JP2005270046A - Fermentation apparatus for hydrogen production and method for producing hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fermentation apparatus for hydrogen production, which enables practical production of hydrogen in high efficiency at a low cost by using a bacterial strain of the genus Clostridium as a hydrogen-producing fermentation bacteria. <P>SOLUTION: An apparatus controls the physical/chemical states of a substrate containing a plurality of microbial species such as heating, drying, moisture control, oxygen concentration and pH and a method for producing hydrogen. Concretely, fermentation reaction is carried out by using the apparatus to cause the selection of the microbial strains by the microbial flora exchanging reaction treatment to remarkably decrease the cell number of unnecessary species which is in an active state at the initial stage and activate a certain kind of hydrogen-producing bacteria of the genus Clostridium necessary for the production of hydrogen. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrogen production fermentation apparatus and a hydrogen production method for producing a hydrogen gas efficiently and inexpensively by fermenting a biomass substrate such as a saccharide with a microorganism.

  Fermentation reactions using microorganisms are known as glycolysis, lactic acid fermentation, butyric acid fermentation, and the like, and produce gases such as carbon dioxide and hydrogen. Further, the produced carbon dioxide gas and hydrogen gas synthesize acetic acid, lactic acid, butyric acid, alcohol and the like due to the presence of lactic acid bacteria, methane bacteria and the like. Treating garbage using these reactions, reducing the volume of garbage, or extinguishing it into water and carbon dioxide gas, or using fermented products as fertilizer, feed, or producing methane gas etc. as biomass energy Has already been studied and industrialized (see Patent Document 1).

Japanese Patent Laid-Open No. 2004-25035

  On the other hand, it may be desirable that a battery such as a fuel cell or a nickel-hydrogen battery, for chemical synthesis, or for fuel is supplied in the state of hydrogen (including hydrogen gas). However, the technology for efficiently and efficiently extracting hydrogen gas by fermentation reaction has not yet been industrially satisfactory despite various studies, and there is room for improvement.

  Algae such as cyanobacterium and green algae and anaerobic bacteria are known as microorganisms that produce hydrogen gas, and hydrogenases (enzymes that catalyze hydrogen production) present in microorganisms including these bacteria produce hydrogen. It is known to be involved in Furthermore, it is also well known that the genus Clostridium, which is a general anaerobic bacterium, generates hydrogen gas by decomposing sugars such as glucose and chitin by the following reaction formula (Non-Patent Document). 1).

Gerhard Gottschalk, `` Bacterial Metabolism '' second edition, Springer-Verlag, 1986, pp.230-231 Japanese Patent Laid-Open No. 2003-102482 (P2003-102482A)

  According to the above reaction formula, theoretically, 4 moles of hydrogen gas should be obtained from 1 mole of glucose, but in reality, only 1 to 2 moles of hydrogen gas is generated. Therefore, a more efficient microbiological hydrogen gas production method has been proposed by one of the present inventors (see Patent Document 2). Patent Document 2 aims to provide a highly efficient hydrogen gas production method by providing a recombinant into which a novel hydrogenase gene has been introduced. However, it was difficult and expensive.

  It is an object of the present invention to provide a practical, highly efficient and inexpensive method of producing hydrogen using a Clostridium bacterium as a hydrogen-producing fermentative bacterium and a hydrogen-producing fermentation apparatus therefor.

  In order to solve the above-mentioned problems, the present inventors paid attention to bacterial flora alternation reaction. The purpose of the bacterial flora alternation reaction is to create a fungus by adding a physical treatment and / or chemical treatment to a substrate containing a plurality of bacterial species, thereby unnecessary bacteria that were active in the initial state. The aim is to drastically reduce the number of bacteria in the species and activate the necessary species. Here, the physical treatment is mainly for temperature management and pressure management such as heating and cooling, and the chemical treatment is treatment mainly for pH management, moisture management and oxygen concentration management. And by developing the apparatus which controls these management conditions appropriately, it became possible to activate the fermentation bacteria required for hydrogen production, and reached the present invention.

  Specifically, in a device for fermenting a saccharide-containing substrate with microorganisms, a heating unit that controls the temperature of the substrate in a range of 60 ° C. to 120 ° C., and a drying unit that controls the moisture ratio of the substrate to 1 to 10% by weight. And a fermentation part for controlling the moisture ratio of the substrate to 15% or more, pH (pH) 6.0 to 10.0, temperature 30 ° C. to 45 ° C. and anaerobic atmosphere, and produced gas outside the system. In a fermentation apparatus for hydrogen production, which is composed of a production gas outlet part to be taken out and an issue residue discharge part to take out fermentation residues out of the system.

  Here, the saccharide-containing substrate refers to a substrate suitable for bacterial culture such as polysaccharide / oligosaccharide / glucose containing an appropriate amount of water, and food containing starch, cellulose, sucrose, fruit juice, chitin, protein, fat, etc. Garbage may be used or artificially synthesized. Garbage is desirable from the viewpoint of effective utilization of resources because it contains the endospore-forming bacilli or Clostridium bacteria that are cocci that are essential for completing the present invention and is available at low cost.

  By the way, it goes without saying that garbage, and substrates such as saccharides generally contain bacteria such as archaea, Gram-positive bacteria or proteobacteria in addition to Clostridium bacteria. However, in the present invention, it is necessary to activate Clostridium bacteria necessary for hydrogen production and to kill or inactivate other bacteria. For this purpose, the substrate is first heated to 60 ° C. to 120 ° C., and the moisture content of the substrate is set to 10% or less, thereby killing bacteria susceptible to heat and / or drying such as Escherichia coli, mold, and yeast. On the other hand, since Clostridium bacteria form endospores, they have heat resistance and drought resistance, and can survive without being killed even after the above-mentioned heat drying step.

  In the next hydrogen production process, it is necessary to provide an environment in which Clostridium bacteria can perform the fermentation reaction most actively. That is, Clostridium bacteria are in an anaerobic state of 30 ° C. to 45 ° C., more preferably 35 ° C. to 40 ° C., and the moisture content of the substrate is 15% or more, desirably 30% or more, and the pH is 6 Hydrogen is efficiently produced by vigorous fermentation under the conditions of 0.0 to 10.0, more preferably 6.5 to 7.5. Here, the heating step and the drying step may be performed separately, but it is more efficient to perform the heating and drying in one step.

  In order to efficiently produce hydrogen in a short time by fermentation, it is necessary to wet the substrate and control the atmosphere in the fermentation apparatus to an anaerobic state. Furthermore, when the pH is 9.5 or higher, Bacillus bacteria are active, while Clostridium bacteria are inactive. In addition, when the pH is 6.0 or less, the activity of Clostridium bacteria is weakened.

  Through the above process, hydrogen is actively produced by Clostridium acetobutyricum, Clostridium tertium, Clostridium sartagoforme, Cross Activates Clostridium butyricum and Clostridium fimetarium. And it becomes possible to produce hydrogen efficiently from a substrate by making 2 or more types of strains into these main bacteria among these bacteria. Of these Clostridium bacteria, some strains of Clostridium butyricum are found to be weakly pathogenic, but other bacteria are considered not to be pathogenic.

  By providing the fermentation apparatus for hydrogen production and the hydrogen production method of the present invention, inexpensive and highly efficient hydrogen production can be achieved. Thus, in addition to supplying hydrogen gas for fuel or hydrogen gas as a fuel cell material, it can be used for biomolecular devices for hydrogen generation or microbial cells. In addition, food waste from agriculture, forestry, fisheries, or households can be used as a raw material for hydrogen production, so resources can be effectively used.

  Although embodiments of the present invention will be described below, the technical scope of the present invention is not limited by the following embodiments, and various modifications can be made without changing the gist of the present invention. Further, the technical scope of the present invention extends to an equivalent range.

  A conceptual diagram of the apparatus in the present invention is shown in FIG. Here, as a method for heating the substrate to 60 ° C. to 120 ° C., a general method such as resistance heating, induction overheating, microwave heating, gas heating, or steam heating can be generally used. Either an external heat type or an internal heat type may be used, but is not necessarily limited thereto. In the next drying step, in addition to the above-mentioned heating and drying, a method of dehydrating by applying pressure to the substrate like a screw feeder, an extruder or a press, a method of dehydrating using a centrifuge, or drying by vacuum dehydration Any method may be used. Here, it is desirable to use a screw feeder, an extruder, or a squeezer because the heating step and the drying step can be performed in one step.

  In the fermentation apparatus of the next step, the raw material substrate input pipe, pH adjustment raw material introduction pipe for pH adjustment, moisture introduction pipe for water replenishment, nitrogen gas or carbon dioxide gas for maintaining anaerobic state, etc. In addition to a gas inlet tube, a production gas outlet tube for extracting hydrogen and carbon dioxide obtained from fermentation outside the system, and a fermentation residue discharge tube for extracting fermentation residue outside the system, a thermocouple for temperature measurement, for pH measurement PH sensor meter and oxygen concentration meter for measuring oxygen concentration are installed. The temperature of the fermentation apparatus is controlled at 30 ° C. to 45 ° C. by a heating or cooling device associated with the fermentation apparatus. Here, the same method as described above can be used for heating, and cooling is generally performed using a refrigerant or cold air, but is not necessarily limited thereto. In addition, you may provide the stirring apparatus for stirring the substrate in fermentation reaction.

  In addition, although hydroxide salt, such as slaked lime, is generally used for pH adjustment, it is not necessarily limited to this. In the present invention, slaked lime is added at the start of fermentation to adjust the pH to 7 to 10. However, since an organic acid is generated by fermentation by bacteria, the pH is gradually lowered, and pH 6.0 is adjusted when pH adjustment is not performed. It becomes as follows. At this pH, the activity of Clostridium bacteria is weak and hydrogen production is not sufficient. Therefore, it is desirable to measure the pH with a pH meter and control it to the optimum pH of 6.5 to 7.5.

  Since the gas produced by fermentation contains carbon dioxide gas, nitrogen gas, etc. in addition to hydrogen gas, when it is desired to extract only hydrogen gas, a standard method such as a physical adsorption method, a chemical absorption method or a separation membrane method is used. Can be separated. The fermentation residue can be effectively used as a fertilizer. By the way, when using garbage etc. as a substrate, since pathogens such as food poisoning bacteria may be included, it is desirable to exclude them by sterilization in advance.

<Bacteria-containing saccharide-based medium and bacterial flora alternation reaction>
Using 500 g of garbage (water 80% by weight, pH 5.5) as a substrate containing Clostridium bacteria, etc., heated and dried at 80 ° C. by resistance heating by the external heating method until the water ratio reaches 7% by weight. did. Next, the substrate is transferred to a fermenter in which carbon dioxide is substituted, and the water ratio is adjusted to 58 wt% by adding water, and the pH is adjusted to 7.0, 8.3, and 12.0 by adding slaked lime. Prepared and left anaerobically at 37 ° C. in the fermenter.

<Evaluation of hydrogen production ability>
100 g of each of the above three types of substrates (moisture ratio: 58% by weight) is left anaerobically in a sealed container at 37 ° C. for 60 hours, and the generated gas is collected in a cylinder and analyzed for gas components by gas chromatography. went. As a result, the total amount of generated gas was 1600 cc, of which 1015 cc was hydrogen gas and the remainder was carbon dioxide gas, confirming highly efficient hydrogen production.

<Identification of hydrogen producing bacteria>
With respect to the above three types of substrates, samples before, during and after hydrogen production were analyzed by the method shown in FIG. 2 to identify hydrogen-producing bacteria. Fig. 3 shows the results of microbiota analysis (DGGE method) by denaturing gradient gel electrophoresis, and Fig. 4 shows the microbial species identified. In the case of pH 7.0 and 8.3, the results are compared with those before hydrogen production. During and after hydrogen production, Clostridium acetobutyricum, Clostridium tertium, Clostridium sartagoforme, Clostridium Butyricum (Clostridium butyricum) and Clostridium fimetarium (Clostridium fimetarium) were remarkably detected, and the microbiota alternation treatment was clearly recognized. On the other hand, at pH 12.0, Bacillus bacteria were detected in the early stage of fermentation, and when fermentation progressed and the pH reached 10.0 or less, Clostridium bacteria were detected instead of Bacillus bacteria, and the fungus replacement treatment phenomenon was observed. Indicated.

It is a conceptual diagram which shows the basic idea of the hydrogen production apparatus in this invention. It is a flowchart which shows the analysis procedure for identifying hydrogen producing bacteria. It is a figure which shows the photograph of the microflora analysis (DGGE method) result by denaturation concentration gradient gel electrophoresis. It is a figure which shows the microbial species identified by the DGGE method.

Claims (3)

  In an apparatus for fermenting a substrate containing saccharides by a microorganism, a heating unit for holding the substrate at 60 ° C. to 120 ° C., a drying unit for controlling the moisture ratio of the substrate to 1 to 10% by weight, and a moisture ratio of the substrate of 15 % Or more, pH (6.0) to 10.0, a temperature of 30 ° C. to 45 ° C. and an anaerobic atmosphere state, a production gas extraction unit for taking out the produced gas out of the system, Fermentation apparatus for hydrogen production composed of a fermentation residue discharge unit that extracts fermentation residue out of the system.   In the said, the heating part and the drying part are united, The fermentation apparatus for hydrogen production of Claim 1 characterized by the above-mentioned. The hydrogen production fermentation apparatus according to claim 1 or 2, wherein hydrogen production fermentation in the fermentation section is performed by Clostridium acetobutyricum, Clostridium tertium, or Clostridium. Depending on the bacterial group consisting of two or more strains of the main constituents: Clostridium sartagoforme, Clostridium butyricum, Clostridium fimetarium A hydrogen production method characterized by being made.

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