JPH0759557A - New microalgae - Google Patents

Abstract

PURPOSE:To accumulate starch in a readily recoverable aggregated granular form in algal bodies by culturing specific microalgae having a wide growth region extending from the acidic to the alkaline sides. CONSTITUTION:These new microalgae are obtained by culturing Lepidochloris sphaerica having a growth pH region at pH4.5-10.5, e.g. Lepidochloris sphaerica Ikemoto et Chihara gen. et sp. nov. strain [in preservation as a preservation No. AU-32 in the Kaiyo Biotechnology Kenkyusho K.K.]. Only the strain can stably be proliferated while suppressing the proliferation of other microalgae, predatoy organisms, etc., not only in a culture medium based on seawater such as an ESM culture medium or a BG-11 culture medium but also in a low-pH or a high-pH culture medium and carbon dioxide can be dissolved in a larger volume based on the unit volume of the culture liquid on the alkaline side. Thereby, the microalgae are advantageous.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a novel microalgae.Lepidoch
loris sphaericaRegardingLepidochloris sphaerica
Is a microalgae useful for producing starch and the like.

[0002]

2. Description of the Related Art Some unicellular algae generally called microalgae are industrially useful. For example, Chlorococcum littorale, which belongs to green algae, and Gardieria sp., Which belongs to red algae, can grow even under high carbon dioxide concentration, so it is expected to be used for separation of carbon dioxide from combustion gas in thermal power plants. (Japanese Patent Laid-Open No.
4-271775, Japanese Patent Application No. 5-041397).

However, the number of species that have been examined for industrial applicability in this way is small from the viewpoint of microalgae as a whole, and it is considered that there are many unknown species that have not yet been clarified taxonomically. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel industrially useful microalgae.

[0005]

[Means for Solving the Problems] The inventors of the present invention have diligently searched for microalgae contained in seawater or bottom sand mud collected at Coral Reef Great Barrier Reef in Queensland, Australia. Le
pidochloris sphaerica Ikemoto et Chihara gen. et s
The present invention was completed by finding a p. nov. strain (hereinafter abbreviated as this strain).

That is, the present invention is a novel microalga Lepidochloris sphaerica having a growth pH range of pH 4.5 to 10.5.
Further, the present invention is a novel microalga Lepidochloris sphaerica Ikemoto et Chihara having a growth pH range of pH 4.5 to 10.5.
gen. et sp. nov. strain. This strain is stored and managed by the Marine Biotechnology Research Institute Co., Ltd. under the storage number AU-32.

The present invention will be described in detail below. The inventors collected seawater or bottom sand and mud at Coral Reef Great Barrier Reef in Queens Island, Australia, and directly collected a few drops of seawater or bottom sand and mud. A few drops of a suspension of 1 g (wet weight) in 100 mL of sterilized seawater was added to 10 ml of BG-11 medium which is an artificial seawater medium.
It was added dropwise into the medium and subjected to an integrated culture at 25 ° C. under light irradiation, and as a result, this strain was isolated.

The algal properties of this strain are as follows. 1. Morphological Properties (1) Vegetative cells are spherical and have a diameter of 5 to 30 μm, and the shapes observed under an optical microscope are those shown in FIGS. 1 and 2. (2) Vegetative cells have cell walls. On the outer periphery of the cell wall, there is a single layer of scaly scale as shown in the transmission electron micrographs of FIGS. 3 and 4.

(3) Mature vegetative cells form 2 to 30 or more endospores. Endospores may be zoospores or immobile spores. In both cases, the endospores have a cell wall and a layer of horny scales. (4) Nuclei, chloroplasts, mitochondria, and one pyrenoid are found in vegetative cells and endospores. Many starch particles are scattered in many cases, and are observed as shown in FIGS. 5 and 6 by an optical microscope and a scanning electron microscope.

(5) Endospores are released to the outside through a hole in a part of the cell wall, and in the case of zoospores, the release is instantly completed. Within a few hours, zoospores cease to move, lose flagella, and become spherical vegetative cells. Immobilized spores become vegetative cells after release. (6) The zoospore has a projecting tip, and four flagella are projected from the tip so as to spread in four lateral directions. When this is observed under a transmission electron microscope, it looks like FIGS. 7 and 8. Of the two pairs of flagella facing each other, one pair is arranged on a straight line, but the other pair has flagella bases which are offset counterclockwise and overlap each other.

(7) When immovable spores are grown in a released state, they may be observed to form colonies, but filaments or agglomerated multicellular bodies are not formed,
There is also no stalk-like cell morphology. (8) No sexual reproduction is observed. 2. Physiological Properties (1) Culture: Culture can be performed using both a seawater-based medium represented by ESM medium and an artificial seawater medium represented by BG-11 medium.

(2) Photosynthetic ability: It can grow photoautotrophically and produce starch as a storage polysaccharide. (3) Photosynthetic pigments: chlorophyll a, chlorophyll b,
Includes siphonaxanthin and other carotenoids. (4) Growth temperature range: 15 ° C to 30 ° C (5) Growth pH range: pH 4.5 to 10.5 The taxonomic position of this strain was determined as follows.

This strain is chlorophyll a as a photosynthetic pigment.
The green alga having b and b has the feature that it has four flagella, of which the bases of a pair of flagella facing each other are offset counterclockwise and overlap. This characteristic is a morphological characteristic specific to the group of Ulvaphyceae, a group of marine green algae. Furthermore, this strain has a unique feature of having a square scale layer on the outer periphery of the cell wall. This horny scale is a morphological feature found in Plasinophyta, which is a primitive green alga believed to have evolved into various groups of green algae. The alga of the order Pyramimonas has three layers of scales on the outer periphery of the cell, the innermost of which is a square scale, but has no cell wall. Algae that have both horny scales and cell walls are known to the genus Pseudendochlonium and the genus Monostroma of the Ulva, suggesting the evolution of the order Pyramimonadales from the Plasnophyceae, to the genus Ulva. The algae are multicellular bodies that grow in size and are sexually reproductive, and the difference with this strain is clear. The photosynthetic pigment siphonaxanthin possessed by this strain is also the Pythanophyta Py.
ramimonadales It is a characteristic pigment of the algae of the order, but it is also contained in some of the algae of the genus Ulva, such as mill.

Among the cell morphology of this strain, the characteristic of forming a large number of endospores and releasing zoospores having four flagella is that the genus Halochlorococcum of the order Codiolales or Chlorocyst
Similar to the characteristics of the is genus. However, these algae differ from this strain in that they also perform sexual reproduction, lack the horny scale layer, have higher photosynthetic pigment composition and do not contain siphonaxanthin. Also Chlorocy of the order Codiolales
The genus stis has the characteristics that zoospores submerge and grow in macroalgae and shells after adhesion, and that sexually reproduced zygotes form floating cells with a stalk-shaped appendage. The strain does not have that characteristic.

[0015] From the above, this strain is a Plasmophyceae Py
It has the characteristics of the orders of ramimonadales and Codiolales, and is considered to correspond to the most primitive new algae of the order Codiolales in the taxonomy. Therefore,
1) It has chlorophyll a, chlorophyll b, and siphonaxanthin as main photosynthetic pigments and grows photoautotrophically.
2) a unicellular spherical microalgae that has a cell wall and one layer of horny scales, and 3) is a unicellular spherical microalgae that forms zoospores or immovable spores as endospores. The pair of bases are offset counterclockwise and overlap,
5) This strain, which is characterized by not performing sexual reproduction and 6) not forming cells with multicellular bodies or stalks, is a new genus and new strain, Lepidochloris sphaerica Ikemoto et Chiha.
It was named ra gen. etsp. nov. The genus name is derived from the morphological characteristics of this strain, which means a green alga having scales. The species name derives from the shape of the vegetative cells, which are spherical.

As the medium for cultivating the alga of the present invention, an ordinary seawater medium or artificial seawater medium containing an inorganic carbon source, an inorganic nitrogen source, an inorganic ion and, if necessary, an organic nutrient source can be used. . As a method of supplying the carbon source, a method of statically culturing while shaking the culture solution in contact with air or shaking the culture solution with air or air to which 0.5 to 5% of carbon dioxide is added is appropriately used. As the nitrogen source, NH ₄ Cl, KNO ₃ , NaNO ₃ , H ₂ NCONH ₂ or the like is appropriately used. Inorganic ions can be supplied by using general seawater or artificial seawater medium, but Fe, Mo, Co, Ni, Mg
And the like can be appropriately supplemented and used. PH during culture
Is 7 to 9, preferably 6 to 9.5, and the temperature is 20 ° C to 25
It is desirable to set the temperature to 15 ° C, preferably 15 to 28 ° C.

The present invention will be described below with reference to examples. However, the technical scope of the present invention is not limited to the examples.

[0018]

[Example] A transparent cylindrical culture tank having an inner diameter of 120 mm and a height of 220 mm was irradiated from the outer periphery with a circlite fluorescent lamp, and 1500 ml of natural seawater was charged with NO ₃ -N, PO ₄ -P and a chelate metal salt. This strain, which had been fortified and aseptically isolated, was inoculated with 5 × 10 ⁸ cells. The culture is performed at a temperature of 25 ° C and an aeration rate (air containing 1% CO ₂ (v / v)) of 0.
05 vol / vol / min, pH was controlled to 8.5 with NaOH and H ₂ PO ₄ . This strain showed good growth even under a wide pH range.

After culturing for 20 days under the above conditions, 0.5 g of this strain
Was recovered. After crushing algal cells with a French press or glass bead cell crusher, use a centrifuge to select 3000
A layer rich in starch granules could be obtained in the pellet by applying a centrifugal acceleration of ~ 5000 g. The starch could be easily collected because it was aggregated in a granular form.

[0020]

EFFECTS OF THE INVENTION Since this strain has a wide growth pH range from the acidic side to the alkaline side, it is not limited to a seawater-based medium, but other microalgae, microorganisms, and It has the advantage that only this strain can be stably grown while suppressing the growth of predators.

When microalgae are photoautotrophically grown on the alkaline side, carbon dioxide serving as a carbon source thereof is dissolved in a large amount per unit volume of the culture solution.
This is advantageous when assembling the culture device. In particular,
Compared with the case of pH 7, in the case of pH 10, carbon dioxide is dissolved in a large amount in the form of hydrogen carbonate ions or carbonate ions, so that the amount of inorganic carbon in a unit volume becomes about 1200 times.

Further, the fixed carbon dioxide is once stored in the algal body in the form of starch, but in the case of this strain, the starch is present in the form of granules, which has the advantage of being easy to collect. That is, in general, when attempting to recover starch from an algal body, the starch dispersed in the algal body is extracted, but in the case of this strain, a method of separating granular aggregates is used. Can be collected.

From the characteristics as described above, the microalgae of the present invention are useful for starch production and the like.

[Brief description of drawings]

FIG. 1 is an optical micrograph of vegetative cells.

FIG. 2 is a photomicrograph of vegetative cells.

FIG. 3 is a transmission electron micrograph of one square scale layer.

FIG. 4 is a transmission electron microscopic photograph of one square scale layer.

FIG. 5 is an optical micrograph of vegetative cells interspersed with starch granules.

FIG. 6 is a transmission electron micrograph of vegetative cells with starch grains scattered.

FIG. 7: Scanning electron micrograph of flagella of migrating cells.

FIG. 8: Scanning electron micrograph of flagella of migrating cells.

Claims (2)

[Claims] 1. A novel microalga Lepidochloris sphaerica having a growth pH range of pH 4.5 to 10.5. 2. A novel microalga Lepidochloris sphaerica Ikemoto et Chiharage having a growth pH range of pH 4.5 to 10.5.
n. et sp. nov. strain.