JPH04346788A - Production of hydrogen with methane-producing bacterium - Google Patents

Abstract

PURPOSE:To effectively-produce hydrogen at the ordinary temperature under a low running cost by supplying a culture substrate for a fermentation tank holding methane-producing bacteria and further adding an inhibitor for inhibiting a methyl reductase enzyme contained in the methane-producing bacteria to the fermentation tank. CONSTITUTION:A methane-producing bacterium (e.g. Methanosarcinasp) is supplied to a fermentation tank 2, and a culture solution having a controlled pH is also supplied to the tank through a supplying pipe 4, the culture solution being produced by mixing a medium containing a substrate such as methanol as a main ingredient with an inhibitor (e.g. 2-bromoethanesulfonic acid) inhibiting a methyl reductase enzyme contained in the methane-producing bacterium. The methane-producing bacterium is cultured in the culture solution to produce hydrogen and carbon dioxide. The hydrogen and the carbon dioxide are recovered and separated through a recovering pipe 6, and the culture solution in the fermentation tank 2 is circulated between the fermentation tank 2 and a precipitation tank 3 through a circulation pipe 5 for the continuous culture of the bacterium, thereby continuously and efficiently producing the hydrogen.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen production method suitable for use in producing hydrogen using methane fermentation using methanogenic bacteria, such as in anaerobic treatment of organic wastewater.

0002

[Prior Art] Conventionally, hydrogen has been produced by synthetic chemical methods such as water electrolysis, natural gas, denaturation of water gas, or complete gasification of coal. Currently, there are very few examples in production.

0003

[Problems to be Solved by the Invention] However, in conventional synthetic chemical methods, reactions are carried out under conditions of high temperature and pressure, using expensive catalysts, and the production process is complicated. Therefore, large-scale equipment and complicated reaction management are required, leading to problems such as high running costs.

[0004] On the other hand, hydrogen production by fermentation using microorganisms is a new technology because, if realized, it would be possible to produce hydrogen at room temperature or a slightly higher temperature range, and under normal pressure. There are high expectations for its development as a hydrogen production method. In addition, there is a strong desire for this to be realized from the standpoint of waste disposal and environmental protection, as inexpensive organic wastewater and carbon dioxide gas from combustion gas can be used as culture substrates for microorganisms.

The present invention has been made in view of the above circumstances, and aims to provide a novel method for producing hydrogen by a fermentation method using microorganisms.

[0006]

[Means for Solving the Problems] The present invention supplies a culture substrate to a fermenter holding methanogenic bacteria, and further adds an inhibitor that inhibits the methyl reductase enzyme system of the methanogenic bacteria to produce hydrogen. The solution was to produce.

[0007]

[Operation] According to the hydrogen production method using methanogenic bacteria of the present invention, a culture substrate and an inhibitor that inhibits the methyl reductase enzyme system of the methanogenic bacteria are supplied to the fermenter holding the methanogenic bacteria. Therefore, methanogenic bacteria produce hydrogen and carbon dioxide gas instead of methane gas.

[0008]

EXAMPLES Hereinafter, the method for producing hydrogen using the methanogenic bacteria of the present invention will be explained with reference to Examples.

FIG. 1 shows an example of a methane fermentation apparatus used in this hydrogen production method. This methane fermentation device roughly consists of an adjustment tank 1, a fermentation tank 2, and a sedimentation tank 3.
It is mainly composed of. The adjustment tank 1 and the fermentation tank 2 are connected by a supply pipe 4 that supplies the culture solution adjusted in the adjustment tank 1 into the fermentation tank 2 in an upward flow. Further, the fermenter 2 and the sedimentation tank 3 are connected by a circulation pipe 5 so that they can circulate with each other, thereby enabling continuous culture in the fermentation tank 2 and the sedimentation tank 3. A recovery pipe 6 for recovering gas generated in the fermenter 2 is connected to the fermenter 2 . A discharge pipe 7 for discharging residual liquid after treatment is connected to the sedimentation tank 3.

Next, a method for producing hydrogen using this apparatus will be explained.

[0011] The fermenter 2 contains methane-producing bacteria Metha.
Inoculate with nosarcinasp. The methanogenic bacteria used for hydrogen production may be either mesophilic methanogenic bacteria or high-temperature methanogenic bacteria, but it is desirable to use a bacterial species that can utilize methanol as a substrate. Further, as the fermenter 2, most conventionally known fermenters may be used as long as they can maintain methane-producing bacteria at a high concentration.

A culture solution containing a substrate such as methanol as a main component is used for culturing the methanogenic bacteria, and is introduced into the adjustment tank 1. Furthermore, an inhibitor that inhibits the methyl reductase enzyme system of methanogenic bacteria is added. As an inhibitor, 2-bromoethanesulfonic acid is preferably used because it has a strong inhibitory effect at low concentrations, but in addition to this, 2-chloroethanesulfonic acid, 2-bromoethanesulfonic acid,
- Coenzyme M analogues such as mercaptopropionic acid, chloroform, etc. may be used. Furthermore, if necessary, the pH and other liquid properties of the culture solution are adjusted in the adjustment tank 1.

[0013] This culture solution is supplied into the fermenter 2 through the supply pipe 4, and the methanogenic bacteria are cultured in this culture solution. Then, the methanogenic bacteria in the fermenter 2 generate hydrogen and carbon dioxide gas using methanol as a substrate. The generated hydrogen and carbon dioxide gas are recovered through the recovery pipe 6. Hydrogen and carbon dioxide gas are separated and recovered by an appropriate method.

The culture solution in the fermenter 2 is circulated between the fermenter 2 and the sedimentation tank 3 through the circulation pipe 5 for continuous cultivation.

[0015] As described above, according to the hydrogen production method using methanogenic bacteria of the present example, a culture substrate and the methyl reductase enzyme system possessed by the methanogenic bacteria are added to the fermenter 2 holding the methanogenic bacteria. Methanogenic bacteria produce hydrogen and carbon dioxide instead of methane gas because they are supplied with inhibitors that inhibit the production of methane gas. Therefore, there are various advantages as described below.

(1) Methanogenic bacteria can be cultured under relatively mild conditions (37-53°C, normal pressure);
Running costs are low.

(2) Organic wastewater containing a culture substrate that can be used by methanogenic bacteria or carbon dioxide gas in combustion gas can be used as a medium instead.

(3) Since 2-bromoethanesulfonic acid, which is an inhibitor that inhibits the methyl reductase enzyme system, is sufficiently effective at low concentrations, only a small amount of the drug is required.

(4) The conventional anaerobic digestion tank system can be used as is.

(5) Since a mixed gas of methane gas and hydrogen is obtained, the heat of combustion per unit volume is high.

(6) Since light irradiation, which is required when photosynthetic bacteria are used, is not required, power consumption can be reduced.

(7) By changing the amount of inhibitor added, it is possible to simultaneously produce hydrogen and methane gas.

[0023] The method for producing hydrogen using methanogenic bacteria of the present invention is not limited to the examples shown in the above examples, and the method for producing hydrogen using methane-producing bacteria is not limited to the examples shown in the above examples. Specific constituent requirements such as the type of inhibitor and the type of inhibitor can be changed as appropriate during implementation.

For example, in the above example, a method of generating hydrogen using methanogenic bacteria Methanosarcinasp as an anaerobic bacterium and methanol as a substrate was explained as an example, but as a substrate for culturing the methanogenic bacteria, In addition to the methanol, acetic acid, methylamine, etc. can also be used, or organic industrial wastewater containing these substrates can also be used. Moreover, as the fermentation tank 2, any tank may be used as long as it can maintain a high concentration of methane-producing bacteria; for example, an anaerobic digestion tank may be used instead. Furthermore, hydrogen production can be similarly performed using an enzyme-immobilized reactor in which only the enzyme involved in methanol oxidation possessed by methanogenic bacteria is extracted and immobilized.

[0025]

Effects of the Invention As explained above, according to the hydrogen production method using methanogenic bacteria of the present invention, a culture substrate and a methyl reductase enzyme possessed by methanogenic bacteria are added to a fermenter holding methanogenic bacteria. Methanogenic bacteria produce hydrogen and carbon dioxide instead of methane gas because they supply inhibitors that inhibit the system. In other words, it has become possible to realize a new hydrogen production method using fermentation using microorganisms.
Various effects such as simplification of the production process, milder culture conditions, and reduction in running costs can be obtained. Furthermore, since it is possible to use organic wastewater, carbon dioxide gas from combustion gas, etc. as a culture substrate for microorganisms, it is advantageous in terms of waste disposal and environmental protection.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing an example of a methane fermentation device used in the hydrogen production method using methanogenic bacteria of the present invention.

[Explanation of symbols]

2 Fermentation tank

Claims (1)

[Claims] Claim 1: In a fermenter holding methane-producing bacteria,
A method for producing hydrogen using methanogenic bacteria, characterized in that hydrogen is produced by supplying a culture substrate and further adding an inhibitor that inhibits the methyl reductase enzyme system of the methanogenic bacteria.