JP2009291718A - Method of decolorizing melanoidin-containing wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of decolorizing melanoidin-containing wastewater by decomposing melanoidin contained in the wastewater. <P>SOLUTION: The method of decolorizing melanoidin-containing wastewater uses Geotrichum candidum Dec 1 (accession number: FERM BP-7033). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for decolorizing wastewater containing melanoidin.

  Melanoidin is a brown polymer compound produced by polymerization of sugars and amino acids when heated, and once suspected of being a carcinogen, it has now been found to have a carcinogenic inhibitory effect. There are also experimental results that show a blood cholesterol lowering action and a blood sugar level suppressing action. Therefore, melanoidin was once recognized only as a pigment such as miso and beer, but is now actively used as a food additive such as a color tone adjusting agent and an antioxidant.

  However, since melanoidin is produced as a by-product in the molasses production process, it is mixed into the wastewater of the molasses production factory and the factory that uses molasses. As a result, the wastewater is colored and cannot be discarded into the river as it is. On the other hand, melanoidins are very difficult to process because they are hardly degradable. For example, it is not decomposed by the activated sludge method, which is a general treatment method for wastewater. Therefore, wastewater containing melanoidin is discarded after being diluted in color after being diluted, or dumped into the ocean. However, dilution requires a large amount of water and uncolored wastewater, and ocean dumping is increasingly criticized from the viewpoint of environmental protection.

  In addition, physicochemical treatment methods such as coagulation sedimentation method, oxidative decomposition method, membrane separation, adsorption method and the like can be applied as treatment methods of melanoidin-containing wastewater, but these methods have the disadvantage of high running costs. .

  Therefore, there is a demand for a method that can efficiently decolorize wastewater containing melanoidin.

By the way, in Patent Documents 1 to 3, the peroxidase enzyme produced by Geotricum candidum Dec1 strain which is a filamentous fungus or the same strain has an effect of decolorizing by decomposing a low molecular weight dye compound or a lignin modified product. It is described. However, these patent documents do not describe melanoidin.
Japanese Patent Laid-Open No. 9-173051 JP 2000-245468 A JP 2001-226210 A

  As described above, melanoidin produced as a by-product in molasses factories is said to be harmless, but since it causes wastewater coloring, it must be decomposed. However, melanoidin is a hardly decomposable polymer substance and is difficult to sufficiently treat.

  Therefore, the problem to be solved by the present invention is to provide a method for decolorizing melanoidin-containing wastewater by decomposing melanoidin contained in the wastewater.

  The present inventors have intensively studied to solve the above problems. As a result, it was found that Geotricum candidum Dec1 strain, which was known to have mainly the degradation action of low molecular dye compounds, was found to be capable of efficiently degrading melanoidin, which is a polymer and hardly decomposed, and completed the present invention. did.

  The method for decolorizing melanoidin-containing wastewater according to the present invention is characterized by using Geotricum candidum Dec1 strain (accession number: FERM BP-7033).

  The method preferably includes a step of culturing Geotrichum candidam Dec1 strain; and a step of adding a culture supernatant of Geotricum candidam Dec1 strain to melanoidin-containing wastewater. For example, if the wastewater contains harmful substances that inhibit the growth of bacteria, it is considered that efficient treatment cannot be performed if the Dec1 strain is added directly to the wastewater, but the culture supernatant is added to the wastewater. If it is an aspect, an efficient process can be implemented more reliably.

  In the said method, it is preferable to implement the process of carrying out a methane fermentation process or an activated sludge process of a melanoidin containing wastewater before a process by Geotrichum candidum Dec1 strain | stump | stock. Although wastewater may contain substances that inhibit the degradation of melanoidin, melanoidin can be more efficiently treated by treating other substances in advance through methane fermentation or activated sludge treatment. It can be decomposed.

  Further, in the embodiment in which the culture supernatant of Geotricum candidam Dec1 is added to the melanoidin-containing waste liquid, two culture vessels are provided for culturing Geotricum candidam Dec1 and the culture and culture supernatant of Geotricum candidam Dec1 are obtained. It is preferable to obtain the liquid alternately. This is because it is possible to efficiently supply culture supernatant with high resolution of melanoidin and culture of bacteria.

  According to the present invention, it is possible to efficiently decompose melanoidin in waste water that has been difficult to treat with conventional methods. Therefore, this invention is very useful industrially as what enables the decolorization process of the wastewater containing melanoidin produced from a molasses manufacturing factory etc.

  The method for decolorizing melanoidin-containing wastewater according to the present invention is characterized by using Geotricum candidum Dec1 strain (accession number: FERM BP-7033).

  Melanoidin is by-produced in the molasses production process and treatment process, and is mixed into wastewater to cause coloring. However, the melanoidin-containing wastewater to be treated by the method of the present invention is not limited to the wastewater of the molasses manufacturing factory, and any wastewater containing melanoidin may be used.

Geotrichum candidum Dec1 strain used in the method of the present invention (
Hereinafter, it may be simply referred to as “Dec1 strain”) is deposited in Japan as described below and then transferred to international deposit.

(I) Domestic deposit (i) Name of depositary institution Name: Institute of Biotechnology, Industrial Technology Institute (ii) Date of deposit: December 15, 1995 (iii) Deposit number: FERM P-15348
(II) International Deposit (i) Name and Address of Depositary Organization Name: Institute of Biotechnology, Institute of Industrial Technology, Ministry of International Trade and Industry Address: 1-3 1-3 Higashi 1-chome Tsukuba City, Ibaraki, Japan (ii) Date of transfer: February 17, 2000 (iii) Accession number: FERM BP-7033

  The Dec1 strain used in the method of the present invention is a filamentous fungus that forms a wide vegetative mycelium and a narrow conidia-forming mycelium, and forms a colorless or white colony of 90 mm or more after 7 days of culture. The optimum temperature is 28 ° C., growth is possible at 10-37 ° C., and growth is sufficient at 20-32 ° C. Moreover, the optimum pH is 5-6, and if it is pH 4-8, it can grow.

  In the method of the present invention, the dec1 strain itself or an extracellular substance produced by the dec1 strain is allowed to act on melanoidin-containing wastewater, and the melanoidin is treated for decolorization. That is, the Dec1 strain may be introduced into an activated sludge tank of a wastewater treatment facility using conventional activated sludge to decolorize the wastewater. However, the Dec1 strain has sufficient wastewater decolorization ability even in its culture supernatant, and in order to avoid inhibition of bacterial growth by harmful substances in the wastewater, the culture supernatant of Dec1 is added to the wastewater. It is preferable to remove the color.

  Specifically, first, the Dec1 strain is precultured. The medium used for the preculture is not particularly limited, and includes, for example, a carbon source or nitrogen source such as glucose, yeast extract or peptone; a metal salt such as magnesium sulfate; a phosphate such as potassium dihydrogen phosphate; Can be used. Moreover, any of a solid culture medium and a liquid culture medium can be used.

  As described above, since the optimal temperature of the Dec1 strain is 28 ° C. and the optimal pH is 5 to 6, it is preferable to perform the pre-culture before and after these conditions. The culture time is not particularly limited, but can be about 5 days.

  During pre-culture, the wastewater to be treated may be conditioned by adding about 0.1 to 2% by mass to the medium. In this case, the culture time is preferably relatively long, for example, about 8 days.

  Further, at the time of preculture, a carrier such as polyurethane foam may be added to fix the Dec1 strain to increase the density of the bacteria.

  The pre-cultured Dec1 strain may be added to the culture tank together with the medium. What is necessary is just to match the temperature in a culture tank, liquid medium pH, etc. with the optimal conditions of a Dec1 stock | strain. However, in order to promote the growth of the Dec1 strain, it is preferable to provide an air pump for aeration.

  The culture time is not particularly limited and may be adjusted as appropriate. For example, when the number of bacteria in the culture tank is small, the Dec1 strain continues to grow, but eventually the growth and death of the bacteria balance and the apparent number of bacteria becomes constant. It is preferable to continue the culture until this state is reached. Usually, the culture supernatant is obtained after culturing for about 5 to 20 days. However, if the steady state continues, the decolorization ability of the culture supernatant may decrease even if the apparent number of bacteria is constant. In that case, a treatment for restoring the decolorization ability is performed. For example, after decreasing the concentration of each component of the medium in the culture tank to cause the Dec1 strain to produce conidia, the concentration of each component is increased again to promote the growth of the Dec1 strain, thereby restoring the decolorization ability. .

  Since the Dec1 strain used in the method of the present invention is a filamentous fungus, its growth status can be visually confirmed. Therefore, if it is about daily inspection, a microscope like a Bacillus bacterium or yeast used in normal microorganism treatment can be used. What is necessary is just to confirm the growth condition visually without observing.

In the embodiment in which the culture supernatant of Dec1 strain is added to the melanoidin-containing waste liquid, it is preferable to provide two culture tanks and alternately culture the Dec1 strain and obtain the culture supernatant. In the case of only one culture tank, when a culture supernatant having decolorizing ability is obtained, it takes time necessary for culturing the bacteria until the culture supernatant is obtained again. Therefore, by providing two culture tanks and appropriately shifting the culture time in each culture tank, the supply of the culture supernatant having decolorization ability can be made efficient.

  As a method for obtaining the culture supernatant, a conventional method may be used. For example, after aeration is stopped and bacteria are precipitated, the culture supernatant may be extracted from above the culture tank, or may be extracted through a filter having a pore diameter of several mm. Moreover, you may isolate | separate a microbe and a culture supernatant liquid with the centrifuge used for concentration of activated sludge.

  Next, melanoidin is decomposed and decolored by adding the culture supernatant of the Dec1 strain obtained above to waste water. More specifically, as shown in FIG. 1, melanoidin-containing wastewater is introduced into the decolorization treatment tank, and a culture supernatant of Dec1 strain is further added. For more efficient decolorization, it is preferable to stir during the decolorization treatment.

  The addition amount of the culture supernatant is not particularly limited and may be adjusted as appropriate. However, it can be said that in general, the higher the proportion of the culture supernatant, the higher the decolorization efficiency. However, according to the experiments conducted by the present inventors, the decolorization rate does not significantly decrease even when the supernatant proportion is decreased. It was. Further, as the amount of the supernatant used is smaller, the increase in the amount of drainage can be suppressed, and efficient treatment becomes possible. Therefore, it can be made into a wastewater: culture supernatant liquid = 1: 1-1-20: 1 normally by a volume ratio.

  When the pH of the wastewater is excessively low or high, the decolorization action by the culture supernatant of Dec1 strain may not be suitably exhibited. Therefore, the pH of the wastewater is preferably adjusted to about 4 to 8.

  The temperature during the decoloring process may be adjusted as appropriate, but is usually about 30 to 40 ° C.

  Further, the decoloring time may be determined by a preliminary experiment or may be determined by appropriately measuring the chromaticity of the sample, but is preferably at least one day, more preferably two days or more. The determination of the time for the decoloring process can also be automated. For example, when a sample is obtained from a decoloring tank every certain time, the absorbance of light derived from melanoidin is measured, the measured value is sent to the control unit, the decoloring rate is calculated, and the decoloring rate reaches a predetermined value In addition, a signal for discharging the wastewater from the decolorization tank can be set.

  The decoloring treatment can be carried out either batchwise or continuously. However, when continuous treatment is performed, it is necessary to adjust the amount of waste water introduced into the decolorization treatment tank and the amount of treated waste water to be extracted so that the waste water is sufficiently decolorized.

  In the method of the present invention, it is preferable that the melanoidin-containing wastewater before the decolorization treatment with the Dec1 strain is subjected to a methane fermentation treatment or an activated sludge treatment in advance. It is because the substance which inhibits decomposition | disassembly of the melanoidin by Dec1 strain | stump | stock is decomposed | disassembled by processing the compound which can be processed also in a methane fermentation process and activated sludge process in advance, and the decomposition | disassembly process of melanoidin advances still more efficiently. Moreover, there is a possibility that the melanoidin itself changes to a form that can be easily treated.

  The methane fermentation treatment and activated sludge treatment may be carried out under normal conditions. For example, in the methane fermentation treatment, an anaerobic cell group having a specific gravity called granule and melanoidin-containing wastewater are brought into contact with each other, and main organic components are decomposed to methane gas. In the methane fermentation treatment, since anaerobic bacteria are used, aeration cannot be performed. Therefore, a so-called upward flow anaerobic sludge blanket treatment (UASB treatment) in which waste water is supplied upward to a reactor filled with granules is preferable.

In activated sludge treatment, melanoidin-containing wastewater before decolorization treatment is introduced into an activated sludge tank that has activated sludge containing aerobic bacteria, and wastewater that has been treated with activated sludge is introduced into a separation tank and separated into waste water and activated sludge. To do. The activated sludge separated in the separation tank is discarded as excess sludge or returned to the activated sludge tank. In the activated sludge tank, oxygen is supplied by aeration with an air pump or the like, and the waste water is efficiently brought into contact with the activated sludge.

  A part of the decolored waste liquid or the waste liquid subjected to the decolorization process after the methane fermentation process or the activated sludge process can be used as a culture medium for the Dec1 strain. According to this aspect, the amount of waste liquid to be discharged can be reduced, and the decolorization rate can be further increased.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a range that can meet the gist of the preceding and following descriptions. These are all included in the technical scope of the present invention.

Example 1
(1) Preparation of melanoidin solution
E. C. Bernardo, R. Egashira, J.H. Kawasaki, Carbon, 35, p. A melanoidin solution was prepared with reference to 1217 (1997). Specifically, glucose (4.5 g), glycine (1.88 g) and sodium hydrogen carbonate (0.42 g) were dissolved in distilled water (0.1 L) and heated at 95 ° C. for 7 hours. Distilled water (0.1 L) was added thereto, and the resulting diluted solution was further diluted 10 times with distilled water.

  The obtained melanoidin solution is put into a small amount of microtube, and the absorbance of the supernatant after centrifuging at 12,000 rpm for 5 minutes is measured with a spectrophotometer, and the Ni-Co standard solution is used. The chromaticity was calculated by the formula: (absorbance measurement value) × 1000 / 1.4 to be 2,600. The pH was 5.8. Furthermore, when the contained saccharide was analyzed by HPLC, it contained 3 g / L of glucose and 1 g / L of fructose.

(2) Cultivation of Dec1 strain Geotricum candidum The spore solution stock of Dec1 strain was plate-cultured for 13 days, followed by gauze filtration to collect spores. For acclimatization, 0.2% by volume of the above melanoidin solution is added to YG medium (150 mL) having the composition shown in Table 1, and the solution is added to a 500 mL shake flask. Further, the above spores (3 mL) are added. The culture was performed at 25 ° C. for 4 days.

(3) Decolorization test 10 days, 17 days, 26 days and 32 days after the start of the culture, the culture supernatant was taken, and the melanoidin solution and the culture supernatant were put into a 2 mL tube and the melanoidin solution: culture supernatant = 10: A volume ratio of 1 was added and incubated at 30 ° C. A sample was taken 2 days after the start of treatment, and the chromaticity was calculated in the same manner as in (1) above, and the decolorization rate relative to the initial chromaticity of the melanoidin solution was calculated. The results are shown in FIG.

Example 2
In December 2006, wastewater was obtained from a factory that produces ethanol from molasses. The wastewater contained melanoidin, and the chromaticity of the 15-fold diluted solution calculated by the same method as in Example 1 (1) was 2,000. Moreover, the pH was 4.3, 8 g / L of glucose was contained, and COD-Cr was 10,000 mg / L.

  The decolorization rate of the Dec1 strain by the culture supernatant was calculated in the same manner as in Example 1 except that the wastewater was used and the Dec1 strain was acclimatized with the wastewater. The results are shown in FIG.

Example 3
In November 2006, UASB treatment (upward flow type anaerobic sludge blanket treatment) of waste water from a factory that produces ethanol from molasses was collected, and the chromaticity was obtained in the same manner as in Example 1 (1) above. Was calculated to be 5,000. Moreover, the pH was 7.8, glucose was below the detection limit, and COD-Cr was 3,400 mg / L.

  The decolorization rate of the Dec1 strain by the culture supernatant was calculated in the same manner as in Example 1 except that the waste water was used and the Dec1 strain was not habituated. The results are shown in FIG.

  As shown in FIG. 2, when the culture supernatant obtained by culturing Dec1 strain for 10 days was used, melanoidin could not be sufficiently treated, and the decolorization rate was low. However, when the culture supernatant liquid cultured for 15 days or more was used, the decolorization rate could be increased. In particular, when the waste water after UASB treatment was treated, the decolorization rate was high. Although this is not necessarily clear, for example, it is considered to be a result of degradation of a substance that inhibits the melanoidin-degrading enzyme of Dec1 strain by UASB treatment, or a result of changing to a form in which melanoidin is easily degraded.

Example 4 Examination of treatment temperature The decolorization rate was calculated in the same manner as in Example 3 except that culture supernatants cultured for 32 days or 45 days were used, and melanoidin-containing wastewater was treated at various treatment temperatures. . The results are shown in FIG.

  As shown in FIG. 3, when the temperature is 30 ° C. or higher, the higher the treatment temperature, the higher the decolorization rate of melanoidin.

Example 5 Examination of mixing ratio The above example except that the volume ratio of the waste water and the culture supernatant of Dec1 strain was changed to waste water: culture supernatant = 10: 1, 1: 1 or 5: 1 In the same manner as in 3, the decolorization rate was calculated. The results are shown in Table 2.

  As shown in Table 2, even when the volume ratio of the culture supernatant to the waste liquid was lowered, the decolorization rate was not greatly reduced.

It is a schematic diagram which shows the system of 1 aspect of this invention. It is a figure which shows the decoloring rate (%) with time of the melanoidin containing waste liquid by the culture supernatant liquid of Dec1 strain | stump | stock. It is a figure which shows the decoloring rate (%) which processed the melanoidin containing waste water at various process temperature using the culture supernatant liquid of Dec1 strain | stump | stock.

Explanation of symbols

  1: First culture tank, 2: Second culture tank, 3: Air pump, 4: Heater, 5: Culture supernatant, 6: Melanoidin-containing waste water, 7: Decolorization treatment tank, 8: Stirrer, 9: Decolorization treatment water

Claims (4)

  A method for decolorizing melanoidin-containing wastewater, using Geotricum candidam Dec1 strain (Accession number: FERM BP-7033). The method for decolorizing melanoidin-containing wastewater according to claim 1, comprising the steps of: culturing Geotricum candidam Dec1 strain; and adding the culture supernatant of Geotricum candidam Dec1 strain to melanoidin-containing wastewater.   The method according to claim 1 or 2, comprising a step of subjecting the melanoidin-containing wastewater to a methane fermentation treatment or an activated sludge treatment before the treatment with Geotricum candidam Dec1 strain.   The method according to claim 2, wherein two culture vessels are provided for culturing Geotrichum candidam Dec1 strain, and culture of Geotricum candidam Dec1 strain and acquisition of culture supernatant are alternately performed.