Method for extracting melanin-chitin compound from mussel shells
The melanin-chitin complex was extracted from mussel shells by acid hydrolysis and Soxhlet extraction, which solved the mussel shell pollution problem, increased yield, and provided a basis for the application of the complex.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INST OF OCEANOLOGY - CHINESE ACAD OF SCI
- Filing Date
- 2025-12-03
- Publication Date
- 2026-04-17
AI Technical Summary
The discarding of mussel shells leads to pollution, and the insects contain relatively little melanin-chitin complex, making extraction difficult and hindering large-scale industrial applications.
A melanin-chitin complex was extracted from mussel shells using acid hydrolysis and Soxhlet extraction, including acid hydrolysis, hot acid reflux deproteinization, and petroleum ether defatting steps, which simplifies the process and increases yield.
This method enables the high-value utilization of mussel shells, increases the yield of melanin-chitin complex, and is purely natural with broad application potential.
Smart Images
Figure CN121873576A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of biomaterial extraction and preparation processes, and in particular to a method for extracting melanin-chitin complex from mussel shells. Background Technology
[0002] The mussel farming industry is enormous. Typically, the meat is harvested and processed into mussels, while the shells are mostly discarded. Improper disposal of these shells can cause air, water, and soil pollution. Therefore, how to utilize discarded mussel shells in a high-value manner is a very important research direction.
[0003] Melanin is an important class of natural pigments widely found in nature, primarily distributed in animals, plants, and microorganisms. Melanin is a complex and diverse class of macromolecules composed of polyhydroxyindole or polyhydroxyphenol polymers. There are five common types of melanin found in nature: eumelanin, pheomelanin, isomelanin, pyomelanin, and neuromelanin. The type of melanin varies among different species. In mussels, the melanin is mainly eumelanin. Eumelanin is a two-molecule indole structure formed by the oxidation of tyrosine, namely DHI (5,6-dihydroxyindole) and DHICA (5,6-dihydroxyindole acid). Therefore, melanin is insoluble in water but soluble in alkali and insoluble in acid.
[0004] Chitin is the second most abundant natural polysaccharide biomolecule after cellulose, mainly found in the shells of crustaceans (such as shrimp and crab), squid bones, insect exoskeletons, and fungal cell walls. Chitin can be classified into three types: α-chitin, β-chitin, and γ-chitin. Chitin is a linear polymer of N-acetyl-D-glucosamine, with a molecular structure similar to cellulose. Due to the presence of nitrogen atoms, it possesses unique physicochemical properties, exhibiting good biocompatibility, biodegradability, and non-toxicity. Furthermore, it is widely available and environmentally friendly.
[0005] Currently, melanin-chitin complexes have only been found in insects, and they have broad application prospects in medical materials, food processing, and other fields. However, the content of melanin-chitin complexes in insects is low, and extraction is difficult, which hinders large-scale industrial applications. Summary of the Invention
[0006] To address the aforementioned technical problems, this invention provides a method for extracting melanin-chitin complex from mussel shells, thereby achieving the goal of waste utilization through a simple extraction method.
[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for extracting melanin-chitoxin complex from mussel shells involves first acid hydrolyzing the mussel shells, then removing the protein by hot acid reflux, and finally defatting with petroleum ether in a Soxhlet extractor to obtain the melanin-chitoxin complex.
[0008] The extraction method described above includes the following steps: Step 1: Wash the mussel shells and dry them at 40-75℃ or in the sun; Step 2: Crush the mussel shells to a diameter of less than 1 cm, slowly add 3-6 M acid at a material-to-liquid ratio of 0.5-1:5, let stand at room temperature for 1-6 h, and then heat to 100-110℃ in a reflux system and reflux for 4-8 h. Step 3: After the reaction is complete, filter the mixture and wash the residue with distilled water in small amounts several times. After washing, freeze-dry the residue. Step 4: Place the freeze-dried filter residue into a Soxhlet extractor and extract with petroleum ether at 70-80℃ for 4-6 hours to obtain the melanin-chitoxin complex.
[0009] In a further technical solution, the acid is hydrochloric acid, nitric acid, acetic acid, or citric acid.
[0010] In a further technical solution, the concentration of the acid is 5 M.
[0011] In a further technical solution, the ratio of mussel shells to acid in the liquid is 1:5.
[0012] In a further technical solution, the ratio of mussel shells to acid is 0.5:5.
[0013] In a further technical solution, in step 2, the temperature of the reflux condensation system is 100°C, and the reflux reaction lasts for 4 hours.
[0014] In a further technical solution, in step 2, the temperature of the reflux condensation system is 110°C, and the reflux reaction lasts for 6 hours.
[0015] In a further technical solution, in step 2, the temperature of the reflux condensation system is 110°C, and the reflux reaction lasts for 8 hours.
[0016] In a further technical solution, in step 4, petroleum ether is used for extraction at 75°C for 5 hours.
[0017] Through the above technical solution, the method for extracting melanin-chitin complex from mussel shells provided by the present invention has the following beneficial effects: This invention is the first to extract melanin-chitoxin complex from mussel shells using a mild and simple method. This not only solves the pollution problem caused by the large number of discarded mussel shells, but also increases the yield of the melanin-chitoxin complex. It is all-natural, has great application potential, and provides a technical foundation for the subsequent application of this complex. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.
[0019] Figure 1 The image shows the appearance of the melanin-chitoxin complex extracted in Example 1. Figure 2 This is a scanning electron microscope image of the melanin-chitoxin complex extracted in Example 1; Figure 3 This is a three-dimensional reconstruction image of the melanin-chitoxin complex extracted in Example 1 using micro-CT. Figure 4 The infrared spectrum of melanin-chitosan extracted in Example 1; Figure 5 The image shows the carbon NMR spectrum of melanin-chitin solid extracted in Example 1. Detailed Implementation
[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
[0021] This invention provides a method for extracting melanin-chitin complex from mussel shells, and specific embodiments are as follows: Example 1 Mussel shells were washed and dried at 75℃. The shells were then broken into pieces less than 1 cm in diameter, and 5 M hydrochloric acid was slowly added at a material-to-liquid ratio of 1:5. After the hydrochloric acid was added, the mixture was allowed to stand at room temperature for 3 hours, then heated to 100℃ in a reflux system and reacted for 4 hours. After the reaction, the mixture was filtered, and the residue was washed with distilled water. The residue was then freeze-dried and placed in a Soxhlet extractor, and extracted with petroleum ether at 75℃ for 5 hours. A melanin-chitoxin complex was obtained; see image below. Figure 1 .
[0022] Example 2 Mussel shells were washed and dried at 75℃. The shells were then broken into pieces less than 1 cm in diameter, and 3 M hydrochloric acid was slowly added at a material-to-liquid ratio of 0.5:5. After the hydrochloric acid was added, the mixture was allowed to stand at room temperature for 3 hours, then heated to 110℃ in a reflux system and reacted for 6 hours. After the reaction, the mixture was filtered, and the residue was washed with distilled water. The residue was then freeze-dried and placed in a Soxhlet extractor, and extracted with petroleum ether at 75℃ for 5 hours. A melanin-chitoxin complex was obtained.
[0023] Example 3 Mussel shells were washed and dried at 75℃. The shells were then broken into pieces less than 1 cm in diameter, and 6 M acetic acid was slowly added at a material-to-liquid ratio of 0.5:5. After the addition of acetic acid, the mixture was allowed to stand at room temperature for 6 h, then heated to 110℃ in a reflux system and reacted for 8 h. After the reaction, the mixture was filtered, and the residue was washed with distilled water. The residue was then freeze-dried and placed in a Soxhlet extractor, and extracted with petroleum ether at 75℃ for 5 h. A melanin-chitoxin complex was obtained.
[0024] Morphological characterization of melanin-chitoxin complex: The melanin-chitoxin complex prepared in Example 1 was observed using a scanning electron microscope. Figure 2 As shown, under a scanning electron microscope, the complex exhibits unique morphological characteristics: magnified surface observation clearly reveals small nanoparticles of melanin, which aggregate to form large, layered structures. The formation of these layered structures may be determined by the internal chitin framework.
[0025] The melanin-chitosan complex prepared in Example 1 was observed using X-ray micro-CT. Based on the scanned image slices, three-dimensional reconstruction and data analysis were performed. Figure 3 As shown, the gray substance is melanin, the purple substance is chitosan, and the cyan substance is other impurities; based on the contrast density, the micro-CT remodeling data can reveal the melanin that occupies most of the volume and the chitosan that acts as the network framework within it.
[0026] Spectral identification of melanin-chitoxin complex: The melanin-chitoxin complex prepared in Example 1 was tested using Fourier transform infrared spectroscopy (FTIR). The wavenumber range for Fourier transform infrared spectroscopy was 400-4000 cm⁻¹. -1 4 cm resolution -1 With a signal-to-noise ratio of 50,000:1 and a total of 32 scans, its FT-IR spectrum clearly shows the characteristic absorption peaks of melanin and chitin. Figure 4 .
[0027] The melanin-chitoxin complex prepared in Example 1 was subjected to solid-state nuclear magnetic resonance (ssNMR) spectroscopy to obtain carbon spectrum data. Figure 5 As shown, solid-state NMR analysis revealed that the carbon spectrum of the melanin-chitoxin complex exhibited both similarities and significant differences compared to the reference spectra of melanin and chitoxin. SSNMR testing essentially confirmed that the interaction between melanin and chitoxin is through hydrogen bonding, completely ruling out the possibility that their interaction was merely a simple physical co-precipitation.
[0028] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for extracting a melanin-chitin complex from a mussel shell, characterized by, First, the mussel shells were acid-hydrolyzed, then deproteinized by hot acid reflux, and finally defatted with petroleum ether in a Soxhlet extractor to obtain a melanin-chitoxin complex.
2. The method of claim 1, wherein the method is characterized by, Includes the following steps: Step 1: Wash the mussel shells and dry them at 40-75℃ or in the sun; Step 2: Crush the mussel shells to a diameter of less than 1 cm, slowly add 3-6 M acid at a material-to-liquid ratio of 0.5-1:5, let stand at room temperature for 1-6 h, and then heat to 100-110℃ in a reflux system and reflux for 4-8 h. Step 3: After the reaction is complete, filter the mixture and wash the residue with distilled water in small amounts several times. After washing, freeze-dry the residue. Step 4: Place the freeze-dried filter residue into a Soxhlet extractor and extract with petroleum ether at 70-80℃ for 4-6 hours to obtain the melanin-chitoxin complex.
3. The method for extracting melanin-chitin complex from mussel shells according to claim 2, characterized in that, The acid is hydrochloric acid, nitric acid, acetic acid, or citric acid.
4. The method for extracting melanin-chitin complex from mussel shells according to claim 2, characterized in that, The concentration of the acid is 5 M.
5. The method for extracting melanin-chitin complex from mussel shells according to claim 2, characterized in that, The ratio of mussel shells to acid in the liquid is 1:
5.
6. The method for extracting melanin-chitin complex from mussel shells according to claim 2, characterized in that, The ratio of mussel shells to acid in the liquid is 0.5:
5.
7. The method for extracting melanin-chitin complex from mussel shells according to claim 2, characterized in that, In step 2, the temperature of the reflux condensation system is 100°C, and the reflux reaction lasts for 4 hours.
8. The method for extracting melanin-chitin complex from mussel shells according to claim 2, characterized in that, In step 2, the temperature of the reflux condensation system is 110°C, and the reflux reaction lasts for 6 hours.
9. A method for extracting melanin-chitin complex from mussel shells according to claim 2, characterized in that, In step 2, the temperature of the reflux condensation system is 110°C, and the reflux reaction lasts for 8 hours.
10. A method for extracting melanin-chitin complex from mussel shells according to claim 2, characterized in that, In step 4, the sample is extracted with petroleum ether at 75°C for 5 hours.