JPH0422555B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing butanol. More specifically, the present invention uses a new extraction solvent (hereinafter referred to as extractant) when culturing by incorporating an extraction operation in acetone and butanol fermentation, which does not show toxicity to the bacteria used. Efficiently extracts butanol, a fermentation product, and removes the inhibition of bacteria by the product.
The present invention relates to a butanol production method that improves the productivity of acetone and butanol fermentation by easily recovering butanol from the extraction phase. It is known that extractive culture can be used as a method of removing inhibition of fermentation products from bacteria or simply as a method of recovering the products. On the other hand, the reasons for the decline of the long-known butanol production method using acetone and butanol fermentation are the deterioration of the economic balance compared to petrochemicals, and the fact that the product, butanol, is toxic to bacteria, making it difficult to produce at high concentrations. There are things that cannot be done. Conventionally, fermentation by absorption using castor oil, a vegetable oil, is known as a method to remove the toxicity of the product in acetone and butanol fermentation. It is not an appropriate method for industrial implementation because it has problems such as poor separability due to the inability to remove the liquid, low partition coefficient for butanol, and difficulty in handling due to high viscosity. . Important criteria in selecting an extractant are that it has a high selectivity that allows more of the extract components in the extract to be dissolved into the extract, and that the required amount of extractant can be reduced. Of course, it is important to consider the partition coefficient, but it is also important that the extractant can be easily separated and recovered. Examples include that the agent does not dissolve, that is, in the case of the present invention, that it is water-insoluble, that the difference in density is large, and that the viscosity is not very large. In recent years, various extractants have been discovered for ethanol production, but they have not yet fully satisfied the above conditions. The present inventors conducted various studies to improve the productivity of acetone and butanol fermentation by using a superior extractant to replace castor oil, and as a result, they discovered an excellent extractant that satisfies the above conditions and arrived at the present invention. It is something. That is, the present invention is a method for producing butanol from a glucose raw material by a fermentation method, in which a fermentation solution and an extractant are brought into contact with each other in a fermentation tank, and butanol is recovered from the extraction phase. The present invention relates to a method for producing butanol characterized by using an unsaturated alcohol or an alcohol having an average carbon number of 16 to 20 and a side chain. According to the present invention, the extraction phase containing butanol produced in the fermentation tank is separated from the fermentation liquor, which is the raffinate phase, in the separation tank, and then the butanol is separated from the extractant in the distillation column and continuously recovered. . On the other hand, the fermentation liquid separated in the separation tank and the extractant separated in the distillation column are circulated to the fermentation tank. The present inventors focused on the fact that alcohols with a large number of carbon atoms are water-insoluble and have a large partition coefficient relative to butanol. When we conducted a fermentation test, it was found to be toxic and no bacterial growth was observed. Separately, we conducted a fermentation test using ricinoleic acid, the main component of castor oil, but no bacterial growth was observed and the product was toxic to bacteria. In general, alcohols with up to 13 carbon atoms are liquid at room temperature, and alcohols with more than 13 carbon atoms become solid at room temperature and cannot be used as extractants. Therefore, the present inventors investigated highly branched alcohols and unsaturated alcohols that are liquid at room temperature and have a large number of carbon atoms, and found that bacteria could grow in side chain alcohols with an average number of carbon atoms of 12 to 15. The concentration of butanol produced was considerably lower than in the control plot without the addition of extractant, indicating inhibition of butanol production. In contrast, with unsaturated alcohols with an average carbon number of 16 to 18 and side chain alcohols with an average carbon number of 16 to 20, bacterial growth was at the same level as in the control group, and the concentration of butanol produced was higher than in the control group. The present invention was based on the finding that the productivity of butanol can be improved. Particularly preferred such alcohols include oleyl alcohol and Guerbet alcohol having 16 to 20 carbon atoms. The extractants used in the present invention, unsaturated alcohols with 16 to 18 carbon atoms and side chain alcohols with 16 to 20 carbon atoms, are water-insoluble, prevent loss of extractants, and are liquid at room temperature. be. In addition, there is a sufficient difference in density from water, and the extractant can be easily separated and recovered from the culture medium. If there is no difference in density from water like castor oil, it will be difficult to separate, and recovery costs will increase. Furthermore, it has a relatively low viscosity, is easy to transport and handle, has a low vapor pressure, and can prevent volatilization loss. Of particular importance is the absence of toxicity to microorganisms. That is, in the main fermentation, when the concentration of produced butanol in the medium reaches 1%, the activity of the bacteria decreases and continuous production of butanol becomes impossible. Since the extractant of the present invention is non-toxic, inhibition can be removed by adding the extractant to the fermentation medium and extracting butanol from the medium, allowing fermentation to proceed while maintaining a low concentration of inhibitors. . According to the method of the present invention, acetone and ethanol, which are produced simultaneously with butanol from the fermentation liquid of acetone and butanol fermentation, are also absorbed and removed by the extractant of the present invention. As the glucose raw material that is the fermentation raw material, molasses, sulfite pulp waste liquid, and saccharified starchy raw materials and fibrous raw materials are used. Suitable bacteria to be used include those belonging to the genus Clostridium, such as Clostridium acetobutylicum. Comparison of separation properties, partition coefficients, etc. of oleyl alcohol, a representative unsaturated alcohol used as an extractant in the method of the present invention, and castor oil, conventionally used in acetone-butanol fermentation, in a test aqueous solution with a butanol concentration of 1%. Then, it will look like the following table.

[Table] Viscosity High Low As shown in the table above, castor oil cannot balance the difference in specific gravity with water, so water is trapped in the oil phase, making it difficult to separate.
It is difficult to handle because it has low distributability to butanol and high viscosity. In contrast, it can be seen that oleyl alcohol has excellent properties as a solvent for extracting butanol. Note that Guerbet alcohol having 16 to 20 carbon atoms also exhibits similar excellent properties. The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. Example 1 800 ml of a complex medium containing 100 g of glucose was inoculated with bacteria (Clostridium acetobutyrium) cultured in potato medium at a rate of 5% relative to the medium, and cultured anaerobically at 37°C. Thirty hours after the start of culture, inhibition by the produced butanol appeared and fermentation became slow. To remove inhibition by butanol, 40% oleyl alcohol was added to the medium as an extractant.
was added to extract the butanol. Through this operation, the bacterium regained its activity and started fermentation production. The added extractant was not toxic to the bacteria, and it was also possible to extract the produced butanol. The total butanol concentration including the extraction phase 70 hours after adding the extractant was 2.5 times the butanol concentration before adding the extractant. The added extractant could be easily recovered from the culture solution and could be used again by removing the absorbed butanol. Example 2 Bacteria (Clostridium acetobutylium) cultured in potato medium were inoculated at 5% of the medium into 700 ml of a complex medium containing 40 g of glucose, and cultured anaerobically at 37°C. In order to extract the produced butanol, a total of 500 ml of oleyl alcohol was sequentially added as an extractant and cultured. After 26 hours of culture,
Supplementation of 40g/glucose and additional 60g of glucose in the extraction phase
% was replaced with new extractant. With the above operations, fermentation could last for 70 hours. In culture without adding an extractant, fermentation stopped when the butanol concentration was 5 g//, but by this operation, the total butanol concentration including the extraction phase could be increased to 12 g//. Example 3 Bacteria (Clostridium acetobutylicum) cultured in potato medium were inoculated into 800 ml of a complex medium containing 60 g/g of glucose at 5% of the medium and cultured anaerobically at 37°C. After 20 hours of culture, Guerbet alcohol with 20 carbon atoms was added as an extractant at a ratio of 60% to the medium to extract the produced butanol. The added extractant was not toxic to the bacteria, and it was also possible to extract the produced butanol. The total butanol concentration, including the extraction phase, 46 hours after adding the extractant was twice the butanol concentration before adding the extractant. The extractant could be easily separated and recovered from the culture solution, and could be reused by removing the recovered butanol.

Claims (1)

[Claims] 1. In a method for producing butanol from glucose raw materials by fermentation, the fermentation solution and extractant are brought into contact in a fermentation tank, and when butanol is recovered from the extraction phase, an unsaturated alcohol with an average carbon number of 16 to 18 is used as the extractant. Or a method for producing butanol, characterized in that an alcohol having an average carbon number of 16 to 20 and a side chain is used.