Antioxidant activity of bovine casein hydrolysates produced by Ficus carica L.-derived proteinase

Magnetic graphene oxide, a suitable support in ficin immobilization

In the present study, we aimed to develop a fast, non-toxic ultrasonic-assisted technique for the preparation of graphene oxide (GO) and GO that were accessorized with Fe₃O₄ (GO-Fe₃O₄) for enzyme immobilization. The structural properties of nanosheets were determined by FTIR, XRD, and SEM. Immobilized enzymes on the GO-Fe₃O₄ and GO were counted. Enzyme activity, reusability, and improvements in enzyme stability were studied. According to the results, the immobilization efficiency was 256.86 mg ficin/GO (g), and 253.63 mg ficin/GO-Fe₃O₄ (g). Furthermore, immobilized ficin was affected in terms of stability by variations in pH and temperature. The immobilized ficin on the GO-Fe₃O₄ could be easily recycled from the reaction medium by applying external magnetic separation, involving 10 cycles for 120 days. Over this period and with this number of cycles, the immobilized enzyme on the GO-Fe₃O₄ retained 74% of its original activity, whereas the immobilized enzyme on the GO was recycled from the reaction medium after centrifuging, thereby retaining 70% of its original activity. Thus, GO and GO-Fe₃O₄ nanosheets were obtained efficiently from the ultrasonic-assisted technique and can be regarded as excellent nanocarriers for enzyme immobilization.

Switch off/switch on of a cysteinyl protease as a way to preserve the active catalytic group by modification with a reversible covalent thiol modifier: Immobilization of ficin on vinyl-sulfone activated supports

The immobilization of ficin (a cysteinyl proteases) on vinyl sulfone agarose produced its almost full inactivation. It was observed that the incubation of the free and immobilized enzyme in β-mercaptoethanol produced a 20 % of enzyme activity recovery, suggesting that the inactivation due to the immobilization could be a consequence of the modification of the catalytic Cys. To prevent the enzyme inactivation during the immobilization, switching off of ficin via Cys reaction with dipyridyl-disulfide was implemented, giving a reversible disulfide bond that produced a fully inactive enzyme. The switch on of ficin activity was implemented by incubation in 1 M β-mercaptoethanol. Using this strategy to immobilize the enzyme on vinyl sulfone agarose beads, the expressed activity of the immobilized ficin could be boosted up to 80 %. The immobilized enzyme presented a thermal stabilization similar to that obtained using ficin-glyoxyl-agarose beads. This procedure may be extended to many enzymes containing critical Cys, to permit their immobilization or chemical modification.

Application of preliminary high-pressure processing for improving bioactive characteristics and reducing antigenicity of whey protein hydrolysates

This study investigated the use of Novo Pro-D® (NPD) and Ficin (FC) as alternative proteases for the production of bioactive peptides with reduced allergenicity from whey protein concentrate (WPC). In addition, the use of high hydrostatic pressure processing as pre-treatment of WPC and its impact on the final characteristics of hydrolysates were also evaluated. NPD treatments generated hydrolysates with a 98% reduction of soluble proteins, greater in vitro antioxidant capacity, and less immunoreactivity when compared to FC ones. However, pre-treatment was an essential tool to improve WPC hydrolysis when FC was used, resulting in hydrolysates with less soluble proteins, enhanced antioxidant capacity, and less allergenicity compared with conventional hydrolysis. As for NPD, the pre-treatment of WPC improved the in vitro antioxidant capacity and resulted in a 100% reduction in immunoreactivity to β-lactoglobulin in a shorter processing time. Importantly, bioactive peptides generated by FC displayed an improved ability to induce in vitro arterial relaxation, compared with those obtained from NPD process. Therefore, this study provides innovative evidence regarding how the proteases used for production of whey hydrolysates can improve its biological effects, and discloses the use of high hydrostatic pressure combined with enzymatic hydrolysis as a promising alternative to produce hydrolysates with improved properties.

Inhibition of low-density lipoprotein oxidation, antioxidative and bile acid-binding capacities of hydrolyzed proteins from carbohydrase-treated oat bran

This study investigated the valorization of oat bran and the use of its proteins to generate polypeptides with antioxidant and bile acid-binding properties. Ten protein hydrolysates were prepared by treating cellulase (CPI) or Viscozyme (VPI) protein isolates with five proteases. VPI-pepsin was the best peroxyl radical scavenger (497 ± 6-μM Trolox equivalents [TE]/g) while VPI-Flavourzyme quenched hydroxyl radicals (28 ± 0.6) and VPI-pepsin superoxide anion radicals (45.3 ± 6.6%). Hydrolysates, except those produced with pepsin, dose-dependently chelated iron whereas VPI-Protamex had the best copper-chelating capacity (59.83 ± 1.40%). These antioxidative capacities were important in preventing by 50% in vitro copper-induced oxidation of human low-density lipoprotein. Furthermore, due to their aromatic amino acid contents and hydrophobicity, the hydrolysates bound up to 46.3% the bile acids taurodeoxycholate and taurocholate. PRACTICAL APPLICATIONS: The presence of oxidants in foods can damage food molecules and decrease their quality. They are also known to increase the risk of developing chronic conditions like cardiovascular disease. Finding new antioxidant molecules are therefore useful in the management of chronic diseases. Data from this work showed that hydrolyzed oat bran proteins can be useful in stabilizing commercial oil as they reduced the oxidation of peanut oil. Additionally, the protein hydrolysates not only prevented the oxidation of linoleic, a common component of both vegetable oils and biological cell membranes, they also inhibited the oxidation of human LDL cholesterol and chelated bile acids. These hydrolysates can then be further explored as multifunctional ingredients for the development of stable functional food products with potential beneficial effects on the cardiovascular system.

Effect of ripening time on peptide dynamics and bioactive peptide composition in Tulum cheese

Skin bag Tulum cheeses traditionally produced in the Central Taurus region of Turkey were studied to identify peptide profiles by liquid chromatography-tandem mass spectrometry over 180 d of ripening. After mass spectrometry analysis, 203 peptides were identified: 59 from α_S1-casein (CN), 11 from α_S2-CN, 129 from β-CN, and 4 from κ-CN. Numbers of α_S1- and β-CN-derived peptides increased with increasing number of ripening days due to the dependence of newly formed peptides on proteolysis. However, similar increases were not observed for α_S2- and κ-CN-derived peptides. Most identified peptides consisted of β-CN-derived peptides, followed by α_S1-, α_S2-, and κ-CN-derived peptides. Among these, bioactive peptides were found, including antihypertensive, antibacterial, antioxidant, dipeptidyl peptidase-4 inhibitory, metal chelating, skin regenerating, glucagon-like peptide-1 secretion enhancing, opioid, cathepsin B inhibitory, prolyl endopeptidase inhibitory, immunomodulatory, brain function improving, antiamnesic, antihypercholesterolemic, anti-inflammatory, and anticarcinogenic peptides.

Sperm Proteomics Analysis of Diabetic Induced Male Rats as Influenced by Ficus carica Leaf Extract

Diabetes mellitus is shown to bring negative effects on male reproductive health due to long-term effects of insulin deficiency or resistance and increased oxidative stress. Ficus carica (FC), an herbal plant, known to have high antioxidant activity and antidiabetic properties, has been used traditionally to treat diabetes. The objective of this study is to determine the potential of the FC leaf extract in improving sperm quality of streptozotocin (STZ) induced diabetic male rats from proteomics perspective. A total of 20 male rats were divided into four groups; normal (nondiabetic rats), negative control (diabetic rats without treatment), positive control (diabetic rats treated with 300 mg/kg metformin), and FC group (diabetic rats treated with 400 mg/kg FC extract). The treatments were given via oral gavage for 21 consecutive days. The fasting blood glucose (FBG) level of FC treated group demonstrated a significant (p < 0.05) decrease compared to negative group after 21 days of treatment, as well as a significant (p < 0.05) increase in the sperm quality parameters compared to negative group. Sperm proteomics analysis on FC treated group also exhibited the increase of total protein expression especially the proteins related to fertility compared to negative group. In conclusion, this study clearly justified that FC extract has good potential as antihyperglycemic and profertility agent that may be beneficial for male diabetic patients who have fertility problems.

In vitro-digested milk proteins: Evaluation of angiotensin-1-converting enzyme inhibitory and antioxidant activities, peptidomic profile, and mucin gene expression in HT29-MTX cells

Over the past decades, several studies investigated the health-promoting functions of milk peptides. However, to date many hurdles still exist regarding the widespread use of milk-derived bioactive peptides, as they may be degraded during gastrointestinal digestion. Thus, the aim of our study was to in vitro digest intact whey protein isolate (WPI) and casein proteins (CNP), mimicking in vivo digestion, to investigate their bioactive effects and to identify the potential peptides involved. Whey protein isolate and CNP were digested using a pepsin-pancreatin protocol and ultra-filtered (3-kDa cutoff membrane). A permeate (<3 kDa) and a retentate (>3 kDa) were obtained. Soy protein was included as a control (CTR). Angiotensin-1-converting enzyme inhibitory (ACE1-I) and antioxidant activity (AOX) were assessed and compared with those observed in undigested proteins and CTR. Furthermore, the permeate was characterized by nano-liquid chromatography electrospray ionization tandem mass spectrometry (LC-nano ESI MS/MS) using a shotgun peptidomic approach, and retentate was further digested with trypsin and analyzed by MS using a shotgun proteomic approach to identify potentially bioactive peptides. Further, the effects of WPI, CNP, and CTR retentate on cell metabolic activity and on mucus production (MUC5AC and MUC2 gene expression) were assessed in intestinal goblet HT29-MTX-E12 cells. Results showed that WPI permeate induced a significant ACE1-I inhibitory effect [49.2 ± 0.64% (SEM)] compared with undigested WPI, CNP permeate, and retentate or CTR permeate (10.40 ± 1.07%). A significant increase in AOX (1.58 ± 0.04 and 1.61 ± 0.02 µmol of trolox AOX equivalents per mg of protein, respectively) upon digestion was found in WPI. Potentially bioactive peptides associated with ACE1-I and antihypertensive effects were identified in WPI permeate and CNP retentate. At specific concentrations, WPI, CNP, and CTR retentate were able to stimulate metabolic activity in HT29-MTX-E12 cells. Expression of MUC5AC was increased by CNP retentate and unaltered by WPI retentate; MUC2 expression was significantly increased by 0.33 mg/g of CNP and reduced by 1.33 mg/g of CNP. Our results confirm that milk proteins may be rich sources of bioactive compounds, with the greatest beneficial potential of CNP at the intestinal goblet cell level.

In-vitro assessment of antioxidant and antimicrobial activity of whole porcine-liver hydrolysates and its fractions

Aim of the study was to evaluate antioxidant and antimicrobial activity of porcine liver-protein hydrolysates (PLHs) and their fractions recovered from enzymatic hydrolysis. Hydrolysates and fractions were assessed for antioxidants such as 2,2-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid, 2,2-diphenyl-1-picrylhydrazyl and ferric-reducing antioxidant power and antimicrobial activity. Inhibition activity for all antioxidant parameters was significantly (P &lt; 0.05) higher for whole PLHs than for its corresponding fractions; however, among their fractions, 5–10 kDa and 1–5 kDa had a relatively higher antioxidant activity than did the other fractions. Trypsin-digested whole PLHs and their fractions exhibited the highest antioxidant and antimicrobial activity, followed by alcalase- and papain-digested PLHs, for all tested microbes. Results accomplished that whole PLHs exhibited better result than its fractions; thus, PLHs can be used as preservatives for food products or utilised for other pharmaceutical purposes.

Chemical characterization and evaluation of the antioxidants in Chaenomeles fruits by an improved HPLC-TOF/MS coupled to an on-line DPPH-HPLC method

An improved method based on HPLC-TOF/MS was developed to catalog the antioxidants in five species of Chaenomeles (Mugua). Forty-four fractions from the Mugua extracts show appreciable levels of antioxidative activity in scavenging the stable free-radical 2,2-diphenyl-1-picrylhydrazyl and the hydroxyl radicals. Twelve major antioxidant's chemical structures are identified. Antioxidant activities differ between species, but intra-species level of antioxidants, regardless of their ripeness, are similar. C. sinensis has the highest antioxidant level. A rigorous quality control procedure was implemented to ensure accuracy of antioxidant quantification. This improved procedure can be used for rapid discovery of antioxidants in other plant extracts.

Thermal and single frequency counter-current ultrasound pretreatments of sodium caseinate: enzymolysis kinetics and thermodynamics, amino acids composition, molecular weight distribution and antioxidant peptides

BACKGROUND

Due to the disadvantages of traditional enzymolysis, pretreatments are crucial to enhance protein enzymolysis. Enzymolysis kinetics and thermodynamics, amino acids composition, molecular weight distribution, fluorescence spectroscopy and antioxidant activity of thermal (HT) and single frequency counter-current ultrasound (SCFU) pretreated sodium caseinate (NaCas) were studied.

RESULTS

Enzymolysis of untreated NaCas (control) improved significantly (P < 0.05) by SFCU and followed by HT. Values of the Michaelis-Menten constant (K_M ) of SFCU and HT were 0.0212 and 0.0250, respectively. HT and SFCU increased (P < 0.05) the reaction rate constant (k) by 38.64 and 90.91%, respectively at 298 K. k values decreased with increasing temperature. The initial activation energy (46.39 kJ mol^-1 ) reduced (P < 0.05) by HT (39.66 kJ mol^-1 ) and further by SFCU (33.42 kJ mol^-1 ). SFCU-pretreated NaCas hydrolysates had the highest contents of hydrophobic, aromatic, positively and negatively charged amino acids. Medium-sized peptides (5000-1000 Da) are higher in SFCU (78.11%) than HT and the control. SFCU induced molecular unfolding of NaCas proteins. Accordingly, SFCU-pretreated NaCas hydrolysate exhibited the highest scavenging activity on DPPH and hydroxyl radicals, reducing power, and iron chelating ability.

CONCLUSION

SFCU pretreatment would be a useful tool for production of bioactive peptides from NaCas hydrolysate. © 2016 Society of Chemical Industry.

Generation of bioactive peptide hydrolysates from cattle plasma using plant and fungal proteases

Four protease preparations from plant and fungal sources (papain, bromelain, FP400 and FPII) were used to hydrolyse plasma which was separated from slaughterhouse cattle blood. The o-phthaldialdehyde assay was used to follow the release of TCA-soluble peptides over a 24h period. Hydrolysis profiles were displayed using SDS-PAGE. The in vitro antioxidant and antimicrobial activities of the hydrolysates were determined. The results showed that hydrolysates of cattle plasma generated with fungal protease FPII had higher antioxidant activities. Overall than hydrolysates generated with papain, bromelain and FP400. None of the hydrolysates demonstrated antimicrobial activity. The FPII peptide hydrolysate was fractionated using gel permeation chromatography, OFFGEL isoelectric focusing and RP-HPLC. The RP-HPLC fraction with highest antioxidant activity contained 15 novel peptide sequences. The use of protease FPII to hydrolyse cattle plasma resulted in a hydrolysate with high antioxidant properties and unique peptide sequences.

Enzymatic generation of whey protein hydrolysates under pH-controlled and non pH-controlled conditions: Impact on physicochemical and bioactive properties

Enzymatic hydrolysis of whey protein (WP) was carried out under pH-controlled and non pH-controlled conditions using papain and a microbial-derived alternative (papain-like activity). The impact of such conditions on physicochemical and bioactive properties was assessed. WP hydrolysates (WPH) generated with the same enzyme displayed similar degree of hydrolysis. However, their reverse-phase liquid chromatograph mass spectrometry peptide profiles differed. A significantly higher oxygen radical absorbance capacity (ORAC) value was obtained for WP hydrolysed with papain at constant pH of 7.0 compared to the associated WPH generated without pH regulation. In contrast, there was no significant effect of pH regulation on dipeptidyl peptidase IV (DPP-IV) properties. WP hydrolysed with papain-like activity under pH regulation at 7.0 displayed higher ORAC activity and DPP-IV inhibitory properties compared to the associated WPH generated without pH regulation. This study has demonstrated that pH conditions during WPH generation may impact on peptide release and therefore on WPH bioactive properties.

Protease from Aspergillus oryzae: Biochemical Characterization and Application as a Potential Biocatalyst for Production of Protein Hydrolysates with Antioxidant Activities

This study reports the biochemical characterization of a protease from Aspergillus oryzae LBA 01 and the study of the antioxidant properties of protein hydrolysates produced with this protease. The biochemical characterization showed that the enzyme was most active over the pH range 5.0–5.5 and was stable from pH 4.5 to 5.5. The optimum temperature range for activity was 55–60°C, and the enzyme was stable at temperatures below 45°C. The activation energy (Ea) for azocasein hydrolysis and temperature quotient (Q10) were found to be 37.98 kJ mol−1 and 1.64–1.53 at temperature range from 30 to 55°C, respectively. The enzyme exhibited t1/2 of 97.63 min and a D value of 324.31 at the optimum temperature for activity (57.2°C). Protease from A. oryzae LBA 01 was shown as a potentially useful biocatalyst for protein hydrolysis, increasing the antioxidant activities of soy protein isolate, bovine whey protein, and egg white protein from 2.0- to 10.0-fold.

Recovery of casein-derived peptides with in vitro inhibitory activity of angiotensin converting enzyme (ACE) using aqueous two-phase systems

Peptides inhibiting the activity of angiotensin converting enzyme (ACE) were obtained by trypsin-catalyzed hydrolysis of bovine milk casein, performed at 37°C, during 1, 2, 5, 8 and 24h. Results of in vitro inhibitory activity ranged between 13.4% and 78.5%. The highest ACE inhibitory activity was evidenced for hydrolysates obtained after 2h of reaction. Aqueous two-phase systems (ATPS) formed by polyethylene glycol of 1500gmol^-1 (PEG 1500)+sodium phosphate or potassium phosphates were produced and evaluated, in terms of partition coefficients (K) and extraction yields (y), to recovery the casein hydrolysates at room temperature. In ATPS containing sodium phosphate, the peptides showed a slightly greater affinity toward the bottom salt-rich phase (0.1≤K≤0.9; 5.7%≤y≤47%). In the case of ATPS containing potassium phosphates, these molecules showed substantially greater affinity toward the top polymer-rich phase (137≤K≤266; y≥99%). These results point out extraction using PEG 1500/potassium phosphate ATPS is an efficient technique to recover casein hydrolysates containing ACE inhibitors peptides. Outlined data will be helpful in integrating such unit operation to larger scale processes.