Housefly larvae hydrolysate: orthogonal optimization of hydrolysis, antioxidant activity, amino acid composition and functional properties

Effects of ultrasonic waves of different powers on the physicochemical properties, functional characteristics, and ultrastructure of bovine liver peptides

In recent years, ultrasound has emerged as a widely used technology for modifying proteins/peptides. In this study, we focused on the intrinsic mechanism of ultrasound-induced modification of bovine liver peptides, which were treated with ultrasound power of 0, 100, 200, 300, 400, and 500 W, and their physicochemical and functional properties, as well as ultrastructures, were investigated. The results show that ultrasound mainly affects hydrogen bonding and hydrophobic interactions to change the conformation of proteins and unfolds proteins through a cavitation effect, leading to an increase in biological activity. Fourier infrared spectroscopy showed that ultrasound inhibited the formation of hydrogen bonds and reduced intermolecular cross-linking. Molecular weight distribution showed that the antioxidant components of bovine liver polypeptides were mainly concentrated in fractions of 500-1,000 Da. Maximum values of ABTS (82.66 %), DPPH (76.02 %), chelated iron (62.18 %), and reducing power (1.2447) were obtained by treating bovine liver polypeptides with 500 W ultrasound. Combined with the scanning electron microscopy results, with the intervention of ultrasound, the impact force generated by ultrasonication may lead to the loosening of the protein structure, which further promotes the release of antioxidant peptides, and these findings provide new insights into the application of ultrasound in the release of antioxidant peptides from bovine liver.

Insect biorefinery: A circular economy concept for biowaste conversion to value-added products

With rapid growing world population and increasing demand for natural resources, the production of sufficient food, feed for protein and fat sources and sustainable energy presents a food insecurity challenge globally. Insect biorefinery is a concept of using insect as a tool to convert biomass waste into energy and other beneficial products with concomitant remediation of the organic components. The exploitation of insects and its bioproducts have becoming more popular in recent years. This review article presents a summary of the current trend of insect-based industry and the potential organic wastes for insect bioconversion and biorefinery. Numerous biotechnological products obtained from insect biorefinery such as biofertilizer, animal feeds, edible foods, biopolymer, bioenzymes and biodiesel are discussed in the subsequent sections. Insect biorefinery serves as a promising sustainable approach for waste management while producing valuable bioproducts feasible to achieve circular bioeconomy.

Influence of the Enzymatic Hydrolysis Using Flavourzyme Enzyme on Functional, Secondary Structure, and Antioxidant Characteristics of Protein Hydrolysates Produced from Bighead Carp (Hypophthalmichthys nobilis)

In the current study, bighead carp fish were used in conjunction with the flavourzyme enzyme to obtain (FPH) fish protein hydrolysates. The optimum conditions of the hydrolysis process included an enzyme/substrate ratio of 4% and a temperature of 50 °C and pH of 6.5. The hydrolysis time was studied and investigated at 1, 3, and 6 h, and the (DH) degree of hydrolysis was recorded at 16.56%, 22.23%, and 25.48%, respectively. The greatest yield value was 17.83% at DH 25.48%. By increasing the DH up to 25.48%, the crude protein and total amino acid composition of the hydrolysate were 88.19% and 86.03%, respectively. Moreover, more peptides with low molecular weight were formed during hydrolysis, which could enhance the functional properties of FPH, particularly the solubility property ranging from 85% to 97%. FTIR analysis revealed that enzymatic hydrolysis impacted the protein's secondary structure, as indicated by a remarkable wavelength of amide bands. Additionally, antioxidant activities were investigated and showed high activity of DDPH radical scavenging, and hydroxyl radical scavenging demonstrated remarkable activity. The current findings demonstrate that the functional, structural, and antioxidant characteristics of FPH might make it an excellent source of protein and suggest potential applications in the food industry.

Influence of the Degree of Hydrolysis on Functional Properties and Antioxidant Activity of Enzymatic Soybean Protein Hydrolysates

Soybean protein hydrolysates were prepared using two proteolytic enzymes (Alcalase and Protamex) and the degree of hydrolysis (DH) and their functional and antioxidant properties were evaluated. The highest DH value was 20%, with a yield of 19.77% and protein content of 51.64%. The total amino acid content was more than 41% for all protein hydrolysates. The protein hydrolysates from Protamex at pH 2.0 had excellent solubility, emulsifying activity, and foaming capacity, at 83.83%, 95.03 m²/g, and 93.84%, respectively. The water-holding capacity was 4.52 g/g for Alcalase, and the oil-holding capacity was 4.91 g/g for Protamex. The antioxidant activity (62.07%), as measured by the samples' reaction with DPPH (2,2-diphenyl-1-picrylhydrazyl) and the reducing power (0.27) were the strongest for Protamex. An ABTS activity rate of 70.21% was recorded for Alcalase. These findings indicated a strong potential for the utilization of soybean protein hydrolysates to improve the functional properties and antioxidant activity of soybeans as well as their nutritional values.

In vitro Antioxidant, Cytotoxic and Antidiabetic Activities of Protein Hydrolysates Prepared from Chinese Pond Turtle (Chinemys reevesii)

Research background

Cardiovascular diseases and diabetes are the biggest causes of death globally. Bioactive peptides derived from many food proteins using enzymatic proteolysis and food processing have a positive impact on the prevention of these diseases. The bioactivity of Chinese pond turtle muscle proteins and their enzymatic hydrolysates has not received much attention, thus this study aims to investigate their antioxidant, antidiabetic and cytotoxic activities.

Experimental approach

Chinese pond turtle muscles were hydrolysed using four proteolytic enzymes (Alcalase, Flavourzyme, trypsin and bromelain) and the degrees of hydrolysis were measured. High-performance liquid chromatography (HPLC) was conducted to explore the amino acid profiles and molecular mass distribution of the hydrolysates. The antioxidant activities were evaluated using various in vitro tests, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), hydroxyl radical scavenging activity, reducing capacity, chelating Fe²⁺ and lipid peroxide inhibition activity. Antidiabetic activity was evaluated using α-amylase inhibition and α-glucosidase inhibition assays. Besides, cytotoxic effect of hydrolysates on human colon cancer (HT-29) cells was assessed.

Results and conclusions

The amino acid composition of the hydrolysates revealed higher mass fractions of glutamic, aspartic, lysine, hydroxyproline and hydrophobic amino acids. Significantly highest inhibition of lipid peroxidation was achieved when hydrolysate obtained with Alcalase was used. Protein hydrolysate produced with Flavourzyme had the highest radical scavenging activity measured by DPPH (68.32%), ABTS (74.12%) and FRAP (A_{700 nm}=0.300) assays, α-glucosidase (61.80%) inhibition and cytotoxic effect (82.26%) on HT-29 cell line at 550 µg/mL. Hydrolysates obtained with trypsin and bromelain had significantly highest (p<0.05) hydroxyl radical scavenging (92.70%) and Fe²⁺ metal chelating (63.29%) activities, respectively. The highest α-amylase (76.89%) inhibition was recorded when using hydrolysates obtained with bromelain and Flavourzyme.

Novelty and scientific contribution

Enzymatic hydrolysates of Chinese pond turtle muscle protein had high antioxidant, cytotoxic and antidiabetic activities. The findings of this study indicated that the bioactive hydrolysates or peptides from Chinese pond turtle muscle protein can be potential ingredients in pharmaceuticals and functional food formulations.

Optimization of the UDP-Xyl biocatalytic synthesis from Crassostrea gigas by orthogonal design method

UDP-Xyl, a nucleotide sugar involved in the biosynthesis of various glycoconjugates, is difficult to obtain and quite expensive. Biocatalysis using a one-pot multi-enzyme cascade is one of the most valuable biotransformation processes widely used in the industry. Herein, two enzymes, UDP-glucose (UDP-Glc) dehydrogenase (CGIUGD) and UDP-Xyl synthase (CGIUXS) from the Pacific oyster Crassostrea gigas, which are coupled together for the biotransformation of UDP-Xyl, were characterized. The optimum pH was determined to be pH 9.0 for CGIUGD and pH 7.5 for CGIUXS. Both enzymes showed the highest activity at 37 °C. Neither enzyme is metal ion-dependent. On this basis, a single factor and orthogonal test were applied to optimize the condition of biotransformation of UDP-Xyl from UDP-Glc. Orthogonal design L9 (3³) was conducted to optimize processing variables of enzyme amount, pH, and temperature. The conversion of UDP-Xyl was selected as an analysis indicator. Optimum variables were the ratio of CGIUGD to CGIUXS of 2:5, enzymatic pH of 8.0, and temperature of 37 °C, which is confirmed by three repeated validation experiments. The UDP-Xyl conversion was 69.921% in a 1 mL reaction mixture by optimized condition for 1 h. This is the first report for the biosynthesis of UDP-Xyl from oyster enzymes.

Degree of hydrolysis, functional and antioxidant properties of protein hydrolysates from Grass Turtle (Chinemys reevesii) as influenced by enzymatic hydrolysis conditions

Grass turtle muscle was hydrolyzed with papain enzyme to produce protein hydrolysate (PH) and the degree of hydrolysis (DH) was determined. Under optimal conditions, the highest DH was 19.52% and the yield was recorded as 17.26%. Protein content of the hydrolysates was ranged from 73.35% to 76.63%. Total amino acids were more than 96.77% for each PH. The PH obtained at DH 19.52% achieved excellent solubility and emulsifying activity which were 95.56% and 108.76 m2/g, respectively at pH 6. Foam capacity amounted 100% in PH of DH 19.52% at pH 2, and water-holding capacity was 4.38 g/g. The antioxidant activity showed the strongest hydroxyl radical scavenging activity (95.25%), ABTS (84.88%), DPPH (75.89%), iron chelating (63.25%), and cupper chelating (66.90%) at DH 11.96%, whereas reducing power (0.88) at DH 19.52%. Thus, the findings indicated that utilization of grass turtle muscle protein hydrolysate is a potential alternative protein resource to improve the nutritional and functional properties in food ingredients and product formulations.

Purification and structure analysis of zinc-binding protein from Mizuhopecten yessoensis

Zn-binding protein was obtained after purification from scallops (Mizuhopecten yessoensis) using gel permeation and ion-exchange chromatography. Amino acid determination showed that the cysteine of the zinc-binding protein accounted for one-third of the total amino acids, which is a typical feature of metallothionein (MT). The spectra of Fourier Transform Infrared Spectroscopy (FTIR) and Circular Dichroism (CD) were analyzed to predict the secondary structure information of zinc-binding protein: the α-helix was 46.55%, the β-sheets was 27.07%, the random coil was 16.48%, and the β-turns was 9.89%. Using a commercial kit to measure its antioxidant activity in vitro, the result showed that it had good scavenging ability to 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical (·OH), and reducing the ability to ferrous iron ions. With the process provided by this study, zinc-binding protein can be prepared in large quantities, which is the basis for its future commercialization. PRACTICAL APPLICATIONS: According to the extraction and purification process established in this study, a large amount of zinc-bound MT from the viscera of scallops can be obtained. And the zinc-bound MT had good antioxidant activity. In addition, the yield of each purification step has been calculated. The zinc-bound MTs from scallop' viscera can be prepared in large quantities by directly using the process in this manuscript or by equal magnification of this process. In the future, large-scale production can be considered to increase the economic value of scallops' viscera.

Digestive characteristics and peptide release from wheat embryo proteins in vitro

Due to the scarcity of the data on digestion and metabolism of wheat embryo proteins WEP, a simulated gastrointestinal digestion (SGID) scheme in vitro was utilized to explain the protein hydrolysis and biological activity of WEP during the digestion process. WEP had a certain degree of resistance to gastric digestion, especially the protein with a molecular weight of 50 kDa. In all the samples, no visually intact protein band emerged in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) during the intestinal phase, which was consistent with a gradually increasing content of released free amino acids. Moreover, the resistant digestion peptides (the amino acid sequences were ISQFXX and GTVX) were identified at the end of the gastrointestinal digestion (GID) product by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Although the complete protein in the sample was degraded, the antioxidant activity was not negatively affected, rather it showed an increasing trend and maintained a higher level of activity. The amount of the β-sheet gradually increased as that of the α-helix declined, the random coil decreased, whereas no obvious change was noticed in β-turn content. The results provide a better understanding for optimal selection of peptide candidates for designing protein products in the food processing industry as well as for WEP digestion and metabolism in the human body.

Purification, secondary structure and antioxidant activity of metallothionein zinc-binding proteins from Arca subcrenata

Zinc-binding proteins named MT-M-I and MT-M-II were obtained after purification from metal-exposed hairy clams (Arca subcrenata) using gel permeation and ion-exchange chromatography. MT-M-I and MT-M-II were resolved by ion-exchange chromatography, and they were found to have similar molecular weights. MT-M-I and MT-M-II can bind 6 and 7 equivalents of Zn²⁺ in vitro, and they showed unusual migration behaviors in Tricine sodium dodecyl sulfate polyacrylamide gel electrophoresis (Tricine-SDS-PAGE). Such migration behaviors may be due to themetal thiolate clusters in these proteins. In terms of amino acid composition, the proportion of cysteine in MT-M-I and MT-M-II was approximately 30%, and glycine accounted for approximately 15%, where as aromatic amino acids were absent. Considering the performance in Tricine-SDS-PAGE and the amino acid compositions, MT-M-I and MT-M-II conform to the molecular characteristics of the metallothionein proteins. The structures were explored using circular dichroism (CD) and Fourier-transform infrared spectroscopy (FTIR). Also determined the antioxidant activities in terms of DPPH radical scavenging ability, hydroxyl radical (·OH) scavenging ability, and ferric-reducing/antioxidant power. The antioxidant activities of MT-M-I were found to be stronger than those of MT-M-II.

Effects of Enzymatic Hydrolysis on the Functional Properties, Antioxidant Activity and Protein Structure of Black Soldier Fly (Hermetia illucens) Protein

Simple Summary

According to the FAO, the world’s population will reach 9 billion by 2050, and in order to provide enough food, meat production must increase by 100% and food production by 70%. Furthermore, more than 80% of fresh water resources are being used for agriculture, and 40% of the total food produced annually, is wasted. One sustainable agricultural practice involves converting by-products from the food and agriculture industry into valuable biomass, such as black soldier flies. Black soldier fly larvae can feed on by-products, and convert them to protein, carbohydrates, and oil. Black soldier flies could be used for feed and food development using different processing methods including enzymatic hydrolysis.

Abstract

The effects of chemical protein extraction, and enzymatic hydrolysis with Alcalase, papain and pepsin, on the functional properties, antioxidant activity, amino acid composition and protein structure of black soldier fly (H. illucens) larval protein were examined. Alcalase hydrolysates had the highest degree of hydrolysis (p < 0.05), with the highest hydrolysate and oil fraction yield (p < 0.05). Pepsin hydrolysates showed the lowest oil holding capacity (p < 0.05), whereas no significant differences were observed among other enzymes and protein concentrates (p > 0.05). The emulsifying stability and foam capacity were significantly lower in protein hydrolysates than protein concentrate (p < 0.05). The antioxidant activity of protein hydrolysates from protein concentrate and Alcalase was higher than that with papain and pepsin (p < 0.05), owing to the higher hydrophobic amino acid content. Raman spectroscopy indicated structural changes in protein α-helices and β-sheets after enzymatic hydrolysis.

Dietary Inclusion of Tenebrio Molitor Meal in Sea Trout Larvae Rearing: Effects on Fish Growth Performance, Survival, Condition, and GIT and Liver Enzymatic Activity

Sea trout (Salmo trutta m. trutta) is a species for which effective methods of rearing are still being developed. They need high-quality protein in their diet, but, considering the ecological consequences of fishmeal production, new sources of protein are needed. Presently, insect meal is one of the most promising alternative sources of protein in the diets of farm animals. Insect production does not result in excessive gas emissions, waste generation or the risk of obtaining low-quality dietary protein. The study on sea trout larvae was carried out for 60 days. Four diets were given to the fish: one control (C), without the inclusion of insect meal, and three experimental, with one unhydrolysed Tenebrio molitor meal (TM) and two hydrolysed Tenebrio molitor meal treatments. The effects of the diets were evaluated on the basis of growth performance (weight and length of the fish, SR, SGR, RGR, FCR and PER), somatic indices (HSI and VSI) and fish condition (CF). We observed that the highest body mass and weight gain were obtained in the control group. However, the lowest mortality and the highest values of RGR were observed only in groups fed diets containing mealworm meal. The results for the hepato- and viscerosomatic indices showed a lack of statistically significant differences between the control group and the unhydrolysed Tenebrio molitor meal group in terms of the enzymatic activities of amylase, lipase and trypsin in the fish intestine and both aminotransferases in the liver. Our study demonstrated that the inclusion of 20% mealworm meal in practical diets for sea trout did not negatively affect growth performance or gastrointestinal tract (GIT) enzyme activity. The hydrolysed mealworm meal and the non-processed mealworm meal had similar effects.

Sonochemical action and reaction of edible insect protein: Influence on enzymolysis reaction-kinetics, free-Gibbs, structure, and antioxidant capacity

We investigated the impact of sonochemical action and the reaction of Hermetia illucens larvae meal protein (HILMP) as regards enzymolysis under varied enzyme concentration and temperature to explain the mechanism and effect of sonication on molecular conformation, limits of kinetics, free-Gibbs energy, and antioxidative capacity. Control treatment was used for comparison. The results showed sonochemical treatment enhanced HILMP-enzymolysis efficiency at various enzyme volume, and temperature. Enzymolysis-kinetics revealed sonochemical treatment increased the rate constant (p < .05) by 17.21%, 25.06%, 26.91%, and 41.38% at 323, 313, 303, and 293 K, respectively. On free-Gibbs, sonochemical treatment reduced the reactants-reactivity energy, enthalpy, and entropy by 30.53%, 35.05%, and 10.71%, respectively (p < .05). Changes in spectra of UV and fluorescence, and micrographic imaging indicated alterations of HILMP by sonochemical treatment. Antioxidative activity of sonochemically-treated HILMP increased, compared to control. Thus, sonochemical treatment may be beneficial in the production of edible insect proteins with smaller molecular weights for different food and/or pharmaceutical applications. PRACTICAL APPLICATIONS: Sonochemical pretreatment of HILMP positively impacted it enzymolysis rate-reaction, stability of reaction products, structure, and bioactivity. Thus, the technique may be beneficial to industry in the processing/development of new (bioactive/pharmaceutical) products involving enzymolysis of edible insects (e.g., Hermetia illucens) protein; particularly at such a time where edible insects are projected to be a source of protein for human nutrition and livestock in the next few years.

Purification and identification of an antioxidative peptide from peony (Paeonia suffruticosa Andr.) seed dreg

The present study demonstrated the hydrolysis of peony seed protein isolate (PSPI) by using alcalase and resulted in the generation of an anti-oxidative peptide. In brief, a model was used to illustrate the enzymolysis of PSPI with the determination of kinetic factors as per investigation information. The model proved suitable to explain the PSPI hydrolysis by alcalase. A novel anti-oxidative peptide was obtained successfully by ultrafiltration and a series of chromatography techniques. Subsequently, a purified fragment was identified with the amino acid sequence of SMRKPPG followed by its synthesis and evaluation of its anti-oxidative activities. After hydrolysis, the peony seed protein hydrolysate (PSPH) with the degree of hydrolysis of 18% displayed the most significant antioxidant action which was further used to isolate the anti-oxidative peptide.

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.

Antioxidant and antimicrobial activity of ultra-filtered fractions of camel milk protein hydrolysates under in-vitro condition

Sequential ultra-filtration technique was used to fractionate camel milk protein hydrolysates products by 3 different proteolytic enzymes, viz. alcalase, α-chymotrypsin and papain. The protein fractions were assessed for antioxidant activities, viz. 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), 2,2-diphenyl-1 picrylhydrazyl (DPPH) and ferric reducing antioxidant power assay (FRAP), and antimicrobial activity (inhibition zone assay). The whole hydrolysates recorded significantly higher inhibition activity in ABTS, DPPH and FRAP assay, whereas among fractions, F2 (1-5 kDa) and F3 (5-10 kDa) of all the 3 hydrolysates had higher activity. Higher antioxidant activities was also observed in α- chymotrypsin hydrolysates samples and its fractions followed by alcalase and papain. The zone of inhibition (mm) was also recorded higher for whole hydrolysates as compared to their fractions; however, different fractions had almost comparable antimicrobial effect. The protein hydrolyastes with alcalase and α- chymotrypsin recorded comperatively higher antimicrobial activity. The findings suggested that camel milk proteins could be valuable source to produce protein hydrolysates and ultra-filtration technique could also be used to get specific molecular weight peptides, however, for application in processed food or for direct human consumption, use of whole hydrolysates could be more beneficial and cost effective.

Antioxidant and antimicrobial activity of protein hydrolysate extracted from porcine liver

Protein hydrolysates were extracted from porcine liver using commercial proteases viz. alcalase, trypsin and papain. Porcine liver revealed appreciable amounts of protein (20.62%). Enzymatic hydrolysis of porcine liver hydrolysate (PLH) resulted in 23.56, 26.82 and 19.12% of degree of hydrolysis, respectively. Antioxidant activity such as 2–2 diphenyl–1-picrylhydrazyl (DPPH) and 2, 2-azino-bis-3-ethyl-benzthiazoline-6-sulphonic acid (ABTS) and ferric ion reducing power (FRAP) radicals were determined for PLH. All PLH samples showed slight decrease in the pH during hydrolysis while, they scavenged 42.27, 57.49 and 40.32% of DPPH radicals, respectively at sixth hour of hydrolysis. Trypsin hydrolysed PLH exhibited highest ABTS radical scavenging activity (86.79%) than alcalase hydrolysed PLH (74.62%) and papain hydrolysed PLH (70.63%). FRAP of PLH samples were found to be 13.69, 14.92 and 12.65% for alcalase, trypsin and papain extracted PLH samples, respectively. PLH obtained from trypsin hydrolysis showed highest antimicrobial activity followed by papain and alcalase PLH, respectively. However, all PLH have the potential to be a protein rich ingredient for use in formulated meat products and possible help in reduction of oxidative and microbial deterioration.

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.

Protective effect of gelatin peptides from pacific cod skin against photoaging by inhibiting the expression of MMPs via MAPK signaling pathway

Chronic exposure to ultraviolet (UV) irradiation causes skin photoaging. This study was undertaken to identify the anti-photoaging mechanisms of gelatin hydrolysate (CH) derived from pacific cod skin. Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) and ELISA assays were used to investigate the effects of CH on matrix metalloproteinases (MMPs) and the signaling pathways after UV irradiation by using a mice skin photoaging model. The average molecular weight of CH was 1200Da, and 273/1000 residues were hydrophobic, Gly-Pro and Gly-Leu sequences and Arg at C-terminus appeared frequently in CH. CH improved pathological changes of collagen fibers and significantly inhibited collagen content reduction in photoaging skin. Moreover, CH blocked the up-regulated expression of interstitial collagenase (MMP-1), stromelysin 1 (MMP-3), and gelatinase (MMP-9) in photoaging skin. Besides, CH suppressed the activities of MMPs by increasing the contents of tissue inhibitors of matrix metalloproteinases (TIMPs). CH significantly reduced the UV irradiation-dependent up-regulated phosphorylation of ERK and p38 in the mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, it inhibited the activation of activator protein 1 (AP-1) by down-regulating the mRNA level of c-Jun and c-Fos, which are the two transcription factors responsible for the regulation of MMPs expression. CH can effectively protect against UV irradiation-induced skin photoaging by inhibiting the expression and the activity of MMPs.