JP2015008676A - Microalga culture method and water drainage method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microalga culture method which enables efficient growth of microalgae.SOLUTION: This invention provides a microalga culture method characterized in that microalgae are cultured in a predetermined liquid.

Description

  The present invention relates to a method for culturing microalgae and a method for treating wastewater.

Conventionally, it has been practiced to grow microalgae and store valuable materials such as lipids, proteins, and vitamins as raw materials for fuel, feed, health food, etc. in the cells of the microalgae. Is used for fuel and food.
The growth of the microalgae is also used for wastewater treatment such as purification of sewage treated water (see Patent Document 1) and exhaust gas treatment for the purpose of carbon dioxide regeneration (see Patent Document 2).

Known culture methods for growing microalgae include autotrophic culture, heterotrophic culture under dark conditions, and photoheterotrophic culture. Conventionally, heterotrophic culture under dark conditions has been known. A method for efficiently carrying out light heterotrophic culture is not well established.
If the microalgae do not grow efficiently, the amount of valuables stored in the cell is not always sufficient, which may make it difficult to effectively use the valuables.
Moreover, if the microalgae do not grow efficiently, the consumption of the substance to be treated by the microalgae may not be sufficient, and there is a possibility that wastewater treatment and exhaust gas treatment will not be performed efficiently.

Japanese Patent Laid-Open No. 05-301097 JP 2010-022331 A

In view of the above-described problems and the like, it is a first object of the present invention to provide a method for culturing microalgae that can efficiently grow microalgae.
Moreover, this invention makes it a 2nd subject to provide the efficient waste water treatment using microalgae in view of said problem.

  The present inventor has intensively studied to solve the above-mentioned problems. As a result, the organic carbon source is provided together with the components of the fermentation broth obtained from the bioethanol production process, and the microalgae are subjected to heterotrophic culture or light dependent under dark conditions. By performing nutrient culture, the microalgae are efficiently proliferated, and when the distillation residue of the fermentation broth is drained, the components contained in the distillation residue are efficiently consumed by the microalgae. Has been found to be efficiently performed, and the present invention has been completed.

  That is, the method for cultivating microalgae according to the present invention for solving the above-described problems is a liquid containing at least a residual liquid after removing ethanol from a fermentation liquid obtained by subjecting biomass to alcohol fermentation in a bioethanol production process. It is characterized by culturing microalgae and supplying an organic carbon source to the microalgae to perform heterotrophic culture or light heterotrophic culture under dark conditions.

  In the method for culturing microalgae having the above-described configuration, the microalgae can be efficiently grown because the microalgae are cultured in the liquid containing the components of the fermentation broth.

  In the method for culturing microalgae according to the present invention, when solid-liquid separation is performed before ethanol is removed from the fermentation broth, it is preferable to supply the generated solid content.

  In the method for culturing microalgae according to the present invention, the culture is preferably heterotrophic culture under dark conditions.

  In the method for culturing microalgae according to the present invention, it is preferable to carry out the culturing in the liquid containing the residual liquid in a volume of 1/40 to 1/2.

  Furthermore, in the method for culturing microalgae according to the present invention, it is preferable to use sugar obtained from biomass as the carbon source.

  Moreover, the wastewater treatment method according to the present invention for solving the above problems is a wastewater treatment method for removing organic substances contained in wastewater, wherein the wastewater is a stock solution for obtaining a stock solution containing sugar from biomass. Step, a fermentation step for obtaining a fermentation broth containing ethanol by subjecting the stock solution to alcohol fermentation, distilling the fermentation broth, a condensate having a higher ethanol concentration than the fermentation broth, and a distillation residue having a lower ethanol concentration than the fermentation broth A distillation step of obtaining a liquid, and the distillation residue in the bioethanol production process in which the microalgae are cultured in the liquid containing the distillation residue and an organic carbon source is supplied to the microalgae. It is characterized in that the organic matter contained in the distillation residue is consumed by the microalgae by performing heterotrophic culture or light heterotrophic culture under dark conditions.

  Furthermore, in the wastewater treatment method according to the present invention, when the solid-liquid separation step is performed after the fermentation step and before the distillation step, the solid content obtained in the solid-liquid separation step is supplied and cultured. Is preferred.

The method for culturing microalgae of the present invention has an effect that microalgae can be efficiently propagated.
Moreover, in this invention, since the component contained in waste_water | drain can be efficiently consumed by microalgae, waste water treatment can be implemented efficiently.

Schematic showing the outline | summary of the apparatus used in the cultivation method of a micro algae, and the outline | summary of another apparatus. The graph which shows one result ((a) microalga content rate change, (b) TOC density | concentration change of a culture solution) of the culture experiment of the microalgae in Experimental example 1. FIG. The graph which shows the other culture experiment result ((a) microalga content rate change, (b) TOC density | concentration change of a culture solution) in the experiment example 1. FIG. The graph which shows the other culture experiment result ((a) microalga content rate change, (b) TOC density | concentration change of a culture solution) in the experiment example 1. FIG. The graph which shows the other culture experiment result ((a) microalga content rate change, (b) TOC density | concentration change of a culture solution) in the experiment example 1. FIG. The graph which shows the culture experiment result (microalga content rate change) of the micro algae in Experimental example 2. FIG.

  Hereinafter, an embodiment of the method for culturing microalgae according to the present invention will be described.

The method for culturing microalgae according to the present embodiment includes culturing microalgae in a liquid containing at least a residual liquid after removing ethanol from a fermentation broth obtained by alcohol fermentation of biomass in a bioethanol production process, and the microalgae. Heterotrophic culture or light heterotrophic culture under dark conditions by supplying an organic carbon source.
More specifically, the method for culturing microalgae of the present embodiment uses a liquid containing a distillation residue after distillation of a fermentation liquid obtained by subjecting biomass to alcohol fermentation in a bioethanol production facility, as a culture liquid. A sugar obtained from biomass is used as an organic carbon source to be contained in the culture solution.

  The microalgae are living organisms that inhabit while floating in water. Further, unlike kelp and seaweed, the microalgae are usually unicellular and are microalgae having a size of several micrometers to several tens of micrometers.

Examples of the microalgae include organisms belonging to the genus Euglena , organisms belonging to the genus Chlorella , organisms belonging to the genus Aurantiochytrium , organisms belonging to the genus Auxenochlorella, botuliococcus Organisms belonging to the genus ( Botryococcus ), organisms belonging to the genus Nannochloris , organisms belonging to the genus Nannochloropsis , organisms belonging to the genus Neochloris , organisms belonging to the genus Pseudochoricystis , Scenedesmus (Scenedesmus) belonging to the genus organism Schizochytrium (Schizochytorium) at least one member selected from the group consisting of organism belonging to the genus are preferred.

Organisms belonging to the Euglena (Euglena) genus, for example, Euglena gracilis, Euglena longa, Euglena caudata, Euglena oxyuris, Euglena tripteris, Euglena proxima, Euglena viridis, Euglena sociabilis, Euglena ehrenbergii, Euglena deses, Euglena pisciformis, Euglena spirogyra, Euglena acus , Euglena geniculata , Euglena intermedia , Euglena mutabilis , Euglena sanguinea , Euglena stellata , Euglena terricola , Euglena klebsi , Euglena rubra , or Euglena cyclopicola .
As the Euglena gracilis, e.g., Euglena gracilis NIES-48, Euglena gracilis EOD-1, and the like (storage lines in National Institute for Environmental Studies microorganism strain preservation facility to be described later).

Examples of the organism belonging to the genus Chlorella include Chlorella vulgaris , Chlorella pyrenoidosa , or Chlorella sorociniana .
As the Chlorella sorociniana, for example, and the like (storage strains in later to Independent Administrative Institution National Institute for Environmental Studies microorganism strain preservation facility) Chlorella sorociniana NIES-2169.

Organisms belonging to the Orchidee Imperiale Seno Chlorella (Auxenochlorella) genus, for example, like Auxenochlorella protothecoides.

Examples of the organism belonging to the genus Botryococcus include Botryococcus braunii .

Organisms belonging to the Nan'nokurorisu (Nannochloris) genus, for example, Nannochloris Bacillaris, like Nannochloris normandinae.

Organisms belonging to the Nannochloropsis (Nannochloropsis) genus, for example, like Nannochloropsis oculata.

Organisms belonging to the Neokurorisu (Neochloris) genus, e.g., Neochloris aquatica, Neochloris cohaerens, Neochloris conjuncta, Neochloris gelatinosa, Neochloris pseudostigmata, Neochloris pseudostigmatica, Neochloris pyrenoidosa, Neochloris terrestris, Neochloris texensis, Neochloris vigensis, Neochloris wimmeri, Neochloris oleoabundans etc. Is mentioned.

Examples of the organism belonging to the genus Pseudochoricystis include Pseudochoricystis ellipsoidea .

Organisms belonging to the Scenedesmus (Scenedesmus) genus, for example, Scenedesmus ovaltermus, Scenedesmus disciformis, Scenedesmus acumunatus, like Scenedesmus dimorphus.

Organisms belonging to the O-lunch Oki thorium (Aurantiochytrium) genus, for example, Aurantiochytrium limacinum, or the like Aurantiochytrium mangrovei.

Examples of the organism belonging to the genus Schizochytorium include Schizochytrium aggregatum .

  The above-mentioned microalgae can be obtained from the National Institute for Environmental Studies (NIES), Patent Evaluation Microorganism Deposit Center (Zip 292-0818, Kisarazu City, Chiba Prefecture, 2-5-8), National Institute for Environmental Studies Zip code 305-8506 16-2 Onagawa, Tsukuba, Ibaraki) or The Culture Collection of Algae at the University of Texas at Austin, USA (http://web.biosci.utexas.edu/utex/default.aspx) It is easily obtained from

As the microalgae, it is possible to produce a large amount of wax ester as a raw material of biodiesel, it contains a lot of valuable substances such as vitamins, carotenoids, highly nutritious proteins, paramylon, and it is easy to culture in large quantities. In this respect, organisms belonging to the genus Euglena are preferred.
In addition, the microalgae can produce a large amount of triglyceride as a raw material for biodiesel, contain a lot of valuable materials such as dietary fiber, vitamins, carotenoids, proteins, linoleic acid, linolenic acid, Organisms belonging to the genus Chlorella are preferred because they can be easily cultured.

Examples of the biomass used as the starting material for the distillation residue and the sugar include plants, processed products thereof, and substances derived from plants. Examples of the plants include land plants and underwater plants. .
The biomass is classified into carbohydrate biomass, starch biomass, and cellulose biomass depending on the component, but the biomass to be used is not particularly limited in the present embodiment.
In addition, the biomass in this embodiment does not contain the micro algae and the thing derived from a micro algae substantially.

  Examples of the sugar biomass include sugar cane, sugar beet, molasses, and molasses.

  Examples of the starch-based biomass include corn, corn, potato, sweet potato, rice, wheat, and cassava.

As said cellulose biomass, the chip | tip which consists of all or one part of trees, such as a thinned timber and the branch cut | disconnected for growth of a trunk, sawdust, etc. are mentioned, for example.
Examples of the cellulosic biomass include wheat straw, rice straw, bagasse, kenaf, hemp, cotton, weed and the like.
The cellulosic biomass also includes so-called energy plants such as Eliansus and Napiergrass.
Also, pulp products such as waste paper can be used as the cellulose biomass.

The method for culturing the microalgae using the biomass as described above will be described in more detail with reference to the drawings.
In the following, description will be made while exemplifying an embodiment in which the microalgae cultivation facility is used as a wastewater treatment facility discharged from a bioethanol production facility.

First, the apparatus used for the algae culture method of this embodiment will be described.
FIG. 1 is a schematic view showing an outline of devices used in the method for culturing microalgae and an outline of other devices, and shows a main configuration of the bioethanol production facility and the microalgae culture facility. It is a thing.
In the present embodiment, as shown in the figure, a bioethanol production facility 10 is attached to the microalgae culture facility 20, and the microalgae culture facility 20 in which the culture method of the present embodiment is implemented is the bioalgae. It is used for wastewater treatment of the ethanol production facility 10.
In addition, the code | symbol A of FIG. 1 represents the biomass supplied to the bioethanol manufacturing equipment 10, and the code | symbol B represents the bioethanol obtained with the bioethanol manufacturing equipment 10. FIG.
Moreover, the code | symbol C of FIG. 1 represents the water supplied to the said micro algae culture equipment 20, and the code | symbol D represents the valuables obtained by culture | cultivating a micro algae.
Below, the case where the said valuables are algae biomass is demonstrated to an example.
In addition, the code | symbol E of FIG. 1 represents the various components supplied to the micro algae culture equipment 20 as needed, and the code | symbol F represents the treated water discharged | emitted from the micro algae culture equipment 20. FIG.

The bioethanol production facility 10 has the following (11) to (14) as main components.
(11) A stock solution production apparatus in which the biomass A is supplied and a stock solution containing sugar is produced from the biomass.
(12) A fermentation apparatus in which the stock solution is supplied from the stock solution production device 11, and the sugar contained in the stock solution is subjected to alcohol fermentation to produce a fermentation solution containing ethanol.
(13) A distillation apparatus in which the fermentation broth is supplied from the fermentation apparatus 12 and is distilled into a condensate having a higher ethanol concentration than the fermentation liquid and a distillation residue having a lower ethanol concentration than the fermentation liquid. .
(14) The condensate is supplied from the distillation apparatus 13, impurities such as water contained in the condensate are removed, and the condensate is separated into a separation liquid containing the impurities and high-purity ethanol. Purification equipment.

On the other hand, the said micro algae culture equipment 20 has the following (21)-(25) as main structures.
(21) The evaporation residual solution is supplied from the distillation device 13 and the stock solution containing sugar is supplied from the stock solution preparation device 11, and these are diluted to an appropriate concentration with water supplied from outside the system, and An adjustment tank in which a culture solution of microalgae is prepared.
(22) A sterilization apparatus for sterilizing the adjusted culture solution in the adjustment tank 21.
(23) A culture apparatus in which the microalgae are accommodated, and the microalgae are heterotrophic or light heterotrophic in a dark condition by a culture solution supplied from the adjustment tank 22 via the sterilizer 22.
(24) The algae-containing liquid containing microalgae is supplied from the culture device 23, and the algae-containing liquid is solid-liquid separated to concentrate the microalgae and is more organic than the culture liquid produced in the preparation tank 21. A concentrator for discharging the treated water F having a low carbon (TOC) concentration.
(25) An extraction device in which lipids, which are valuable resources, are extracted from microalgae contained in the concentrate concentrated by the concentration device 24 and liquid fuel E mainly composed of the lipids is discharged.

As described above, the microalgae culture facility 20 in the present embodiment is used for the wastewater treatment of the bioethanol production facility 10.
And in the bioethanol manufacturing equipment 10, the following processes are implemented in the process in which bioethanol is manufactured.
(1a) A stock solution production step for obtaining a stock solution containing sugar from biomass.
(1b) A fermentation process for obtaining a fermentation broth containing ethanol by subjecting the sugar contained in the stock solution to alcohol fermentation.
(1c) A distillation step of distilling the fermentation broth to obtain a condensate having a higher ethanol concentration than the fermentation broth and a distillation residue having a lower ethanol concentration than the fermentation broth.
(1d) A purification step in which impurities such as moisture are removed from the condensate to obtain bioethanol D having a higher ethanol concentration than the condensate.

  When the biomass A is a saccharide-based biomass, the stock solution preparation process in the stock solution preparation device 11 is obtained by, for example, squeezing sugar cane or sugar beet to obtain molasses, and appropriately diluting the molasses with water. When the saccharide biomass is waste molasses, the stock solution can be produced by diluting the waste molasses with water or the like.

  In addition, when the biomass A is a cellulosic biomass, the stock solution preparation step includes, for example, pulverizing the biomass to an appropriate size, hydrolyzing the biomass using an enzyme, an acid or an alkali, and deriving from hemicellulose and cellulose The saccharified solution containing the saccharide can be obtained, and the saccharified solution can be neutralized as necessary to obtain a stock solution.

  In the case where the biomass A is starch-based biomass, for example, in the stock solution preparation step, a saccharified solution is obtained by hydrolyzing the glycoxide bond of starch contained in the biomass with an enzyme or an acid, and the saccharified solution is required. Accordingly, it can be carried out by adopting a method of neutralizing to make a stock solution.

  In addition, when the undiluted | stock solution contains solid substances, such as a fiber, it is preferable to supply to the said fermentation apparatus 12 after removing this solid substance.

  The fermentation process in the fermenter 12 can be carried out, for example, by adopting a batch (batch) method in which yeast is added to the stock solution for a predetermined time in an anaerobic environment.

As the yeast, yeasts can be used, for example, those belonging to the genus Saccharomyces .
More specifically, Saccaromyces cerebisiae etc. can be used as said yeast.
Moreover, as said yeast, you may use what is called sake yeast, what is called wine yeast, or what is called beer yeast.

In addition, it is preferable to supply the fermented liquor produced in the said fermentation process to the said distillation apparatus 13, after collect | recovering the said yeast by filtration.
The recovered yeast can be reused, for example, in the fermentation process after the next batch.
The yeast contains components such as proteins, amino acids, vitamins, phosphorus and potassium.
Therefore, if necessary, the yeast recovered in the fermentation process can be supplied to the preparation tank 21 or the culture device 23 and used for culturing microalgae.
In addition, when utilizing for culture | cultivation of micro algae, it is preferable to utilize yeast as a yeast extract.
Examples of the yeast extract that can be used include those extracted by contacting with hot water to destroy the cell wall of yeast, or those extracted by destroying the cell wall of yeast by enzymatic treatment. .
In addition, the yeast extract may be produced by self-digestion of the yeast.
That is, the yeast extract used in the fermentation process may be produced by decomposing components constituting yeast using an enzyme possessed by yeast.
The self-digestion of the yeast can be caused, for example, by placing the yeast under conditions where there are no organic nutrients such as sugars.
Thus, in order to make yeast into yeast extract, before supplying to the said adjustment tank 21 or the said culture | cultivation apparatus 23, you may provide the apparatus by the process by a hot water, the process by an enzyme, and a self-digestion separately, and it mentions later. It is also possible to use a sterilization apparatus or the like.

The distillation step in the distillation apparatus 13 can be performed by a general method using a distillation still and a condenser, for example.
And the distillation residual liquid, which is the residual liquid after ethanol is removed and recovered from the fermentation liquid as a condensate in this distillation process, usually contains organic substances etc. It is difficult to reuse as process water.
In the present embodiment, the distillation residual liquid that is drained from the bioethanol production facility 10 is drained by the microalgae culture facility 20.

Note that the purification step in the purification apparatus 14 can be performed by removing impurities such as moisture from the condensate by, for example, molecular sieve or membrane separation.
In this step, the separation liquid separated from the condensate during the regeneration of the molecular sieve and the membrane separation becomes drainage and is discharged from the purifier 14. It can be processed by the algae culture equipment 20.

Next, the method for culturing microalgae according to the present embodiment, which is implemented as wastewater treatment of the microalgae culture facility 20 together with the production of algal biomass D, will be described.

In the microalgae culture facility 20 of the present embodiment, the following steps are performed in the process of producing the algal biomass D.
(2a) The sugar is introduced into the preparation tank 21 from the raw water preparation device 11 together with the distillation residue, and water C for appropriately diluting the distillation residue is introduced into the preparation tank 21. A culture solution preparation step of preparing a culture solution for culturing microalgae by diluting the distillation residue and the sugar to an appropriate concentration.
(2b) A sterilization step of removing bacteria that may inhibit the growth of microalgae from the adjusted culture solution using the sterilization apparatus 22.
(2c) A culturing step of introducing a culture solution from the preparation tank 21 to the culturing apparatus 23 via the sterilization apparatus 22 and growing microalgae in the culturing apparatus.
(2d) A solid-liquid separation step in which an algae-containing liquid is introduced from the culture device 23 into the concentration device 24, and the algae-containing liquid is solid-liquid separated by the concentration device 24.
(2e) An extraction step for obtaining valuable resources (algae biomass D) from the concentrate obtained by concentrating the algae-containing liquid in the solid-liquid separation step.

In the culture solution preparation step performed in the preparation tank 21, for example, if the culture solution having an excessively small content of the distillation residue is prepared, the effect of the present invention may not be sufficiently exhibited.
On the other hand, a culture solution having an excessively high content of the distillation residue may not be suitable for efficient cultivation of microalgae.
Therefore, in the point that the effect of the present invention can be made more remarkable, it is preferable that the culture solution prepared in the step contains the evaporation residual liquid in a volume of 1/40 or more and 1/2 or less. More preferably, the remaining solution is contained in the culture solution at a ratio of 1/20 to 1/5.

The sugar to be contained in the culture solution together with the distillation residue is a carbon source for microalgae. If the distillation residue contains a carbon source that can be used by the microalgae, it is cultivated. Although it is not necessary to make it contain in a liquid, normally the organic carbon source which can utilize a micro algae is not fully contained in the distillation residual liquid.
Therefore, it is usually necessary for the culture solution to contain a substance that becomes an organic carbon source that can be used by microalgae in some form.
When the organic carbon source is contained in the culture solution, a substance other than sugar obtained from biomass may be used as the organic carbon source. However, in the bioethanol production process, sugars such as glucose and fructose are inexpensive. Since the method for culturing microalgae according to the present embodiment has many advantages from an economical point of view, the organic carbon source contained in the culture solution is sugar obtained from biomass. It is preferable that
Moreover, when there is little addition amount of saccharide | sugar, there exists a possibility that the carbon source required for the growth of a micro algae cannot fully be obtained, but the efficiency of culture | cultivation of a micro algae falls.
On the other hand, when the addition amount of sugar is large, there is a possibility that the algae cannot be used and the sugar may remain, and the added sugar may be wasted.
Further, when the amount of added sugar is large, when the microalgae are used for waste water treatment as in the present embodiment, the remaining sugar may result in deterioration of water quality and the purpose may not be sufficiently achieved.
In addition, in the point which can make the effect of this invention more remarkable, when using Euglena as a micro algae, the said saccharide | sugar is contained in the said culture solution produced in the said process in the ratio of 5 g / L or more. Preferably, it is more preferably contained at a rate of 10 g / L or more.
Moreover, it is preferable to contain the sugar at a rate of 25 g / L or less, more preferably at a rate of 20 g / L or less, and particularly at a rate of 15 g / L or less. preferable.

Further, in the culture solution preparation step, it is preferable to adjust the culture solution so as to exhibit a pH value suitable for the growth of microalgae.
Microalgae grown, for example, in the case of Euglena (Euglena) genus organisms, particularly pH of but not limited the culture solution is preferably in the 3.0 to 5.5.
In order to adjust the pH of the culture solution, an inorganic acid such as hydrochloric acid or an organic acid such as acetic acid is adopted as each main component E, and these acids are introduced into the preparation tank 21. That's fine.
The acid introduced into the preparation tank 21 at this time is preferably an organic acid in that microalgae can be used as a nutrient source.

In the present embodiment, a substance containing inorganic nutrients and vitamins necessary for the growth of microalgae apart from the carbon source may be introduced into the preparation tank 21 as the various components E.
Examples of the inorganic nutrient include potassium ion, iron ion, manganese ion, cobalt ion, zinc ion, copper ion, molybdenum ion, nickel ion and the like.

  The sterilization step of sterilizing the culture solution thus prepared with the sterilization apparatus 22 is preferably performed without using a drug that may adversely affect the growth of the bacterium, such as water vapor. It is preferable to carry out by heat sterilization using the heat of this, removal of bacteria using a filtration membrane, or the like.

  In the present embodiment, by using the culture solution, it is possible to more efficiently culture the microalgae in the culture device 23.

As long as the heterotrophic culture is performed in the culture device 23, the microalgae may be cultured under either light conditions (light heterotrophic culture) or dark conditions. In terms of form, heterotrophic culture is preferably performed under dark conditions in which microalgae are not substantially irradiated with light.
Especially when microalgae grown is Euglena (Euglena) genus organism, in the culturing step, the aeration was carried out on a mixture of the microalgae culture, dark conditions and good microalgae It is preferable to culture under atmospheric conditions.

The “dark condition” in the present specification means that when light irradiation intensity is averaged throughout the culture period, the value is several μmol / m ² / s or less (at most 10 μmol / m ² / s does not exceed). Means that
In addition, the aeration can use a general aeration method, and is not limited to a method in which a gas is simply aerated in a liquid, but also includes a method in which a gas is taken in by stirring or shaking.
Moreover, air, pure oxygen, and these mixed gas can be utilized also as gas to aerate.

  The temperature of the culture solution in the culturing step is not particularly limited as long as it is a temperature at which microalgae can grow. Specifically, for example, 20 ° C to 35 ° C is employed as the culture temperature (temperature of the culture solution).

The culture process may employ a batch system in which all of the microalgae are extracted from the culture apparatus 23, or a semi-batch culture method in which a part of the cultured microalgae is periodically extracted from the culture apparatus 23. Alternatively, any of the continuous types in which the algae-containing liquid continuously flows from the adjustment tank 21 to the culture device 23 via the sterilization device 22 in accordance with the growth rate of the microalgae may be employed. .
In the case where the culturing step is carried out by a continuous culture method or a semi-batch culture method, the culture solution in the preparation tank 21 has the distillation residue concentration, sugar concentration, pH, etc. And the prepared culture solution may be continuously supplied to the culture apparatus 23.
On the other hand, when the culture process is carried out by the semi-batch culture method, the concentration of the culture solution in the preparation tank 21 is adjusted by adjusting the concentration of the culture solution in the culturing device 23, the sugar concentration, the pH, etc. It is preferable to implement so that it may become a preferable range.
That is, in the culture process by the semi-batch culture method, as a result of mixing the culture solution remaining without being removed from the culture apparatus 23 and the new culture solution prepared in the preparation tank 21, the sugar concentration in the mixed culture solution is obtained. Is preferably 5 g / L to 25 g / L (particularly 10 g / L to 20 g / L), and the pH in the culture solution after mixing is preferably in the above-described preferable range.
The same applies to the evaporation residual liquid. For example, when the replacement of the culture solution in the semi-batch culture method is half of the total amount, the culture solution prepared in the preparation tank 21 has the above-mentioned preferable range (capacity). It is preferable that the evaporation residual liquid is contained at a concentration of 1/40 to 1/2, more preferably 1/20 to 1/5.

  In the solid-liquid separation step carried out after this culturing step, for example, the algae-containing liquid introduced from the culturing device 23 to the concentrating device 24 is subjected to microalgae by flotation concentration, gravity concentration, membrane concentration, belt concentration, or the like. A method of obtaining concentrated microalgae by concentrating, or after the concentration, for example, vacuum dehydrator, pressure dehydrator (filter press), belt press, screw press, centrifugal concentration dehydrator (screw decanter), or Further, it is possible to employ a method in which further concentration is performed by a multiple disk dehydrator or the like, and microalgae is finally obtained in a dehydrated cake state.

The microalgae thus obtained can be effectively used as a valuable resource.
For example, the obtained microalgae are cultured under anaerobic conditions or submerged under anaerobic conditions to accumulate lipids such as wax esters in the individual.
The microalgae in which the wax ester is accumulated can be used as fuel as it is.
Further, the accumulated lipid can be used as a fuel containing the lipid as a main component by being extracted from microalgae.
The extraction step can be performed, for example, by a solvent extraction method using a solvent such as hexane. In addition, the lipid after extraction may be modified by a known method to make it easier to use.
Moreover, microalgae If a Euglena (Euglena) genus organisms usually contain in an individual as a valuable resource polysaccharides and vitamins such as paramylon.
These polysaccharides and vitamins can also be extracted separately from the lipids for effective use.
Further, Euglena may be effectively used as it is for the fuel, feed, etc. without solvent extraction.

In the present embodiment, the microalgae efficiently proliferate by incorporating various components contained in the distillation residue into the individual.
That is, the increase amount per unit time of the microalgae in the culturing step is larger than that in the case where the microalgae are cultured in a culture solution that does not contain the distillation residue.
Therefore, the yield of microalgae in the solid-liquid separation process is also larger than before, and the algal biomass D is also produced more efficiently than before.

  At the same time, the treated water F obtained by removing microalgae from the algae-containing liquid flowing down from the culture device 23 toward the concentration device 24 has a state in which the TOC concentration and the like are greatly reduced as compared with the culture solution and the evaporation residual solution. It becomes.

That is, the treated water F is in a state that is easier to reuse as effluent water or some process water than the distillation residual liquid discharged from the bioethanol production facility 10, and is supposed to be effluent water. Even when further processing is required for reuse as process water, it is possible to reduce the labor of the processing compared to the evaporation residual liquid.
Further, the treated water F can be returned to the preparation tank 21 and effectively used to reduce the amount of the water C introduced from the outside.
In addition, it does not specifically limit as the water C introduce | transduced from the outside, Ordinary waters, such as a tap water, groundwater, and factory water, can be utilized.

  As described above, in the present embodiment, the use of the distillation residue makes it possible to efficiently culture the microalgae in the microalgae culture facility 20 and the wastewater treatment in the bioethanol production facility 10 to be efficient. In addition, the bioethanol production facility 10 and the microalgae culture facility 20 are in a state where they can obtain a profit due to the existence of each other.

In the present embodiment, the microalgae culture method is applied as a method for treating the wastewater discharged in the bioethanol production process in that the above can mutually benefit, but the microalgae of the present invention is applied. The purpose of the culture method is not necessarily limited to the wastewater treatment.
For example, in the present embodiment, the TOC concentration of the treated water F discharged from the concentrating device 24 is necessarily lower than that of the distillation residue by adding sugar and various components to the culture solution in addition to the distillation residue. Although it is not restricted, also when the TOC density | concentration of the treated water F becomes higher than a distillation residual liquid, it is a thing of the range intended as a microalgal culture method of this invention.

Moreover, in this embodiment, although the specific illustration is performed about the algae biomass D, it is the range which this invention intends also when utilizing the micro algae which were propagated other than the said illustration.
Furthermore, even matters that are not specifically described above can be employed as long as they are conventionally known technical matters in the microalgae cultivation method and wastewater treatment method as long as the effects of the present invention are not significantly impaired.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Experimental example 1)
(Seed algae)
Microalgae (" Euglena gracilis EOD-1 strain") on the following culture medium (NITE-IPOD) on March 25, 2013, National Institute of Technology and Evaluation (NITE-IPOD) No. 305-8566 Tsukuba City, Ibaraki Prefecture, 1-chome, East 1-chome, 1-Chuo 6)) under the provisions of the Budapest Treaty, internationally deposited as receipt number FERM ABP-11530) in heterotrophic culture for 4 days, did.
Medium: A modified Hutner medium (hereinafter also referred to as “Modified Hutner”) added with 25 g / L of glucose, specifically as shown in Table 1, and with the exception of nutrients contained in the liquid, is there.

As the trace metal-containing solution in Table 1, a trace metal-containing solution having the composition shown in Table 2 below was used.
Water other than the trace metal component is water.

(Culture method)
In order to culture the seed algae, the following culture solution was prepared and cultured under the following conditions.
“Composition of culture medium”:
Four types of culture solutions were prepared by diluting the residue (distilled residue) after distilling ethanol from the fermentation solution obtained by alcohol fermentation of biomass with pure water 5 times, 10 times, 20 times, and 40 times.
Among these, about 5 times dilution culture solution, glucose was contained in the ratio used as 0g / L and 15g / L, and two types of culture solutions were prepared.
In addition, 10-fold diluted, 20-fold diluted, and 40-fold diluted culture solutions were mixed with glucose at a rate of 0 g / L, 10 g / L, 15 g / L, 20 g / L, and 25 g / L, respectively. Various types of culture solutions were prepared.
Each culture solution was adjusted to pH 3.5 with hydrochloric acid and sterilized.
“Culture container”: 500 mL Sakaguchi flask “Culture conditions”:
Preparation: 200 mL of culture solution and 20 mL of seed algae are stored in the Sakaguchi flask. Culture temperature: 28 ° C.
Light / dark conditions: Dark conditions (in a constant temperature bath where no external light is inserted)
Aerobic conditions: Set the Sakaguchi flask on the shaker and supply air into the culture medium by operating with reciprocal shaking at 130 rpm.

(Confirmation of results)
The algae were cultured under the above conditions for 8 days using a 5-fold diluted culture solution, and the solution in each flask was sampled every day.
Then, the volume of the sampled liquid: V (mL) and the mass of the microalgae contained in the liquid (dry mass): M (mg) are obtained, and the mass (M) is calculated as the volume (V). The alga content: M / V (g / L) was calculated.
Furthermore, the TOC concentration was measured for a single culture solution obtained by removing microalgae from the sampled solution at the start of culture and at the end of 8 days of culture.
The results are shown in FIGS. 2 (a) and 2 (b).
Similarly, culture of algae under the above conditions was carried out for 5 days using 10-fold diluted solution, 20-fold diluted solution, and 40-fold diluted culture solution, and the solution in each flask was sampled every day.
Furthermore, the TOC concentration was measured for the culture solution alone from which microalgae were removed from the sampled solution at the start of culture, the second day of culture, and the end of culture for 5 days.
The results are shown in FIGS.

From the above results, it can be seen that the culture solution is effective for the growth of microalgae by containing the distillation residue together with the carbon source in the culture solution.
In addition, it can be seen from the above results that a great merit can be obtained by implementing the microalgae culture method for the purpose of wastewater treatment including a distillation residue.
In addition, it can be seen from the above results that at a glucose content of 10 g / L, the microalgae are in a state where there is a surplus in their ability to consume and grow sugar.
That is, the above results show that microalgae can be more efficiently grown by using a culture solution containing 10 g / L or more of glucose.
On the other hand, when focusing on the TOC concentration, it can be seen that the TOC concentration in the culture solution can be greatly reduced by using a culture solution containing glucose at a ratio of less than 20 g / L.

(Experimental example 2)
(Culture method)
As in Experimental Example 1, the following culture solution was prepared for culturing microalgae.
However, the culture conditions were changed as follows, and algae were cultured.
“Composition of culture medium”:
Three types of culture solutions obtained by diluting the residue (distilled residue) after distilling ethanol from the fermentation solution obtained by alcohol fermentation of biomass with pure water 5 times, 10 times, and 20 times, and glucose to these Three types of culture solutions were prepared that contained at a rate of 15 g / L.
Each culture solution was adjusted to pH 3.5 with hydrochloric acid and sterilized.

“Culture vessel”: 300 mL Erlenmeyer flask

“Culture conditions”:
Preparation: 100 mL of culture solution and 5 mL of seed algae are stored in the Erlenmeyer flask. Culture temperature: 25 ° C.
Aerobic condition: Set Erlenmeyer flask to shaker and supply air into culture medium by operating at 120 rpm. Light / dark condition: Light / dark condition (12 hours light irradiation environment and 12 hours dark environment) (The photosynthetic photon flux density (PPFD) in the light irradiation environment was about 100 μmol / m ² / s)
The culture results are shown in FIG.

  In the above results, for example, from the comparison between FIG. 6 and FIGS. 2 to 4, it is advantageous that the algae culture method of the present embodiment is more advantageous for culturing algae more efficiently under dark conditions. Recognize.

The method for culturing microalgae of the present invention uses microalgae in which organic compounds such as hydrocarbons and polysaccharides are stored in cells for uses such as health foods, pharmaceuticals, feeds, chemical products, and fuels. It can be suitably used.
Specifically, the method for culturing microalgae of the present invention employs, for example, an organism belonging to the genus Euglena as a microalgae, and cultivates the microalgae so that oil is contained in the cells of the microalgae. It can be suitably used for storing and taking out the oil and using it as a raw material for fuel.

10: Bioethanol production equipment 13: Distillation equipment 20: Microalgae culture equipment 23: Culture equipment A: Biomass B: Bioethanol C: Water D: Liquid fuel F: Treated water

Claims (7)

  Microalgae are cultured in a liquid containing at least the residual liquid after ethanol is removed from the fermentation broth obtained by alcohol fermentation of biomass in the bioethanol production process, and an organic carbon source is supplied to the microalgae under dark conditions. A method for culturing microalgae, comprising performing heterotrophic culture or light heterotrophic culture in   The culture of microalgae according to claim 1, wherein the heterotrophic culture or the photoheterotrophic culture under dark conditions is carried out in the liquid further containing a solid content generated when the fermentation broth is subjected to solid-liquid separation. Method.   The microalgae according to claim 1 or 2, wherein the heterotrophic culture or the photoheterotrophic culture under dark conditions is performed in the liquid in which the residual liquid is contained in a volume of 1/40 or more and 1/2 or less. Culture method.   The method for culturing microalgae according to any one of claims 1 to 3, wherein the culture is heterotrophic culture under dark conditions.   The method for culturing microalgae according to any one of claims 1 to 4, wherein sugar obtained from biomass is used as the organic carbon source. A wastewater treatment method for removing organic substances contained in wastewater,
The drainage
A stock preparation process for obtaining a stock solution containing sugar from biomass;
A fermentation process for obtaining a fermentation broth containing ethanol by subjecting the stock solution to alcohol fermentation;
The distillation residue in the bioethanol production process in which the fermentation liquid is distilled to obtain a condensate having a higher ethanol concentration than the fermentation liquid and a distillation residue having a lower ethanol concentration than the fermentation liquid. Liquid,
It is contained in the distillation residue by culturing microalgae in a liquid containing the distillation residue and supplying an organic carbon source to the microalgae to perform heterotrophic culture or light heterotrophic culture under dark conditions. A wastewater treatment method, wherein the organic matter is consumed by the microalgae. A solid-liquid separation step of separating the solid content in the fermentation liquor after the fermentation step and before the distillation step,
The wastewater treatment method according to claim 6, wherein the solid content obtained in the solid-liquid separation step is supplied into the liquid.