What You Need to Know About Astaxanthin？

What Is Astaxanthin?

Astaxanthin is a red pigment widely found in living organisms. Also known as shrimp xanthin, lobster shell pigment, is a carotenoid, but also carotenoid synthesis of the highest level of product, dark pink, chemical structure similar to beta-carotene. It has strong antioxidant properties.

Astaxanthin is commonly found in living organisms, especially in some common aquatic plants and animals (e.g. salmon, shrimp, various algae and some bird feathers), and is the most important carotenoid in the cells of aquatic organisms. Astaxanthin, which exists in nature, has a variety of prominent physiological functions, such as preventing cell oxidation, enhancing immunity, anti-tumor, anti-fatigue, etc. Astaxanthin is considered to be one of the strongest natural antioxidants, which can effectively scavenge intracellular oxygen radicals, maintain the balance of the internal environment and reduce the accumulation of senescent cells, as well as maintain the stability of the cells and DNA from the inside out [3].

What Are the Sources of Astaxanthin?

Natural Extraction

Naturally occurring astaxanthin is often found in certain animals, algae and microorganisms, particularly in shrimp, crab, fish and bird feathers, and is safe to use and environmentally friendly.

Haematococcus Pluvialis

Haematococcus pluvialis is a kind of single-celled microalgae, which is the most abundant astaxanthin in nature, and its astaxanthin content can reach 3.0% of the dry weight, or even higher, which is known as the natural astaxanthin "concentrate". And the rain of red algae astaxanthin whether in function or safety and other sources of astaxanthin have other incomparable advantages. Therefore, the haematococcus pluvialis is considered to be the best biological source of natural astaxanthin, with high nutritional and medicinal value.

Synthesis

Chemically synthesised astaxanthin still has some competitive advantages, but it may be contaminated by other harmful substances during the production process, leaving the product with unnatural isomers. The U.S. FDA has only approved structural astaxanthin for use as an additive in aquaculture.

At present, there are 4 main methods to synthesize astaxanthin [4]:

1) Chemical synthesis.

According to the difference of the specific principle, this method can be divided into semi-synthetic method and total synthesis method: semi-synthetic method is the use of carotenoids such as keratine, lutein and zeaxanthin as the synthesis material of astaxanthin, while the total synthesis method is mainly based on the use of chemical raw materials as the main raw materials, through a series of complex chemical synthesis reaction to prepare astaxanthin. The outstanding advantages of chemical synthesis of astaxanthin are low production cost, stable astaxanthin yield and high purity. However, the astaxanthin synthesized by this method often suffers from poor stability, safety and low antioxidant activity.

(2) Red algae [5].

Among all known astaxanthin-synthesizing algae, the astaxanthin content of Rhodococcus aureus is the highest, and among all the organisms synthesizing astaxanthin, the astaxanthin accumulation of Rhodococcus aureus is exceptionally outstanding, and it is one of the best organisms for synthesizing astaxanthin, and the maximum amount of astaxanthin accumulated can be up to 4% of the dry weight of its cells. However, the disadvantages of this method are: slow growth, usually requiring a long culture period; astaxanthin synthesis is limited under normal growth conditions, which is a great disadvantage for the large-scale production of astaxanthin [6].

3) Crustacean processing [7].

Another type of raw material for astaxanthin extraction is the scraps from the processing of marine crustaceans, where astaxanthin exists in the form of pigment-protein conjugates by combining with effective proteins. Depending on the extraction method, the current domestic and international methods include alkaline extraction, oil solubilization and organic solvent method [8]. As lye can realize the effect of efficient deproteinization, treating crustacean scraps with hot lye, astaxanthin will be dissolved along with proteins, so as to achieve the purpose of efficient collection; taking advantage of the good fat solubility of astaxanthin, oil solubilization method usually uses edible oleoresin such as soybean oil as the medium of extraction.

4) Fungi.

In nature, fungal microorganisms such as red yeast and red yeast have the ability to synthesize astaxanthin [9]. Among them, the astaxanthin expression of red yeast [10] is the most prominent, the astaxanthin content of wild-type red yeast can be up to 0.05% of the dry weight of the bacterium, and some red yeast mutant strains can even reach 0.3%, and its synthesis of carotenoids, astaxanthin is the most important component, so the red yeast is the most common microbial fermentation production of astaxanthin strains [ 11]. 11]. For this reason, S. rosenbergii is often considered to be the best source of astaxanthin after Rhodococcus pyrenoidus.

Generally speaking, the results of microbial fermentation are controlled by both the genetic characteristics of the bacteria and the culture environment. By altering the genetic information of microorganisms through the improvement of breeding technology, high astaxanthin yielding S. rosenbergii strains can be obtained [12]; at the same time, altering the cultivation environment of yeasts can also improve the production of astaxanthin, which includes optimizing the composition of culture medium (seed medium, fermentation medium, supplementation medium), pH condition, substrate concentration, dissolved oxygen condition, additive type and fermentation process [13]. The optimization of the culture conditions of red fermentation yeast (RFY) is a major step in the development of RFY in China and abroad [13]. Many scholars at home and abroad have chosen different directions for the optimization of the fermentation process of red yeast, and have come up with some valuable conclusions and rules.

Astaxanthin extraction method

Astaxanthin is synthesized in the cell, which is an intracellular substance, and the red yeast is mainly oval-shaped single cell, and astaxanthin accounts for about 0.12% of its dry weight. The cell wall is a typical yeast “sandwich” configuration composed of mannan, glucan and protein, and is about 24 nm thick, which also increases the difficulty of astaxanthin extraction. Therefore, in order to effectively promote the release of astaxanthin, some scholars chose the method of autolysis by distilled water or citric acid, or first destroy the cell structure of the bacteria by mechanical crushing, and then extracted by organic solvents [14]. Comparison of the various methods, the ideal way to achieve industrial production is the organic solvent extraction method, in this solid-liquid extraction process, including solvent penetration, pigment dissolution, solubility diffusion and a series of steps.

In addition to astaxanthin, there are usually astaxanthin derivatives, lipids and other impurities in the crude extract of astaxanthin, which affect the results of astaxanthin analysis and detection, so it is necessary to separate and purify it in order to obtain high purity astaxanthin. Commonly used purification methods include column chromatography, high performance liquid chromatography, thin-layer chromatography, recrystallization, etc. In addition, new techniques such as high-speed counter-current chromatography have emerged in recent years [15].

What Are the Efficacy and Application of Astaxanthin？

Astaxanthin is similar to the properties of vitamin A, is a natural "eye health vitamin", can eliminate eye fatigue, help vision recovery. Elderly people and students often eat astaxanthin, help to regulate the biological clock, restore the normal rhythm of life. Widely used in functional food, health products and cosmetics and other anti-aging products.

Astaxanthin has excellent colouring properties and antioxidant properties. Its excellent colouring properties can improve the meat quality of certain fish, improve colour and deepen the colour of egg yolks. Astaxanthin in feed is an ideal "nutritional" colouring agent, and its active ingredients have a certain protective effect on the skin.

References:

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