JPS62106822A - Desulfurizing method utilizing sulfur oxidizing - Google Patents

Abstract

PURPOSE:To remove a sulfor compound by the metabolic action of sulfur- oxidizing bacteria, by contacting growth-immobilizing particles for sulfur- oxidizing bacteria with a gaseous or liquid phase containing an org. or inorg. sulfur compound. CONSTITUTION:A liquid medium is inoculated with a strain of sulfur-oxidizing bacteria grown on an agar medium and said sulfur-oxidizing bacteria are multi plied under aeration to prepare a bacteria-immobilizing bath. A dried silica gel is added to an aqueous solution of gamma-aminoporopyltriethoxysilane (gamma-APES) and the resulting suspension is heated, cooled and subsequently washed and dried to drain a carrier wherein the -OH group of the silica gel is bonded to the Si-part of gamma-APES through a covalent bond and this carrier is immersed in the bacteria-immobilizing bath to immobilize bacteria. A column 3 is packed with the obtained growth-immobilizing particles for sulfur-oxidizing bacteria in a multiplication possible form and gas containing CH3SH, SO2 etc. is passed through said column 3 to perform desulfurization. When a liquid such as an amino acid solution containing a sulfur compound is desulfurized, the liquid is passed through the column 3 while aeration is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing sulfur compounds from a gas or liquid phase containing organic or inorganic sulfur compounds by utilizing the sulfur assimilation ability of sulfur oxidizing bacteria.

Sulfur-oxidizing bacteria are known to survive in environments where hydrogen sulfide is produced or sulfur is deposited, such as soil, sea mud, mine water that handles acids, sewage sludge, sulfur springs, or sulfur deposits. Sulfur-oxidizing bacteria obtain energy by oxidizing sulfur compounds in a reduced state, such as elemental sulfur, sulfides, thiosulfates, polythionates, and sulfites, and carry out carbon dioxide assimilation, producing chemosynthetic inorganic nutrients. It is a bacterium that proliferates.

On the other hand, sulfur or sulfur compounds are indispensable and important substances in human life, and exist in various forms in the general living environment. For example, synthetic raw materials for pharmaceuticals and agricultural chemicals,
Aromatic components of foods (flavor of green onions, flavor of meat, mustard,
It is an important element in the spiciness of wasabi, grated radish, etc.). However, on the other hand, sulfur dioxide gas, which is produced as a by-product during the synthesis of pharmaceuticals, agricultural chemicals, and other industrial chemicals, pollutes the environment. In particular, sulfur dioxide gas, which is the main component of air pollution, is subject to emissions regulations by law, or hydrogen sulfide, Wastewater and exhaust gas containing mercaptans are regulated by the Offensive Odor Law. In addition, there are sulfur components that harm the flavor of foods, and there are many sulfur compounds that are harmful or unnecessary for human life. Even in the presence of contaminants, these substances give off unpleasant odors, pose a serious hygienic problem, and affect the taste of the foods produced.

It has been known for a long time that sulfur-oxidizing bacteria have the ability to oxidize sulfur compounds, and numerous academic studies have been conducted to classify the bacteria themselves and elucidate their metabolic mechanisms. It is not uncommon to think of using these sulfur-oxidizing bacteria to remove harmful sulfur compounds and deodorize. However, there is no fact that this has been implemented in a manner that can be used industrially, or there are no documents that describe this.

Based on the above idea, the present inventors have conducted research on the production of sulfur-oxidizing bacteria growth-immobilized particles that can fully exhibit the characteristics of sulfur-oxidizing bacteria and their effects, and have found that extremely excellent results can be achieved. Therefore, the present invention provides growth-immobilized particles of sulfur-oxidizing bacteria formed by immobilizing sulfur-oxidizing bacteria in a form that allows them to grow;
A gas or liquid phase desulfurization process comprising contacting a gas or liquid phase containing an organic or inorganic sulfur compound.

Many studies have been published on the immobilization of microorganisms for some purpose, and in the production of so-called enzyme catalysts, 1. Bacteria containing bacteria or enzymes are immobilized on a carrier and their catalytic action contributes to the production of the target substance. Research is developed corporately. For example, high fructose sugar can be produced from glucose by binding gluten isomerase or a bacterial cell containing it to a suitable carrier. For immobilization, a carrier binding method, a gel entrapment method, or a combination thereof is known.

In immobilizing the sulfur-oxidizing bacteria used in the present invention,
Unlike the enzyme catalysts mentioned above, which utilize the catalytic action of enzymes,
Since sulfur compounds are ingested and oxidized by the assimilation action of sulfur-oxidizing bacteria, it is necessary to carry out the process under conditions that allow the immobilized bacteria to constantly proliferate. In this respect, the immobilization of sulfur-oxidizing bacteria in the present invention is essentially different from the immobilization of enzyme catalysts.

Therefore, the present invention establishes conditions under which the bacteria constantly proliferate when immobilizing sulfur-oxidizing bacteria. This objective can only be achieved by confirming the effectiveness of removing (ingesting) virtually all trace amounts of inorganic or organic sulfur compounds.

The present invention will be specifically explained below along with the progress of experiments conducted by the present inventors.

[I] The sulfur oxidizing bacteria used was Thobacillus thio
novellus (hereinafter referred to as T, T-novellus) and Th1obacillus thiooxida
nsa (referred to as T, T-oxidans).

T, T-nopelas is aerobic and autotrophic, with short culm sails of 4 to 10 × O, 4 to 4.0 μm spherical or oblong spherical cells, and the optimal growth temperature is 30CX optimal growth TI
I( is 7.0 to 9.0, and the growth range is pH 5.0 to 9.0.
It is 2.

T, T-oxydans is also aerobic and autotrophic, short culm 0.4-1.0 am % k suitable growth temperature 28-30
c1 growth range 10-37C1 optimum growth pH 2.0-3.
5, and the growth range is pH 0.5 to 6.0.

[■] Culture of the bacterial strain on agar medium 1. Inoculating the cultured strain of T, T-Novelas on a medium with the following components 1-. Culture is carried out at 30C±2.0C, and subculture is carried out every 1.5 to 2 months for preservation.

Medium component (r) +4) Beptone 5.0 Aspartic acid 2
．． 0 Meat juice extract 3.0 Agar 15. .

NaC 15.0 Distilled water 1,000 pH 6.0-7
．． Adjust to 0.2, T, T-oxydans agar culture culture strain was inoculated into a medium with the following components, statically cultured at 3°C ± 2.07°C, and subcultured every 3 to 4 weeks. Do and save.

Medium component (r) (P) (NH4)2S
O42, ONazSz03"5H10s,.

KNOs 3.0 Na2MoO4・2H
zOO,0003KHIPO43-0 yeast! Ki7.
0, IMgCLs' 61Hto O-5 sulfur powder 1.0CaCtz" 2%0 0.2
5 2elA7c/+ 0.01FeSαg
”7Hz 0.01 cold weather
15.0 Distilled water 1,000 pI (adjusted to 4.0 to 4.6 [■] Culture of bacterial strains in liquid medium Agar from the optimal agar medium (described above) for each of T, T-Novelas, T, and T-Oxydans Each strain grown on the agar medium in section [il] was inoculated into a liquid medium from which only the components had been removed, and the humidity was kept at 30C±2. Keep it under OC and perform aeration to allow bacteria to grow.

In these operations, it is necessary not only to sterilize the instruments used, but also to prevent the contamination of bacteria from the outside as much as possible by passing the air for aeration through a sterile cotton column.

The concentration of bacteria in the liquid medium increases over time, and in about 4 to 5 days, both reach a saturated state of about 2 to 4 x 10' cells/go. This state in which bacteria grow saturated in the mushroom culture solution is called a bacteria fixation bath, and is used as a source of bacteria for immobilization.

[■] Investigation of immobilization growth method The immobilization growth method for sulfur-oxidizing bacteria described in the present invention involves immersing carrier particles in the bacteria fixation bath and adsorbing (accumulating) bacteria on the carrier at a high degree. Thereafter, a test liquid containing a sulfur compound and a test gas are passed through a layer filled with bacteria-immobilized growth particles. In the case of a test liquid, it is aerated and oxygen is supplied to maintain an aerobic state while promoting the digestion of sulfur compounds in the liquid. If the bacteria have degenerated, the bacteria can be grown again by replacing the circulating fluid and gas with a culture solution, and the activation of the bacteria can be maintained by repeating this operation.

We investigated two methods for immobilizing bacteria: covalent bonding and comprehensive bonding. All of these immobilization methods have been reported in the literature as methods for immobilizing enzymes, but little is known about the immobilization of microorganisms. I can't kick it. therefore,
In the present invention, the enzyme immobilization method was modified to be compatible with microorganisms.

(1) Immobilization by covalent bonding This method uses r-aminopropyltriethoxysilane (γ-APE) on silica gel containing many 5t-OH groups on the surface.
This is a method of immobilizing bacteria by binding sulfur-oxidizing bacteria with S) and making the amine 7 group of sulfur-oxidizing bacteria a ligand.◇ The silica gel carrier used has a surface area of 550 to 600
, pore volume 0.4-0.6/2, average pore diameter 10-6
It is 0A. This silica gel has an average particle size of 1 to 1.5, and is heated at a temperature of 1.3 to 1.5 atm and a water vapor temperature of 115 to 1.
Heat treatment is performed in an autoclave at 20 C for about 1 to 1.5 hours to form a large number of 10H groups on the surface. The treated silica gel is dried at a low temperature of 50-60c.

On the other hand, r-APES was diluted twice with water, and after adjusting the pH to 3 to 4 by adding hydrochloric acid, the dry silica gel was added to this solution, and 8011:' was added to the solution in a container equipped with a reflux condenser.
, heat for 2 hours. After cooling, wash thoroughly with water, 50 to 60 tl.
When dried at l', the 10H group of silica gel becomes γ~APE
A carrier covalently bound to the 81 moiety of S is obtained. This carrier was added to the bacteria fixation bath prepared in [■], and the temperature was 30±2.
．． When aeration is continued for about 4 days while maintaining the temperature at Oc, the terminal 7 groups of γ-APES and the protein of the sulfur-oxidizing bacteria form a gantt, and the bacteria are immobilized on the carrier.

In both cases of T, T-novelas and T, T-oxidans, a large amount is immobilized on a carrier, and the surface thereof is covered with parasites that can be discerned with the naked eye.

(2) Inclusive binding using immobilized calcium alginate and aluminum was carried out using the inclusive binding method. (T obtained by the method of I[[).

T-novelas or T, T-oxydans bacteria fixation bath (
Prepare a 1.5% sodium alginate solution (containing a large amount of bacteria), stir well, and leave at a temperature of 5-6C for about 2 hours to degas to produce J mixed heaste. This paste was added to a 16% calcium chloride solution (5~S
r) and left for 2 hours to precipitate spherical gel particles entrapping and immobilizing calcium alginate. The gel particles were mixed with an aluminum mixture [A7z(SO2)s 2 f,
Glucose IL? .

Mg5O+ 0.2? and K) 11PO40,Q2
Water 4007 to T! Prepare by adding and dissolving. temperature 5
~6C] and subjected to ion exchange to obtain aluminum entrapping and immobilized grains. This particle is ion-exchanged (
Ca2-1-→AZ3+) changes it into a strong three-dimensional structure, which further increases its hardness. The voids in this three-dimensional structure provide a place for bacteria to grow. This gel grain was used for T, T-nopelas and T, T-oxydans.
When it is added to a bacteria fixation bath heated at 14'A and aerated, the cells inside and on the surface of the gel particles proliferate, and the gel surface is covered with spores that can be observed with the naked eye, and the bacteria are comprehensively bound without being killed. Indicates that

For the immobilization of bacteria, it has been found that both the covalent bonding method and the entrapping bonding method using the above-mentioned operations are suitable for the growth and immobilization of sulfur-oxidizing bacteria. Specifically, it is convenient to immobilize and propagate the bacteria-immobilized particles obtained in (1) and (2) of [) using the apparatus shown in FIG.

In the figure, 1 is a glass column filled with fixed bacteria with a diameter of 2.40 mm, a layer 2 of glass spheres with a diameter of 3 fi (each about 3 layers thick) is arranged at the top and bottom, and a height of about 15 cr IT is placed in the middle. A fixed layer 3 of bacteria is filled.

A bacteria immobilization bath (bacteria source) containing the bacteria shown in [II[) is placed in the Erlenmeyer flask 4, and sterile air is introduced into the liquid through the inlet thread 6.7. The bacteria fixation bath solution is circulated from the bottom of the column through the bacteria fixation Kj by a pump action. The introduced air is discharged from the outlet 8.

For example, when T, T-nopelas is immobilized and propagated by the inclusive binding method, the above-mentioned T is placed in an Erlenmeyer flask.

Add 200rnt of bacteria fixation bath (bacteria source) solution for T-Novelas, and fill the column with entrapping immobilization gel particles prepared by immobilizing bacteria using the method described above to a height of 15crn. While passing clean air into the bath, the bacterial source bath is fed into the column and circulated for a long time.

Through this treatment, the T and T-nopelas on the carrier further proliferate, showing linear proliferation over time until about 30 hours, but after that, it gradually becomes sluggish, and substantial proliferation occurs after 4 days and about 96 hours. seems not to be seen. As shown in the examples below, this lXj N-ization time was 30.40.90
In a test using a methyl mercaptan gas flow method using immobilized particles over a period of time, 30 cm in 30 hours and 75 cm in 40 hours.
It has been found that 100% removal can be achieved in 90 hours. At this point, the T, T-novellas bacteria immobilized on the carrier with a particle size of 2 to 3 g corresponds to 20 to 25 inches in weight.

The particles are covered with yellowish-white particles. In the case of T,T-oxidans, exactly the same effect can be obtained by this operation.

Immobilized growth of sulfur-oxidizing bacteria by a covalent bonding method can also be carried out in the same manner using the apparatus shown in FIG. Using T,T-oxidans as the bacterial cells, a bacterial fixation bath (bacterial source) 2001n/ indicated by (I[['']) was placed in an Erlenmeyer flask, while the above [F/] (1) The bacteria-fixed silica gel particles (particle size 1-1-5 wa, specific gravity 2.3) obtained in
Fill the column to a height of n1, and circulate the bacteria fixation bath solution through the column while passing clean air through the bacteria fixation bath in the Erlenmeyer flask. Through this treatment, bacteria further proliferate on the surface of the carrier in the column, and after 4 days or about 96 hours, T and T
- In the case of novelas, a bacterial growth coating is formed on the surface of the carrier. T.

If this operation is performed on the T-Novelas, results that are exactly the same will be obtained. In the above experiments, it was confirmed that the immobilization of T, T-novelas or T, T-oxidans in Oyu bacteria is possible by both the inclusive binding method and the covalent binding method.

In this way, a column containing an immobilized layer of fixed bacteria with sulfur-oxidizing bacteria immobilized and multiplied on the surface of the carrier can directly absorb sulfur contained in the gas phase or liquid phase, depending on the capacity of the prepared column. Can be used for oxidation and desulfurization of compounds.

When oxidizing and removing sulfur compounds in a liquid sample, the first
The fixed layer of sulfur-oxidizing bacteria in column 1 of the apparatus shown in the figure is washed with distilled water and left for 2 hours to remove water droplets. The liquid sample is placed in place of the culture solution in the Erlenmeyer flask 4, and the liquid is circulated for a certain period of time using a pump while introducing clean air into the sample solution.

It is preferable to keep the pH of the liquid at 7 or less. The degree of oxidation of the sulfur compound can be determined by sampling the sample solution over time and measuring the sulfur concentration. When containing interfering ions such as an amino acid solution, a method for measuring S2- ions using an electrode method is used.

In order to remove sulfur compounds from a gas sample by oxidation, the gas sample is similarly passed through the column using the sulfur-oxidizing bacteria immobilized odor amplification '1 column shown in FIG. Gas chromatography is used to measure sulfur compounds in treated samples. FIG. 2 is a schematic diagram of the apparatus used in the gas sample experiment, in which 9 is a sulfur compound cylinder, 10 is an air cylinder, and 11 is a mixer.

After use, wash with distilled water only when the fixed bed in the column is significantly contaminated, and leave it for about 3 hours to remove water droplets.
By circulating the culture medium corresponding to the sulfur-forming bacteria used, the bacteria are grown and prepared for the next operation.

When the sample is relatively large and the processing time is long, the processing can be interrupted and growth can be performed using a culture solution. The immobilized growth layer of bacteria in the column thus prepared can be used substantially semi-permanently.

Hereinafter, the effects achieved by the present invention will be specifically explained using examples.

Example I Oxidation experiments of gaseous samples containing various sulfur compounds were carried out using the experimental apparatus shown in FIG. 2, including a fixed bed column of T, T-nopelas bacteria and T, T-oxydans bacteria.

(1) Sample gas (a) Methyl mercaptan gas: Cll3 SHm
(diluted with air) (b) Sulfur dioxide gas: 802 concentration 6.5 ppm
(diluted with air) (c) Hydrogen sulfide gas aH1s concentration 6.5 pprn
(Dilute with air) Use gas chromatography to measure concentration.

(2) Gas flow condition temperature of sample gas proliferation immobilized particle layer (
Room temperature) 10-12r The gas concentration per person was 6.5 ppm, the sample gas flow rate was 40-7 minutes, the sample gas passage time was 60 hours, and the outlet gas concentration was measured and recorded every 10 hours.

(3) Immobilized particles used in the experiment A: T, T −/by Hellas inclusive bonding method B: T, 'l'-/l2/to bound bond method C:
D by inclusive combination method of T, T-oxidans:
Experiment 1 using the covalent bonding method of T,T-oxidans An oxidation experiment was conducted under the above conditions using the methyl mercaptan gas described in (a) above as the sample gas. However, it should be noted that the degree of saturation of the bacterial cells formed inside and on the surface of the immobilized and proliferated particles of each type of bacteria differs depending on the time of the proliferating and immobilizing treatment, which may cause differences in effectiveness. As confirmed in the experiment, the immobilized particles packed in the column are
The desulfurization test was conducted with three treatment times: 30 hours, 40 hours, and 90 hours.

The results are shown in the table below.

During the 60-hour gas flow period, the outlet concentration was exactly the same from the start time to the stop time, and no change in concentration was observed. From this result, almost no deviations due to the bacterial species and immobilization method in (A), (B), (C), and (D) are observed. In addition, in both cases, the desulfurization performance at 30 hours is approximately 30%, 75%, and 100 hours, respectively.
It was found that if the circulation treatment was carried out for 90 hours or more, immobilization showed saturated growth regardless of the method, and 100% of the methyl mercaptan-containing gas was desulfurized.

Experiment 2 In this experiment, in addition to using a propagation fixed bed that had been circulated for 96 hours, oxidation experiments of (b) sulfur dioxide gas and (c) hydrogen sulfide gas were conducted under the same conditions as in Experiment 1.

In this experiment, as in the case of methyl mercaptan gas, the outlet concentration was always 0 throughout the 60 hour gas passage time, indicating that 100% oxidation occurred. Also,
Almost no deviations due to bacterial species or immobilization methods were observed.

Although the gas flow was conducted at a temperature of 10 to 12C (room temperature), even better results can be expected if the gas flow is performed at a temperature of 25 to 30R, at which the bacteria become active.

Example 2 Using the experimental apparatus shown in Figure 1, an aqueous solution of p15.2 containing a total of 19 g of seed amino acids and 20 g of salt was measured using the ion electrode method.
m is 15.6 ppm. Pour this solution into a flask.
The fixed layer of the column was circulated and passed through the immobilized layer at a temperature of 30C and a sample flow rate of 40-/min. 8 of liquid over time
2- As a result of measuring the concentration, the results shown in the following table were obtained. A in the table
, B, C and D are the same as in Example 1.

(Unit: ppm) From the results in the two tables, it can be seen that an amino acid aqueous solution containing 15.6 ppm of sulfur was completely desulfurized in approximately 3 hours for immobilized growth particles A and C, and in 2.5 hours for particles B and D. Figure 3 shows this result in a graph.

One particle of immobilized and expanded array of sulfur-oxidizing bacteria used in the present invention has a specific gravity of about 2.3 and has physical strength. Having described the method utilized, one skilled in the art will readily understand that gas or liquid phases containing sulfur compounds may be treated in a fluidized reactor by well-known fluidized bed techniques.

Generally, it is considered difficult to remove trace amounts of sulfur from the gas or liquid phase, and the present invention is extremely advantageous in that it can be easily operated when the p)I of the gas or liquid is 7 or less at room temperature. It can be said.

Moreover, since sulfur is used for bacterial metabolism, its effects can be expected to last semi-permanently. In particular, the present invention can suitably solve the problems of removing SO2 caused by air pollution, eliminating sulfur-based malodors, and industrially removing sulfur, which is a problem in the production of foods and medicines such as Ami 7-year-old.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an experimental apparatus used for liquid phase treatment according to the present invention, and FIG. 2 is a schematic diagram of an experimental apparatus used for gas phase treatment. FIG. 3 is a graph showing the results of an experiment on processing an amino acid solution according to the present invention as a function of passage time and changes in S2 concentration in the amino acid solution. Patent applicant: Cosmo Foods Co., Ltd. Agent: Patent attorney Hirayama - Car distance: Patent attorney Kaizu Tamotsu (Author's seal issued by the third proceeding chief) June 18, 1986

Claims (1)

[Claims] A gas phase or liquid phase consisting of contacting sulfur oxidizing bacteria growth-immobilized particles formed by immobilizing sulfur oxidizing bacteria in a form capable of growth and a gas phase or liquid phase containing an organic or inorganic sulfur compound. desulfurization method.