Physical, biochemical, densitometric and spectroscopic techniques for characterization collagen from alternative sources: a review based on the sustainable valorization of aquatic by-products

Simple Summary Collagen is useful in many applications including cosmetics, medicine, yarn production and packaging. Collagen can be recovered from skins of animals raised for meat. Here, we review methods for the extraction and purification of collagen from animal skins. Abstract Collagen is the most abundant structural protein in animals. It is the major component of skin. It finds uses in cosmetics, medicine, yarn production and packaging. This paper reviews the extraction of collagen from hides of most consumed animals for meat with the focus on literature published since 2000. The different pretreatment and extraction techniques that have been investigated for producing collagen from animal skins are reviewed. Pretreatment by enzymatic, acid or alkaline methods have been used. Extraction by chemical hydrolysis, salt solubilization, enzymatic hydrolysis, ultrasound assisted extraction and other methods are described. Post-extraction purification methods are also explained. This compilation will be useful for anyone wishing to use collagen as a resource and wanting to further improve the extraction and purification methods.

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Collagen Extraction from Animal Skin

Protein inactivation either during the production process or along the gastrointestinal tract is the major problem associated with the development of oral delivery systems for biological drugs. This work presents an evaluation of the structural integrity and the biological activity of a model protein, catalase, after its encapsulation in glyceryl trimyristate-based solid lipid microparticles (SLMs) obtained by the spray congealing technology. Circular dichroism and fluorescence spectroscopies were used to assess the integrity of catalase released from SLMs. The results confirmed that no conformational change occurred during the production process and both the secondary and tertiary structures were retained. Catalase is highly sensitive to temperature and undergoes denaturation above 60 °C; nevertheless, spray congealing allowed the retention of most biological activity due to the loading of the drug at the solid state, markedly reducing the risk of denaturation. Catalase activity after exposure to simulated gastric conditions (considering both acidic pH and the presence of gastric digestive hydrolases) ranged from 35 to 95% depending on the carrier: increasing of both the fatty acid chain length and the degree of substitution of the glyceride enhanced residual enzyme activity. SLMs allowed the protein release in a simulated intestinal environment and were not cytotoxic against HT29 cells. In conclusion, the encapsulation of proteins into SLMs by spray congealing might be a promising strategy for the formulation of nontoxic and inexpensive oral biotherapeutic products.

Solid Lipid Microparticles for Oral Delivery of Catalase: Focus on the Protein Structural Integrity and Gastric Protection.

Lignin-based spherical particles have recently gained popularity due to their characteristic and the usage of biopolymeric material. In this study, lignin-based spherical particles were prepared using choline chloride at different pH values, ranging from 2 to 10. Their dispersive, microstructural, and physicochemical properties were studied by a variety of techniques, including scanning electron microscopy, Fourier transform infrared spectroscopy, and zeta potential analysis. The best results were obtained for the particles prepared at pH 5 and 7, which had a spherical shape without a tendency to form aggregates and agglomerates. The lignin-based spherical particles were used for the immobilization of lipase, a model enzyme capable of catalyzing a wide range of transformations. It was shown that the highest relative activity of immobilized lipase was obtained after 24 h of immobilization at 30 °C and pH 7, using 100 mg of the support. Moreover, the immobilized lipase exhibited enhanced stability under harsh process conditions, and demonstrated high reusability, up to 87% after 10 cycles, depending on the support used. In the future, the described approach to enzyme immobilization based on lignin spheres may play a significant role in the catalytic synthesis of organic and fine chemicals, with high utility value.

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Tailoring Lignin-Based Spherical Particles as a Support for Lipase Immobilization

Due to the high moisture-associated typical rheology and the changeable and harsh processing conditions in the production process, packaging materials for meat products have higher requirements including a sufficient mechanical strength and proper ductility. Collagen, a highly conserved structural protein consisting of a triple helix of Gly-X-Y repeats, has been proved to be suitable packaging material for meat products. The treated animal digestive tract (i.e. the casing) is the perfect natural packaging material for wrapping meat into sausage. Its thin walls, strong toughness and impact resistance make it the oldest and best edible meat packaging. Collagen casing is another wisdom of meat packaging, which is made by collagen fibers from hide skin, presenting a rapid growth in casing market. To strengthen mechanical strength and barrier behaviors of collagen-based packaging materials, different physical, chemical, and biological cross-linking methods are springing up exuberantly, as well as a variety of reinforcement approaches including nanotechnology. In addition, the rapid development of biomimetic technology also provides a good research idea and means for the promotion of collagen's assembly and relevant mechanical properties. This review can offer some reference on fundamental theory and practical application of collagenous materials in meat products.

A rethinking of collagen as tough biomaterials in meat packaging: assembly from native to synthetic.

Based on the excellent biocompatibility of collagen, collagen was extracted from pig skin by acid-enzymatic method. The films were prepared by the self-aggregation behavior of collagen, and the catalase was immobilized by adsorption, cross-linking and embedding. The experiment investigated the effects of glutaraldehyde on the mechanical properties, external sensory properties, and denaturation temperature of the films. The results showed that self-aggregating material could maintain the triple helix structure of pig skin collagen. The self-aggregation treatment and cross-linking treatment can improve the mechanical properties to 53 MPa, while the glutaraldehyde cross-linking agent can increase the denaturation temperature of the pig skin collagen self-aggregating membrane by 20.35% to 84.48 °C. This means that its application to immobilized catalase has better stability. The comparison shows that the catalase immobilized by the adsorption method has strong activity and high operational stability, and the cross-linking agent glutaraldehyde and the initial enzyme concentration have a significant effect on the immobilization, and the activity can reach 175 U g−1. After 16 uses of the film, the catalase was completely inactivated. This study provides a reference for the preparation of a catalase sensor that can be used to detect hydrogen peroxide in food by a catalase sensor.

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Characterization of biocompatible pig skin collagen and application of collagen-based films for enzyme immobilization

Provided are preparation of chicken feather nitrogen-doped carbon quantum dots based fluorescent probes and a paraquat detection method. The method for preparing chicken feather nitrogen-doped carbon quantum dots comprises: mixing chicken feather material and deionized water uniformly in a mass-to-volume ratio of 0.2g 1.5g: 60mL, and then adding to the solution 0.2mL-3mL of a nitrogen-containing solution as a dopant, and ultrasonically dispersing the solution for 2min-10min, thus obtaining a solution to be reacted; placing the solution to be reacted in an airtight reaction kettle and reacting at a temperature between 100°C and 300°C for 1.5h to 48h to obtain a hydrothermal reaction product solution, naturally cooling the hydrothermal reaction product solution, and taking the solution out; and centrifuging the hydrothermal reaction product solution, taking the supernatant of the centrifuged brown liquid, and filtering the supernatant, thus obtaining a chicken feather nitrogen doped carbon quantum dot solution. A corresponding fluorescent probe is obtained through the chicken feather nitrogen-doped carbon quantum dot solution; through the exploration on the excitation wavelength and emission wavelength, the linear regression equation is fitted with a standard solution, and the equation is used to complete the detection. With environmentally friendly waste biomass material as raw material, the biomass atom-doped fluorescent carbon quantum dots are prepared by a one-step hydrothermal method, and the provided "on-off N-CQDs/Hg fluorescent probe solution can be used for detecting the content of paraquat. Ai2M 1 lox Drawing f4 Fig. 1 1600 kvjem320/386 Iooo cp p800 o 300 400 500 600 Wavength(nm) Fig. 2

Preparation of chicken feather nitrogen-doped carbon quantum dots based fluorescent probes and paraquat detection method

The invention discloses a preparation method and application of a collagen nano-silver material. The collagen nano-silver material is in a sol state, and a nano-silver material which is obtained by adopting collagen as a stabilizer, by adopting silver nitrate as silver salt, and by adding a reductant serves as the collagen nano-silver material. By the utilization of the preparation method, nano-silver can be rapidly and safely prepared, and nano-silver sol obtained through the preparation method is high in dispersibility and stability. The nano-silver material can be used for the rapid detection of Cr(3+) in water and shows high selectivity to Cr(3+), the linearity range of the nano-silver material reaches 0-10 ug/ml, and the linear correlation coefficient R2 reaches 0.98. When the nano-silver sol is used for the actual detection of Cr(3+) in tap water and river water, the recovery rate of Cr(3+) in the tap water reaches 81-97.8%, the recovery rate of Cr(3+) in the river water reaches79.5-97.6%, and the relative standard deviation of six independent measurement results is less than or equal to 3%.

Preparation method and application of collagen nano-silver material

The invention provides a collagen TiO2 composite catalyst and a preparation method thereof. The collagen TiO2 composite catalyst is a nano-particle composite catalyst prepared by taking collagen as acarrier to support nano-scale titanium dioxide active components. The preparation method comprises the following steps: degreasing the cleaned pigskin, and removing impure proteins after degreasing iscompleted; carrying out enzymolysis on the pigskin subjected to impure protein removal, and carrying out filtering after the enzymolysis is ended; salting out the filtrate, and carrying out centrifuging to obtain a collagen crude extract after salting out is completed; carrying out dialysis on the collagen crude extract with a acetic acid solution and ultra-pure water in sequence, and then carrying out freeze-drying to obtain a collagen pure product; preparing a nano-scale titanium dioxide sample by taking tetrabutyl titanate and a diluted acid as raw materials; dissolving the collagen pure product in an acetic acid solution, adding the nano-scale titanium dioxide sample, carrying out ultrasonic dispersion, then carrying out dipping, and sequentially carrying out drying, crushing, calcining and crushing to obtain the collagen TiO2 composite catalyst.

Dong Lei

Papers

Characterization of biocompatible pig skin collagen and application of collagen-based films for enzyme immobilization

Preparation of chicken feather nitrogen-doped carbon quantum dots based fluorescent probes and paraquat detection method

Preparation method and application of collagen nano-silver material

Collagen TiO2 composite catalyst and preparation method thereof