JP2000144149A - Biological desulfurization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject method for desulfurizing petroleum (product) through setting the ratio of the petroleum to water within a specified range to raise biological reaction rate so as to improve oil/water separation efficiency and reduce the oil/water separation cost. SOLUTION: This method comprises desulfurizing petroleum or a petroleum product (e.g. light oil, desulfurized light oil) by its reaction with microorganisms having the ability to degrade organosulfur compounds suspended in an aqueous system such as Rhodococcus erythropolis KA2-5-1 strain (FERN P-16277) in the weight ratio of water to the petroleum of (3:1) to (8:1).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for desulfurizing petroleum or petroleum products using a microorganism having the ability to decompose organic sulfur compounds.

[0002]

2. Description of the Related Art It is required to reduce the amount of sulfur dioxide gas, which is a pollutant in the atmosphere. From October 1997, the concentration of sulfur contained in light oil was regulated to 0.05%. (Revision of the Japanese Industrial Standards, Air Pollution Control Law, and Quality Assurance Law) Hydrodesulfurization is carried out for the desulfurization of gas oil, but dibenzothiophene, its alkyl derivative,
It is known that dibenzothiophenes having an alkyl group at the position are hardly decomposed. Recently, using microorganisms that easily oxidize and decompose these dibenzothiophenes,
Research and development have been made on a method for desulfurizing gas oil by converting organic sulfur compounds in gas oil into water-soluble substances and removing it from gas oil. (Daniel J. Monticello, CHEMTECH JULY 1998 38
-45)

[0003] In this method, the light oil is mixed with water in which microorganisms are suspended, and the desulfurization reaction proceeds under appropriate reaction conditions such as aeration and stirring. After the reaction, the gas oil having a reduced sulfur concentration is separated into water in which microorganisms are suspended, and then turned into a product. Conventionally, in the reaction of producing useful substances from petroleum fractions by microorganisms, for example, in the production of yeast cells, long-chain dicarboxylic acids, and citric acid from n-paraffins, the ratio of petroleum components to microorganism suspension water in a reaction tank is 1/1. The usual method is to increase the water fraction as in 1/10 (Joji Oiwa, Fermentation and Industry, 43 (5), 442-452 (1985), Shunichi Akiyama,
Oil Chemistry, 23 (8), 438-444 (1984), Minami Uemura, Chemical Industry, May 1987, 48-53 (1987)). Also, in the desulfurization reaction of light oil by microorganisms, the oil-water ratio is 1/2 to 1/9.
(US 5,358,870, WO 95/16762, U
S 5,468,626, US 5,525,235, US 5,772,901).

[0004] The reason has been considered that it is necessary to reduce the oil-water ratio because microorganisms take nutrients from water.
Furthermore, oil has been thought to damage cell membranes and cell walls due to oil, making it more difficult for biological activities to occur (Oliver Favre-Bulle, Toine Schouten,
Jaap Kingma and Bernard Witholt, BIOTECHNOLOGY 9AP
RIL 1991, 367-371). However, it is clear that in a reaction composed of an oil-water mixture for substances in oil, the reaction rate per volume decreases as the amount of water increases.
Therefore, when applied to a continuous reaction, there are disadvantages in that the volume of the reaction tower increases and the transfer cost of the aqueous bacterial cell slurry also increases.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for desulfurizing petroleum or petroleum products using a microorganism having the ability to decompose organic sulfur compounds. To provide a way to increase

[0006]

In order to increase the speed of the biodesulfurization reaction in the oil-water mixing reaction tank, suppress the generation of emulsions that hinder oil-water separation after the reaction, and perform oil-water separation efficiently, the oil-water mixture in the reaction tank is required. We find it important to optimize the mixing ratio, and the ratio is 2/1
To 20/1, preferably 3/1 to 8/1, and completed the present invention. That is, the present invention relates to a method for desulfurizing petroleum or petroleum products by reacting petroleum or petroleum products with microorganisms having the ability to decompose organic sulfur compounds suspended in an aqueous system, wherein the ratio of petroleum to water is from 3/1. A desulfurization method for petroleum or petroleum products, characterized in that the range is 8/1. The petroleum products include light oil or desulfurized light oil.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The microorganism used for the desulfurization reaction of the present invention is a normal temperature bacterium, a type of thermophilic bacterium, and a cleavage site of the organic sulfur compound is CC bond,
Any of C—S bonds may be used. That is,
Any of the microorganisms described below can be used.
For example, there have been many reports on a method for removing sulfur from petroleum using bacteria at room temperature. Bauch et al.
The desulfurization rate of 60-80% was observed in 2 days by continuously treating the heavy oil fraction having a high viscosity at 30 ° C. using eudomonas HECC39 strain (Bauch, J., Herbert. , Hieke,
W., Eckart, V., Koehler, M., Babenzin, HD, Chemi
cal Abstracts 82530y vol.83 (1975)). Yuda, Pseudo
It has been reported that monas haconensis is brought into contact with petroleum to convert it into a water-soluble compound (Yuda, S., JP-A-50
-107,002 ： Chemical Abstracts 46982j vol.84 (1976))
. Lee et al. Reported that Thiobacillus, a sulfur-oxidizing bacterial strain,
Reported desulfurization of crude oil, heavy gas oil, kerosene, and naphtha by thiooxidans and sulfur reducing bacteria strain Pseudomonassp. (Lee, MJ, Hah, YC, Lee, KW Chemical Abstr.
acts 145448s vol.85 (1976)). They examined the desulfurization capacity of various sulfur-oxidizing and sulfur-reducing bacteria and found that Thioba
cillusthiooxidans have the most effective sulfur oxidizing ability, Pseudomonas putrefaciens and Desulfovibrio desulf
uricans have the most effective sulfur reducing ability (Lee, MJ, Hah, YC, Lee. KW Chemical A
bstracts 156414d vol.85 (1976)). Sulfur reducing Pseu
Isolation of seven domonas strains has also been reported by the same group. Eckart and colleagues also reported that Romashkino crude oil and fuel oil Ps
Oxidative desulfurization by eudomonas desmolyticum has been reported (Eckart, V., Hieke, W., Bauch, J., Gentzsch, H.
Chemical Abstracts 142230q vol.94 (1981); Eckart,
V., Hieke, W., Bauch, J., Gentzsch, H. Chemical Ab
stracts 147259c vol.97 (1982)). Regarding these desulfurization reactions carried out by bacteria of the genus Pseudomonas, their degradation products have been identified, and in microorganisms whose desulfurization reaction mechanism has been elucidated, all reactions that break the C-C bond in sulfur compound molecules in oil We know that we use.

In addition to the above, several microorganisms are known to attack the carbon skeleton in the same manner as described above, catalyze the partial oxidation of organic sulfur heterocycles, and convert them to water-soluble products. ing. Pseudomonas sp., Pseudomonas a
eruginosa, Beijerinckia sp. Pseudomonas alcaligene
s, Pseudomonas stutzeri, Pseudomonas putida (partially oxidized), Brevibacterium sp. (mineralization = mineral formation). The genetic determinants of these enzymatic reactions are generally considered to be plasmids and represent biotransformations characteristic of the oxidation of aromatic hydrocarbons (Monticel
lo, DJ, Bakker, D., Finnerty, WR Appl. Environ,
Microbiol., 49, 756-760 (1985)).

[0009] There have been reported microorganisms that decompose model compounds containing sulfur as well as crude oil and coal, and selectively remove sulfur, which is a heteroatom, to produce sulfates and hydroxylated compounds. Considering the structure of the metabolite, this type of reaction is considered to be a reaction that specifically cleaves the C—S bond in the sulfur compound, thereby releasing sulfur in the form of sulfate. Are aerobic and heterotrophic non-acidic soil bacteria Pseudomonas CB1, Acinetobacte
r CB2 was reported to convert thiophene sulfur to sulfate (Isbister. JD and Kobylinski, EA (Microb
ial desulfurization of coal. in Coal Science and T
echnology, Ser. 9, p.627 (1985)). When using a bench-scale continuous bioreactor, CB1 reduced the organic sulfur content of lllinois # 6 coal by 47%. Dibenzothiophenesulfoxide, dibenzothiophenesulfone, and 2,2'-dihydroxybiphenyl have been identified as intermediates in the desulfurization of dibenzothiophene. Separately, unidentified soil isolates produce 35-45 of organic sulfur as sulfate from four different types of coal.
% Has been reported (Finnerty, WR a
nd Robinson, M., Biotechnol. Bioengineer. Symp. # 1
6, 205-221 (1986)). Also, Rhodococcus rhodochrous
The isolate ATCC 53968 has been shown to have a sulfur-attacking pathway to convert dibenzothiophene to hydroxybiphenyl and sulfate, but the fungus reduces the organic sulfur content in crude oil and coal by 70% (Kilbane, JJ R
esources, Conservation and Recycling, 3, 69-70 (199
0)). A dibenzothiophene degradation pathway is also described for bacteria of Corynebacterium sp., Which also oxidizes dibenzothiophene to produce 2-hydroxybiphenyl and sulfate through dibenzothiophene sulfoxide and dibenzothiophene sulfone (Ohmori, T. .,
Monna, L., Saiki, Y. and Kodama, T. Appl.Enviro
n, Microbiol., 58, 911-915, 1992). Arthrobacter K
3b has been reported to perform a similar reaction with Brevibacterium, and sulfite and benzoic acid are produced when dibenzothiophene sulfone is used as a substrate (Dahiberg,
MD (1992) Third International Symposium on the Bi
biological Processing of Coal, May 4-7, Clearwater B
each, FL, pp. 1-10, Electric Power Research Institut
e, Palo Alto, CA.). On the other hand, a novel system in which a sulfur-containing aromatic heterocyclic compound is converted to hydrogen sulfide in a non-aqueous solvent has also been reported (Finnerty, WR Fuel 72, 1631-16
34, 1993). Unidentified strain FE-9 converts dibenzothiophene to biphenyl and hydrogen sulfide in 100% dimethylformamide under a hydrogen atmosphere and to hydroxybiphenyl and sulfate in the presence of air. This strain is also reported to convert thianthrene to benzene and hydrogen sulfide in the same solvent under a hydrogen atmosphere and to benzene and sulfate in the presence of air. Apart from these aerobic dibenzothiophene-degrading bacteria, anaerobic sulfate-reducing bacteria have also been shown to convert dibenzothiophene to biphenyl and hydrogen sulfide, and also bio-convert petroleum organic sulfur to hydrogen sulfide ( Ki
m, HY, Kim, TS and Kim, BH, Biotechnol. Lett.
12, 757-760, 1990a; Kim, TS, Kim, HY and Kim,
BH Biotechnol. Lett. 12, 761-764, 1990b).

[0010] All of the above-described biodesulfurization using microorganisms utilizes a microbial metabolic reaction that proceeds under a temperature condition of about 30 ° C. On the other hand, it is known that the rate of a chemical reaction generally increases depending on temperature. Also,
In the desulfurization step in the petroleum refining process, fractional distillation and desulfurization reaction are performed under high temperature and high pressure conditions. Therefore, if the bio-desulfurization step is incorporated into the petroleum refining process, it would be desirable to be able to perform the bio-desulfurization reaction at a higher temperature during cooling without cooling the petroleum fraction to near normal temperature. Reports on high temperature biodesulfurization include:

Most attempts to perform desulfurization reactions at elevated temperatures using microorganisms can be found in coal desulfurization. Coal contains various sulfur compounds. The main inorganic sulfur compound is pyrite, but a wide variety of organic sulfur compounds are mixed, and many are known to contain thiol, sulfide, disulfide and thiophene groups. The microorganism used was
Bacteria of the genus Sulfolobus, all of which are thermophilic. Leaching of metals from mineral sulfide (Brierley
CL & Murr, LE, Science 179, 448-490 (1973)) and sulfur removal of pyrite from coal.
Examples using lfolobus strains have been reported (Kargi, F. & R
obinson, JM, Biotechnol.Bioeng. 24, 2115-2121 (1
982); Kargi, F. & Robinson, JM, Appl.Environ.M
icrobiol., 44, 878-883 (1982); Kargi, F. & Gervoni.
TD, Biotechnol. Letters 5, 33-38 (1983); Kargi,
F. and Robonson, JM, Biotechnol. Bioeng., 26, 68
7-690 (1984); Kargi, F. & Robinson, JM, Biotechno
l. Bioeng. 27, 41-49 (1985); Kargi, F., Biotechnol.
Lett., 9, 478-482 (1987)). According to Kargi and Robinson, one strain of Sulfolobus acidocaldarius isolated from an acidic hot spring in Yellowstone National Park in the United States had 45-7
Grows at 0 ° C but oxidizes elemental sulfur at optimal pH 2
(Kargi. F. andRobinson, JM, Appl. Environ. Micro
biol., 44, 878-883 (1982)). Also, two other Sulfolo
Pyrite oxidation by bus acidocaldarius strains has also been reported (Tobita, M., Yokozeki, M., Nishikawa, N. & Ka).
wakami.Y., Biosci. Biotech.Biochem. 58, 771-772 (1
994)).

Among the organic sulfur compounds contained in fossil fuels, dibenzothiophene and its substituted derivatives are known to be less susceptible to hydrodesulfurization in ordinary petroleum refining processes. Its dibenzothiophene Sulfol
High-temperature decomposition by obus acidocaldarius has also been reported
(Kargi, K. & Robinson, JM, Biotechnol. Bioeng. 2
6, 687-690 (1984); Kargi, F., Biotechnol. Letters
9, 478-482 (1987)). According to these reports, when model aromatic heterocyclic sulfur compounds such as thianthrene, thioxanthene, and dibenzothiophene were reacted with this microorganism at a high temperature, these sulfur compounds were oxidized and decomposed. Oxidation of these aromatic heterocyclic sulfur compounds by S. acidocaldarius has been observed at 70 ° C., producing sulfate ions as reaction products. However, this reaction is a reaction in a medium containing no carbon source other than the sulfur compound, and the sulfur compound is also used as a carbon source. That is, it is clear that the CC bond in the sulfur compound is decomposed. Furthermore, this Sulfolobus acidocaldarius
Can grow only in acidic media, and the oxidative degradation of dibenzothiophene requires progression under harsh acidic conditions (pH 2.5). It is considered that such severe conditions cause deterioration of petroleum products, and at the same time, require an acid-resistant material in a step relating to desulfurization, which is considered to be undesirable in the process.
When grown under autotrophic conditions, Sulfolobus acidocaldarius gains the required energy from reduced iron-sulfur compounds and uses carbon dioxide as a carbon source.
Sulfolobus acidocaldarius, when grown under heterotrophic conditions, can utilize various organic compounds as carbon and energy sources. That is, it is considered that the presence of fossil fuel is utilized as a carbon source.

[0013] Finnerty et al., Pseudomonas stutzeri, Ps
It has been reported that eudomonas alcaligenes and strains belonging to Pseudomonas putida decompose dibenzothiophene, benzothiophene, thioxanthene and thianthrene and convert them to water-soluble substances (Finnerty, WR, Shockiey,
K., Attaway, H. in Microbial Enhanced Oil Recover
y, Zajic, JE et al. (eds.) Penwell. Tulsa, Okla.,
83-91 (1983). In this case, the oxidation reaction proceeds even at 55 ° C. However, the degradation product of dibenzothiophene by these Pseudomonas strains was 3-hydroxy-2-formylbenzothiophene reported by Kodama et al. (Monticello, DJ, Bakker, D., Finnerty, WR).
Appl. Environ. Microbiol., 49, 756-760 (1985)). The oxidation activity of dibenzothiophene by these Pseudomonas strains is induced by naphthalene and salicylic acid, which are aromatic hydrocarbons containing no sulfur, and blocked by chloramphenicol. From this, these Pseu
The degradation reaction of dibenzothiophene by domonas strain
It can be seen that it is based on decomposition by breaking the CC bond in the aromatic ring. In addition, valuable aromatic hydrocarbons contained in the petroleum fraction other than the sulfur compound may be simultaneously decomposed, which lowers the value of the fuel and the quality of the petroleum fraction.

Rhodococcus erythropolis KA2-5-1 strain (F
ERM P-16277) can decompose the organosulfur compound by culturing the cells and then bringing the cultured cells into contact with an organic sulfur compound intended for decomposition. The cultivation of the microorganism is performed according to a usual culture method of the microorganism. The form of culture is preferably liquid culture. Commonly used nutrients for the medium are widely used. Any available carbon compound may be used as the carbon source, and for example, glucose, sucrose, lactose, fructose, ethanol and the like are used. Any available nitrogen compound may be used as the nitrogen source. For example, organic nutrients such as peptone, polypeptone, meat extract, yeast extract, soybean powder, and casein hydrolyzate can be used. If it is desired to culture in a medium that does not contain sulfur compounds that can affect the desulfurization reaction, inorganic nitrogen compounds such as ammonium chloride can also be used. In addition, phosphates, carbonates, magnesium, calcium, potassium, sodium, iron, manganese, zinc, molybdenum, tungsten, copper, vitamins, and the like are used as needed. The cultivation is carried out aerobically for 1 to 3 days under shaking or aeration at pH 6 to 8 and at a temperature around 30 ° C.

The desulfurization reaction of the petroleum fraction is performed by leaving the petroleum fraction in contact with the culture solution and leaving it under conditions suitable for the reaction. A method can be used in which the mixture is allowed to stand under conditions suitable for the reaction while contacting the fraction. Such a quiescent cell reaction can be performed, for example, as follows.

The cells can be prepared by inoculating a fresh medium with an appropriate amount of, for example, 1 to 2% by volume of inoculum, and performing reciprocal or rotary shaking culture at 30 ° C. In this case, the inoculum is preferably in the late logarithmic growth phase, but may be in any state from the initial logarithmic growth phase to the stationary phase. Also, the amount of inoculation can be increased or decreased as needed. The medium is desirably a room temperature desulfurization bacterium, but may be another medium. Commonly used nutrients for the medium are widely used. Any available carbon compound may be used as the carbon source, and for example, glucose, sucrose, lactose, fructose, ethanol and the like are used. Any available nitrogen compound may be used as the nitrogen source. For example, organic nutrients such as peptone, polypeptone, meat extract, yeast extract, soybean powder, and casein hydrolyzate can be used. If it is desired to culture in a medium that does not contain sulfur compounds that can affect the desulfurization reaction, inorganic nitrogen compounds such as ammonium chloride can also be used.
In addition, phosphates, carbonates, magnesium, calcium, potassium, sodium, iron, manganese, zinc, molybdenum, tungsten, copper, vitamins, and the like are used as needed. Normal culture is performed aerobically for 1 to 3 days at about 30 ° C. under shaking or aeration. However, the culture temperature is preferably 30 ° C., but may be any temperature in the temperature range of about 25 ° C. to 37 ° C.

It is desirable that the cells obtained by culturing are separated and collected by means such as centrifugation, and the cells are washed, collected again, and used for a resting cell reaction. At this time, the cells are preferably collected in the middle to late stages of the logarithmic growth phase, but may be those in the early to stationary phase of the logarithmic growth phase. As a means for separating and collecting bacteria, any method such as filtration or sedimentation may be used in addition to centrifugation. For washing the cells, any buffer such as physiological saline, phosphate buffer and Tris buffer can be used, and the cells may be washed using water.

The resting cell reaction is carried out by adding a substrate to a cell suspension prepared by suspending cells in a suitable buffer. Various buffers can be used as the buffer. The pH of the buffer is pH
6 to 7 is preferred, but other pHs may be used. Further, instead of the buffer solution, water or a medium may be used. The concentration of the cell suspension is preferably between OD ₆₆₀ of 1 to 50, but can be increased or decreased as necessary. As a substrate for the resting bacterial cell reaction, for example, dibenzothiophene, a dibenzothiophene derivative, benzothiophene, or a benzothiophene derivative can be used. These sulfur concentrations are 50pp
Although m to 10,000 ppm are preferred, they are contained in the gas oil to be subjected to the desulfurization reaction.

In place of the quiescent cells in the above reaction, an alkylated benzothiophene and / or an alkylated dibenzothiophene-based compound separated and purified from the cells is used.
Enzymes involved in the selective cleavage of CS bonds may be used. The extraction of the reaction product can be performed as follows. After adjusting the pH of the reaction solution to about 2 using 6N hydrochloric acid, the mixture is extracted with stirring using ethyl acetate. However, the solvent used for extraction is not limited to ethyl acetate, and any solvent may be used as long as the desired reaction product can be extracted. The amount of ethyl acetate is preferably equal to the amount of the reaction solution, but can be increased or decreased as needed. The reaction product can be separated using a reversed-phase C18 column or a normal-phase silica column, but another column may be used if necessary. The method used for the separation is not limited to these methods, and any method may be used as long as the reaction product can be separated. The reaction product is analyzed using gas chromatography, gas chromatography / mass spectrum analysis, gas chromatography / atomic emission detection analysis, gas chromatography / Fourier transform infrared spectroscopy, nuclear magnetic resonance, and the like. be able to. Further, other analysis methods may be used together as needed. Furthermore, the methods used for analysis are not limited to these methods,
Any method may be used as long as the reaction product can be analyzed.

The use of this method can achieve higher reaction rates than can be obtained with a normal oil-water ratio. In addition, after the reaction, the generation of an emulsion that hinders oil-water separation is suppressed, and centrifugation can be performed at a low speed, so that improvement in oil-water separation efficiency and reduction in separation cost can be expected.

[0021]

The present invention will be described below in more detail with reference to examples. However, the technical scope of the present invention is not limited to these examples.

Example 1 Rhodococcus erythropolis K
A 2-5-1 (FERM P-16277) strain and 25% dibenzothiophene
inoculated in a growth medium containing 1 ppm (Table 1), cultivated at 30 ° C for 3 days, centrifuged 12,000 ml of the culture at 10,000 G, and dried
72 g of cells are obtained. All cells are suspended in a 1 / 15M buffer at pH 7.0 to make the volume 2000 ml. 0.047% sulfur concentration
(Sulfur 14.7 mM) in light oil
(Oil / water ratio 1/2), 1000/1000 (1/1), 1333/667 (2/1),
1500/500 (3/1), 1600/400 (4/1), 1667/333 (5/1), 17
15/285 (6/1), 1750/250 (7/1), 1778/222 (8/1), 1800
/ 200 (9/1), 1882/182 (10/1) and 1867/133 (11/1).

Each mixed solution is put into a 3 L small fermenter and left for 13 hours at a stirring speed of 400 rpm, aeration speed of 0.5 vvm and a temperature of 30 ° C. The reaction solution was centrifuged (12,000 rpm, 10 minutes), and the sulfur content of the supernatant was measured by a pyrofluorescence method (Antech sulfur meter model 7000). Table 2 shows the results. From this table, to maximize the product production rate, increase the oil / water mixture ratio from 3/1.
It turns out that it is necessary to be in the range of 8/1.

[0024]

[Table 1]

[0025]

[Table 2]

Example 2 The cells obtained by the cultivation of Example 1 were diluted to a concentration of 3 g / L to 60 g / L with a concentration of 1/15 of pH7.
Suspended in M phosphate buffer, the light oil (sulfur concentration 0.047%) used in Example 1 and the above suspension were passed through a continuous reaction tank so as to have a ratio of 1/2 to 10/1. After performing the reaction for 7 hours, the sulfur concentration of the reaction solution is analyzed in the same manner as in Example 1. Table 3 shows the results. It can be seen that the reaction rate per unit volume reaches the maximum level when the mixing ratio of oil and water is 3/1 to 8/1.

[0027]

[Table 3]

[Example 3] The oil-water reaction solution after the desulfurization reaction in Example 1 is separated into an oil and a cell suspension by centrifugation for 30 seconds. The oil phase turbidity is shown in Table 4 as the optical density OD measured in a 1 cm thick cell at a wavelength of 660 nm. From this table, it can be seen that the oil-water mixture ratio needs to be 3/1 or more to minimize the oil phase turbidity.

[0029]

[Table 4]

[0030]

According to the method of the present invention, the reaction rate of the desulfurization reaction can be increased. In addition, when the product is recovered from the desulfurized solution after the reaction, the generation of an emulsion that hinders the separation of oil-water bacteria can be suppressed. Reduction can be achieved.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuo Sugaya 3-51-1, Nomidai, Kanazawa-ku, Yokohama-shi, Kanagawa F-term town C-106 F term (reference) 4B064 AB01 CC03 CD04 CD11 CD16

Claims (2)

[Claims] 1. A method for desulfurizing petroleum or petroleum products by reacting petroleum or petroleum products with microorganisms having the ability to decompose organic sulfur compounds suspended in an aqueous system, wherein the ratio of petroleum to water is 3/1 to 8 A desulfurization method for petroleum or petroleum products, characterized in the range of / 1. 2. The method for desulfurizing petroleum or petroleum products according to claim 1, wherein the petroleum product is gas oil or desulfurized gas oil.