequences were found to be APPTAYAQS (SP-A) and NWDMEKIWD (SP-B) with calculated molecular masses of 904.98 Da and 1236.38 Da, respectively. Both showed strong antioxidant activities. SP-A and SP-B exhibited good scavenging activities on HO· (EC50 0.390 and 0.176 mg/mL), DPPH· (EC50 0.614 and 0.289 mg/mL), and O2-· (EC50 0.215 and 0.132 mg/mL) in a dose-dependent manner. SP-B was also effective against lipid peroxidation in the model system. The aromatic (2Trp), acidic (2Asp and Glu), and basic (Lys) amino acid residues within the sequences of SP-B might account for its pronounced antioxidant activity. The results of this study suggested that protein hydrolysate and peptides from skate muscle might be effective as food additives for retarding lipid peroxidation occurring in foodstuffs.

Marine protein hydrolysates: their present and future perspectives in food chemistry – a review

Marine protein hydrolysates are usually prepared by the enzymatic digestion with different proteases at controlled pH and temperature.

Antioxidant and functional properties of collagen hydrolysates from Spanish mackerel skin as influenced by average molecular weight

In the current study, the relationships between functional properties and average molecular weight (AMW) of collagen hydrolysates from Spanish mackerel (Scomberomorous niphonius) skin were researched. Seven hydrolysate fractions (5.04 ≤ AMW ≤ 47.82 kDa) from collagen of Spanish mackerel skin were obtained through the processes of acid extraction, proteolysis, and fractionation using gel filtration chromatography. The physicochemical properties of the collagen hydrolysate fractions were studied by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), gel filtration chromatography, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The results indicated that there was an inverse relationship between the antioxidant activities and the logarithm of the AMW of the hydrolysate fractions in the tested AMW range. However, the reduction of AMW significantly enhanced the solubility of the hydrolysate fractions, and a similar AMW decrease of the hydrolysate fractions negatively affected the emulsifying and foaming capacities. This presented as a positive correlation between the logarithm of AMW and emulsion stability index, emulsifying activity index, foam stability, and foam capacity. Therefore, these collagen hydrolysates with excellent antioxidant activities or good functionalities as emulsifiers could be obtained by controlling the effect of the digestion process on the AMW of the resultant hydrolysates.

The influence of the extent of enzymatic hydrolysis on antioxidative properties and ACE-inhibitory activities of protein hydrolysates from goby (Zosterisessor ophiocephalus) muscle

Antioxidant properties and angiotensin-converting enzyme (ACE) inhibitory activities of protein hydrolysates from goby (Zosterisessor ophiocephalus) muscle, with different degrees of hydrolysis (DH) from 5 to 25%, prepared by treatment with crude proteases extract from smooth hound intestines, were investigated. Goby protein hydrolysates (GPHs) are rich in Gly and Thr, which accounted for 14.1-15% and 11.6-13.2% of the total amino acids, respectively. The antioxidant activities of GPHs were investigated by using several in vitro assay systems. All GPHs exhibited significant metal chelating activity and DPPH free radical-scavenging activity, and inhibited linoleic acid peroxidation. For the ACE-inhibitory activity, as the DH increased, the activity of GPHs increased. The obtained results revealed that antioxidant and ACE-inhibitory activities of GPHs were influenced by the degree of hydrolysis. A medium degree of enzymatic hydrolysis was appropriate to obtain GPHs with good antioxidant activity, while small peptides were essential to obtain high ACE inhibitory activity.