Recently, a report on the reprocessing of fish scraps has attracted attention. Scientists from Scotland want to turn fish scraps into adipic acid and other useful by-products. If this research is successful, fish scraps can be used to make more environmentally friendly nylon and other synthetic materials, which will be the world’s first.
Adipic acid is mainly used as a raw material for nylon 66 and engineering plastics. It is also a raw material for medicine, yeast purification, pesticides, adhesives, synthetic leather, synthetic dyes and fragrances. It can be used to produce various ester products. Used as a raw material for polyurethane elastomers and as an acidulant for various foods and beverages, its effect is sometimes better than that of citric acid and tartaric acid.
The research was carried out by plastic experts from Impact Solutions, biotechnology researchers from the University of Edinburgh, seafood producer Farne Salmon, and the Industrial Biotechnology Innovation Center. The group is using advanced molecular biology technology to explore the feasibility of creating more environmentally friendly man-made fibers for use in clothing and other daily necessities.
How to make deep use of fish scraps is a topic that has been discussed at home and abroad. This research topic is not only of great significance for the comprehensive utilization of aquatic product processing and environmental protection, but also can support and promote the development of aquatic fishing and aquaculture production.
Fish scraps include fish heads, fish bones, fish scales and offal, which account for about 40% to 55% of raw fish. For example, the production of 100t of frozen surimi requires about 400t of raw fish and 200t to 250t of scraps. In addition to a large amount of protein, these wastes also contain a variety of biologically active substances.
High-value fish scraps
Fish heads and fish bones contain a lot of calcium and protein, which are natural high-quality calcium and protein sources that can promote the growth and development of the human body. They can be used to develop fish bone calcium products and fish protein products.
The protein content in fish skin is higher than that in fish muscle, and the highest collagen content can account for more than 80% of its total protein, which is much higher than other parts of the fish body.
Fish scales are deformations of the dermis of the fish skin, accounting for about 1% to 5% of the total weight of the fish. The scales are rich in protein, lecithin and various trace elements, and have less lipid content. Compared with other collagen production For raw materials such as pig and cowhide, it is more conducive to the extraction and purification of collagen.
At present, the utilization value of fish viscera is not very high. It is mainly used to extract fish oil, extract EPA and DHA products, and can be used as fish feed.
Processing methods of fish scraps
01 chemical degradation method
of chemical degradation method using an acid, alkaline protein solution, although simple and inexpensive, but because of severe reaction conditions, amino acid production process serious damage, such as: alkali hydrolysis cause racemization of amino acids, acid hydrolysis It will destroy tryptophan and serine, and it is difficult to control the hydrolysis according to the specified degree of hydrolysis, so it is rarely used.
02 enzyme degradation
enzyme degradation is mainly for hydrolysis of fish protein, enzymatic hydrolysis method is mainly divided into two stages, one protein extraction, purification and enzymatic hydrolysis is two. The enzymatic hydrolysis method has mild conditions and does not destroy the amino acid composition. It is suitable for use as a method for fish scraps to produce fish hydrolyzed protein.
03 microbial fermentation method
commonly used in the fermentation of bacteria have molds, yeasts and bacteria into three categories. Using fish scraps as raw materials, after microbial fermentation, after being used in aquatic feeds, it can protect the ingredients in animal feeds, obviously inhibit the occurrence of digestive tract diseases, and improve the immunity of animals. The main reason is that the raw materials are fermented. The functional small peptides and amino acids produced at the time can improve the digestion, absorption and utilization of feed by the fish body.
04 Other methods
molecular distillation, extraction chromatography resin, silver fish oil DHA, EPA; dilute alkali salt concentration, extraction chondroitin sulfate; hot water extraction, microwave extraction and salt extraction skin, fish scale collagen and the like.
Common types of fish
Scientific and technological progress has brought us many advanced technologies, such as high performance liquid chromatography, supercritical extraction, membrane separation, etc. How to apply these technologies to aquatic processing, so as to obtain high recovery rate, high purity and high value-added products, it is worth explore.
The Scottish team mentioned above is using engineered bacteria to convert fish waste into adipic acid, a raw material for nylon, but the specific biotransformation process is not mentioned.
Simon Rathbone, Development Manager of Impact Solutions, said: “The initial feasibility study brought us into an exciting time where we can begin to see the potential to generate value from materials that would otherwise be discarded. In addition to adipic acid, we also It is hoped that through research on other components that can be extracted from fish waste, such as fatty acids and fish oil, the overall value of the process will be maximized.”
However, the current research process produces nitrous oxide as a by-product. Nitrous oxide can be used for surgical anesthesia, but it is a greenhouse gas. Some reports indicate that it may be more harmful to the climate than carbon dioxide.
The researchers also stated that this study is an important first step towards finding sustainable, bio-based alternatives to the production of adipic acid, which is usually derived from petrochemicals.
Exploring sustainable bio-based alternative petrochemical processes is an important step in efforts to achieve net zero emissions, but there is a long way to go.