Extraction and characterization of acid-soluble and pepsin-soluble collagen from skin of loach (Misgurnus anguillicaudatus)

A review on the processing technique, physicochemical, and bioactive properties of marine collagen

Collagens are conventionally derived from bovine and porcine sources. However, these sources were commonly associated with infectious diseases such as bovine spongiform encephalopathy, foot and mouth disease, autoimmune and allergic reactions, and religious constraints. The significant amount of collagen available in marine species, especially fish skins, scales, fins, and bones, shows that marine species can be a potential alternative source to mammalian collagen. Therefore, this review aims to give a clearer outlook on the processing techniques of marine collagen and its physicochemical and bioactive properties as a potential alternative to mammalian collagen. The two most suitable extraction methods for marine collagen are pepsin-soluble extraction and ultrasound-assisted extraction. Additionally, marine collagen's physicochemical and bioactive properties, such as antioxidants, wound healing, tissue engineering, and cosmetic biomaterial have been thoroughly discussed in this review. PRACTICAL APPLICATION: Collagen extracted from marine sources showed its potential in physicochemical and bioactive properties, including antioxidants and wound-healing capabilities, as an alternative to mammalian collagen. The significant amount of collagen found in marine species, particularly in fish skins, scales, bones, and sea cucumbers, suggests that marine sources could be a viable alternative to land mammal collagen due to their abundance and accessibility. The ultrasound-assisted extraction technique has improved the extracted marine collagen's physicochemical and bioactivity properties and quality properties.

Valorisation of salmon backbones: Extraction of gelatine and its applicability in biodegradable films

Salmon backbones make up about 10 % of the total fish weight and contain valuable proteins, collagen and lipids that can be used for marine ingredients production. Gelatine is derived from the collagen fraction and this study evaluated how different fractionation and extraction procedures can affect the yield and composition of extracted gelatine. Fractionation by mild thermal treatment of backbones (10 min in 40-42 °C) leads to structural changes of muscle, which improves separation of meat from bones and gives better yield of de-muscled backbone fractionation compared to mechanical meat removal. The highest yield of the gelatine (9.3 ± 0.3g dry gelatine from 100g de-muscled backbone dry material) was obtained from mechanically de-muscled backbones. De-muscled backbones were pre-treated with alkaline (0.04 N NaOH) followed by EDTA and 10 % ethanol for de-calcification and lipid extraction, respectively. Gelatine from pretreated backbones was extracted with 60 °C water. The amount of gelatine amino acids (sum of hydroxyproline, proline and glycine) was 43.4 ± 0.2 % of all amino acids in the gelatine. Extracted backbone gelatines showed film-forming ability. Gelatine films were obtained by casting procedure. Resulted salmon backbone 6 % gelatine and 30 % sorbitol films showed properties (e.g. water vapour permeability, colour difference, transparency value) similar to films obtained with commercial gelatine, indicating the capability of the extracted gelatines for its valorisation as edible coatings or bio-based film layers in packaging.

Marine Antioxidants from Marine Collagen and Collagen Peptides with Nutraceuticals Applications: A Review

Collagen peptides and marine collagen are enormous resources currently utilized. This review aims to examine the scientific literature to determine which collagen peptides derived from marine sources and which natural active antioxidants from marine collagen have significant biological effects as health-promoting nutraceuticals. Marine collagen is extracted from both vertebrate and invertebrate marine creatures. For vertebrates, this includes fish skin, bones, scales, fins, and cartilage. For invertebrates, it includes mollusks, echinoderms, crustaceans, and poriferans. The method used involved data analysis to organize information for isolating and identifying marine biocompounds with antioxidant properties. Specifically, amino acids with antioxidant properties were identified, enabling the use of hydrolysates and collagen peptides as natural antioxidant nutraceuticals. The methods of extraction of hydrolyzed collagen and collagen peptides by different treatments are systematized. The structural characteristics of collagen, collagen peptides, and amino acids in fish skin and by-products, as well as in invertebrate organisms (jellyfish, mollusks, and crustaceans), are described. The antioxidant properties of different methods of collagen hydrolysates and collagen peptides are systematized, and the results are comparatively analyzed. Their use as natural antioxidant nutraceuticals expands the range of possibilities for the exploitation of natural resources that have not been widely used until now.

Preparation, structural and morphological characterization of cartilage type II collagen peptide assemblies from sturgeon head

BACKGROUND

Sturgeon cartilage type II collagen peptides (SHCPs) can self-assemble and be used to prepare collagen peptide assemblies. Self-assembled peptides have great potential for applications in the food industry. In the present study, self-assembled peptides were prepared from sturgeon cartilage and then characterized.

RESULTS

The SHCPs self-assembled and formed collagen peptide assemblies. After response surface experiment optimization, the optimal enzyme digestion process comprised 43.1 °C, 3.37 h and 0.96% enzyme addition, and the peptide yield was 78.46%. Physicochemical analysis showed that the SHCPs were amphiphilic, with an average molecular weight of 1081 Da, and were rich in hydrophobic amino acids. Peptide sequence identification showed that the peptides of SHCPs with polar amino acids followed by hydrophobic amino acids could be self-assembled through hydrogen bonding and hydrophobic interaction. Through turbidity experiments, Fourier transform infrared spectroscopy and scanning electron microscopy, we demonstrated that SHCPs can self-assemble into reticular and tubular structures under specific conditions. Furthermore, both the SHCPs-Ca and SHCPs-Mg assemblies were stabilized within a pH range consistent with that of the human gastrointestinal tract.

CONCLUSION

The present study provides a simple and safe method for preparing novel self-assembled peptide materials from sturgeon by-products, providing a scientific basis for the exploitation of sturgeon cartilage and potentially reducing resource wastage. © 2024 Society of Chemical Industry.

Molecular characterization, spatiotemporal expression, and background adaptation regulation of tyrosinase in loach (Misgurnus anguillicaudatus)

The Poyang Lake region is home to large-blackspot loaches (LBL), small-blackspot loaches (SBL), and non-blackspot loaches (NBL), Misgurnus anguillicaudatus. To investigate the impact of tyrosinase on spot development, the complementary DNAs (cDNA) of tyrosinase in M. anguillicaudatus (designated as Matyr) were cloned using the rapid amplification of cDNA ends (RACE)-PCR method. The full-length cDNA for Matyr was 2020 bp, and the open-reading frame comprised 1617 bp, encoding a predicted protein with 538 amino acids. Phylogenetic studies revealed that MaTyr was first grouped with Tyr of Triplophysa tibetana and Leptobotia taeniops, and then Tyr of other cyprinid fish. The quantitative reverse-transcription-PCR results show that Matyr was highly expressed in the muscle, caudal fin, and dorsal skin. The Matyr gene's messenger RNA expression pattern steadily increased from the fertilized ovum period to the somitogenesis period, and from the muscle effect stage to 6 days after fertilization, it considerably increased (p < 0.01). The Matyr hybridization signals with similar location could be found in all developmental stages of three kinds of loaches using whole-mount in situ hybridization (WISH) technology and were the strongest during the organ development period and melanin formation period. Dot hybridization signals in LBLs rapidly spread to the back of the body beginning at the period when the eyes first formed melanin, and their dimensions were larger than those of NBLs during the same time period. The body color of loaches could change reversibly with black/white background adaptation. The α-msh, mitfa, and tyr are mainly expressed in loaches adapted with a black background. Tyr gene could be involved in the development of blackspots and body color polymorphism, and contribute to organ development in the loach.

Intrafibrillar mineralization of type I collagen with calcium carbonate and strontium carbonate induced by polyelectrolyte-cation complexes

Calcium carbonate (CaCO3), possessing excellent biocompatibility, bioactivity, osteoconductivity and superior biodegradability, may serve as an alternative to hydroxyapatite (HAp), the natural inorganic component of bone and dentin. Intrafibrillar mineralization of collagen with CaCO3 was achieved through the polymer-induced liquid precursor (PILP) process for at least 2 days. This study aims to propose a novel pathway for rapid intrafibrillar mineralization with CaCO3 by sequential application of the carbonate-bicarbonate buffer and polyaspartic acid (pAsp)-Ca suspension. Fourier transform infrared (FTIR) spectroscopy, zeta potential measurements, atomic force microscopy/Kelvin probe force microscopy (AFM/KPFM), and three-dimensional stochastic optical reconstruction microscopy (3D STORM) demonstrated that the carbonate-bicarbonate buffer significantly decreased the surface potential of collagen and CO32-/HCO3- ions could attach to collagen fibrils via hydrogen bonds. The electropositive pAsp-Ca complexes and free Ca2+ ions are attracted to and interact with CO32-/HCO3- ions through electrostatic attractions to form amorphous calcium carbonate that crystallizes gradually. Moreover, like CaCO3, strontium carbonate (SrCO3) can deposit inside the collagen fibrils through this pathway. The CaCO3-mineralized collagen gels exhibited better biocompatibility and cell proliferation ability than SrCO3. This study provides a feasible strategy for rapid collagen mineralization with CaCO3 and SrCO3, as well as elucidating the tissue engineering of CaCO3-based biomineralized materials.

Characterization of Collagen from Jellyfish Aurelia aurita and Investigation of Biomaterials Potentials

Marine collagen sources are potent alternatives due to abundant yield, low pathogen infection risk, high biocompatibility, and any religious and ethical restrictions compared to terrestrial collagen sources. In this research, we aim to investigate the biomaterials potential of the collagen from Aurelia aurita, which is a native jellyfish species in the Marmara Sea. Spectroscopic techniques were used to investigate the structure of jellyfish collagen (JCol) from acid-soluble fraction and compared to Jellagen® from Rhizostoma pulmo. MALDI-TOF showed the main peak of Jellagen® at 276,765.161 Da and jellyfish collagen at 276,761.687 Da. SDS-PAGE indicated α1 and α2 bands at about 122 kDa and 140 kDa, respectively. In FTIR and Raman spectra, the locations of amide bands of both species were almost the same. The pI of JCol was determined as 4.46. The particle size decreased abruptly at 43 oC from 890 to 290 nm. Water, organic and inorganic ratios of collagen were determined at 7.14%, 63.59, and 29.27 respectively. In DSC, the denaturation temperature (Td) of JCol was found at 43.7 oC and found to be higher than that of the collagens from jellyfishes that have been reported so far in the literature. Biocompatibility testing by metabolic assay revealed significantly higher fibroblast proliferation on collagen film than on the Tissue Culture Plate. To conclude, Aurelia aurita collagen would be a suitable source of collagen when biomaterials are needed to have high biocompatibility and unique macromolecular properties such as high denaturation temperatures.

Effect of pH on the Structure, Functional Properties and Rheological Properties of Collagen from Greenfin Horse-Faced Filefish (Thamnaconus septentrionalis) Skin

Collagen is an important biopolymer widely used in food, cosmetics and biomedical applications. Understanding the effect of pH on the structure and properties of collagen is beneficial for its further processing and exploitation. In this study, greenfin horse-faced filefish skin collagen (GHSC) was prepared and identified as a type I collagen. We systematically investigated the effect of pH on the structural, functional and rheological properties of GHSC. Scanning electron microscopy showed that the collagen morphology changed from an ordered stacked sheet structure to a rough silk-like structure as pH increased. Gaussian-fitted Fourier infrared spectroscopy results of the collagen revealed that it unfolded with increasing pH. Moreover, the ordered structure was reduced, and random coils became the dominant conformation. Its β-sheet and random coil contents increased from 18.43 ± 0.08 and 33.62 ± 0.17 to 19.72 ± 0.02 and 39.53 ± 1.03%, respectively, with increasing pH. α-helices and β-turns decreased from 35.00 ± 0.26 and 12.95 ± 0.01 to 29.39 ± 0.92 and 11.36 ± 0.10%, respectively. The increase in β-sheets and random coils allowed the pI-treated collagen to exhibit maximum water contact angle. The emulsification and foaming properties decreased and then increased with increasing pH in a V-shape. The increased net surface charge and β-sheets in collagen benefited its emulsification and foaming properties. The rheological results showed that the protoprotein exhibited shear-thinning properties in all pH ranges. The collagen solutions showed liquid-like behaviour in low-pH (2, 4) solutions and solid-like behaviour in high-pH (6, 7.83 and 10) solutions. Moreover, the frequency-dependent properties of the storage modulus (G') and loss modulus (G″) of the collagen solutions weakened with increasing pH. Collagen has considerable frequency-dependent properties of G' and G″ at low pH (2, 4). Thus, the importance of collagen raw material preparation for subsequent processing was emphasised, which may provide new insights into applying collagen-based materials in food, biomaterials and tissue engineering.

Marine collagen: Unveiling the blue resource-extraction techniques and multifaceted applications

Marine organisms such as fish and shellfish are composed of compounds with properties and characteristics that have been proven useful in a variety of sectors such as cosmetics, healthcare (wound healing), food industries, and tissue engineering. Collagen extraction from fish waste as a "blue resource" has attracted research attention over the past decade. Around 75 % of fish waste contains a high concentration of collagen. This has driven research in the conversion of these low-cost by-products into valuable products. Collagen extracted by acidic or/and enzymatic methods is gaining a lot of attention today due to its low cost and high yield. Fermentation and enzymatic hydrolysis stand out as one of the most environmentally sustainable and ecologically friendly methods for collagen extraction. Because of its great biocompatibility, excellent bioactivity, and low antigenicity, marine collagen is receiving more attention. Furthermore, collagen-derived peptides may exhibit interesting antioxidant activity, potent antihypertensive activity, and antimicrobial activity against different strains of bacteria. This review focuses on the advancements in extraction and detection methods of marine collagen, both from a technological and legislative standpoint, in addition to exploring its diverse range of application domains.

Preparation of Enzyme-Soluble Swim Bladder Collagen from Sea Eel (Muraenesox cinereus) and Evaluation Its Wound Healing Capacity

In the present research, the enzyme-facilitated collagen from sea eel (Muraenesox cinereus) swim bladder was isolated, and the collagen characteristics were analyzed. Then, the collagen sponge was prepared and its potential mechanism in promoting skin wound healing in mice was further investigated. Collagen was obtained from the swim bladder of sea eels employing the pepsin extraction technique. Single-factor experiments served as the basis for the response surface method (RSM) to optimize pepsin concentration, solid-liquid ratio, and hydrolysis period. With a pepsin concentration of 2067 U/g, a solid-liquid ratio of 1:83 g/mL, and a hydrolysis period of 10 h, collagen extraction achieved a yield of 93.76%. The physicochemical analysis revealed that the extracted collagen belonged to type I collagen, and the collagen sponge displayed a fibrous structure under electron microscopy. Furthermore, in comparison to the control group, mice treated with collagen sponge dressing exhibited elevated activities of superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), and glutathione peroxidase (GSH-Px), and decreased levels of malondialdehyde (MDA), interleukin (IL)-1β, interleukin (IL)-6, and tumor necrosis factor (TNF)-α. The collagen sponge dressing effectively alleviated inflammation in the wound area, facilitating efficient repair and rapid healing of the skin tissue. During the initial phase of wound healing, the group treated with collagen sponge dressing exhibited an enhancement in the expressions of cluster of differentiation (CD)31, epidermal growth factor (EGF), transforming growth factor (TGF)-β1, and type I collagen, leading to an accelerated rate of wound healing. In addition, this collagen sponge dressing could also downregulate the expressions of CD31, EGF, and type I collagen to prevent scar formation in the later stage. Moreover, this collagen treatment minimized oxidative damage and inflammation during skin wound healing and facilitated blood vessel formation in the wound. Consequently, it exhibits significant potential as an ideal material for the development of a skin wound dressing.

Collagen from Iris squid grafted with polyethylene glycol and collagen peptides promote the proliferation of fibroblast through PI3K/AKT and Ras/RAF/MAPK signaling pathways

Collagens from marine sources have been used widely in food, cosmetics and tissue engineering application due to their excellent functional and biological properties. In the present study, a novel protein, collagen from iris squid skin (SSC) was characterized, grafted with polyethylene-glycol (PEG) and Acid-Green 20 (AG) and was investigated the molecular signaling pathways in L-929 fibroblast cells along with their structural peptide analogs. SDS-PAGE and IR spectrum of SSC analysis showed the typical structure of type I collagen. The fibroblast proliferation was evaluated for SSC, SSC grafted PEG (SSC-PEG) and their structural analogs including Gly-Pro-Leu-Gly-Leu-Leu (PEP1), Gly-Pro-Leu-Gly-Leu-Leu-Gly-Phe-Leu (PEP2), Gly-Pro-Leu-Gly-Leu-Leu-Gly-Phe-Leu-Gly-Pro-Leu (PEP3) and Gly-Pro-Leu-Gly-Leu-Leu-Gly-Phe-Leu-Gly-Pro-Leu-Gly-Leu-Ser (PEP4). The optimal concentration of SSC and its derivative was 0.07 μ mol/L. The fibroblast growth-promoting factors were promoted by all the treatment groups by accelerating the PI3K/AKT and Ras/RAF/MAPK signaling pathways in L-929 cells, and inhibiting the secretion of apoptotic factors. Compared to the control group, mRNA and protein expression of AKT in the PI3K/AKT and Ras in Ras/RAF/MAPK signaling pathway were accelerated significantly by PEP4, respectively, while the Bax value was significantly lower (P < 0.01). The promoting effect of PEP1, PEP2, PEP3 and PEP4 on L-929 cells was closely related to the length of the peptides. Therefore, this study disclosed that PEP1, PEP2, PEP3 and PEP4 were novel analogs that greatly promote the proliferation of L-929 cells through PI3K/AKT and Ras/RAF/MAPK signaling pathways.

The transcriptome sequencing analysis reveals immune mechanisms of soybean fermented powder on the loach (Misgurnus anguillicaudatus) in response to Lipopolysaccharide (LPS) infection

The loach (Misgurnus anguillicaudatus), a small commercial fish that is widely cultivated for its high-quality protein, vitamins, minerals, and essential amino acid, is a member of the genus Misgurnus and the family Cyprinidae. In this study, we gave the LPS-injected loach fermented soybean meal and used transcriptome sequencing to investigate the impact of the fermented soybean powder on the loach's immune system. 3384 up-regulated genes and 12116 down-regulated genes were found among the 15500 differentially expressed genes, according to the results. The differentially expressed genes were shown to be involved in cellular processes, metabolic processes, cellular anatomical entities, and binding, according to the Go functional annotation. Meanwhile, the KEGG enrichment analysis indicated that the soybean fermented powder treated groups showed significant differences in DNA replication, Nucleotide excision repair, Fanconi anemia pathway, and Base excision repair pathways, suggesting that these pathways are closely related to the enhancement of the immune function of loach by soybean fermented powder. The particular conclusions not exclusively can provide a new conception for the rational utilization of soybean fermented powder but also can provide theoretical guidance for the subsequent healthy breeding of loach.

Structural Identification and Antioxidant Activity of Loach Protein Enzymatic Hydrolysates

Loach, rich in nutrients, such as proteins, amino acids, and mineral elements, is being gradually favored by consumers. Therefore, in this study, the antioxidant activity and structural characteristics of loach peptides were comprehensively analyzed. The loach protein (LAP) with a molecular weight between 150 and 3000 Da was graded by ultrafiltration and nanofiltration processes, which exhibited excellent scavenging activity against DPPH radical (IC50 2.91 ± 0.02 mg/mL), hydroxyl radical (IC50 9.95 ± 0.03 mg/mL), and superoxide anion radical (IC50 13.67 ± 0.33 mg/mL). Additionally, LAP was purified by gel filtration chromatography, and two principal components (named as LAP-I and LAP-II) were isolated. A total of 582 and 672 peptides were identified in LAP-I and LAP-II, respectively, through structural analysis. The XRD results revealed that LAP-I and LAP-II had an irregular amorphous structure. The 2D-NMR spectroscopy results suggested that LAP-I had a compact stretch conformation in the D₂O solution, while LAP-II had a folded conformation. Overall, the study results suggested that loach peptide could be a potential antioxidant agent and might provide valuable information for chain conformation and antioxidant mechanism research further.

Effects of ultrasound on the structural and functional properties of sheep bone collagen

The study evaluated the effect of an ultrasound-assisted treatment on the structural and functional properties of sheep bone collagen (SBC). The type and distribution of SBC were analyzed by proteome (shotgun) technology combined with liquid chromatography-tandem mass spectrometry. Compared with pepsin extraction, the ultrasound-assisted treatment significantly increased the collagen extraction rate by 17.4 pp (P < 0.05). The characteristic functional groups and structural integrity of collagen extracted by both methods were determined via Fourier transform infrared spectroscopy, ultraviolet absorption spectroscopy, and fluorescence spectroscopy. Circular dichroism spectra revealed that the ultrasound-assisted pretreatment reduced α-helix content by 1.6 pp, β-sheet content by 21.9 pp, and random coils content by 28.4 pp, whereas it increased β-turn content by 51.9 pp (P < 0.05), compared with pepsin extraction. Moreover, ultrasound-assisted treatment collagen had superior functional properties (e.g., solubility, water absorption, and oil absorption capacity) and foaming and emulsion properties, compared with pepsin extraction. Furthermore, the relative content of type I collagen in ultrasound-assisted extracted SBC was highest at 79.66%; only small proportions of type II, VI, X, and XI collagen were present. Peptide activity analysis showed that SBC had potential antioxidant activity, dipeptidyl peptidase 4 inhibitory activity, and angiotensin-converting enzyme inhibitory activity; it also had anticancer, antihypertensive, anti-inflammatory, and immunomodulatory effects.

A novel peptide isolated from Catla skin collagen acts as a self-assembling scaffold promoting nucleation of calcium-deficient hydroxyapatite nanocrystals

Catla collagen hydrolysate (CH) was fractionated by chromatography and each fraction was subjected to HA nucleation, with the resultant HA-fraction composites being scored based on the structural and functional group of the HA formed. The process was repeated till a single peptide with augmented HA nucleation capacity was obtained. The peptide (4.6 kDa), exhibited high solubility, existed in polyproline-II conformation and displayed a dynamic yet stable hierarchical self-assembling property. The 3D modelling of the peptide revealed multiple calcium and phosphate binding sites and a high propensity to self-assemble. Structural analysis of the peptide-HA crystals revealed characteristic diffraction planes of HA with mineralization following the (002) plane, retention of the self-assembled hierarchy of the peptide and intense ionic interactions between carboxyl groups and calcium. The peptide-HA composite crystals were mostly of 25-40 nm dimensions and displayed 79% mineralization, 92% crystallinity, 39.25% porosity, 12GPa Young's modulus and enhanced stability in physiological pH. Cells grown on peptide-HA depicted faster proliferation rates and higher levels of osteogenic markers. It was concluded that the prerequisite for HA nucleation by a peptide included: a conserved sequence with a unique charge topology allowing calcium chelation and its ability to form a dynamic self-assembled hierarchy for crystal propagation.

Extraction and Characterization of Pepsin- and Acid-Soluble Collagen from the Swim Bladders of Megalonibea fusca

There is a growing demand for the identification of alternative sources of collagen not derived from land-dwelling animals. The present study explored the use of pepsin- and acid-based extraction protocols to isolate collagen from the swim bladders of Megalonibea fusca. After extraction, these acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) samples respectively were subjected to spectral analyses and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) characterization, revealing both to be comprised of type I collagen with a triple-helical structure. The imino acid content of these ASC and PSC samples was 195 and 199 residues per 1000 residues, respectively. Scanning electron microscopy demonstrated that samples of freeze-dried collagen exhibited a compact lamellar structure, while transmission electron microscopy and atomic force microscopy confirmed the ability of these collagens to undergo self-assembly into fibers. ASC samples exhibited a larger fiber diameter than the PSC samples. The solubility of both ASC and PSC was highest under acidic pH conditions. Neither ASC nor PSC caused any cytotoxicity when tested in vitro, which met one of the requirements for the biological evaluation of medical devices. Thus, collagen isolated from the swim bladders of Megalonibea fusca holds great promise as a potential alternative to mammalian collagen.

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.

Physicochemical and functional properties of egg white peptide powders under different storage conditions

This study aims to evaluate the effects of different storage conditions (temperature and relative humidity) on the physicochemical and functional properties of egg white peptide powders (EWPPs). The samples (EWPPs) were stored for 28 d under four conditions (4 °C, 50% RH; 4 °C, 75% RH; 25 °C, 50% RH; 25 °C, 75% RH). Results showed that storage temperature and relative humidity had a significant effect on the physicochemical and functional properties of EWPPs. The contents of antioxidant amino acids such as histidine, tyrosine, tryptophan, and lysine were reduced significantly under different storage conditions, which resulted in the decrease of the antioxidant activity of EWPPs. Circular dichroism spectroscopy analysis indicated that the secondary structure of EWPPs changed from the regular structure to the irregular coiled structure during the storage. Additionally, the hydrophobic groups of the EWPPs originally embedded inside the molecules were exposed to the surface of the molecules during the storage, which led to an aggregation of EWPPs molecule and a decrease in solubility of EWPPs. The aggregation of EWPPs molecules resulted in a decrease in emulsification, emulsification stability, foaming ability and foaming stability of the EWPPs. Therefore, different storage conditions do have an impact on the physicochemical and functional properties of EWPPs. Lower temperature and humidity storing conditions were beneficial to retain the functional property of the EWPPs.

Cutting Edge Aquatic-Based Collagens in Tissue Engineering

Aquatic-based collagens have attracted much interest due to their great potential application for biomedical sectors, including the tissue engineering sector, as a major component of the extracellular matrix in humans. Their physical and biochemical characteristics offer advantages over mammalian-based collagen; for example, they have excellent biocompatibility and biodegradability, are easy to extract, and pose a relatively low immunological risk to mammalian products. The utilization of aquatic-based collagen also has fewer religious restrictions and lower production costs. Aquatic-based collagen also creates high-added value and good environmental sustainability by aquatic waste utilization. Thus, this study aims to overview aquatic collagen's characteristics, extraction, and fabrication. It also highlights its potential application for tissue engineering and the regeneration of bone, cartilage, dental, skin, and vascular tissue. Moreover, this review highlights the recent research in aquatic collagen, future prospects, and challenges for it as an alternative biomaterial for tissue engineering and regenerative medicines.

Collagen Derived from Fish Industry Waste: Progresses and Challenges

Fish collagen garnered significant academic and commercial focus in the last decades featuring prospective applications in a variety of health-related industries, including food, medicine, pharmaceutics, and cosmetics. Due to its distinct advantages over mammalian-based collagen, including the reduced zoonosis transmission risk, the absence of cultural-religious limitations, the cost-effectiveness of manufacturing process, and its superior bioavailability, the use of collagen derived from fish wastes (i.e., skin, scales) quickly expanded. Moreover, by-products are low cost and the need to minimize fish industry waste's environmental impact paved the way for the use of discards in the development of collagen-based products with remarkable added value. This review summarizes the recent advances in the valorization of fish industry wastes for the extraction of collagen used in several applications. Issues related to processing and characterization of collagen were presented. Moreover, an overview of the most relevant applications in food industry, nutraceutical, cosmetics, tissue engineering, and food packaging of the last three years was introduced. Lastly, the fish-collagen market and the open technological challenges to a reliable recovery and exploitation of this biopolymer were discussed.

Sustainable production of biofuels and bioderivatives from aquaculture and marine waste

The annual global fish production reached a record 178 million tonnes in 2020, which continues to increase. Today, 49% of the total fish is harvested from aquaculture, which is forecasted to reach 60% of the total fish produced by 2030. Considering that the wastes of fishing industries represent up to 75% of the whole organisms, the fish industry is generating a large amount of waste which is being neglected in most parts of the world. This negligence can be traced to the ridicule of the value of this resource as well as the many difficulties related to its valorisation. In addition, the massive expansion of the aquaculture industry is generating significant environmental consequences, including chemical and biological pollution, disease outbreaks that increase the fish mortality rate, unsustainable feeds, competition for coastal space, and an increase in the macroalgal blooms due to anthropogenic stressors, leading to a negative socio-economic and environmental impact. The establishment of integrated multi-trophic aquaculture (IMTA) has received increasing attention due to the environmental benefits of using waste products and transforming them into valuable products. There is a need to integrate and implement new technologies able to valorise the waste generated from the fish and aquaculture industry making the aquaculture sector and the fish industry more sustainable through the development of a circular economy scheme. This review wants to provide an overview of several approaches to valorise marine waste (e.g., dead fish, algae waste from marine and aquaculture, fish waste), by their transformation into biofuels (biomethane, biohydrogen, biodiesel, green diesel, bioethanol, or biomethanol) and recovering biomolecules such as proteins (collagen, fish hydrolysate protein), polysaccharides (chitosan, chitin, carrageenan, ulvan, alginate, fucoidan, and laminarin) and biosurfactants.

Extraction and Characterization of Type I Collagen from Parrotfish (Scarus sordidus Forsskål, 1775) Scale solubilized with the Aid of Acetic Acid and Pepsin

Waste from marine fish processing is an important source of valuable products. Fish collagen is considered a alternative biomaterial due to its excellent properties, and it is widely used for industrial purposes. Thus, this present study aimed to characterize acid and pepsin-soluble collagens from the waste of parrotfish (Scarus sordidus Forsskål, 1775) scales. The yields (p > 0.05) of acid-soluble collagen (ASC-PFS) and pepsin-soluble collagen (PSC-PFS) were 1.17 g/100 g and 1.00 g/100 g, respectively. Both collagen samples were categorized as type I owing to the presence of two alpha chain subunits (α1 and α1) after being confirmed by a sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Under the fourier transform infrared (FTIR) test, the triple helical structure of type I collagens from the ASC-PFS and PSC-PFS was maintained. Moreover, the study of UV visible spectra and X-ray diffraction (XRD) showed the similarity of collagens derived from different fish species, and the thermostability (T _max) evaluation of all extracted collagens was in the range of 36.22-37.78°C, and their values were comparable to previous research on the fish scale collagens. The effect of various pH and sodium chloride (NaCl) treatments on solubility exhibited that the ASC-PFS and PSC-PFS were highly soluble in an acidic condition (pH < 5.0) and low concentration of sodium chloride (<30 g/L). Taken together, collagens extracted from parrotfish scale waste can be an alternative source for industries.

Characterization of Acid- and Pepsin-Soluble Collagen Extracted from the Skin of Purple-Spotted Bigeye Snapper

Fish processing waste is a prospective source of collagen and a cost-effective environmental pollutant. The skin of the purple-spotted bigeye snapper (Priacanthus tayenus) was extracted utilising various acid soluble collagens (ASC) including acetic acid (AAC), lactic acid (LAC), citric acid (CAC) and pepsin soluble collagens (PSC). In this study, PSC (6.65%) had the highest collagen yield, followed by AAC (5.79%), CAC (4.15%), and LAC (3.19%). The maximum temperatures (Tmax) denaturation of AAC, LAC, CAC, and PSC were 31.4, 31.7, 31.5, and 33.2 °C, respectively. UV-VIS absorption spectra showed all extracted collagens had a range of absorbance at 230 nm, due to the presence of glycine, proline, hydroxyproline, and triple-helical collagen. Additionally, they exhibited amide A, B, amide I, II, and III peaks. SDS−PAGE identified all extracted collagens as type I. The PSC had a significantly higher (p < 0.05) hydroxyproline content than acidic extraction 66.3 ± 1.03 (mg/g sample). Furthermore, all samples were extremely soluble in acetic conditions at pH 5, and all collagen was soluble in NaCl up to 3% (w/v). Therefore, PSC was the best treatment since it did not impact collagen triple helical and acetic acid yielded the most collagen in ASC extraction. Overall, the analysis revealed that fish skin waste might be used as an alternate source of collagen in diverse applications, particularly in food applications.

Valorization of Fish Processing By-Products: Microstructural, Rheological, Functional, and Properties of Silver Carp Skin Type I Collagen

The objective of this study was to develop aquatic collagen production from fish processing by-product skin as a possible alternative to terrestrial sources. Silver carp skin collagen (SCSC) was isolated and identified as type I collagen, and LC-MS/MS analysis confirmed the SCSC as Hypophthalmichthys molitrix type I collagen, where the yield of SCSC was 40.35 ± 0.63% (dry basis weight). The thermal denaturation temperature (Td) value of SCSC was 30.37 °C, which was superior to the collagen of deep-sea fish and freshwater fish. Notably, SCSC had higher thermal stability than human placental collagen, and the rheological experiments showed that the SCSC was a shear-thinning pseudoplastic fluid. Moreover, SCSC was functionally superior to some other collagens from terrestrial sources, such as sheep, chicken cartilage, and pig skin collagen. Additionally, SCSC could provide a suitable environment for MC3T3-E1 cell growth and maintain normal cellular morphology. These results indicated that SCSC could be used for further applications in food, cosmetics, and biomedical fields.

A Comprehensive Review on Collagen Type I Development of Biomaterials for Tissue Engineering: From Biosynthesis to Bioscaffold

Collagen is the most abundant structural protein found in humans and mammals, particularly in the extracellular matrix (ECM). Its primary function is to hold the body together. The collagen superfamily of proteins includes over 20 types that have been identified. Yet, collagen type I is the major component in many tissues and can be extracted as a natural biomaterial for various medical and biological purposes. Collagen has multiple advantageous characteristics, including varied sources, biocompatibility, sustainability, low immunogenicity, porosity, and biodegradability. As such, collagen-type-I-based bioscaffolds have been widely used in tissue engineering. Biomaterials based on collagen type I can also be modified to improve their functions, such as by crosslinking to strengthen the mechanical property or adding biochemical factors to enhance their biological activity. This review discusses the complexities of collagen type I structure, biosynthesis, sources for collagen derivatives, methods of isolation and purification, physicochemical characteristics, and the current development of collagen-type-I-based scaffolds in tissue engineering applications. The advancement of additional novel tissue engineered bioproducts with refined techniques and continuous biomaterial augmentation is facilitated by understanding the conventional design and application of biomaterials based on collagen type I.

Physicochemical and Microstructural Analyses of Pepsin-Soluble Collagens Derived from Lizardfish (Saurida tumbil Bloch, 1795) Skin, Bone and Scales

Reducing food waste is critical for sustainability. In the case of fish processing, more than sixty percent of by-products are generated as waste. Lizardfish (Saurida tumbil Bloch, 1795) is an economically important species for surimi production. To address waste disposal and maximize income, an effective utilization of fish by-products is essential. This study aims to isolate and characterize pepsin-soluble collagens from the skin, bone and scales of lizardfish. Significant differences (p < 0.05) in the yields of collagen were noted with the highest yield recorded in pepsin-soluble skin collagen (PSSC) (3.50 ± 0.11%), followed by pepsin-soluble bone collagen (PSBC) (3.26 ± 0.10%) and pepsin-soluble scales collagen (PSCC) (0.60 ± 0.65%). Through SDS−polyacrylamide gel electrophoresis, the presence of two alpha chains were noted and classified as type I. From Fourier transform infrared spectroscopy (FTIR) analysis, the triple-helix structure of the collagen was maintained. The X-ray diffraction and UV visible spectra characteristics of the lizardfish collagens in this study are similar to the previously reported fish collagens. In terms of thermostability, PSSC (Tmax = 43.89 °C) had higher thermostability in comparison to PSBC (Tmax = 31.75 °C) and PSCC (Tmax = 30.54 °C). All pepsin-soluble collagens were highly soluble (>70%) in acidic conditions (particularly at pH 4.0) and at low sodium chloride concentrations (0−30 g/L). Microstructural analysis depicted that all extracted collagens were multi-layered, irregular, dense, sheet-like films linked by random coiled filaments. Overall, pepsin-soluble collagens from lizardfish skin, bone and scales could serve as potential alternative sources of collagens.

Microstructural and Physicochemical Analysis of Collagens from the Skin of Lizardfish (Saurida tumbil Bloch, 1795) Extracted with Different Organic Acids

Marine fish collagen has attracted considerable attention due to its characteristics, including its biodegradability, biocompatibility, and weak antigenicity, and is considered a safer material compared to collagen from terrestrial animals. The aim of this study was to extract and characterize collagen from the skin of lizardfish (Saurida tumbil Bloch, 1795) with three different acids. The yields of acetic acid-extracted collagen (AESkC), lactic acid-extracted collagen (LESkC), and citric acid-extracted collagen (CESkC) were 11.73 ± 1.14%, 11.63 ± 1.10%, and 11.39 ± 1.05% (based on wet weight), respectively. All extracted collagens were categorized as type I collagen with mainly alpha chains (α₁ and α₂) detected and γ and β chains to some extent. Fourier transform infrared (FTIR) spectra showed an intact triple-helical structure in the AESkC, LESkC, and CESkC. UV-vis spectra and X-ray diffraction further demonstrated the similarity of the extracted collagens to previously reported fish skin collagens. AESkC (T_max = 40.24 °C) had higher thermostability compared to LESkC (T_max = 38.72 °C) and CESkC (T_max = 36.74 °C). All samples were highly soluble in acidic pH and low concentrations of NaCl (0-20 g/L). Under field emission scanning electron microscopy (FESEM) observation, we noted the loose, fibrous, and porous structures of the collagens. The results suggest that the lizardfish skin collagens could be a potential alternative source of collagen, especially the AESkC due to its greater thermostability characteristic.

Therapeutic Effect of Nile Tilapia Type II Collagen on Rigidity in CD8+ Cells by Alleviating Inflammation and Rheumatoid Arthritis in Rats by Oral Tolerance

Fibrillins are microfibril-associated macro glycoproteins found in connective tissues and structurally related to latent TGF-β-binding proteins (LTBPs). The special cellular immunity and blocking glycoprotein receptors IIb and IIIa of fibrillins are emerging topics in recent years. In this study, Nile Tilapia type IIcollagen (NTCII) was extracted and purified from the skull cartilages by a pepsin-soluble method. Amino acid analysis indicated that NTCII consisted of 315/1000 glycine residues, 72/1000 hydroxyproline residues and 108/1000 proline residues. SDS-PAGE analysis showed that NTCII was composed of three identical 130 kDa α-chains. The results of glycoprotein/carbohydrate assay indicated that the total polysaccharide content of NTCII was 5.6–19.0%. The IR spectrum of NTCII displayed five characteristic peaks of amide I, II, III, A, B. NTCII at 10–100 μg/mL concentration downregulated the content of cytokines in the presence or absence of LPS, especially the secretion of cytokines IL-6, IL-1β and TNF-α. Interestingly, NTCII promoted the secretion of Fas/Apo-1 compared to the control group and 25 μg/mL of NTCII resulted in a higher Fas/Apo-1 secretion level in CD8⁺ T cells. FITC-TCII fluorescence images confirmed that NTCII could bind to the membrane surface of CD8⁺ T cells, leading to the induction of rigidity. NTCII could bind to the membrane surface of CD8⁺ T cells that leads to the induction of rigidity, as evidenced by the FITC-NTCII fluorescence images. The qRT-PCR gene expression analysis of caspase-8 collected with Fas/Apo-1 was upregulated significantly in the 1 and 50 μg/mL NTCII-treated groups compared with the control group. Overall, the results conclude that the rigidity did not lead to an increase in inflammatory factors in CD8⁺ T cells treated with NTCII. The oral administration of NTCII 3 mg/kg dosage caused more prominent repair of damaged ankle cartilage than the 1 mg/kg dosage in Freund’s adjuvant-induced model of arthritis in rats. Therefore, this study disclosed the immunological and anti-arthritic effect of fibrillar collagen, which could be a potential biomaterial for practical applications with lower toxicity.

Analysis of pigment cell composition, pigment content, tyrosinase content and activity of three kinds of loaches Misgurnus anguillicaudatus from Poyang Lake

Pigment cell composition, pigment content, tyrosinase content and activity analysis were investigated on three kinds of loaches Misgurnus anguillicaudatus: big blackspot loaches (BBL), small blackspot loaches (SBL) and non-blackspot loaches (NBL), from Poyang Lake. Results showed that there were three types of skin pigment cells, namely melanophores, xanthophores and iridophores. Melanophores in dorsum were more than those in abdomen. Melanophore cytosomes in BBL were larger than those in SBL and NBL, and melanosomes were the largest in stage four. The melanophores in dorsal skin of SBL or NBL were small cell bodies, spindle-like and in chain distribution. There was an extremely significant difference in melanin content in BBL between the dorsum and abdomen (P < 0.01). There were no significant differences in melanin abdominal content, lutein and carotenoid contents among three kinds of loaches (P > 0.05). In dorsal skin, tyrosinase content was the highest in BBL, and it was significantly lower in NBL than in BBL and SBL (P < 0.01). This study reveals the differences in pigment and tyrosinase content in three kinds of loaches and provides a theoretical basis for further study of the mechanism of black spot formation.

Collagen-Based Bioactive Bromelain Hydrolysate from Salt-Cured Cod Skin

Considerable amounts of fish processing by-products are discarded each year. About 30% of this material may be skin and bone. Fish skin has more than 80% of its total protein content as collagen. Furthermore, in recent years, there has been a growing demand for collagen-based peptides due to their beneficial health effects. So, the objective of the present study was to optimise the obtaining bioactive hydrolysates from salt-cured cod skin using the protease Bromelain at 0.5% (w/w) concentration. This study developed a sustainable process that consumes less time and energy and uses an alternative source as raw material. In addition, bromelain allows hydrolysates with important antioxidant (ORAC, 514 μmol Trolox Equivalent/g protein) and antihypertensive activities (inhibition of ACE, IC50 of 166 μg protein/mL) as well as excellent biocompatibility with dermal and subcutaneous cells.

Current Insights into Collagen Type I

Collagen type I (Col-I) is unique due to its high biocompatibility in human tissue. Despite its availability from various sources, Col-I naturally mimics the extracellular matrix (ECM) and generally makes up the larger protein component (90%) in vasculature, skin, tendon bone, and other tissue. The acceptable physicochemical properties of native Col-I further enhance the incorporation of Col-I in various fields, including pharmaceutical, cosmeceutical, regenerative medicine, and clinical. This review aims to discuss Col-I, covering the structure, various sources of availability, native collagen synthesis, current extraction methods, physicochemical characteristics, applications in various fields, and biomarkers. The review is intended to provide specific information on Col-I currently available, going back five years. This is expected to provide a helping hand for researchers who are concerned about any development on collagen-based products particularly for therapeutic fields.

Characterization of an intracellular aspartic protease (PsAPA) from Penicillium sp. XT7 and its application in collagen extraction

An intracellular aspartic protease, PsAPA, was identified from Penicillium sp. XT7. This protease was belonged to penicillopepsin and was expressed in Pichia pastoris GS115. The recombinant PsAPA had a specific activity of 4289.7 ± 261.7 U/mg. The pH and temperature maxima of the enzyme were 3.0 and 30 °C, respectively. The PsAPA was stable in the pH range from 3.0 to 6.0 and was completely inactivated after incubation at 50 °C for 15 min. Presence of Mn²⁺ and Cu²⁺ increased the proteolytic activity and β-mercaptoethanol and SDS showed inhibitory effects, whereas 0.05 M pepstatin A strongly inhibited it. PsAPA could effectively hydrolyze animal proteins, including myoglobin, and hemoglobin but not collagens. PsAPA increased the yield of collagen extraction compared to the acid extraction method. The above properties show that the novel low-temperature acidic protease, PsAPA, is comparable to commercial proteases (porcine pepsin) and has great potential for collagen extraction.

Collagens made from giant salamander (Andrias davidianus) skin and their odorants

Two collagens were made from giant salamander (Andrias davidianus) skin by using acid and pepsin extraction methods. The yields of acid-soluble and pepsin-soluble collagens were 26.9 and 58.7%, respectively. The results of spectrum, electrophoresis and amino acid analysis showed that they were type 1 collagen with two α and one β peptides and high imino acid content. They had low solubility at a pH above 6 or salt concentration over 5%. The pepsin-soluble collagen had a better emulsion activity index. The odorants in raw skin and collagens were identified and evaluated using gas-chromatography mass-spectrometer and olfactometry methods and sensory analysis. The fishy and fatty off-odors in skin were not perceivable in the collagens. Sour, ammonia-like, and acrid off-odors were found in the collagens due to acid and enzymatic hydrolysis and protein degradation. The off-odor intensity of pepsin-soluble collagen was low. It could be considered a good and safe collagen material.

Electrospun porous bilayer nano-fibrous fish collagen/PCL bio-composite scaffolds with covalently cross-linked chitooligosaccharides for full-thickness wound-healing applications

The development of tissue-engineered biodegradable artificial tissue substitutes with extracellular matrix-mimicking properties that govern the interaction between the material and biological environment is of great interest in wound-healing applications. In the present study, novel bilayer nanofibrous scaffolds composed of fish collagen (FC) and poly(ε-caprolactone) (PCL) were fabricated using electrospinning, with the covalent attachment of chitooligosaccharides (COS) via carbodiimide chemistry. The architecture and fiber diameter of the non-cross-linked nanofibrous scaffolds remained consistent irrespective of the polymer ratio under different electrospinning conditions, but the fiber diameter changed after cross-linking in association with the FC content. Fourier-transform infrared spectroscopy analysis indicated that the blend of biomaterials was homogenous, with an increase in COS levels with increasing FC content in the nanofibrous scaffolds. Based on cytocompatibility analysis (i.e., the cellular response to the nanofibrous scaffolds and their interaction), the nanofibrous scaffolds with high FC content were functionally active in response to normal human dermal fibroblast‑neonatal (NHDF-neo) and HaCaT keratinocyte cells, leading to the generation of a very effective tissue-engineered implant for full-thickness wound-healing applications. In addition to these empirical results, an assessment of the hydrophilicity, swelling, and mechanical integrity of the proposed COS-containing FC-rich FC/PCL (FCP) nanofibrous scaffolds confirmed that they have significant potential for use as tissue-engineered skin implants for rapid skin regeneration.

Ultrasound-assisted extraction of collagen from clown featherback (Chitala ornata) skin: yield and molecular characteristics

BACKGROUND

Clown featherback (Chitala ornata) skin, a by-product from the filleting process line, could serve as a good aquatic collagenous source. Nevertheless, the typical collagen extraction method is a time-consuming process providing a relatively low yield. Ultrasound had been reported to be an alternative technique for enhancing the extraction efficiency of several compounds, although the harsh conditions of ultrasound could affect their physicochemical and molecular characteristics. Thus, the application of ultrasonication under appropriate conditions could comprise a promising means for improving the extraction efficiency of collagen from clown featherback skin.

RESULTS

Ultrasonication using different amplitudes (20-80%) and times (10-30 min) was implemented during extraction. An ultrasound-assisted process (UAP) was able to increase the yield of collagen (P ˂ 0.05) and could also result in a collagen purity decrease as evaluated by hydroxyproline content. There was no dramatic change in the solubility of resulting collagens. UAP induced protein degradation, particularly with an increasing amplitude and time, where slight changes in the isoelectric point value of collagen were observed. UAP had no adverse effect on molecular structure, where a triple-helical structure was still retained when an 80% amplitude was employed for 10 min (UAP-80/10-C). The amino acid composition of UAP-80/10-C reconfirmed the unique characteristic of collagen containing imino acid.

CONCLUSION

An UAP under appropriate conditions could be used to improve the extraction yield with minimal effects on the molecular integrity of the resulting collagen. In addition, fish skin waste from the cutting process line, particularly clown featherback skin, could be exploited as a value-added product, comprising fish skin collagen. © 2020 Society of Chemical Industry.

Physicochemical characterization and self-assembly of human amniotic membrane and umbilical cord collagen: A comparative study

The diverse application of collagen has created a need to discover renewable and economical sources with prevailing/improved physico-chemical properties. To address this scenario, the present study has extracted collagen from Human Amniotic Membrane (AM) and Umbilical cord, which are treated as medical waste and compared its physico-chemical properties. Collagen was extracted by pepsin solubilization using various salt concentrations (1 M, 2 M and 4 M). Umbilical Cord Collagen (UC) yield was 10% higher than Amniotic Membrane Collagen (AC). UC reported 58% higher sulphated glycosaminoglycan content than AC. Electrophoretic pattern of AC and UC in both disulphide bond reducing and non-reducing conditions showed bands corresponding to collagen type I, III, IV, V and XV. Collagen morphology was examined using SEM and the amino acid content was quantified by HPLC and LC-MS/MS. Triple helicity was confirmed by CD and FTIR spectra. Thermal transition temperature of AC and UC was found equivalent to animal collagen. Self-assembly, fibril morphology and spatial alignment was studied using AFM and DLS. Biocompatibility was analyzed using 3T3 fibroblast cells. In conclusion, UC with higher yield, presented with better physico-chemical, structural and biological properties than AC could serve as an efficient alternative to the existing animal collagen for diverse applications.

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.

Factors affecting thermal stability of collagen from the aspects of extraction, processing and modification

Abstract

Collagen, as a thermal-sensitive protein, is the most abundant structural protein in animals. Native collagen has been widely applied in various fields due to its specific physicochemical and biological properties. The beneficial properties would disappear with the collapse of the unique triple helical structure during heating. Understanding thermal stability of collagen is of great significance for practical applications. Previous studies have shown the thermal stability would be affected by the different sources, extraction methods, solvent systems in vitro and modified methods. Accordingly, the factors affecting thermal stability of collagen are discussed in detail in this review.

Graphical abstract