JP2012044923A - Green alga scenedesmus, lipid producing method including culture process of green alga scenedesmus, and dried alga body of scenedesmus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide green alga Scenedesmus accumulating fatty acid-based hydrocarbons in alga body even under a culture condition rich in nutrient salt, a lipid producing method including a culture process of the Scenedesmus, and a dried alga body of the Scenedesmus.SOLUTION: There are provided: (1) the green alga Scenedesmus belonging to species pleiomorphus, genus Desmodesmus and accumulating fatty acid-based hydrocarbons in the alga body in a culture liquid having a nitrogen content of ≥40 mg/L in terms of nitrate-nitrogen content; (2) the green alga Scenedesmus comprising SUHL0708 strain of species pleiomorphus, genus Desmodesmus; (3) the lipid producing method including a culture process of the green alga Scenedesmus; (4) the production method wherein the culture process is devoid of an operation to switch from a culture liquid containing a nutrient salt to a culture liquid deficient in nutrient salt; (5) the production method wherein the lipid contains fatty acid-based hydrocarbons (16C to 18C); (6) the dried alga body obtained by drying the green alga Scenedesmus; and (7) a biomass fuel produced by using the green alga Scenedesmus as a biomass raw material.

Description

  TECHNICAL FIELD The present invention relates to a green alga squid damo belonging to the genus Desmodesmus, a method for producing lipids having a culture step of the green alga squid damo, and a dry alga body of the green alga squid damo. More specifically, a green alga squid damo belonging to the genus Desmodesmus that can accumulate fatty acid-based hydrocarbons in algal bodies even under nutrient-rich culture conditions, a method for producing lipids having a cultivation process of the green alga squid damo, and the green algae It relates to the dried alga body of squid damo.

  Technological development of biomass fuel production is being promoted on a global scale as a countermeasure against global warming or as a preparation for fossil fuel depletion. Microalgae have high biomass productivity per unit area compared to other plants, and are expected as next-generation biomass fuel production means. Here, out of many microalgae that exist in nature, it is an R & D issue to secure a strain that is excellent in growth and exhibits good characteristics as a fuel.

Many microalgae require abundant nutrients for growth. On the other hand, when various substances are accumulated in cells, nutrient salt depletion (reduction) is required. From this, in order to produce fuel substances (lipids) in microalgae, it is grown in conditions rich in nutrients at the beginning of the culture process, and switched to conditions lacking nutrients in the final stage of the culture process. A two-stage production method is widely used (see Non-Patent Document 1).
In addition, an ethanol production method is disclosed in which ethanol is released outside the algal cells by switching to dark and anaerobic conditions at the end of the microalgae culture process (see Patent Document 1).

  At the end of the culture process of the conventional method, the target substance is produced by switching to culture conditions that are deficient in nutrient salts, light, carbon dioxide, etc., and suppressing the growth of microalgae. However, in order to switch the culture conditions, it is necessary to change the culture solution or control the atmosphere of the culture tank (culture solution), which makes the culture operation complicated, prolongs the culture process, and increases production costs. There is a problem. Conventionally used microalgae has a problem that the content of the target substance that accumulates in the algal cells remains low if such a laborious culture condition change is not performed. For example, in the Seddesmus microalgae (JPCC GA24 strain) described in Non-Patent Document 1, lipid accumulation in culture conditions rich in nutrients is less than 10% of the dry algal body weight.

Japanese Patent Laid-Open No. 11-196885

Tadashi Matsunaga, Mitsufumi Matsumoto, Yoshiaki Maeda, Hiroshi Sugiyama, Reiko Sato, and Tsuyoshi Tanaka; Characterization of Marine microalga, Scenedesmus sp. Strain JPCC GA0024 toward biofuel production. Biotechnol Lett (2009) 31: 1367-1372.

  The present invention has been made in view of the above circumstances, and is a green alga squid damo that can accumulate fatty acid-based hydrocarbons in algal bodies even under culture conditions rich in nutrient salts, a method for producing lipids having a culture process of the green alga squid damo, and An object of the present invention is to provide a dry algal body of the green alga squid damo.

The inventors of the present invention have made extensive studies to solve the above problems, and have reached the following invention.
The green alga squid damo according to claim 1 is capable of accumulating fatty acid-based hydrocarbons in the algal body in a culture solution having a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen, and belongs to the genus Desmodesmus pleiomorphus. Belongs to the species.
The green alga squid damo according to claim 2 is the Desmodesmus pleiomorphus sp. SUHL0708 strain (FERM P-21960) according to claim 1.
The method for producing a lipid according to claim 3 includes the step of culturing the green alga squid damo according to claim 1 or 2.
The method for producing lipid according to claim 4 is the method according to claim 3, wherein the green alga squid is cultured in a culture solution having a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen, The method for producing lipid according to claim 3, further comprising a step of recovering the green alga squid duck.
The method for producing a lipid according to claim 5 is characterized in that in claim 3 or 4, the lipid contains a fatty acid hydrocarbon.
The method for producing lipid according to claim 6 is characterized in that, in claim 5, the fatty acid hydrocarbon includes a fatty acid hydrocarbon having 16 to 18 carbon atoms.
The dry alga body according to claim 7 is obtained by drying the green alga squid damo according to claim 1 or 2.
The biomass fuel according to claim 8 is obtained by extracting and purifying the green alga squid damo according to claim 1 or 2 as a biomass raw material.

  In the claims and specification, “lipid” refers to a crude fat composed of an organic compound. Examples of the organic compound include fatty acid hydrocarbons, phospholipids, and photosynthetic pigments. Here, the “fatty acid hydrocarbon” means an ester compound in which a free fatty acid and a fatty acid and glycerol are ester-bonded. The ester compound includes monoglycerides, diglycerides, and triglycerides. The fatty acid includes saturated fatty acid and unsaturated fatty acid.

The green alga squid duck of the present invention can accumulate fatty acid hydrocarbons in the algal body even under culture conditions rich in nitrogen content. When cultivating the green alga squid duck of the present invention and accumulating fatty acid hydrocarbons at a high concentration in the algae, it is not necessary to switch from a nitrogen-rich culture solution to a nitrogen-deficient culture solution in the culture process.
According to the method for producing lipids of the present invention, a green alga squid duck that accumulates high-concentration fatty acid hydrocarbons can be obtained by a simpler culturing process, and lipids containing the fatty acid hydrocarbons can be produced. The lipid can be used as a fuel or a raw material in the food / chemical industry.
Since the dry alga body of the present invention contains fatty acid hydrocarbons, it is flammable and can be used as a fuel.

It is an optical micrograph of SUHL0708 strain. It is a scanning electron micrograph of SUHL0708 strain (winter type cell), (a) is a double cell, (b) is a quadruple cell. It is a scanning electron micrograph of SUHL0708 strain (summer type cell), (a) is a double cell, (b) is a quadruple cell. It is (a) optical microscope photograph and (b) G excitation fluorescence photograph of SUHL0708 strain (winter type cell) which carried out Nile red dyeing | staining process. It is a UVA-visible region absorption curve of a cell fat-soluble fraction of SUHL0708 strain, (a) is an absorption spectrum of a carotenoid-based photosynthetic pigment, and (b) is an absorption spectrum of a chlorophyll-based photosynthetic pigment. It is a growth curve of SUHL0708 strain. It is a graph which shows the growth of SUHL0708 stock | strain, the accumulation amount of fatty-acid type hydrocarbon, and the nutrient salt density | concentration in a culture solution.

In the present specification, nutrient salts refer to salts containing essential nutrients essential for the growth of the green alga squid damo. As the essential nutrients, a nutrient salt containing nitrogen and a nutrient salt containing phosphorus are particularly important for the growth of the green alga squid duck. Iron, manganese, magnesium, various vitamins, etc. are also essential nutrients.
Examples of the nutrient salt containing nitrogen include a salt containing nitrate ion (NO ₃ ⁻ ), a salt containing nitrite ion (NO ₂ ⁻ ), and a salt containing ammonium ion (NH 4 ⁺ ).
Examples of the nutrient salt containing phosphorus include a salt containing phosphate ion (PO ₄ ³⁻ ).
Nitrate nitrogen means nitrogen present in the form of (NO ₃ ⁻ ) nitric acid. Therefore, the amount of nitrate nitrogen of 40 mg / L or more means that the nitrate ion concentration is 2.9 mmol / L or more.

The present invention will be described in detail below.
<Green alga Idadamo belonging to the species of Desmodesmus pleiomorphus>
The green alga squid damo belonging to the genus Desmodesmus pleiomorphus in the present invention (hereinafter, the green alga squid duck of the present invention) has a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen. It can accumulate hydrocarbons in the algae.

  The green alga squid duck of the present invention is obtained by, for example, cultivating the green algae squid damo in a sample collected from nature in a culture solution having a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen and rich in nutrient salts. It can be obtained by selecting a strain having a large amount of lipid in the obtained culture and establishing a clone culture strain. Among them, it is preferable to use a green alga squid duck collected by installing a culture tank of an upper open type (no lid type) in the field, adding a culture medium, agitating with aeration, and naturally collecting seedlings. By such an operation, a strain that can be successfully cultured under non-aseptic conditions can be selected.

  The green alga squid damo of the present invention is usually cultured under conditions where the green alga squid duck is cultured, for example, in a culture solution containing the necessary nutrients (pH is in the range of 4 to 11) and the culture temperature is in the range of 4 to 40 ° C. Can be cultured. Especially, it can culture | cultivate favorably by culture | cultivating in the culture solution whose nitrogen content is 40 mg / L or more by the amount of nitrate nitrogen.

  In particular, the green alga squid damo of the present invention has an excellent feature that fatty acid hydrocarbons can be accumulated in the algal body in a state of good growth. In fact, when cultured in a culture solution having a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen content, the green alga squid duck of the present invention does not undergo a treatment to deplete nitrogen from the culture solution, but does not carry out the treatment. The lipid content in is 50% by weight or more.

  The green alga Ikadamo is abbreviated as Desmodesmus pleiomorphus sp. SUHL0708 (FERM P-21960) (hereinafter referred to as SUHL0708) from the viewpoint that the content of fatty acid hydrocarbons in the alga body is high and can be easily cultured. ) Is more preferable.

  The inventors isolated and identified the SUHL0708 strain from a group of microorganisms floating in the atmosphere of the Yoshino River basin. This strain is a new strain of the green alga Ikadamo in the fresh water belonging to the species Pleiomorphus spp. The method for isolating and identifying SUHL0708 strain will be described below.

(Method for isolating SUHL0708 strain)
A 0.1% by volume solution of KW21 (Daiichi Seimyo Co., Ltd.) (nitrogen content is 40 mg / L or more in terms of nitrate nitrogen) is used as the culture solution, and an open top (no lid type) culture tank is installed outdoors. Then, the culture solution was added and aerated and agitated to recover the grown microalgae. From the collected microalgae, those having excellent both outdoor growth ability and lipid productivity were selected, and a clone culture strain was established. Furthermore, mass cultivation was performed by enlarging the culture container every passage. Specifically, starting from test tube culture, a large-scale cultivation test was carried out by sequentially increasing the culture vessel from a 100 L volume, a 500 L volume, a 1000 L volume, and a 20 t volume to a 100 t volume circular water tank. The practicality of was investigated.

(Morphological properties of SUHL0708 strain)
FIG. 1 is an optical micrograph of SUHL0708 strain. It is a quadruple cell in which four cell bodies (algae) are connected. One cell body has a major axis of about 14 μm and a minor axis of about 8 μm, and the cell body is well enlarged. Observed when cultured under relatively strong light irradiation conditions such as natural light in fine weather.
FIG. 2 is a scanning electron micrograph of SUHL0708 strain (winter cell), where (a) is a double cell and (b) is a quadruple cell. Compared to summer-type cells, the volume of the cell body is small, the length of the spines is short, and the number of spines is small. It is a form observed when cultured under relatively weak light irradiation conditions such as artificial light or natural light during cloudy weather in winter.
FIG. 3 is a scanning electron micrograph of SUHL0708 strain (summer type cell), where (a) is a double cell and (b) is a quadruple cell. Compared to winter cells, the volume of the cell body is large, the length of the spines is long, and the number of spines is large. It is a form observed when cultured under relatively strong light irradiation conditions such as natural light in fine weather.

(Biochemical properties of SUHL0708 strain)
When SUHL0708 strain in the growth phase is stained with Nile red and observed with a fluorescence microscope, it is confirmed that lipid (crude fat) is accumulated in the algal cells (see FIG. 4).
The lipid contains a fatty acid hydrocarbon such as triglyceride having a fatty acid having 16 to 18 carbon atoms and a fatty acid (acyl group) having 16 to 18 carbon atoms in the molecule.

(Photosynthetic dye of SUHL0708 strain)
A portion (10 ml) of the culture solution is centrifuged at 3000 rpm for 5 minutes to recover algal cells, and the yellow substance is extracted with dichloromethane: methanol (mixing ratio 2: 1) and the green pigment component is extracted with ethyl alcohol at 800 nm. Absorption curves in the range of 300 nm to 300 nm were measured. The result is shown in FIG.
The cell wall of the green alga Idadamo of the present invention is different from the microalgae of the genus Senedesmus, and it is carotenoid yellow pigment that is mainly extracted with dichloromethane: methanol (mixing ratio 2: 1) (FIG. 5 (a )). The green pigment chlorophyll a was extracted with alcohol (FIG. 5B). In addition, the green pigment | dye component once melt | dissolved in alcohol showed the property melt | dissolved in hexane and xylene after that.

(Physiological properties of SUHL0708 strain)
It can grow on CHU-13 * 2 in urea-added Gillard medium or complete inorganic medium. In particular, a 0.1% by volume solution of KW21 (manufactured by Daiichi Seimyo Co., Ltd.), which is a commercially available algal culture solution, is suitable.
One liter of the KW21 medium prepared to 0.1% by volume contains abundant nutrients necessary for the growth of the green alga squid damo. Specifically, in 1 L of the KW21 medium, nitrogen content is 49 mg as N, and phosphoric acid is P as 4 mg. The KW21 medium is sufficiently rich in complex vitamins (various vitamins) such as boron, manganese, iron, cobalt, zinc, EDTA, complex amino acids (various amino acids), B1, B12, and biotin.

  The SUHL0708 strain can grow if the pH of the culture solution is in the range of 4-11. Moreover, it can proliferate if culture | cultivation temperature is the range of 4-40 degreeC.

For example, using a KW21 culture solution (0.1% by volume) sufficiently containing nutrient salts at a temperature of 30 ° C. or 35 ° C. by irradiating 160 μmol / m ² / s light with a white fluorescent lamp. When cultured according to a conventional method, the growth curve shown in FIG. 6 was obtained.
Furthermore, air (mixed with 5% by volume of CO ₂ gas) was aerated and stirred at a temperature of 15 to 30 ° C. by irradiating light of 2000 to 3000 μmol / m ² / s, and sufficient nutrient salts were obtained. When cultured according to a conventional method using KW21 culture solution (0.1% by volume), about 50% by weight of lipid per unit weight of dry algal bodies is accumulated in the algae of SUHL0708 strain in the growth phase. It was.

The quantification of the lipid in the dry alga body was calculated by extracting the lipid from the dry alga body and performing ¹ H-NMR measurement. Specifically, lipids were extracted by irradiating microwaves of dried algal bodies in the presence of methyl alcohol. How this extract was dissolved in a small amount of deuterated chloroform, based on the amount of hydrogen chloroform contained in a trace amount in the polymerization chloroform _{(CDCL 3) (CHCL 3)} , to the ¹ H-NMR measurement of hydrogen nuclei hydrocarbon chain I went there.

(Genetic properties of SUHL0708 strain)
DNA was extracted from SUHL0708 by a conventionally known method, and the base sequence analysis of the ITS-2 region of 18S rDNA was performed. The obtained base sequence is shown in SEQ ID NO: 1 in the sequence listing.
As a result of collation with the database, the base sequence of the known green alga Ikadamo belonging to the genus Desmodesmus pleiomorphus was found.

The database is described in the following document A.
Reference A; Hegewald, E., Schumidt, A., Braband, A. & Tsarenko, P. (2005): Revision of the Desmodesmus (Sphaeropleales, Scenedesmaceae) species with lateral spines. 2. The multi-spined to spineless taxa. Arch.Hydrobiol./Algolog. Stud. 116: 1-38.

From the morphological, physiological and biochemical properties described above, the composition of the photosynthetic pigment, and the genetic properties, the SUHL0708 strain was presumed to be an algae belonging to the genus Desmodesmus of the green alga class.
Furthermore, the SUHL0708 strain of the present invention is known in that it can contain a high concentration of oils and fats containing the fatty acid hydrocarbons in the algae in a culture solution having a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen. Since it is different from the green alga Ikadamo, it was judged to be a new strain belonging to the genus Desmodesmus pleiomorphus, and was named Desmodesmus pleiomorphus sp. SUHL0708.

  The SUHL0708 strain was deposited at the Patent Microorganism Depositary, National Institute of Advanced Industrial Science and Technology under the accession number FERM P-21960 by the applicant (Reception date: April 30, 2010).

<Method for producing lipid>
The method for producing lipids according to the present invention is characterized in that the green alga squid damo according to the present invention is cultured and lipids are accumulated in the algal bodies. Specifically, it has the culture | cultivation process of the green alga squid duck concerning the above-mentioned this invention.
The main steps in the method for producing lipids of the present invention include the step of cultivating the green alga squid damo, the step of collecting the green alga squid duck grown in the culture step from the culture solution, and the lipid from the collected algal body of the green alga squid damo The process of extracting is mentioned.

(Culture process)
As the green alga Ikadamo used in the method for producing lipids of the present invention, SUHL0708 strain is preferable from the viewpoint of high lipid content in algal cells and easy culturing.

  As the method for culturing the green alga squid damo, a known method capable of culturing the green alga squid damo belonging to the genus Desmodesmus pleiomorphus can be applied. Moreover, mass cultivation can be performed by enlarging a culture container for every passage. At the time of culture, it is preferable to perform aeration culture under light irradiation while stirring to such an extent that algal bodies do not precipitate.

  The culture solution is not particularly limited as long as it is a liquid medium capable of growing the green alga squid damo, and a known one can be used. For example, urea-added Gillard medium, complete inorganic medium CHU-13 * 2, and KW21 can be used. Among these, a 0.1% by volume solution of KW21 is preferable.

Light irradiation conditions may be appropriately adjusted depending on the algal body concentration in the culture solution and the depth of the culture tank, and natural light or artificial light of 10 to 4000 μmol / m ² / s is preferable, and 100 to 3000 μmol / m ² / s. Natural light or artificial light is more preferable, and natural light or artificial light of 500 to 3000 μmol / m ² / s is further preferable. If it is in the above range, the green alga Ikadamo can perform photosynthesis and grow smoothly.

  The culture temperature may be a known culture temperature suitable for the growth of the green alga Ikadamo. When SUHL0708 strain is used, it can be grown usually at 4 to 40 ° C, preferably 10 to 40 ° C, more preferably 15 to 35 ° C, and further preferably 20 to 35 ° C.

  The culture period is not particularly limited. The culture can be continued as long as the culture conditions under which the growth of the green alga Ikadamo is not inhibited can be maintained. When the SUHL0708 strain is used, it can be collected in a culture period of usually about 3 to 60 days after inoculating the culture solution. The culture period is preferably 3 to 30 days, more preferably 3 to 14 days, and further preferably 3 to 7 days.

The algal body density (cell density) in the culture solution is preferably 1 × 10 ⁵ to 10 × 10 ⁷ cells / ml, more preferably 1 × 10 ^{6 to} 5 × 10 ⁷ cells / ml, and 2 × 10 ⁶ to 1 × 10 ⁷ pieces / ml is more preferable.
Within the above range, the growth speed of the green alga squid damo can be increased, and the lipid content in the alga can be increased.

The green alga squid damo of the present invention contains a high concentration of lipid in the growth phase. For this reason, a lipid can be obtained by collect | recovering the green algae Ikadamo in a growth phase.
From the viewpoint of making the best use of such advantages, it is preferable that the method for producing a lipid of the present invention does not perform an operation of switching from a nutrient salt-containing culture solution to a nutrient-deficient culture solution in the culture step. That is, the green alga squid duck can be directly recovered without performing an operation of switching from a nutrient-rich culture solution such as a nitrogen-containing compound to a nutrient-deficient culture solution.
For example, in the method for producing lipids of the present invention, the culture step and the recovery step can be continuously operated in parallel by always keeping the culture solution rich in nutrient salts.

  In the lipid production method of the present invention, it is preferable to recover the green alga squid duck in the growth phase. When the green alga squid duck is in a growth phase where it grows smoothly, the number of cells (number of alga bodies) usually doubles in the culture period of one day. The green alga Idadamo in this growth phase contains 15 to 50% by weight of lipid per unit weight of the dried alga body, depending on the culture conditions.

  As described above, as long as the inventors know, there is no algae containing lipids at a high concentration in the growth phase other than the green alga Ikadamo of the present invention. In conventionally known microalgae, the lipid content in the growth phase is less than 10% by weight (see Non-Patent Document 1).

The green alga squid duck of the present invention is preferably cultured in a culture solution having a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen. This is because the lipid content in the algal body of the green alga squid damo can be increased.
From the viewpoint of increasing the lipid content in the green algae squid duck while steadily growing the green algae squid damo, the nitrogen content of the culture solution is more preferably 45 mg / L or more in terms of nitrate nitrogen, 48 mg / L or more is more preferable.
Here, the nitrogen content is an amount that depends on the number of moles of nitrogen in the culture solution, and does not depend on the type of nitrogen-containing compound in the culture solution.
The upper limit of the nitrogen content of the culture solution is not particularly limited as long as the green alga squid duck grows smoothly, but it may usually be 200 mg / L or less.

  Examples of the culture solution rich in nutrient salts in which the green alga Ikadamo grows smoothly include, for example, nitrogen-containing nutrient salts of 100 μmol / L to 2000 μmol / L (about 10 mg / L to 200 mg / L in terms of potassium nitrate, A nutrient salt containing phosphorus of 10 μmol / L or more and 200 μmol / L or less (about 1.6 mg / L or more and 32 mg / L or less in terms of trisodium phosphate) can be used.

  As a method for recovering the cultured green alga squid damo, for example, by adding a sulfate band (aluminum sulfate) or alum (potassium aluminum sulfate) to the culture solution, or by culturing for a relatively long period of time, the algal bodies are flocked (aggregated). A method of coagulating and collecting so as to form a lump), a method of precipitating and collecting alga bodies by centrifuging the culture solution, a method of collecting and recovering algal bodies through a filter and the like It is done.

As a method for extracting lipid contained in the algal body of the green alga squid duck, a conventional method for extracting lipid from known microalgae can be applied. You may further refine | purify the extracted lipid according to a use.
As a suitable method for extracting lipids from the green alga squid damo, for example, a dried algal powder obtained by freeze-drying the algal bodies is packed in a pressurized column, and methyl alcohol becomes supercritical at 240 ° C., 8 MPa or more. A method of simultaneously performing extraction and methyl esterification under the reaction conditions described above. By this method, it is possible to produce a high-energy fatty acid hydrocarbon that can be used as an alternative liquid fuel for petroleum. In the extraction of methyl alcohol from the lipid, an effect of efficiently promoting methyl esterification can be obtained also by irradiating a microwave of about 600 W under heat and pressure (for example, 8 MPa, 150 ° C.).

The lipid (crude fat) obtained by the method for producing a lipid of the present invention contains a fatty acid hydrocarbon. The fatty acid hydrocarbon may contain an ester compound such as a triglyceride having a fatty acid having 16 to 18 carbon atoms and / or a fatty acid having 16 to 18 carbon atoms (acyl group) as a main component.
The fatty acid hydrocarbon can be methylated by adding methanol at high temperature and pressure.
Moreover, the said linear unsaturated fatty acid can be induced | guided | derived to a high energy hydrocarbon fuel by the conversion to the saturated hydrocarbon by hydrogenation.

Since the lipid obtained by the above-mentioned method is flammable, it may be used as a fuel as it is, or after purification, it can be used as a fuel or a raw material for the food / chemical industry.
Further, the collected green alga squid damo can be processed into a dried alga body dried by a conventional method such as air drying or freeze drying. The dry alga body is combustible because it contains the fatty acid hydrocarbon, and can be used as it is as a fuel for combustion.

<Dried algae>
The dry alga body in the present invention is obtained by drying the alga body of the green alga Ikadamo belonging to the genus Desmodes pleiomorphus that can accumulate fatty acid hydrocarbons in the algal body.
As the green alga squid duck, SUHL0708 strain having a high lipid content in the alga is preferable.
The method for drying the green alga squid duck is not particularly limited as long as it is a method capable of removing moisture in the algal bodies, and includes a method of air drying in a dry atmosphere and a method of freeze drying.
The obtained dry algal bodies are flammable because they contain fatty acid hydrocarbons, and can be used as fuel. In the case of burning in a flame, a freshly dried alga body that has been drained may be put into the flame. In this case, the algal bodies become dry algal bodies and burn in the flame.

<Biomass fuel>
The green alga Ikadamo according to the present invention can be used as a biomass fuel as a dry powder or as a lipid obtained by extraction and purification from the algal body of the green alga Ikadamo.

  EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to a following example.

The SUHL0708 strain was cultured under the following conditions. The SUHL0708 strain grew smoothly during the 16-day culture period. During the culture period, alga bodies were collected from a part of the culture solution, and the number of cells (cells / ml), dry alga body weight (g / L), and lipid (g / L) were measured.
The result is shown in FIG.

-Type of culture solution: KW21 aqueous solution (0.1% by volume)
・ Temperature of culture solution: 25 ℃
-Aeration and agitation of the culture solution: Gently agitate the air (mixed with 5% by volume of CO ₂ gas) and gently so that the algal bodies do not settle.-Light irradiation condition: Natural light (sunshine duration: 12 hours, intensity range) : 500~3000μmol ^{/ m} 2 ^/ s, average intensity: 1000μmol ^/ m 2 ^/ s)
・ Culture period: 16 days after seeding the seed alga

The lipid quantification method is as follows.
Microwave extraction was used. First, lipids were extracted from algal bodies by microwave irradiation in the presence of methyl alcohol. This extract was dissolved in a small amount of deuterated chloroform, and the method was performed by measuring the hydrogen nuclei of the hydrocarbon chain by NMR.

Algae collected on the 4th day after the start of culture contained 50% by weight or more of lipid per unit weight of the dried alga bodies (see FIG. 7). In addition, the algal bodies collected on the 16th day after the start of the culture contained about 18% by weight of lipid per unit weight of the dried algal bodies (see FIG. 7).
The average lipid content during the culture period was about 28% by weight per unit weight of the dried alga bodies.

Changes in the concentration of nitrate ions (NO ₃ ⁻ ) and phosphate ions (PO ₄ ³⁻ ) contained in the culture solution were measured using a pack test (Kyoritsu Riken).
The nitrate ion concentration in the culture period of 16 days (0 to 384 hours) is shown in FIG. Moreover, in the same culture period, phosphate ions were contained at 10 μmol / L or more. That is, the culture solution during the culture period contained abundant nutrient salts.

  An optical microscope image of the SUHL0708 strain in the growth phase recovered from a part of the culture solution is shown in FIG. 1, and a scanning electron microscope image is shown in FIG. Further, FIG. 4 shows a fluorescence microscope image obtained by staining the algal bodies with Nile red by a conventional method.

  From the above results, it is clear that lipids can be produced by culturing SUHL0708 strain in a culture medium rich in nutrient salts and recovering algal bodies in the growth phase.

  The green alga Ikadamo according to the present invention can be used for biofuel production because lipids can be accumulated at a high concentration in the algae during the growth phase. In addition, carbon dioxide in the atmosphere can be absorbed by the green alga Ikadamo, which can contribute to the prevention of global warming.

FERM P-21960

Claims (8)

  A green alga squid duck belonging to the genus Desmodesmus pleiomorphus, which can accumulate fatty acid hydrocarbons in algal cells in a culture solution having a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen.   Desmodesmus genus pleiomorphus sp. SUHL0708 strain (FERM P-21960), a green alga squid duck.   The manufacturing method of the lipid which has a culture | cultivation process of the green alga Ikadamo of Claim 1 or 2.   4. The method according to claim 3, further comprising the steps of culturing the green alga squid duck in a culture solution having a nitrogen content of 40 mg / L or more in terms of nitrate nitrogen, and recovering the green alga squid damo from the culture solution. A method for producing the described lipid.   The method for producing a lipid according to claim 3 or 4, wherein the lipid contains a fatty acid-based hydrocarbon.   The method for producing lipid according to claim 5, wherein the fatty acid hydrocarbon includes a fatty acid hydrocarbon having 16 to 18 carbon atoms.   A dry alga body obtained by drying the green alga squid damo according to claim 1 or 2.   A biomass fuel obtained by extracting and purifying the green alga Ikadamo according to claim 1 or 2 as a biomass raw material.