WO2014208621A1 - Microalga culture method and drainage water treatment method - Google Patents

Abstract

Provided is a microalga culture method which comprises carrying out heterotrophic culturing or photoheterotrophic culturing of a microalga under dark conditions for the microalga in the presence of an organic carbon source in a liquid that contains at least a residual liquid obtained after the collection of ethanol from a fermentation liquor produced by the alcoholic fermentation of a biomass in the process of producing bioethanol. Also provided is a drainage water treatment method for removing an organic substance contained in drainage water, which comprises carrying out heterotrophic culturing or photoheterotrophic culturing of a microalga under dark conditions for the microalga in the presence of an organic carbon source in a liquid that contains a distillation residual liquid produced in the process of producing bioethanol, thereby allowing an organic substance contained in the distillation residual liquid to be consumed by the microalga.

Description

Microalgae culture method and wastewater treatment method Cross-reference of related applications

This application claims the priority of Japanese Patent Application No. 2013-136559 filed on June 28, 2013, which is incorporated herein by reference.

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

2. Description of the Related Art Conventionally, microalgae are proliferated, and lipids as raw materials for fuels, feeds, health foods, etc., or valuables such as proteins and vitamins are stored in the cells of microalgae. In addition, the stored valuables are used for fuel, food, and the like.
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. However, a method for efficiently performing heterotrophic culture or light heterotrophic culture under dark conditions has not been well established.
If microalgae do not proliferate efficiently, the amount of valuables stored in the cell will not necessarily be sufficient, and there is a risk that effective use of the valuables will be difficult.
Moreover, if the microalgae do not grow efficiently, the consumption of the substance to be treated by the microalgae may not be sufficient, and the wastewater treatment and exhaust gas treatment may not be performed efficiently.

Japanese Unexamined Patent Publication No. 05-301097 Japanese Unexamined Patent Publication No. 2010-022331

In view of the above points, an object of the present invention is to provide a method for culturing microalgae that can efficiently grow microalgae.
Another object of the present invention is to provide efficient wastewater treatment using microalgae in view of the above points.

The present inventor has intensively studied to solve the above-mentioned problems. As a result, the organic carbon source is given to the microalgae together with the components of the fermentation broth obtained from the bioethanol production process, and the heterotrophic culture of the microalgae under dark conditions is performed. Alternatively, the microalgae can be efficiently proliferated by carrying out the photoheterotrophic culture, and the components contained in the distillation residue can be efficiently removed when the distillation residue of the fermentation liquid is drained. The present invention was completed by finding that the waste water treatment can be performed efficiently.

That is, the method for culturing microalgae according to the present invention is a liquid containing at least a residual liquid after recovering ethanol from a fermentation broth obtained by alcohol fermentation of biomass in a bioethanol production process, in the presence of an organic carbon source. The heterotrophic culture or the photoheterotrophic culture of dark algae under dark conditions is performed.

As one aspect of the method for culturing microalgae according to the present invention, heterotrophic culture or photoheterotrophic culture under dark conditions is performed in a liquid further containing a solid content generated by solid-liquid separation of the fermentation broth. The mode to implement is employ | adopted.

As another aspect of the method for culturing microalgae according to the present invention, an aspect in which the culture 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 is employed.

As another aspect of the method for culturing microalgae according to the present invention, an aspect in which the culture is heterotrophic culture under dark conditions is employed.

Furthermore, as another aspect of the method for cultivating microalgae according to the present invention, an aspect in which sugar obtained from biomass is used as the carbon source is employed.

The wastewater treatment method according to the present invention is a wastewater treatment method for removing organic substances contained in wastewater,
The drainage is
A stock preparation process for obtaining a stock solution containing sugar from biomass;
A fermentation step of subjecting the stock solution to alcohol fermentation to obtain a fermentation broth containing ethanol, and
The distillation residue in a bioethanol production process comprising distilling the fermentation solution to obtain a condensate having a higher ethanol concentration than the fermentation solution and a distillation residue having a lower ethanol concentration than the fermentation solution. ,
In the liquid containing the distillation residue, by subjecting the microalgae to heterotrophic culture or photoheterotrophic culture under dark conditions in the presence of an organic carbon source, the organic matter contained in the distillation residue is converted to the microalgae. It is a wastewater treatment method to be consumed.

As one aspect of the wastewater treatment method according to the present invention, there is an aspect in which solids obtained by solid-liquid separation from the fermentation liquor are provided in the liquid after the fermentation process and before the distillation process. Adopted.

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 (microalga content rate change) of the culture experiment of the micro algae in Experimental example 1. FIG. The graph which shows one result (TOC density | concentration change of a culture solution) of the culture experiment of the micro algae in Experimental example 1. FIG. The graph which shows the other culture experiment result (microalga content rate change) in the micro algae in Experimental example 1. FIG. The graph which shows the other culture experiment result (TOC density | concentration change of a culture solution) in the micro algae in Experimental example 1. FIG. The graph which shows the other culture experiment result (microalga content rate change) in the micro algae in Experimental example 1. FIG. The graph which shows the other culture experiment result (TOC density | concentration change of a culture solution) in the micro algae in Experimental example 1. FIG. The graph which shows the other culture experiment result (microalga content rate change) in the micro algae in Experimental example 1. FIG. The graph which shows the other culture experiment result (TOC density | concentration change of a culture solution) in the micro algae in Experimental 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 of this embodiment is a liquid containing at least a residual liquid after recovering ethanol from a fermentation broth obtained by alcohol fermentation of biomass in the bioethanol production process, in the presence of an organic carbon source. The algae are subjected to heterotrophic culture or light heterotrophic culture under dark conditions.
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.

In the method for culturing microalgae of this embodiment, since microalgae are cultured in a liquid containing the components of the fermentation broth, the microalgae can be efficiently propagated.
That is, the method for culturing microalgae of the present embodiment has an effect that microalgae can be efficiently propagated.

The microalgae are living organisms that live 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 (Botryococcus) belonging to the genus organism, Nan'nokurorisu (Nannochloris) belonging to the genus organism, Nannochloropsis (Nannochloropsis) belonging to the genus organism, Neokurorisu (Neochloris) belonging to the genus organism, shoe DoCoMo lysis Chis (Pseudochoricystis) belonging to the genus organism, 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 .
The Euglena as the gracilis, for example, Euglena gracilis NIES-48, Euglena gracilis EOD-1, ( original date of deposit independence in 2013 March 25 date National Institute of Technology and Evaluation, Patent Organism Depositary Center (NITE-IPOD (zip code 292-0818 Room No. 2-5-8 Kazusa-Kamashita, Kisarazu City, Chiba Prefecture, Japan)))) under the provisions of the Budapest Treaty, the international deposit has been made under the deposit number FERM BP-11530).

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 microalgae are preserved by the National Institute for Environmental Studies, National Institute for Environmental Studies, National Institute for Environmental Studies, National Institute for Environmental Studies, National Institute for Environmental Studies Facility (Postal Code 305-8506, 16-2 Onagawa, Tsukuba City, Ibaraki, Japan), or The Culture Collection of Algae at the University of Texas at Austin, USA (http://web.biosci.utexas.edu/utex/ default.aspx).

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 biomass that is a starting material for the distillation residue and the sugar include plants, processed products thereof, and substances derived from plants. Examples of the plant 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.

In addition, examples of the sugar-based biomass include sugarcane, 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. FIG. 1 shows a main configuration of the bioethanol production facility and the microalgae culture facility.
In the present embodiment, as shown in the figure, a bioethanol production facility 10 is attached to the microalgae culture facility 20. The microalgae culture facility 20 in which the culture method of the present embodiment is implemented is used for wastewater treatment of the bioethanol production facility 10.
In addition, the code | symbol A of FIG. 1 represents the biomass supplied to the bioethanol manufacturing equipment 10. FIG. The symbol B represents bioethanol obtained at the bioethanol production facility 10.
Moreover, the code | symbol C of FIG. 1 represents the water supplied to the said micro algae culture equipment 20. FIG. 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. The symbol F represents treated water discharged from the microalgae culture facility 20.

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) The fermentation broth is supplied from the fermentation apparatus 12, the fermentation broth is distilled and ethanol is collected, and a condensate having a higher ethanol concentration than the fermentation broth and a distillation residue having a lower ethanol concentration than the fermentation broth are obtained. Distillation equipment to be separated.
(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.
The bioethanol production facility 10 may further include a solid-liquid separation device that separates the fermentation broth into solid and liquid at the subsequent stage of the fermentation apparatus 12 and before the distillation apparatus 13.

On the other hand, the microalgae cultivation facility 20 has the following (21) to (25) as main components.
(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 A preparation tank in which a culture solution of microalgae is prepared.
(22) A sterilization apparatus for sterilizing the prepared culture solution in the preparation tank 21.
(23) The microalgae are stored in the heterotrophic culture or light heterotrophic condition in the presence of an organic carbon source in the presence of an organic carbon source by the culture solution that contains the microalgae and is supplied from the preparation tank 21 via the sterilizer 22. A culture device to be cultured.
(24) An algae-containing liquid containing microalgae is supplied from the culturing device 23, the algae-containing liquid is separated into a solid content and a liquid content, and the microalgae are concentrated and cultured in the preparation tank 21. A concentrator that discharges the treated water F having a lower total organic carbon (TOC) concentration than the liquid.
(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 valuable materials (liquid fuel) mainly composed of the lipids are discharged.
The microalgae culture facility 20 may be configured to supply the culture device 23 with the solid content that has been solid-liquid separated by the solid-liquid separation device.

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 recovering ethanol by 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 B having a higher ethanol concentration than the condensate.
In the process of producing bioethanol, a solid-liquid separation process for subjecting the fermentation liquid to a solid-liquid separation process may be performed after the fermentation process and before the distillation process.

In the stock solution preparation process in the stock solution preparation device 11, when the biomass A is a saccharide-based biomass, for example, sugar cane and sugar beet are squeezed to obtain molasses, and the molasses is diluted appropriately with water. To prepare a stock solution. When the saccharide biomass is waste molasses, in the stock solution production step, for example, the waste molasses can be produced by diluting the waste molasses with water.

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 the said fermentation apparatus 12 after removing this solid substance.

The fermentation process in the fermentation apparatus 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 that the fermented liquor produced in the said fermentation process is supplied 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, the yeast recovered in the fermentation step can be supplied to the preparation tank 21 or the culture device 23 as needed, and can be used for culturing microalgae.
In addition, when utilizing for culture | cultivation of a micro algae, it is preferable that yeast is utilized 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 walls of yeast, or those extracted by destroying the cell walls 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, it is an apparatus for converting yeast into a yeast extract, and before supplying the yeast extract to the preparation tank 21 and the culture apparatus 23, the yeast is subjected to a hot water treatment, an enzyme treatment, and a self-digestion treatment. This device may be provided separately. You may make it use the microbe elimination apparatus etc. which are mentioned later.

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 recovered as the condensate from the fermentation liquid in this distillation step usually contains organic substances etc., so it can be used as effluent as it is, or any process It is difficult to reuse as water.
In the present embodiment, the distillation residual liquid discharged 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 is discharged as a waste water from the purifier 14. If necessary, this waste water can also be treated by the microalgae cultivation facility 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 stock solution 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 prepared culture solution using the sterilization apparatus 22.
(2c) A culturing step for 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 concentration step of concentrating microalgae by introducing an algae-containing liquid from the culture device 23 into the concentration device 24 and separating the solid content and the liquid content of the algae-containing liquid with the concentration device 24.
(2e) An extraction step of obtaining valuable material (algae biomass) D from the concentrate obtained by concentrating the algae-containing liquid in the concentration step.
In addition, in the process in which the algal biomass D is manufactured, the solid content separated in the solid-liquid separation step can be supplied to the culture solution (a liquid containing a distillation residue).

In the culture solution preparation step performed in the preparation tank 21, for example, if a culture solution with 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. It is not necessary to include in the liquid. However, usually, the organic carbon source that can be used by microalgae is not sufficiently contained in the distillation residue.
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 an 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. On the other hand, in the bioethanol production process, sugars such as glucose and fructose are produced in large quantities at low cost. When the microalgae cultivation method of the present embodiment has many advantages from an economical viewpoint, the organic carbon source contained in the culture solution is preferably a sugar obtained from biomass.
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 may fall.
On the other hand, when the amount of sugar added is large, there is a possibility that the microalgae cannot use the sugar 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.
When the microalgae to be grown is, for example, an organism belonging to the genus Euglena , the pH of the culture solution is not particularly limited, but is preferably 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 employed as the main component E, and these acids are introduced into the preparation tank 21. do it.
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, for example. The sterilization step is preferably performed by heat sterilization using heat such as water vapor or removal of bacteria using a filtration membrane.

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

In the culturing process in the culturing apparatus 23, microalgae may be cultured under either light conditions (light heterotrophic culture) or dark conditions as long as heterotrophic culture is performed. In this embodiment, heterotrophic culture is preferably performed under dark conditions in which microalgae are not substantially irradiated with light.
In particular, when microalgae grown is Euglena (Euglena) genus organism, wherein in the culturing step, the aeration was carried out on a mixture of the microalgae culture microalgae dark conditions and It is preferable to culture under aerobic conditions.

In the present specification, the “dark condition” means that when the 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). Means that
As the aeration, a general aeration method can be used. Aeration is not limited to a method in which gas is simply aerated in a liquid, but also includes a method in which gas is taken in by stirring or shaking.
As the gas to be aerated, air, pure oxygen, or a mixed gas thereof can be used.

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 (culture solution temperature).

In the culturing step, a batch type in which all of the microalgae are extracted from the culture device 23, a semi-batch culture method in which a part of the cultured microalgae is periodically extracted from the culture device 23, and the growth rate of the microalgae are adjusted. Any of the continuous methods in which the algae-containing liquid is allowed to continuously flow down from the preparation tank 21 to the culture device 23 via the sterilization device 22 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 the mixing is preferably in the above-mentioned preferable range.
The same applies to the evaporation residual liquid. For example, assuming that 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 includes the above preferred range (1-40 or more and 1/2 or less in volume, More preferably, the evaporation residual liquid is contained at a concentration of 1/20 or more and 1/5 or less.

In the concentration step performed after this culturing step, for example, the algae-containing liquid introduced from the culturing device 23 to the concentration device 24 is concentrated by floating concentration, gravity concentration, membrane concentration, belt concentration, etc. Thus, a method for obtaining concentrated microalgae can be employed. Further, after the concentration, further concentration is performed by, for example, a vacuum dehydrator, a pressure dehydrator (filter press), a belt press, a screw press, a centrifugal concentration dehydrator (screw decanter), or a multiple disk dehydrator. Finally, a method of obtaining microalgae in a dehydrated cake state can be employed.

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.
The accumulated lipid can also be used as a fuel containing the lipid as a main component by extraction 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 concentration step is larger than that in the past, and algal biomass D is also produced more efficiently than in the past.

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 more easily reused as effluent water or some process water than the distillation residue discharged from the bioethanol production facility 10. Even if the treated water F requires further treatment to be discharged water or reused as process water, the treated water F can reduce the labor of the treatment compared to the evaporation residual liquid. It has become a thing.
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, ground water, and factory water, can be utilized.

As described above, in the present embodiment, the use of the distillation residue makes it possible to efficiently cultivate microalgae in the microalgae culture facility 20 and to efficiently perform the wastewater treatment in the bioethanol production facility 10. ing. That is, 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.

As described above, the wastewater treatment method of the present embodiment is a wastewater treatment method for removing organic matter contained in wastewater,
The wastewater includes a stock solution preparation step for obtaining a stock solution containing sugar from biomass, a fermentation step for obtaining a fermented solution containing ethanol by subjecting the stock solution to alcohol fermentation, and distilling the fermented solution. A distillation step for obtaining a condensate having a high concentration and a distillation residue having a lower ethanol concentration than the fermentation solution, and the distillation residue in a bioethanol production process,
In the liquid containing the distillation residue, by subjecting the microalgae to heterotrophic culture or photoheterotrophic culture under dark conditions in the presence of an organic carbon source, the organic matter contained in the distillation residue is converted to the microalgae. It is a wastewater treatment method to be consumed.
Since the wastewater treatment method of the present embodiment can efficiently consume the components contained in the wastewater by the microalgae, the wastewater treatment can be carried out efficiently.

In the present embodiment, the microalgae culture method is applied as a method for treating the wastewater discharged during the production process of bioethanol, in the point that it is possible to obtain profits as described above. The purpose of the microalgae culture method of the present invention 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. Not exclusively. The microalgae culture method of the present invention is intended even when the TOC concentration of the treated water F is higher than that of the distillation residue.

Moreover, in this embodiment, the specific illustration is performed about the algal biomass D. FIG. Even when the grown microalgae are used for purposes other than the above examples, it is within the intended scope of the present invention.
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.
That is, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the intended scope of the present invention. Moreover, the effect of this invention is not limited to the said embodiment.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims. Further, the scope of the present invention is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

(Experimental example 1)
(Seed algae)
In the following medium, microalgae ("Euglena genus ( Euglena gracilis EOD-1 strain)" (NITE-IPOD) (National Institute of Technology and Evaluation) Postal deposit 292-0818, Kazusa Kamashizu, Chiba, Chiba, Japan, room 2-5-8, 120), under the provisions of the Budapest Treaty, internationally deposited as receipt number FERM BP-11530) in heterotrophic culture for 4 days. And seed algae.
Medium: A modified Hutner medium (hereinafter also referred to as “Modified Hutner”) supplemented with 25 g / L of glucose. Specifically, as shown in Table 1. Water other than the nutrients contained in the liquid.

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.
Moreover, about 10 times dilution, 20 times dilution, and 40 times dilution culture solution, these are made to contain glucose in the ratio used as 0g / L, 10g / L, 15g / L, 20g / L, 25g / L, Five types of culture solutions were prepared for each.
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)
Algae was cultured for 8 days under the above conditions using a 5-fold diluted culture solution. The liquid in each flask was sampled every day.
And the volume of the sampled liquid: V (mL) and the mass (dry mass) of microalgae contained in the liquid: M (mg) were determined. Algae content: M / V (g / L) was calculated by dividing the mass (M) by the volume (V).
Furthermore, the TOC concentration was measured with respect to the culture solution alone from which microalgae were removed from the sampled solution at the start of the culture and the end of the 8-day culture.
The results are shown in FIGS. 2A and 2B.
Similarly, algae was cultured for 5 days under the above conditions using 10-fold diluted solution, 20-fold diluted solution, and 40-fold diluted culture solution. The liquid in each flask was sampled every day.
Furthermore, the TOC concentration was measured with respect to the culture medium alone from which microalgae were removed from the sampled liquid 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 is understood 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 carrying out the microalgae culture method for the purpose of wastewater treatment including 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 paying attention to 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 container”: 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: Valuables (algae biomass, liquid fuel)
F: treated water

Claims (7)

1. Heterotrophic culture under dark conditions of microalgae in the presence of an organic carbon source in a liquid containing at least the residual liquid after recovering ethanol from the fermentation liquid obtained by alcohol fermentation of biomass in the bioethanol production process or A method for culturing microalgae that performs light heterotrophic culture.
2. The culture of microalgae according to claim 1, wherein the heterotrophic culture or the photoheterotrophic culture under the dark condition is performed in the liquid further containing a solid content generated by solid-liquid separation of the fermentation broth. Method.
3. The microalgae according to claim 1 or 2, wherein the heterotrophic culture or the photoheterotrophic culture under the dark condition is performed in the liquid containing the residual liquid in a volume of 1/40 to 1/2. Culture method.
4. The method for culturing microalgae according to any one of claims 1 to 3, wherein the culture is heterotrophic culture under dark conditions.
5. 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.
6. 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 step of subjecting the stock solution to alcohol fermentation to obtain a fermentation broth containing ethanol, and
   The distillation residue in a bioethanol production process comprising distilling the fermentation solution to obtain a condensate having a higher ethanol concentration than the fermentation solution and a distillation residue having a lower ethanol concentration than the fermentation solution. ,
   In the liquid containing the distillation residue, by subjecting the microalgae to heterotrophic culture or photoheterotrophic culture under dark conditions in the presence of an organic carbon source, the organic matter contained in the distillation residue is converted to the microalgae. Wastewater treatment method to be consumed.
7. The wastewater treatment method according to claim 6, wherein a solid content obtained by solid-liquid separation from the fermentation broth is supplied into the liquid after the fermentation process and before the distillation process.
   
   
   
   
   

Images