Rapid isolation of high purity pepsin-soluble type I collagen from scales of red drum fish (Sciaenops ocellatus)

Impact of changes in collagen construction and molecular state on integrin - binding properties

The interaction between the integrin and collagen is important in cell adhesion and signaling. Collagen, as the main component of extracellular matrix, is a base material for tissue engineering constructs. In tissue engineering, the collagen structure and molecule state may be altered to varying degrees in the process of processing and utilizing, thereby affecting its biological properties. In this work, the impact of changes in collagen structure and molecular state on the binding properties of collagen to integrin α2β1 and integrin specific cell adhesion were explored. The results showed that the molecular structure of collagen is destroyed under the influence of heating, freeze-grinding and irradiation, the triple helix integrity is reduced and molecular breaking degree is increased. The binding ability of collagen to integrin α2β1 is increased with the increase of triple helix integrity and decays exponentially with the increase of molecular breaking degree. The collagen molecular state can also influences the binding ability of collagen to cellular receptor. The collagen fibrils binding to integrin α2β1 and HT1080 cells is stronger than to collagen monomolecule. Meanwhile, the hybrid fibril exhibits a different cellular receptor binding performance from corresponding single species collagen fibril. These findings provide ideas for the design and development of new collagen-based biomaterials and tissue engineering research.

Physicochemical and thermal properties of pepsin- and acid-soluble collagen isolated from the body wall of sea cucumbers (Stichopus hermanni)

The main objective of this work was to characterize the acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from the body wall of the sea cucumber scientifically called, Stichopus hermanni. For the extraction of ASC and PSC, the pre-treated sea cucumber body walls were subjected to 0.5 M acetic acid and 5 g L-1 pepsin, respectively. The yield of ASC (7.30% ± 0.30%) was found to be lower than the PSC (23.66% ± 0.15%), despite both ASC and PSC having similar chemical compositions except for the quantity of protein. The collagens produced from ASC and PSC show maximum peaks on ultraviolet-visible spectroscopic profiles at wavelengths of 230 and 235 nm, respectively, with no significant difference in the maximum temperature (Tmax ) of the extracted ASC and PSC. The ASC's coloration was whiter than that of the PSC. As a result, the collagen obtained from the body wall of the sea cucumber showed promise for usage as a substitute for collagen derived from marine sources. PRACTICAL APPLICATION: The two most popular methods of collagen extraction were acid hydrolysis and enzymatic hydrolysis. To determine whether the extracted collagen is a suitable substitute for animal collagen in different industries, it is required to characterize its physicochemical qualities. This study discovered a new application for marine collagen in the food industry: The sea cucumber has collagen with a greater yield in pepsin extraction with good physicochemical qualities.

Trash to Treasure: An Up-to-Date Understanding of the Valorization of Seafood By-Products, Targeting the Major Bioactive Compounds

Fishery production is exponentially growing, and its by-products negatively impact industries' economic and environmental status. The large amount of bioactive micro- and macromolecules in fishery by-products, including lipids, proteins, peptides, amino acids, vitamins, carotenoids, enzymes, collagen, gelatin, chitin, chitosan, and fucoidan, need to be utilized through effective strategies and proper management. Due to the bioactive and healthy compounds in fishery discards, these components can be used as functional food ingredients. Fishery discards have inorganic or organic value to add to or implement in various sectors (such as the agriculture, medical, and pharmaceutical industries). However, the best use of these postharvest raw materials for human welfare remains unelucidated in the scientific community. This review article describes the most useful techniques and methods, such as obtaining proteins and peptides, fatty acids, enzymes, minerals, and carotenoids, as well as collagen, gelatin, and polysaccharides such as chitin-chitosan and fucoidan, to ensure the best use of fishery discards. Marine-derived bioactive compounds have biological activities, such as antioxidant, anticancer, antidiabetic, anti-inflammatory, and antimicrobial activities. These high-value compounds are used in various industrial sectors, such as the food and cosmetic industries, owing to their unique functional and characteristic structures. This study aimed to determine the gap between misused fishery discards and their effects on the environment and create awareness for the complete valorization of fishery discards, targeting a sustainable world.

The diagenetic fate of collagen as revealed by analytical pyrolysis of fossil fish scales from deep time

The mechanism of protein degradation has remained a topic of debate (specifically concerning their preservation in deep time), which has recently been invigorated due to multiple published reports of preservation ranging from Miocene to the Triassic that potentially challenge the convention that protein preservation beyond the Cenozoic is extremely uncommon or is expected to be absent altogether, and thus have attracted skepticism. In this paper, we analyze fossil fish scales from the Cretaceous, Jurassic, and Triassic using comprehensive pyrolysis gas chromatography coupled with time-of-flight mass spectrometry and compare the pyrolytic products so obtained with a well-preserved fish scale from Late Pliocene, in an attempt to better understand the effects of diagenesis on protein degradation at the molecular level through deep time. We find that the Pliocene fish scale displays a large number of N-bearing pyrolytic products, including abundant substituted cyclic 2,5-diketopiperazines (2,5-DKPs) which are diagnostic products of peptide and amino acid pyrolysis. We identify N-bearing compounds in the Mesozoic fish scales-however, among the 2,5-DKPs that were identified in the Pliocene scale, only diketodipyrrole (or cyclo (Pyr-Pyr)) is present in the Mesozoic scales. We discuss the implications of N-bearing pyrolytic products with emphasis on 2,5-DKPs in geological samples and conclude that the discrepancy in abundance and variety of N-bearing products between Pliocene and Mesozoic scales indicates that the protein component in the latter has been extensively diagenetically altered, while a suite of DKPs such as in the former would imply stronger evidence to indicate preservation of protein. We conclude that analytical pyrolysis is an effective tool for detecting preservation of intact proteins, as well as for providing insights into their degradation mechanisms, and can potentially be utilized to assign proteinaceous origin to a fossil sample of unknown affinity.

Effect of Ultrasound Pre-Treatment on Extraction and Characterization of Collagen from Bactrian Camel Skin

The objective of this study was to evaluate the effect of ultrasound pre-treatment on the characterization from Bactrian camel skin. It was possible to produce and characterize collagen extracted from Bactrian camel skin. The results showed that the yield of collagen was higher in ultrasound pre-treatment (UPSC) (41.99%) than the pepsin-soluble collagen extraction (PSC) (26.08%). All extracts were identified as type I collagens using sodium dodecyl sulfate polyacrylamide gel electrophoresis and retained their helical structure, as confirmed through Fourier transform infrared spectroscopy. The scanning electron microscopy analysis of UPSC revealed that some physical changes were caused by sonication. UPSC had smaller particle size than PSC. The viscosity of UPSC always plays a leading role in the range of 0-10 Hz. However, the contribution of elasticity to the solution system of PSC increased in the range of 1-10 Hz. Moreover, ultrasound-treated collagen had superior solubility property at pH 1-4 and at <3% (w/v) NaCl than non-ultrasound treated collagen. Therefore, the utilization of ultrasound for the extraction of pepsin soluble collagen is a good alternative technology to expand the application at industrial level.

Biochemical and Microstructural Characteristics of Collagen Biopolymer from Unicornfish (Naso reticulatus Randall, 2001) Bone Prepared with Various Acid Types

Biopolymer-like collagen has great industrial potential in terms of its excellent properties, such as strong biocompatibility, high degradability, and low antigenicity. Collagen derived from fish by-products is preferable as it is safer (free from transmittable diseases) and acceptable to most religious beliefs. This study aimed to characterize the unicornfish (Naso reticulatus Randall, 2001) bone collagens prepared with different type of acids, i.e., acetic acid, lactic acid, and citric acid. A higher yield (Y) (p < 0.05) was obtained in the citric-acid-soluble collagen (CASC) (Y = 1.36%), followed by the lactic-acid-soluble collagen (LASC) (Y = 1.08%) and acetic-acid-soluble collagen (AASC) (Y = 0.40%). All extracted collagens were classified as type I due to the presence of 2-alpha chains (α1 and α2). Their prominent absorption spectra were located at the wavelengths of 229.83 nm to 231.17 nm. This is similar to wavelengths reported for other fish collagens. The X-ray diffraction (XRD) and infrared (IR) data demonstrated that the triple-helical structure of type I collagens was still preserved after the acid-extraction process. In terms of thermal stability, all samples had similar maximum transition temperatures (T_max = 33.34-33.51 °C). A higher relative solubility (RS) of the unicornfish bone collagens was observed at low salt concentration (0-10 g/L) (RS > 80%) and at acidic condition (pH 1.0 to pH 3.0) (RS > 75%). The extracted collagen samples had an irregular and dense flake structure with random coiled filaments. Overall, bones of unicornfish may be used as a substitute source of collagen.

Type I Collagen from the Skin of Barracuda (Sphyraena sp.) Prepared with Different Organic Acids: Biochemical, Microstructural and Functional Properties

This study was carried out to compare the extractability and characteristics of barracuda (Sphyraena sp.) skin collagen using various organic acids. Acetic-solubilized collagen (ASBS), lactic-solubilized collagen (LSBS) and citric-solubilized collagen (CSBS) yielded 6.77 g/100 g, 10.06 g/100 g and 8.35 g/100 g, respectively, and those yields were significantly different (p < 0.05). All acid-solubilized collagens were considered as type I because of their two alpha chains (α1 and α2) detected in acrylamide gel after electrophoresis. Ultraviolet-visible (UV-vis) analysis confirmed that ASBS, LSBS and CSBS had similar absorption peaks (230.5 nm) and the results were in accordance with other fish collagens. Under infrared (IR) and X-ray diffraction (XRD) analysis, the triple helical structure of type I collagens extracted from barracuda skin was maintained. From a thermostability study, all type I collagens showed a higher maximum transition temperature (T_max = 40.16 to 41.29 °C) compared to other fish skin collagens. In addition, the functional properties of the extracted collagens revealed the ASBS had higher water and oil absorption capacities than the CSBS and LSBS samples. The highest level of the emulsion ability index (EAI) (>200 m²/g) was detected under acidic conditions (pH 4), while lower EAIs were recorded under the alkaline (pH 10) and neutral treatments (pH 7). All type I collagens had a higher relative solubility (>60%) at a low pH test but the solubility level sharply decreased at a neutral pH. In addition to this, a lower concentration of NaCl (0-20 g/L) showed the higher percentage of solubility (>60%) while adding over 30 g/L of NaCl decreased solubility (>40%). From a microstructural test, all type I samples had an irregular and dense flake structure with random coiled filaments. Overall, collagen extracted from the barracuda skin may be applied as an alternative collagen from an industry perspective.

Valorization of Fish Waste: Isolation and Characterization of Acid- and Pepsin-Soluble Collagen from the Scales of Mediterranean Fish and Fabrication of Collagen-Based Nanofibrous Scaffolds

In search of alternative and sustainable sources of collagenous materials for biomedical applications, the scales of five Mediterranean fish species-fished in high tonnage in the Mediterranean region since they represent popular choices for the local diet-as well as those of the Atlantic salmon for comparison purposes, were comparatively studied for their acid- and pepsin-soluble collagen content. Fish scales that currently represent a discarded biomass of no value could be efficiently exploited for the production of a high added-value biomaterial. The isolated collagenous materials, which showed the typical electrophoretic patterns of type I collagen, were morphologically and physicochemically characterized. Using scanning electron microscopy the fibrous morphology of the isolated collagens was confirmed, while the hydroxyproline content, in conjunction with infrared spectroscopy and X-ray diffraction studies verified the characteristic for collagen amino acid profile and its secondary structure. The acid- and pepsin-soluble collagens isolated from the fish scales were blended with the bioactive sulfated marine polysaccharide ulvan and polyethylene oxide and electrospun to afford nanofibrous scaffolds that could find applications in the biomedical sector.

Impact of ultrasound on extractability of native collagen from tuna by-product and its ultrastructure and physicochemical attributes

The effect of ultrasound treatment (300 W; 0, 5, 10, 15, 20 and 25 min) on the extractability of acid soluble collagen from yellowfin tuna skin and its structural, physicochemical and functional properties were investigated. Ultrasound treatments significantly increased collagen extraction yield from the tuna skin up to 2.7 times, compared to the conventional extraction with acetic acid. The level of proline, hydroxyproline and thermal stability of collagens increased by applying ultrasound while their native triple-stranded helical structure was well-preserved, as revealed by X-ray diffraction and FTIR spectroscopy. However, ultrasound treatment reduced the particle size of the collagens which increased their pH and salt induced solubility. The water holding capacity and the emulsifying properties of ultrasound treated collagens were also higher than those produced with the conventional method. Altogether, the results suggested that ultrasonication can be a promising assistant technology for improving native collagen extraction efficiency from tuna skin and its functionality but its duration should be carefully optimized.

Cloning, tissue distribution and mRNA expression of type I collagen alpha 1 gene from Chu's croaker (Nibea coibor)

The demand for collagen has been increasing over years due to its wide application in food, cosmetics and biomedicine industries. The synthesis of collagen protein in fish depends on instructions provided by collagen, type I, alpha 1 (COL1A1) gene. However, cloning, tissue distribution and mRNA expression of COL1A1 gene in a gel-producing Chu's croaker (Nibea coibor) is currently unknown. This study cloned the cDNA of COL1A1 gene (GenBank accession number: MK641512) from six N. coibor fish. The distribution and mRNA expression pattern of COL1A1 was analyzed in eight tissues of N. coibor. The COL1A1 cDNA had a full length of 6130 bp and contained a 4344 bp open reading frame (ORF) encoding a polypeptide of 1448 amino acids. The homology of N. coibor COL1A1 amino acid had 98% similarity with Larimichthys crocea, indicating conservatism with other members in same family (Sciaenidae). The deduced polypeptide contained the same signal peptides, C-propeptide and N-propeptide domains, and triple helix domains, which are the characteristics of type I collagen in vertebrates. The mRNA of COL1A1 gene was expressed significantly higher in the spine of N. coibor than in all other tissues (P < 0.05), followed by swim bladder, skin and scales. The swim bladder had higher collagen and hydroxyproline contents than other tissues, followed by spine >, scales > and > skin (P < 0.05). Our study successfully cloned the COL1A1 gene from N. coibor for the first time. The COL1A1 gene contained all the features of collagen pro-α1(I) chain proteins, and shared high homology with other marine teleost. COL1A1 gene in N. coibor is highly expressed in spine and swim bladder, consistent with collagen distribution. Our study contributes to better understanding on collagen biosynthesis in N. coibor tissues for various industrial uses.

Extraction and characterization of bovine collagen type and its effects on cell behaviors

Collagen Type V (Col. V) plays an essential role in cell behaviors and has attracted increasing attention in recent years. High-purity Col. V is needed for evaluating its biological properties. In this research, the enzymatic hydrolysis process was combined with ultrafiltration to purify Col. V from the bovine cornea. The purity of Col. V was determined to be above 90% by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and high-performance liquid chromatography methods. The effect of Col. V on cell behaviors was evaluated. The circular dichroism spectroscopy results demonstrated that the extracted Col. V exhibited a complete triple helix structure. SDS-PAGE suggested that the molecular weight of Col. V was 440 kDa. The self-assembly experiment revealed that the proportion of Col. V in the collagen mixture can affect the Col. I fiber diameter. The cell culture results implied that Col. V can inhibit fibroblasts (L929) proliferation. The L929 showed maximum mobility when the addition of Col. V was 30%. Thus, Col. V has the effect of inhibiting L929 proliferation and promoting migration. The high-purity Col. V provides useful information for further understanding its biological implications.

Biochemical and Microstructural Properties of Lizardfish (Saurida tumbil) Scale Collagen Extracted with Various Organic Acids

The purpose of this research was to extract collagen from the scales of lizardfish (Saurida tumbil) using various acids. Acetic acid-extracted collagen (AScC) produced a higher yield (1.8 mg/g) than lactic acid-extracted collagen (LScC) and citric acid-extracted collagen (CScC) although not significantly different (p > 0.05). All extracted collagens were categorized as type I collagens with the presence of alpha chains (α1 and α2) based on the SDS-PAGE profiles. The triple-helical structure of the collagen was maintained in the AScC, LScC, and CScC as confirmed by the FTIR spectra. The UV-vis and X-ray diffraction spectra observed in all collagens were in agreement with previous work on fish scale and calfskin (commercial) collagens. The thermal stability of AScC (Tmax = 31.61 °C) was greater than LScC (Tmax = 30.86 °C) and CScC (Tmax = 30.88 °C). The microstructure of acid-extracted collagens was characterized as complex, fibrous, and multilayered, with irregular sheet-like structures. All samples were highly soluble in acidic pH (1.0−4.0) and in low concentrations of NaCl (0−20 g/L). In conclusion, the lizardfish scale collagen, particularly AScC, may be used as an alternative to terrestrial animal collagen.

Evaluation of Scales of Tilapia Sp. and Sciaenops ocellatus as Low Cost and Green Adsorbent for fluoride Removal From Water

Water containing more than 1.5 mg/L of fluoride is considered toxic as it causes dental, kidney, and other health problems. With the purpose of helping alleviate these problems by exploring a treatment method for fluoride contamination, this study was to assess the suitability of scales of Tilapia Sp. and Sciaenops ocellatus as a cheaper source of adsorbent for the removal of fluoride from drinking water. The samples which were obtained from the Lapaz Market in Accra, Ghana, underwent treatment to eliminate any impurities. They were then ground into powder and treated with aluminum hydroxide [Al(OH)₃]. The treated samples were used for the removal of fluoride from spiked solutions prepared in the laboratory. Batch adsorption was performed by varying parameters such as adsorbent dose (1–8 g/L), initial concentration (2 mg/L to 10 mg/L), and contact time (30–300 min) at pH of 7. A one-way ANOVA was used to validate the significance of the defluoridation process with respect to the different experimental conditions. The optimum adsorbent dose, initial concentration, and contact time were found to be 4 g/L, 10 mg/L, and 300 min, respectively. The results revealed that the maximum percentage removal of fluoride was 76% by Tilapia Sp. and 70% by Sciaenops ocellatus at the optimum conditions. This is an indication that both Tilapia Sp. And Sciaenops ocellatus scales are suitable adsorbents for the removal of fluoride from water. The fluoride adsorption kinetics followed the pseudo-second-order model, and the adsorption isotherm fitted the Freundlich Isotherm model better than the Langmuir Isotherm model. The adsorption intensity and adsorption capacity for Tilapia Sp. were 3.484 L/mg and 0.065 mg/g, and that of Sciaenops ocellatus 3.195 L/mg and 0.045 mg/g respectively.

Comparative Study of The Yield and Physicochemical Properties of Collagen from Sea Cucumber (Holothuria scabra), Obtained through Dialysis and the Ultrafiltration Membrane

Collagen was extracted from the body wall of sea cucumber (Holothuria scabra) using the pepsin-solubilized collagen method followed by isolation using dialysis and the ultrafiltration membrane. The yield and physicochemical properties of the collagen obtained from both isolation methods, denoted as D-PSC and UF-PSC, were compared. The ultrafiltration method affords a higher yield of collagen (11.39%) than that of the dialysis (5.15%). The isolated collagens have almost the same amino acid composition, while their functional groups, referred to as amide A, B, I, II, and III bands, were in accordance with commercial collagen, as verified by Fourier Transform Infrared (FT-IR) spectroscopy. The UV-Vis absorption peaks at 240 nm and 220 nm, respectively, indicated that the collagens produced are type-I collagen. The D-PSC showed interconnecting sheet-like fibrils, while the UF-PSC exhibited a flaky structure with flat-sheets arranged very close to each other. The higher yield and comparable physicochemical properties of the collagen obtained by ultrafiltration as compared with dialysis indicate that the membrane process has high potential to be used in large-scale collagen production for food and pharmaceutical applications.

Physicochemical and Biological Performance of Aloe Vera-Incorporated Native Collagen Films

Collagen was obtained from porcine skin by mechanical pretreatments with the aim of preserving the triple helix structure of native collagen, which was indirectly corroborated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) results. Moreover, aloe vera (AV), with inherent biological properties, was incorporated into collagen film formulations, and films were prepared by compression and characterized to assess their suitability for biomedical applications. SEM images showed that the fibrillar structure of collagen changed to a rougher structure with the addition of AV, in accordance with the decrease in the lateral packaging of collagen chains observed by XRD analysis. These results suggested interactions between collagen and AV, as observed by FTIR. Considering that AV content higher than 20 wt % did not promote further interactions, this formulation was employed for biological assays and the suitability of AV/collagen films developed for biomedical applications was confirmed.

Effects of single- and tri-frequency ultrasound on self-assembly and characterizations of bionic dynamic rat stomach digestion of pepsin-soluble collagen from chicken leg skin

Chicken feet, aplenty by-products in the chicken industry, are rich in collagen and contain abundant amino acids so that it can be used as an important source for the collagen market. Pepsin-soluble collagen (PSC) was extracted from chicken leg skin and explored the effects of single- and tri-frequency ultrasound on the self-assembly and vitro digestion characteristics. By the diverging and tri-frequency ultrasound reactor, PSC was treated with 20 kHz/270w (C20H5m), 40 kHz/270w (C40H5m), 60 kHz/270w (C60H5m), 20/40/60 kHz/90w × 3 (CtH5m) for 5 min. Results showed that ultrasound could accelerate the process of collagen self-assembly, and 60 kHz/270w was the fastest. Microfiber diameters of C60H5m were 65-89 nm, which was significantly lower than the control without ultrasound (80-161 nm). The digestion results indicated polypeptides with relative molecular weights founded in the range 200-5000 Da were exceeded 85%. The final digested product had the highest content of oligopeptide, consistent rheological properties, and elastic behavior. The cavitation and mechanical of ultrasound have effects on the self-assembly process and collagen gel structure and digestion characteristics, which is of great significance for the development of the chicken industry and collagen market.

Characterization and comparison of collagen extracted from the skin of the Nile tilapia by fermentation and chemical pretreatment

Chemical pretreatment of collagen raw materials is time-consuming and environmentally hazardous. Collagen extraction after fermentation pretreatment has not been reported. We extracted and characterized acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from Nile tilapia (Oreochromis niloticus) skin following fermentation and chemical treatments and comparatively evaluated the feasibility of fermentation. Fermentation-ASC (FASC) and fermentation-PSC (FPSC) yields (4.76 and 8.14 wt%, respectively) were slightly but not significantly higher than chemical-ASC (CASC) and chemical-PSC (CPSC) yields (4.27 and 7.60 wt%, respectively). All extracts were identified as type I collagens by SDS-PAGE and retained their triple helical structure well, as confirmed through Fourier transform infrared spectroscopy. All collagen microstructures under scanning electron microscopy were multi-layered aggregates. These collagens also had similar biochemical properties (i.e. denatured between 36.5 and 37.1 °C, high soluble at pH 1-4 and at <3% [w/v] NaCl). Therefore, fermentation method is a viable alternative for pretreating collagen extraction materials.

Does Subunit Composition Influence the Intermolecular Crosslinking of Fish Collagen? A Study with Hake and Blue Shark Skin Collagens

Acid-soluble collagens from European hake and Blue shark skin were isolated, characterized, and compared. As the structure of collagen determines its function, the final objective of this study was to investigate biochemical differences between both collagens to identify future potential applications. Chromatographic behavior revealed differences in collagen from both species. Increases of temperature and stirring time produced no effect on European hake collagen solubility in the mobile phase, resulting in the same chromatographic profiles. Conversely, the application of temperature and stirring-time increments showed a positive effect on Blue shark collagen solubility, resulting in different chromatographic profiles and observing higher molecular weight components when sample is incubated at 50 °C (15 min) after 48 h stirring. To test if the different chromatographic behavior exhibited by both collagens could be influenced by differences in subunit composition (alpha-chains), cation exchange chromatography was employed to separate collagen subunits. The electrophoretic patterns and gel permeation chromatography with light-scattering detection (GPC-LS) results of the obtained cation exchange peak fractions revealed differences regarding subunit composition between both species, influencing the crosslinking pattern. This is the first comparative study using GPC-LS to provide information of European hake and Blue shark collagen subunit composition.

Structural feature and self-assembly properties of type II collagens from the cartilages of skate and sturgeon

Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted and purified from the cartilages of skate and sturgeon. Their typical structure and physicochemical properties were evaluated by circular dichroism (CD), X-ray diffraction (XRD), and so on. Results showed that the extracted collagen was likely identified as collagen-II composed of three α-chains (135 kDa), with the typical peptide sequence of Gly-X-Y. It showed the collagen retained the native and intact triple helical structure, and its intensity ratio of the positive and negative absorption peaks (Rpn) was 0.19-0.25. In addition, the extracted collagen exhibited obvious self-assembly behavior with the concentration above 0.3 mg/mL, the adjustment of pH 7.4-7.6 and the NaCl concentration of 120 mmol/L. The critical aggregate mass concentrations of pepsin-soluble collagens from skate and sturgeon were 0.93 and 0.86 g/L, respectively. Therefore, collagens from skate and sturgeon cartilages have potential commercial application.

Effect of ultrasound power on extraction kinetic model, and physicochemical and structural characteristics of collagen from chicken lung

Abstract

The effects of ultrasound power on extraction kinetic model, and physicochemical and structural characteristics of collagen from chicken lung were studied. Ultrasound power caused a significant increase in extraction rate and equilibrium concentration, with the maximum extraction yield (31.25%) at 150 W. The experimental data were consistent with the predicted ones in this empirical equation, in which the percentage error differences was 0.026–4.159%. Besides, ultrasound treatment did not affect their triple-helical structure. The thermal stability of pepsin-soluble collagen by ultrasound pre-treatment (UPSC) was higher, due to the higher imino acid content (20.76%). UPSC also exhibited better solubility and fibril forming capacity. Overall, the kinetic model of UPSC from chicken lung could serve the purpose of obtaining collagen, which displayed a potential alternative source to mammal collagens for application in food, biomaterials and biomedical fields.

Graphical abstract

Preparation of self-assembled collagen fibrillar gel from tilapia skin and its formation in presence of acidic polysaccharides

Fibrillar gel of pepsin-solubilized collagen from tilapia skin was prepared by self-assembly in neutral phosphate buffer at 28 °C. Then effects of acidic polysaccharides, such as sodium alginate (SA), chondroitin sulfate (CS), and hyaluronic acid (HA), on the formation and properties of self-assembled fibrillar gel were investigated. SA and CS prolonged gelling time, whereas HA had no obvious effect. SA made fibril network denser, while CS and HA induced the presence of larger ordered structures. All the acidic polysaccharides broadened the D-periodicity of fibrils. SA and HA increased the maximum mechanical strength of gel to 39.64 and 34.49 kN/m², respectively, significantly higher than that of pure collagen gel (14.53 kN/m²), while that only 17.20 kN/m² after CS introduced. HA had no evident effect on enzymatic resistance, while SA and CS decreased. Therefore, tilapia skin collagen with HA has a higher potential as a biomaterial than that with CS or SA.

Extraction and Characterization of Self-Assembled Collagen Isolated from Grass Carp and Crucian Carp

Collagens were extracted from grass carp skin (GCC), grass carp scales (GSC), and crucian carp skin (CCC) using an acid-enzyme combination method, and their characteristics and self-assembly properties were analyzed. Electrophoretic patterns characterized all three as type I collagens. An ultraviolet analysis identified the optimal wavelengths for collagen detection, while a Fourier transform infrared spectroscopy analysis confirmed the triple-helical structure of the collagens. The GCC, GSC, and CCC had denaturation temperatures of 39.75, 34.49, and 39.05 °C, respectively. All three were shown to self-assemble into fibrils at 30 °C in the presence of NaCl, but the fibril formation rate of CCC (40%) was slightly higher than those of GCC (28%) and GSC (27%). The GSC were shown to form a more strongly intertwined fibril network with a characteristic D-periodicity. The fish collagens extracted in this study have potential applications in the development of functionalized materials.

Fish Scale Valorization by Hydrothermal Pretreatment Followed by Enzymatic Hydrolysis for Gelatin Hydrolysate Production

Protein hydrolysates from fish by-products have good process suitability and bioavailability in the food industry. The objective of this work was to develop a method for protein recovery from fish scales and evaluate the hydrolysis of the scale protein. The effect of the hydrothermal process on protein recovery, degree of hydrolysis (DH) and structural properties of the hydrolysates was investigated. Results showed that hydrothermal treatment could enhance protein recovery of tilapia scales without demineralization and dramatically improve the DH of the hydrolysates. The hydrothermal treated scales showed a better protein recovery (84.81%) and DH (12.88%) and released peptides more efficiently than that of the conventional treated samples. The obtained gelatin hydrolysates mainly distributed in the range of 200–2000 Da with an angiotensin I-converting enzyme (ACE) IC₅₀ value of 0.73 mg/mL. The ACE inhibitory activity of gelatin hydrolysates was stable under high temperature, pH and gastrointestinal proteases. Hydrothermal treatment followed by enzymatic hydrolysis offers a potential solution for preparation of gelatin hydrolysates for food ingredients from fish processing by-products.

Extraction and characterization of collagen from the skin of Pterygoplichthys pardalis and its potential application in food industries

The primary objective of this study was to extract collagen from underutilized fish species owing to its cost effective nature and also its ability to address the demand of type I collagen arising from food and pharmaceutical industries. Acid and pepsin soluble collagen (ppASC and ppPSC) were extracted from the skin of sucker catfish (Pterygoplichthys pardalis) with a yield of 19.6 and 23.8% on wet weight basis respectively. The same were characterized and confirmed as type I collagen by SDS-PAGE, FTIR and UV-Vis spectroscopy, amino acid analysis, and Zeta potential. Taking into consideration the application of collagen in food industry, a food product was developed by incorporating with fresh cheese. This fortification was found to be acceptable and had not altered the taste, odor and other sensory properties of the product.

Electrodialysis Extraction of Pufferfish Skin (Takifugu flavidus): A Promising Source of Collagen

Collagen is widely used in drugs, biomaterials, foods, and cosmetics. By-products of the fishing industry are rich sources of collagen, which can be used as an alternative to collagen traditionally harvested from land mammals. However, commercial applications of fish-based collagen are limited by the low efficiency, low productivity, and low sustainability of the extraction process. This study applied a new technique (electrodialysis) for the extraction of Takifugu flavidus skin collagen. We found electrodialysis to have better economic and environmental outcomes than traditional dialysis as it significantly reduced the purification time and wastewater (~95%) while maintaining high extraction yield (67.3 ± 1.3 g/100 g dry weight, p < 0.05). SDS-PAGE, amino acid composition analysis, and spectrophotometric characterization indicated that electrodialysis treatment retained the physicochemical properties of T. flavidus collagen. Heavy metals and tetrodotoxin analyses indicated the safety of T. flavidus collagen. Notably, the collagen had similar thermal stability to calf skin collagen, with the maximum transition temperature and denaturation temperature of 41.8 ± 0.35 and 28.4 ± 2.5 °C, respectively. All evidence suggests that electrodialysis is a promising technique for extracting collagen in the fishing industry and that T. flavidus skin collagen could serve as an alternative source of collagen to meet the increasing demand from consumers.

Efficacy evaluation of electric field frequency and temperature on dielectric properties of collagen cross-linked by glutaraldehyde

Solid-state dielectric properties are reported for unmodified collagen (Col) and glutaraldehyde-modified collagen (Col-GA) over the frequency range from 100Hz to 100kHz and at temperatures from 25 to 145°C. In the full temperature and frequency range the average values of the relative permittivity and dielectric loss for Col samples are higher than those recorded for Col-GA samples. The peak temperature of these both parameters associated with the release of loosely bound water is around 73 and 77°C for Col and Col-GA samples, respectively. The activation energy for the reorientation and breaking of hydrogen bonds takes the values 32kJmol^-1 for Col and 23kJmol^-1 for Col-GA. The relative permittivity decrement and conductivity increment of Col-GA samples fall by 40 and 30% on average in the temperature range 25-75°C, as compared to Col samples. Dielectric properties of Col-GA may be helpful in designing scaffolds for tissue engineering.

Preparation and functional evaluation of collagen oligopeptide-rich hydrolysate from fish skin with the serine collagenolytic protease from Pseudoalteromonas sp. SM9913

Although several serine collagenolytic proteases from bacteria were reported, none has been used to prepare bioactive collagen peptides. MCP-01 is the most abundant extracellular protease of deep-sea Pseudoalteromonas sp. SM9913 and is a serine collagenolytic protease with high efficiency on fish collagen hydrolysis. Here, we set up a pilot scale process to ferment SM9913 for extracellular protease production. With SM9913 extracellular protease as a tool, a process to prepare collagen oligopeptide-rich hydrolysate from codfish skin was set up, which was further scaled up to pilot (100 L) and plant (2000 L) levels with yields >66%. The hydrolysates from laboratory-, pilot- and plant-scales had quite similar quality, containing ~95% peptides with molecular weights lower than 3000 Da and approximately 60% lower than 1000 Da, in which collagen oilgopeptides account for approximately 95%. Bioactivity analyses showed that the hydrolysate had moisture-retention ability, antioxidant activity, and promoting effect on cell viability of human dermal fibroblasts. Safety evaluation showed that the hydrolysate was nontoxic and nonirritating to skin. Therefore, SM9913 extracellular protease is a good enzyme to prepare bioactive oligopeptides from fish skin. The results also suggest that the collagen oligopeptides-rich hydrolysate may have potentials in biomedical, functional food, pharmaceutical and cosmetic industries.

Effect of ultrasound assisted extraction on the physicochemical and functional properties of collagen from soft-shelled turtle calipash

The aim of the present study was to evaluate the physicochemical and functional properties of acid-soluble collagen by ultrasound assisted extraction (UASC) from calipash of soft-shelled turtle (Pelodiscus sinensis). The results showed the collagen content was increased by 16.3% in UASC over the collagen from the conventional extraction (ASC). Both ASC and UASC contained a moderate amount of imino acid (197 and 216 residues/1000 residues, respectively) and hydrophobic amino acid (353 and 391 residues/1000 residues, respectively) in amino acid composition. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses confirmed that the ultrasound treatment did not disrupt the triple-stranded helical structures in UASC. UASC had higher thermal stability compared with ASC by viscosity and differential scanning calorimetry (DSC) measurements, therefore, UASC might have the advantage to be used. In dynamic elastic behavior measurement, UASC showed a larger elasticity than ASC. With a mild modification by ultrasound, UASC had superior functional properties to ASC, including water/oil absorption capacity, water-holding capacity, emulsifying properties and foaming properties. These results suggested that UASC from the soft-shelled turtle calipash had a potential to be used widely in food, medicine, cosmetics and biomedical materials.