JP2001061466A - Production of astaxanthin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain astaxanthin-contg. algae for producing astaxanthin having potent antioxidative effect and useful as a medicinal active ingredient or the like by adding an active oxygen-forming substance to a cultured product of Haematococcus pluvialis followed by conducting a culture in a bright place. SOLUTION: Astaxanthin-contg. algae capable of efficiently mass-producing astaxanthin useful as a medicinal active ingredient or the like owing to its potent antioxidative effect are obtained by the following steps: Haematococcus pluvialis NIES 144 seeds are inoculated upon a culture medium put into a sterilized flask and subjected to preliminary culture in dark place and bright place, for example, at 20 deg.C for 4 days under an illuminance of 1,500 lux in a 12h- bright/dark cycle, and an active oxygen-forming substance such as iron ion is then added to the resultant cultured product followed by conducting the main culture in a bright lace at 20 deg.C for 8 days.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing astaxanthin from a green alga Haematococcus pluvialis in a large amount and efficiently.

[0002]

2. Description of the Related Art Astaxanthin is available in shellfish shells and eggs,
It is a type of red carotenoid that is extremely widely distributed in the animal kingdom, such as salmon meat and skin of the sea bream. Use of red yeast cells containing astaxanthin, such as Phaffia rhodozyma, as a colored feed for cultured trout and, in recent years, as a colored feed for cultured red sea bream has been studied for use as a substitute for Antarctic krill. Also, due to the strong antioxidant action of astaxanthin, its use as a pharmaceutically active ingredient is being studied.

The green alga Haematococcus pluvialis also contains astaxanthin, but it is not well known about detailed culture conditions for efficiently increasing the astaxanthin content and a method for efficiently obtaining astaxanthin from cells. Generally, it has been considered that green algae do not grow unless cultured in a light place to obtain energy by photosynthesis, and further do not synthesize astaxanthin. Haematococcus pluvialis has also been conventionally cultured in a light place using carbon dioxide or acetic acid as a carbon source. Since light is required during culturing, there is a drawback that mass production is difficult. Therefore, a culturing method using a photobioreactor has been studied in order to increase the light efficiency. In addition, the culture of green algae Donariella and cyanobacterium Spirulina is carried out in outdoor ponds and oceans using sunlight.However, in the case of green algae Haematococcus pluvialis, the optimal growth temperature is low, Has the disadvantage that it cannot be cultured.

[0004]

SUMMARY OF THE INVENTION The present invention provides a method for producing astaxanthin efficiently by increasing the astaxanthin content by improving the method for cultivating the green alga Hematococcus pluvialis. It is an object of the present invention to provide a method for producing astaxanthin, which comprises culturing in situ.

[0005]

Means for Solving the Problems The present inventors have repeatedly studied the production method of astaxanthin by the green alga Haematococcus pluvialis, and as a result, cultivated Haematococcus pluvialis in the dark under aerobic conditions. At this time, it was found that astaxanthin was accumulated in a vegetatively proliferating cell with cell division in conjunction with growth. Furthermore, by adding an active oxygen generating substance and a carbon source to the culture medium cultured in this dark place and transferring to a light place, cyst formation is induced and astaxanthin synthesis is promoted,
In that case, it was also found that even if the cells were cultured in the dark as described above before the induction of cyst formation, astaxanthin synthesis equivalent to that in the cells cultured in the light was obtained. The present invention has been accomplished based on these findings.

[0006] The present invention provides a method for growing Haematococcus pluvialis containing astaxanthin by culturing Haematococcus pluvialis in a dark place and under aerobic conditions, and then culturing an active oxygen-generating substance and a carbon source. And culturing in a light place to induce cyst formation of the Haematococcus pluvialis to promote astaxanthin synthesis, and collecting astaxanthin from the culture.

[0007] The present invention further provides a method for producing astaxanthin, which comprises a step of treating Haematococcus pluvialis with a protease and applying osmotic shock to a cell wall.

BEST MODE FOR CARRYING OUT THE INVENTION

[0008] The green alga Haematococcus pluvialis used in the present invention is a single cell having a cell size of 20 to 25 µm, and is plankton that inhabits fresh water and can be easily collected. For example, Haematococcus pluvialis
ASIB BS2, CALU 9, CALU 333, CAUP G1002, CCAO, IBAS
U 38, IPPAS H-23, MUR 01, 02, 62, 63, 64, 65, 66,
67, 68, 69, 71, 72, 75, 76, 77, NIES 144, NIVA CHL
9, There is SMBA. Some Haematococcus lacustris are identical to Haematococcus pluvialis, such as ATCC 30402, SAG 34-1a, 1b, 1
There are c, 1d, 1e, 1f, 1h, 1k, 1l, 1m, 1n, and UTEX 16.
Haematococcus pluvialis preferably used in the present invention was deposited with the National Institute for Environmental Studies (NIES) under the deposit number NIES144.
Has been deposited as

[0009] Vegetative cells of the green alga Haematococcus pluvialis usually exist as floating cells having two flagella and, like the green alga Chlamydomonas, divide and proliferate in the wall of the parent cell. Around the vegetative cells,
It has a gelatinous cell wall. The vegetative cells develop a thick solid cell wall inside the gelatinous material by transferring to a medium lacking a nitrogen source, and eventually the cells stop swimming,
Asexually or sexually, a cyst (cyst, also known as aplanosp) with a hard cell wall and high astaxanthin content
ore, akinet).

The culture of Haematococcus pluvialis in the dark and under aerobic conditions is performed under the following conditions. The green alga Haematococcus pluvialis, in nature,
Because it is a photosynthetic organism that grows on carbon dioxide and light energy, it is necessary to use a medium containing a sufficient amount of carbon source that can substitute for carbon dioxide as a heterotrophic nutrient in order to culture it in the dark and under aerobic conditions. There is. As a carbon source, for example,
In addition to conventionally known acetic acid, there are pyruvic acid, ethanol, and TCA-related organic acids. Examples of TCA-related organic acids include citric acid, α-ketoglutaric acid, succinic acid, fumaric acid, malic acid and the like. A medium is used in which one or more selected from the group containing each of the above carbon sources and a nitrogen source such as an amino acid such as asparagine, glycine, and glutamine is further combined with a yeast extract. Yeast extract is essential, but when amino acids such as glycine and glutamine are used, the growth of Haematococcus pluvialis can be observed at the same level as when the yeast extract is added, even when the yeast extract is omitted. Preferred media are, for example, yeast extract 2.0 g / l, sodium acetate 1.2 g / l, L-asparagine 0.4 g / l, MgC
_{l 2 · 7H 2 O 985μM,} FeSO 4 · 7H 2 O 36
μM, 136 μM of CaCl ₂ .2H ₂ O, pH 6.8. The culture conditions are 15 to 25 ° C, preferably about 20 ° C, in a dark place and under aerobic conditions.

The Haematococcus cultivated in this manner is
Despite the darkness of Pluvialis, accumulation of astaxanthin is observed in vegetative cells with cell division from the early growth phase. The astaxanthin content per cell is not different from that in a light culture under the same conditions.

Although it is possible to collect astaxanthin in the vegetative cells, it is possible to induce a morphological change from vegetative cells to cysts by artificially adjusting the composition of the components in the culture medium to artificially produce astaxanthin. It is advantageous to maximize the function. To do so, add the active oxygen-generating substance and the carbon source at relatively high concentrations during the culture,
Induce morphological changes. After adding the active oxygen-generating substance and the carbon source, the culture is transferred from a dark place to a bright place. Examples of the active oxygen generating substance used include substances capable of generating iron ions, methylene blue, methyl viologen, hydrogen peroxide (H ₂ O ₂ ), and 2,2′-azobis (2-amidinopropane) dihydrochloride. In particular, compounds capable of generating iron ions are preferred. Iron ions formed is a divalent or trivalent, as the compound capable of forming such an iron ion, for example _{FeSO 4 · 7H 2 O, FeSO} 4 (N
H ₄ ) ₂ SO ₄ .6H ₂ O, FeNH ₄ (SO ₄ ) ₂ .12H ₂
O. The amount of the active oxygen-generating substance added varies depending on the type of the substance.For example, the concentration of iron ions in the culture medium is several times or more the amount used in the culture medium before cyst formation induction, up to 600 μM, preferably 450 μM. Is added. As described above, iron ions are thought to promote astaxanthin synthesis to generate active oxygen. In order to protect cells from various oxidative stresses, it is considered that astaxanthin having a strong antioxidant action is synthesized in cells of Haematococcus pluvialis.

As the carbon source used, any of the above-mentioned ones is used, and acetic acid is preferably used. The acetic acid concentration is added to the culture medium to a maximum of 60 mM, preferably 45 mM. Use at a concentration exceeding the above is unfavorable because it conversely suppresses astaxanthin production. Cyst formation is induced by only the carbon source, and astaxanthin production is increased. However, when iron ions are added simultaneously with the carbon source, astaxanthin production is further increased.

[0014] The above two-stage culturing method allows the period of astaxanthin synthesis to be shortened quickly so that it can be produced from the beginning. Since it is sufficient to be in a dark place during the growth period, it is possible to culture in a large amount in a normal fermenter without considering the change in light exposure due to the growth, so that the culture is easy.

[0015] The harvested green alga Haematococcus pluvialis can be completely destroyed by protease treatment in a reaction solution without an osmotic pressure regulator. Cell wall degrading enzymes conventionally used for preparing cell protoplasts of higher plants and many algae are roughly classified into enzymes that degrade cellulose components (cellulase,
Hemicellulase) and those that degrade pectin substance (pectinase). As for the cell wall of Haematococcus, there is a report using a cell wall lysing enzyme (drylase) having the above two components, but a sufficiently crushed alga body cannot be obtained. The cell wall of Haematococcus differs greatly from higher plants and other algae in that it lacks cellulose, hemicellulose, pectin and lignin as constituent components and consists only of glycoproteins. Therefore, the cell wall can be effectively lysed by using the protease for destruction of the cell wall by focusing on the protein instead of the sugar of the glycoprotein. Hematococcus pluvialis,
Protoplast cells are obtained by the action of protease in the presence of an osmotic agent, and when osmotic shock is applied by protease treatment in a reaction solution without osmotic agent, the cells are completely destroyed. As the protease, various proteases having different origins, pronase E and proteinase K can be used. The reaction conditions are near neutral pH, room temperature (20-40 ° C), preferably around 35 ° C, and the enzyme concentration is 0.1%. And react for 30 minutes to 2 hours.

For the crushing of Haematococcus pluvialis cells, a method of crushing by adding other glass beads and grinding, or a method using a French press, or a known physical method such as an ultrasonic crushing method is applied.
It can be recovered by extraction with a highly polar solvent such as methanol or acetone. In addition, cells obtained by treating cells in bulk or by crushing can be used for deep-coloring of fish. In the purification of astaxanthin, astaxanthin having a desired purity can be obtained by appropriately utilizing a known separation and purification means.

The method for disrupting cells using the above protease is used not only for collecting astaxanthin from Haematococcus pluvialis, but also for destroying the cell walls of various microalgal cells containing glycoproteins as cell wall components. It can be suitably used.

[0018]

Next, the present invention will be described in more detail with reference to examples using acetic acid as a carbon source.

(Example 1) 100 ml of a culture medium shown in Table 1
Was placed in a 200 ml flask and sterilized at 121 ° C. for 15 minutes. Haematococcus pluvialis NIES 1 separately cultured in a culture medium for maintenance
44) and inoculated in a dark place and a light place, for example, under a light intensity of 1500 lux, at a light-dark cycle of 12 hours at 20 ° C.
For 4 days, and precultured.

Each 10 ml of this culture solution was inoculated into 100 ml of a culture medium having the same composition as the above, and main-cultured at 20 ° C. for 8 days in a dark place or a light place, respectively.

FIG. 1 shows the growth of vegetative cells of Haematococcus pluvialis and the change in the amount of carotenoid produced in the dark or light place during the main culture.
After measuring the amount of carotenoids from the absorbance at 480 nm, extraction was performed, and it was confirmed that about 90% of the carotenoids was astaxanthin.

Hematococcus pluvialis grew reliably in the dark using acetic acid as a carbon source. In addition, when the yeast extract was removed from the culture medium shown in Table 1, Haematococcus
Although growth of Pluvialis deteriorated, the growth was restored to the same level by adding amino acids such as glycine and glutamine, and the yeast extract could be replaced. The optimum range of the carbon source concentration is up to 45 mM. Haematococcus pluvialis obtained in the dark contained the pigments chlorophyll and carotenoids per cell as well as in the light. The pigment was accumulated in the cells with growth, and the content was 10 to 20 mg / g dry weight of chlorophyll and 10 mg / g dry weight of carotenoid.

[0023]

[Table 1]

[0024] In the same manner as Example 2 Example 1, after 4 days of culture, the concentration of acetic acid 45mM as a carbon source, iron ion concentration (FeSO ₄ · 7H ₂ O) is added to a 450MyuM, 9000 Lux under continuous light irradiation for 24 hours, 20
Cultivation was continued at 4 ° C for 4 days. Iron ions may be trivalent. The amount of astaxanthin was measured in the same manner as in Example 1. The vegetative cells of Haematococcus pluvialis started to form cysts after adding acetic acid and iron ions as carbon sources, and accumulated a large amount of astaxanthin in the cells (FIG. 2). At the same time, the chlorophyll that has been produced has undergone rapid decomposition.

Thus, the vegetative cells of Haematococcus pluvialis cultured for 4 days in the dark or in the light are:
By adding acetic acid and iron ions as carbon sources, a large amount of astaxanthin could be accumulated in cells. After 8 days of culture, carotenoids with a high concentration exceeding 20 mg / l (of which astaxanthin content is about 90%)
%).

(Example 3) An osmotic pressure regulator (sorbitol / sorbitol) was added to vegetative cells of Haematococcus pluvialis in the growth phase.
When protease treatment was performed in the reaction solution containing mannitol) as described below, 50% of protoplast cells were obtained in about 1 hour. Protease treatment in the reaction without osmotic agent completely destroyed the cells. The protease used was pronase E (0.15%) and proteinase K (0.1%); the reaction solution was sorbitol /
Mannitol 0.2M, triethanolamine buffer 1
0 mM, pH 7.5; reaction condition was 35 ° C. for 1 hour.

[0027]

According to the present invention, astaxanthin can be accumulated in an algal body from an early stage, and astaxanthin can be efficiently synthesized by artificial cyst induction. A method for efficiently producing astaxanthin in large quantities is provided. The astaxanthin obtained is highly safe and can contribute to fish farming and other industries.

[Brief description of the drawings]

1 shows the growth of vegetative cells of Haematococcus pluvialis and the production of carotenoids.

FIG. 2 shows the effects of iron ion and acetic acid addition on the growth and carotenoid production of Haematococcus pluvialis.

Claims (5)

[Claims] 1. A method for producing an astaxanthin-containing algal body, comprising adding an active oxygen-generating substance to a culture of Haematococcus pluvialis and culturing it in a light place. 2. A method for producing an astaxanthin-containing algal body, comprising adding an active oxygen-generating substance and a carbon source to a culture of Haematococcus pluvialis and culturing it in a light place. 3. The method according to claim 1, wherein the active oxygen generating substance is an iron ion. 4. An astaxanthin-containing algal body obtained by the method according to any one of claims 1 to 3,
A method for producing astaxanthin, which comprises collecting astaxanthin. 5. The method for producing astaxanthin according to claim 4, wherein collecting the astaxanthin comprises subjecting the astaxanthin-containing Haematococcus pluvialis to a protease treatment.