Microbial conversion of bile acids

Abstract: The present invention provides a microorganism of the genus Bacillus capable of selectively oxidising a 7α and/or 12α -hydroxy group of a 3α-hydroxy-5β-cholanic acid having a 7α- and/or 12α- hydroxy group and a process for selectively oxidising a 7α- and/or 12α- hydroxy group of a 3α-hydroxy-5β-cholanic acid having a 7α- and/or 12α-hydroxy group, comprising culturing such a microorganism in a culture medium containing one or more of such 3α-hydroxy-5β-cholanic acids to produce a corresponding 7-and/or 12-keto derivative. More particularly, the preparation of 3α-hydroxy-7-keto-5β-cholanic acid from chenodeoxycholic acid and of 3α-hydroxy-7-keto-5β-cholanic and3α,12α-dihydroxy-7-keto-5β-cholanic acid from cholic acids is described.

Description: The invention relates to novel microorganisms capable of converting bile acids and more particularly to a method for specifically oxidising hydroxyl groups at particular positions in the di-hydroxycholanic acids. More specifically, this invention relates to such microorganisms of the genus Bacillus , and to methods for preparing and use of such microorganisms, to produce 3α-hydroxy-7-keto 5β-cholanic acid, a useful intermediate in the preparation of 3α, 7β-dihydroxy-5β-cholanic acid (hereinafter referred to as ursodeoxycholic acid, itself useful as a cholagogue), from 3α, 7α-dihydroxy-5β-cholanic acid (hereinafter referred to as chenodeoxycholic acid). Heretofore, ursodeoxycholic acid has been synthesised from chenodeoxycholic acid using a process which comprises chemically converting the α-hydroxyl group at the 7-position of chenodeoxycholic acid to a β-hydroxyl group, namely a process which comprises selectively oxidizing the α-hydroxyl group at the 7-position of chenodeoxycholic acid to give 3 α-hydroxy-7-keto-5β-cholanic acid and then stereoselectively reducing this 7-keto group to give ursodeoxycholic acid at whose 7-position is a β-hydroxyl group. The preparation of 3α-hydroxy-7-keto-5β-cholanic acid from chenodeoxycholic acid using a microorganism of the genus Pseudomonas has also been described (Japanese Published Examined Patent Application No. 25356/1987). However, the prior art chemical synthesis method has problems in reactivity, selectivity and safety on operation and has not been found to be satisfactory even in terms of yield and the purity of resulting products. The above microbial preparation process has similarly not proved to be satisfactory since the concentration of chenodeoxycholic acid as a substrate how to be kept low (about 1%) and its conversion to 3α-hydroxy-7-keto-5β-cholanic acid is also low (about 30.5%). Our co-pending European Application No. 0539216 describes microorganisms of the genus Bacillus capable of selectively oxidising the 12α hydroxy group of cholic acid to form 3α,7α-dihydroxy-12-keto-5β-cholanic acid including strain TTUR 2 - M4 (Ferm BP 3393), which specifically produces 3α-hydroxy-7,12-diketo-5β-cholanic acid when incubated in a medium containing cholic acid. This publication is available as prior art against the present application under Art 54(3) EPC only. In view of such prior art problems, the present inventors have intensely studied the preparation of 3α-hydroxy-7-keto-5β-cholanic acid from chenodeoxycholic acid as substrate at high concentrations, and as a result we have found that novel microorganisms belonging to the genus Bacillus produce 3α-hydroxy-7-keto-5β-cholanic acid in high yield from chenodeoxycholic acid in high concentration as a substrate. These microorganisms were isolated from the soil in Yonezawa City, Yamagata Prefecture, and have been designated Bacillus sp. TTUR 2-2 (FERM BP-365), Bacillus sp. TTUR 4-1 (FERM P-11862) and Bacillus sp. TTUR 4-2 (FERM P-11863). The strains have been deposited at the Fermentation Research Institute in Japan on November 13, 1991 (for strain TTUR 2-2) and May 13, 1991 respectively, and the accession numbers are given in brackets above. All these strains have an ability to oxidize the hydroxyl group(s) mainly at the 7-position of chenodeoxycholic acid to keto group(s), although to a lesser extent a weak, ability to oxidize the hydroxyl group at the 3-position to a keto group was also demonstrated, but they do not appear to otherwise utilize or decompose the substrate chenodeoxycholic acid. By subjecting such naturally occurring microorganisms to mutagenesis treatments we have also obtained mutant strains of microorganisms capable of converting chenodeoxycholic acid as a substrate to 3α-hydroxy-7-keto-5β-cholanic acid in even higher yields (in some cases in a yield of up to 100% as later-described). Such strains appear to oxidise the 7α hydroxy group much more specifically than the parent strains. Such mutant strains have been obtained for example subjecting the above-mentioned Bacillus sp. TTUR 2-2 to conventional mutation treatments, for example by irradiating it with ultraviolet rays, X-ray, τ rays or the like or by contacting it with a mutagenic agent such as N-methyl-N'-nitro-N-nitrosoguanidine, 4-nitroquinoline-N-oxide, acriflavine or ethyl methanesulfonate. The following strains can be mentioned as exemplary of such mutant strains which have been obtained: (1) Bacillus sp. TTUR 2-M4 (FERM BP-3393) (2) Bacillus sp. TTUR 2-M5 (FERM BP-3398) (3) Bacillus sp. TTUR 2-M4-250 (FERM BP-3395) (4) Bacillus sp. TTUR 2-M4-294 (FERM BP-3396) Such mutant strains have an ability to produce 3α-hydroxy-7-keto-5β-cholanic acid from chenodeoxycholic acid in a conversion of 100%, or almost 100% and in a selectivity of 100% or almost 100% namely in a yield of 100% or almost 100%. One aspect of the invention provides a microorganism of the genus Bacillus capable of selectively oxidising a 7α hydroxy group of a chenodeoxycholic acid other than Bacillus sp. TTUR 2-M4 (accession No. FERM-BP 3393). In a further aspect the invention provides a process for selectively oxidising a 7α hydroxy group of a chenodeoxycholic acid, comprising culturing a microorganism as defined above in a culture medium containing said chenodeoxycholic acid to produce 3α-hydroxy-7-keto-5β-cholanic acid. In one of its more particular aspects the invention provides a process for preparing 3α-hydroxy-7-keto-5β-cholanic acid which comprises culturing a microorganism belonging to the genus Bacillus and capable of converting chenodeoxycholic acid to 3α-hydroxy-7-keto-5β-cholanic acid, in a nutrient medium containing chenodeoxycholic acid, and optionally recovering the product thus obtained. The above-mentioned Bacillus strains Bacillus sp. TTUR 2-2, Bacillus sp. TTUR 4-1, Bacillus sp. TTUR 4-2, Bacillus sp. TTUR 2-M5, Bacillus sp. TTUR 2-M4 250 and Bacillus sp, TTUR 2-M4 294 and mutant strains thereof having the necessary metabolic activity form particularly preferred aspects of the invention. This invention is described in more detail below. Separation of the wild strains Bacillus sp. TTUR 2-2, Bacillus sp. TTUR 4-1 and Bacillus sp. TTUR 4-2 from the soil was carried out to the following methods. A small amount of the soil was suspended in Horikoshi Medium I (1% glucose, 0.5% yeast extract, 0.1% dipotassium hydrogenphosphate, 0.02% magnesium sulfate heptahydrate, 1% sodium carbonate, pH10) containing 5% sodium cholate and subjected to enrichment culture at 30°C for 5 days. One platinum loopful amount of the resulting culture broth was streak cultured on a Horikoshi Medium agar plate containing 5% sodium cholate and individual strains were isolated. These strains were each cultured at 30°C for 2 days in Horikoshi Medium I containing 5% sodium chenodeoxycholate, 3α-hydroxy-7-keto-5β-cholanic acid in the culture broth was quantitatively determined, whereby strains were obtained having a highconversion ability to 3α-hydroxy-7-keto-5β-cholanic acid. The bacteriological characteristics of these strains are shown in the following Tables 1 to 8. These tests and classifications were carried out according to "BERGEY'S MANUAL of Systematic Bacteriology", and in the respective tests were used media adjusted to pH 10 by addition of sodium carbonate unless otherwise noted. From the above investigation results, it is apparent that the TTUR 2-2, TTUR 4-1, and TTUR 4-2 strains are microorganisms belonging to the genus Bacillus because they are aerobic sporogenous bacteria. However, they differ from general microorganisms of the genus Bacillus in that their optimum pH values for growth are on the alkaline side, at around pH10. Further, when these strains were compared with respective type strains of Bacillus alcalophilus and Bacillus alcalophilus subsp. halodurans , the former strains were remarkably different from the latter strains in the shape of colony and the appearance of the peripheral portion of colony. Bacillus cereus 8-1 (FERM P-2885, Japanese Published Examined Patent Application No.13708/1978 ) and Bacillus alcalophilus 202-1 (FERM P-2674, Japanese Published Examined Patent Application No.27786/1978 ) were reported as alkalophilic strains wherein their colonies were irregular in an alkaline atmosphere and the periphery of the colonies was lobate, but the present strains are yet different from these strains in many characteristics. In Table 9 were shown the main characteristics of the TTUR 2-2, TTUR 4-1 and TTUR 4-2 strains, and in Table 10 the main characteristics of Bacillus alcalophilus , Bacillus alcalophilus subsp. halodurans , Bacillus cereus 8-1 and Bacillus alcalophilus 202-1. Therefore, although the TTUR 2-2 and TTUR 4-1 and TTUR 4-2 strains are aerobic sporogenous bacteria, they are distinguished from known species belonging to the genus Bacillus , as stated above, in various bacteriological characteristics, particularly in that the optimum pH for growth exists in the alkali side around 10, and in that these strains have an ability to convert chenodeoxycholic acid to 3α-hydroxy-7-keto-5β-cholanic acid. Thus, it is suitable to acknowledge these strains as novel species. A specific method for obtaining mutant strains Bacillus sp. TTUR 2-M4, Bacillus sp. TTUR 2-M5, Bacillus sp. TTUR 2-M4-250 and Bacillus sp. TTUR 2-M4-294 is exhibited in the later-described example. Further, The bacteriological properties of the above mutant strains are shown in Tables 11 to 20, together with the bacteriological properties of their parent strain Bacillus sp. TTUR 2-2 for reference. As is the case with the parent strain, the tests in the tables and classification were carried out according to "BERGEY'S MANUAL OF Systematic Bacteriology", and in the respective tests were used media adjusted to pH 10 by addition of sodium carbonate unless otherwise noted. Since mutant strains are considered in general to belong to the same species as that of their patent strains, it was concluded that all the mutant strains of Bacillus sp. TTUR 2-2 belong to the same novel species. Thus, the mutant strains of the invention are not limited to Bacillus sp. TTUR 2-M4, TTUR 2-M5, TTUR 2-M4-250 and TTUR 2-M4-294, and include any strains which belong to the genus Bacillus and produce 3α-hydroxy-7-keto-5β-cholanic acid using chenodeoxycholic acid as a substrate, and any strains which belong to the genus Bacillus and produce either 3α-hydroxy-7,12-diketo-5β-cholanic acid or 3α, 12α-dihydroxy-7-keto-5β-cholanic acid using cholic acid as a substrate. According to this invention, 3α-hydroxy-7-keto-5β -cholanic acid can be produced by culturing a microorganism belonging to the genus Bacillus and capable of converting chenodeoxycholic acid to 3α-hydroxy-7-keto-5β-cholanic acid in a nutrient medium containing chenodeoxycholic acid. Further, according to this invention, 3α, 12α-dihydroxy-7-keto -5β-cholanic acid can be produced by culturing a mutant strain belonging to the genus Bacillus and capable of converting cholic acid to 3α, 12α-dihydroxy-7-keto- 5β-cholanic acid in a nutrient medium containing cholic acid. Although there is no particular limitation as to the concentration of the substrate in the nutrient medium, namely chenodeoxycholic acid, or cholic acid, it is suitable in view of the yield of the desired conversion product and culture conditions, that the concentration is in the range of 5 to 500 g/l, preferably 40 to 300 g/l. Any media can be used in this invention so long as the microorganisms used in the invention can proliferate therein example, there can be used as carbon sources various saccharide raw materials such as glucose, fructose, sucrose, glycerol, starch, bran and blackstrap molasses, and as nitrogen sources organic nitrogen-containing substances such as peptone, meat extract, yeast extract, corn steep liquor, soybean meal, rapeseed oil cake, urea, various amino acids and amino-sugars, and inorganic nitrogen compounds such as ammonium nitrate,ammonium chloride and sodium nitrate. Further, it is preferred to further add very small amounts of inorganic metal salts, vitamins, growth promoting factors, etc. Culture in the process of the invention can be carried out under an aerobic condition, for example by an aeration stirring culture method or reciprocal shaking method. Culture conditions are not particularly limited, but in general a temperature of 20 to 40°C, a pH of 7 to 11 and a culture time of the order of 1 to 6 days. When culture is carried out at a high alkaline pit, for example at a pH of 10, the fear of contamination with various germs during culture the operation of sterilization of media usually carried out can be omitted. Of course, even in such a case, there is no hindrance in carrying out sterilization operation. In recovering the desired conversion product, namely, 3α-hydroxy-7-keto- 5β-cholanic acid, 3α-hydroxy-7,12-diketo-5β-cholanic acid or 3α,12α-dihydroxy-7-keto-5β-cholanic acid from the culture broth, first, the microorganism and insoluble matters in the culture broth are removed by filtration, centrifugation or the like, and the resulting culture filtrate or supernatant was acidified by addition of hydrochloric acid or sulfuric acid. By this, the formed conversion product precipitates in a good yield. Then, this precipitate is separated by filtration and recrystallized, and thereby the conversion product can be recovered in a highly pure state. Any of these conversion products can be converted to ursodeoxycholic acid by further subjecting it to microbial conversion alone or in combination with chemical This invention is further described below according to examples, but it goes without saying that the invention is not limited to these examples. In each example, products were identified by thin layer chromatography or high performance liquid chromatography under the following conditions, respectively. (1) Thin layer chromatography Carrier; Kieselgel 60 (0.25mm thick, produced by Merck Co.) Developing solvent; (1) Benzene/isopropyl alcohol/acetic acid (40/10/1, volume ratio) (2) Chloroform/acetone/acetic /acetic acid (7/2/1, volume ratio) Coloring; An phosphomolybdic acid-sulfuric acid reagent ( obtained by dissolving 1g of phosphomolybdic acid in 20 ml of methanol and adding 1 ml of concentrated sulfuric acid ) is sprayed, and the resulting carrier is subjected to coloring with heating until the bile acid spot becomes deep blue. Charge volume of a sample; 1µl of the culture broth (2) High performance liquid chromatography (1) Column; Capcell Pak C18 (type AG 120, S- 5µm, column size 4.6 ×150mm, produced by Shiseido. Co., Ltd.) Moving phase; methanol/purified water/phosphoric acid (70/30/0.02 M, weight ratio ) Flow rate; 1.7ml/min (2) Column; Inertcil ODS column (column size 4.6 ×250mm, produced by GL Science Co.) Moving phase; methanol/purified water/phosphoric acid (70/30/0.02 M, weight ratio ) Flow rate; 1.0ml/min Detection; RI Identification of peak; compared with a standard substance The mutant strains were separated by the following methods. (1) Bacillus sp. TTUR 2-M4 and Bacillus sp. TTUR 2-M5 One platinum loopful of Bacillus sp. TTUR 2-2 grown on a slant of an alkaline NA medium ( composition: 1.8% nutrient broth "Eiken" ( trade name, produced by Eiken Chemical Co., Ltd.), 1.8% agar, 0.75% sodium carbonate, pH10) was inoculated into 20 ml of Horikoshi Medium I ( composition: 1% glucose, 0.5% peptone, 0.5% yeast extract, 0.1% dipotassium hydrogenphosphate, 0.02% magnesium sulfate heptahydrate, 1% sodium carbonate, pH 10) in a test tube (30 × 190 mm), and cultured with shaking at 30°C for 16 hours. Then, the above cells during the logarithmic phase were aseptically collected by centrifugation, and washed three times with 10 ml of a 0.1 M Tris-maleate buffer (pH 8,0). The cells after washing were suspended in 25 ml of the same buffer, N-methyl-N'-nitro-N-nitrosoguanidine (hereinafter referred to as NTG) was added so that its final concentration became 60 µg/ml, and the cells were incubated at 30 °C for 30 minutes to conduct mutation treatment. The death rate of Bacillus sp. TTUR 2-2 was 85% under this treatment condition. Then, 1 ml of this cell suspension was taken and immediately diluted with 9 ml of a 0.1 M sodium carbonate buffer (pH 9.5), and the cells were collected by centrifugation. After the same washing operation using the above buffer was repeated twice, the resulting cells were suspended in 10 ml of an alkaline NB medium ( composition: 1.8% nutrient broth "Eiken", 0.75% sodium carbonate, pH 10). The cell suspension was appropriately diluted with the alkaline NB medium, applied onto the alkaline NA plate medium so that 10 to 100 colonies could emerge, and cultured at 30 °C for 2 days. Among the emerged colonies, those growing after the 2 days and having a medium colony size were isolated, transplanted on a slant of a 5% CA agar medium (pH 10, obtained by adding 5% cholic acid, 0.5% sodium hydroxide and 1.8% agar to Horikoshi Medium I), and cultured at 30°C for 3 days. Sufficiently grown strains were selected, and one loopful portions of the strains were inoculated into 4 ml portions of a 5% CA liquid medium (pH 10, comprising the 5% CA agar medium from which agar was removed ) in test tubes (16.5×165mm), respectively, and cultured with shaking at 30 °C for 3 days. Conversion products in the resulting respective culture broths were investigated by thin layer chromatography, and thereby mutant strains ( Bacillus sp. TTUR 2-M4 and Bacillus sp. TTUR 2-M5) were found both of which completely lacked an ability to convert the hydroxyl group at the 3-position of cholic acid to a keto group. Hereinafter, the above method of obtaining a mutant strain is merely referred to as the NTG treatment. (2) Bacillus sp. TTUR 2-M4-250 and Bacillus sp. TTUR 2-M4-294 The NTG treatment was repeated using as a parent strain Bacillus sp. TTUR 2-M4 obtained by the NTG treatment of (1), except that the 5% CA liquid medium was used as a starting medium for cell proliferation. An NTG concentration of 60 µg/ml was adopted at the time of NTG treatment. As a result, mutant strains ( Bacillus sp. TTUR 2-M4-250 and Bacillus sp. TTUR 2-M4-294) were found both of which completely lacked an ability to convert the hydroxyl groups at the 3- and 12- positions of cholic acid to keto groups, respectively. The death rate of Bacillus sp. TTUR 2-M4 was 15% in this operation. The mutant strains obtained by the NTG treatments of (1) and (2) were cultured with shaking at 30°C for 3 days in 4 ml portions of Horikoshi Medium I containing 5% chenodeoxycholic acid in test tubes ( 16.5×165mm), and the resulting conversion product was investigated by thin layer chromatography, and thereby specific production of the desired 3α-hydroxy-7-keto-5β-cholanic acid was confirmed. Example 1 Bacillus sp. TTUR 2-2 (FERM BP-3651) was cultured according to the method shown below. 10g of glucose, 5g of peptone, 5g of yeast extract, 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 50g of chenodeoxycholic acid, 5g of sodium hydroxide and 10g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121 °C for 15 minutes and, after cooling, were mixed to give a medium (pH 10). 20 ml of this medium was put in a test tube ( 3×19cm), 0.1 ml of a culture broth was aseptically inoculated therein which had been obtained by culturing the strain at 30°C for 20 hours in 20 ml of a medium in a test tube having the same composition as in the above medium except that chenodeoxycholic acid and sodium hydroxide were excluded. Thereafter, the strain was cultured with shaking at 30°C for 2 days. After the culture, the cells were removed by centrifugation, and the culture supernatant was acidified with dilute sulfuric acid to precipitate 3α-hydroxy-7-keto-5β-cholanic acid and nonconverted chenodeoxycholic acid. This precipitate was collected and dried to obtain 0.98g of white powder. Part of the powder was taken and subjected to high performance liquid chromatography to determine the production ratio of chenodeoxycholic acid, 3α-hydroxy-7-keto-5β-cholanic acid, and other chenodeoxycholic acid oxidation products ( hereinafter referred to as "other bile acids"). As a result, the production ratio was 2.8% of chenodeoxycholic acid, 85.9% of 3α-hydroxy-7-keto-5β-cholanic acid and 11.3% of other bile acids. This mixture was subjected to recrystallization from methanol to obtain pure 3α-hydroxy-7-keto-5β-cholanic acid. Example 2 The procedure of Example 1 was repeated except that Bacillus sp. TTUR 4-1 (FERM P-11862) was substituted for the strain of Example 1. The determined production ratio was 1.6% of chenodeoxycholic acid, 75. 3% of 3α-hydroxy-7-keto-5β-cholanic acid and 23.1% of other bile acids. Example 3 The procedure of Example 1 was repeated except that Bacillus sp. TTUR 4-2 (FERM P-11863) was substituted for the strain of Example 1. The determined production ratio was 0% of chenodeoxycholic acid, 87.7% of 3α-hydroxy-7-keto-5β-cholanic acid and 12.3% of other bile acids. Example 4 10g of glucose, 5g of peptone, 5g of yeast extract, 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 100g of chenodeoxycholic acid, 10g of sodium hydroxide and 10g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121°C for 15 minutes and, after cooling, were mixed to give a medium (pH 10). 100ml of this medium was put in a Sakaguchi flask ( volume:500ml), 0.1 ml of a culture broth was aseptically inoculated therein which had been obtained by culturing Bacillus sp. TTUR 2-2 at 30 °C for 20 hours in 20 ml of a medium in a test tube (3×19cm) having the same composition as in the above medium except that chenodeoxycholic acid and sodium hydroxide were excluded. Thereafter, the strain was cultured with shaking at 30 °C for 4 days. The resulting culture broth was, then, treated in the same manner as in Example 1 to obtain 3α-hydroxy-7-keto-5β-cholanic acid. The production ratio was 4.2% of chenodeoxycholic acid, 88.5% of 3α-hydroxy-7-keto-5β-cholanic acid and 7.3% of other bile acids. Example 5 The procedure of Example 2 was repeated except that the use amount of sodium hydroxide in Example 2 was changed to 7g (pH 10.5). The determined production ratio was 4.2% of chenodeoxycholic acid, 85.9% of 3α-hydroxy-7-keto-5β-cholanic acid and 9.9% of other bile acids. Example 6 The procedure of Example 3 was repeated except that the use amount of chenodeoxycholic acid and sodium hydroxide were changed to 150g and 15g, respectively and the number of days of culture was changed to 4 days in Example 3. The determined production ratio was 22.2% of chenodeoxycholic acid, 65.3% of 3α-hydroxy-7-keto-5β-cholanic acid and 12.5% of other bile acids. Example 7 Bacillus sp. TTUR 2-M4 (FERM BP-3393) was cultured according to the following method. 10g of glucose, 5g of peptone, 5g of yeast extract, 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 50g of chenodeoxycholic acid, 5g of sodium hydroxide and 10g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121°C for 15 minutes and, after cooling, were mixed to give a medium (pH 10). 20 ml of this medium was put in a test tube ( 3×19cm), and 0.1 ml of a culture broth was aseptically inoculated therein which had been obtained by culturing with shaking the strain at 30°C overnight in 20ml of a medium in a test tube having the same composition as in the above medium except that chenodeoxycholic acid and sodium hydroxide were excluded. Thereafter, the strain was cultured with shaking at 30 °C for 3 days. After the culture, the cells were removed by centrifugation, the resulting culture supernatant was acidified with dilute sulfuric acid to form a precipitate. This precipitate was collected and dried to obtain 0.999g of white powder. Part of this precipitate was taken and subjected to high performance liquid chromatography to determine the production ratio of chenodeoxycholic acid and 3α-hydroxy-7-keto-5β-cholanic acid. The production ratio was 0% of chenodeoxycholic acid, and 100% of 3α-hydroxy-7-keto-5β-cholanic acid ( recovery 99.9%). Example 8 The procedure of Example 7 was repeated except that Bacillus sp. TTUR 2-M5 (FERM BP-3398) was substituted for the strain of Example 7. The production ratio was 0% of chenodeoxycholic acid and 100% of 3α-hydroxy-7-keto-5β-cholanic acid ( recovery 99.9%). Example 9 The procedure of Example 7 was repeated except that Bacillus sp. TTUR 2-M4-250 (FERM BP-3395) substituted for the strain of Example 7. The production ratio was 0% of chenodeoxycholic acid and 100% of 3α-hydroxy-7-keto-5β-cholanic acid ( recovery 99.9%). Example 10 The procedure of Example 7 was repeated except that Bacillus sp. TTUR 2-M4-294 (FERM BP-3396) substituted for the strain of Example 7. The production ratio was 1.4% of chenodeoxycholic acid and 98.6% of 3α-hydroxy-7-keto-5β-cholanic acid ( recovery 99.9%). Example 11 The procedure of Example 7 was repeated except that a medium (pH 10) comprising the medium of Example 7 from which glucose was excluded was used. The production ratio was 0% of chenodeoxycholic acid and 100 % of 3α-hydroxy-7-keto-5β-cholanic acid. Example 12 The procedure of Example 10 was repeated except that a medium (pH 10) comprising the medium of Example 10 from which glucose was excluded was used. The production ratio was 0% of chenodeoxycholic acid, and 100% of 3α-hydroxy-7-keto-5β-cholanic acid. Example 13 Bacillus sp. TTUR 2-M5 was cultured by the following method. 5g of yeast extract, 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 50g of chenodeoxycholic acid, 5g of sodium hydroxide and 4g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121 °C for 15 minutes and, after cooling, were mixed to give a medium (pH 9.7). Thereafter, the procedure of Example 8 was repeated. The production ratio was 0% of chenodeoxycholic acid and 100% of 3α-hydroxy-7-keto-5β-cholanic acid. Example 14 The procedure of Example 13 was repeated except that Bacillus sp. TTUR 2-M4-250 was used as a strain. The production ratio was 0% of chenodeoxycholic acid and 100% of 3α-hydroxy-7-keto-5β-cholanic acid. Example 15 Bacillus sp. TTUR 2-M4 was cultured by the following method. 10g of soybean protein (Ajipron E3 ; trade name, produced by Ajinomoto Co., Ltd.), 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 50g of chenodeoxycholic acid, 5g of sodium hydroxide and 2g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121 °C for 15 minutes and, after cooling, were mixed to give a medium (pH 10.2). Thereafter, the procedure of Example 7 was repeated. The production ratio was 0% of chenodeoxycholic acid and 100% of 3α-hydroxy-7-keto-5β-cholanic acid. Example 16 The procedure of Example 15 was repeated except that Bacillus sp. TTUR 2-M5 was used as a strain. The production ratio was 0% of chenodeoxycholic acid and 100% of 3α-hydroxy-7-keto-5β-cholanic acid. Example 17 Bacillus sp. TTUR 2-M5 was cultured by the following method. 10g of glucose, 5g of peptone, 5g of yeast extract, 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 100g of chenodeoxycholic acid, 10g of sodium hydroxide and 10g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121°C for 15 minutes and, after cooling, were mixed to give a medium (pH 10). 100 ml of this medium was put in a Sakaguchi flask ( volume:500ml), and 2 ml of a culture broth was aseptically inoculated therein which had been obtained by culturing the strain at 30 °C for 48 hours in 20ml of a medium in a test tube ( 3 ×19cm) having the same composition as in the above medium. Thereafter, the strain was cultured with shaking at 30 °C for 6 days. Thereafter, the same procedure as in Example 8 was repeated. The production ratio was 5.8% of chenodeoxycholic acid and 94.2% of 3α-hydroxy-7-keto-5β-cholanic acid. Example 18 Bacillus sp. TTUR 2-M4 was cultured by the following method. 10g of glucose, 5g of peptone, 5g of yeast extract, 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 50g of cholic acid, 5g of sodium hydroxide and 10g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121 °C for 15 minutes and, after cooling, were mixed to give a medium (pH 10). 20 ml of this medium was put in a test tube ( 3×19cm), and 0.1 ml of a culture broth was aseptically inoculated therein which had been obtained by culturing the strain at 30 °C overnight in 20ml of a medium in a test tube having the same composition as in the above medium except that cholic acid and sodium hydroxide were excluded. Thereafter, the strain was cultured with shaking at 30°C for 3 days. Thereafter, the procedure of Example 7 was repeated to determine the production ratio of cholic acid and 3α-hydroxy-7,12-diketo-5β-cholanic acid. The ratio was 0% of cholic acid and 100% of 3α-hydroxy-7, 12-diketo-5β-cholanic acid ( recovery 99.7%). Example 19 The procedure of Example 18 was repeated except that Bacillus sp. TTUR 2-M5 was used as a strain and the number of days of culture of 2 days was adopted. The production ratio was 0% of cholic acid and, 98.2% of 3α-hydroxy-7,12-diketo-5β-cholanic acid, 1.4% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid and 0.3% of 3α,7α-dihydroxy-12-keto-5β-cholanic acid ( recovery 99.6%). Example 20 The procedure of Example 18 was repeated except that Bacillus sp. TTUR 2-M4-250 was used as a strain. The production ratio was 0% of cholic acid and 100% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid. Example 21 The procedure of Example 18 was repeated except that Bacillus sp. TTUR 2-M4-294 was used as a strain. The production ratio was 0.8% of cholic acid and 99.2% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid. Example 22 The procedure of Example 19 was repeated except that a medium (pH 10) comprising the medium of Example 19 from which glucose was excluded was used. The production ratio was 0% of cholic acid and 100% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid. Example 23 The procedure of Example 21 was repeated except that a medium (pH 10) comprising the medium of Example 21 from which glucose was excluded was used. The production ratio was 0% of cholic acid and 100% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid. Example 24 Bacillus sp. TTUR 2-M4 was cultured by the following method. 10g of soybean protein ( Essanmeat ; trade name, produced by Ajinomoto Co., Ltd.), 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 50g of cholic acid, 5g of sodium hydroxide and 2g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121°C for 15 minutes and, after cooling, were mixed to give a medium (pH 10.2). Thereafter, the procedure of Example 18 was repeated. The production ratio was 0% of cholic acid, 99.5% of 3α-hydroxy-7,12-diketo-5β-cholanic acid, 0.3% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid and 0.2% of 3α,7α-dihydroxy-12-keto-5β-cholanic acid. Example 25 The procedure of Example 24 was repeated except that Bacillus sp. TTUR 2-M4-250 was used as a strain. The production ratio was 0.5% of cholic acid and 99.5% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid. Example 26 Bacillus sp. TTUR 2-M4 was cultured by the following method. 10g of glucose, 5g of peptone, 5g of yeast extract, 1g of dipotassium hydrogenphosphate and 0.2g of magnesium sulfate heptahydrate were dissolved in 500 ml of purified water. Separately, 100g of cholic acid, 10g of sodium hydroxide and 10g of sodium carbonate were dissolved in 500 ml of purified water. Both solutions were sterilized at 121°C for 15 minutes, and, after cooling, were mixed to give a medium (pH 10). 20 ml of this medium was put in a test tube ( 3×19cm), and 0.1 ml of a culture broth was aseptically inoculated therein which had been obtained by culturing the strain at 30 °C 24 hours in 20ml of a medium having the same composition as above in a test tube. Then, shaking culture was carried out at 30 °C for 4 days. Thereafter, the procedure of Example 19 was repeated. The production ratio was 2.0% of cholic acid, 74.0% of 3α-hydroxy-7,12-diketo-5β-cholanic acid, 12.8% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid and 11.2% of 3α,7α-dihydroxy-12-keto-5β-cholanic acid. Example 27 The procedure of Example 26 was repeated except that Bacillus sp. TTUR 2-M4-250 was used as a strain. The production ratio was 5.0% of cholic acid and 95.0% of 3α, 12α-dihydroxy-7-keto-5β-cholanic acid. Example 28 Bacillus sp. TTUR 2-M5 was cultured by the following method. 10g of soybean protein (Ajipron E3), 1g of yeast extract, 2g of dipotassium hydrogenphosphate and 0.4g of magnesium sulfate heptahydrate were dissolved in 1000 ml of purified water. Separately, 100g of chenodeoxycholic acid, 10g of sodium hydroxide and 5g of sodium carbonate were dissolved in 1000 ml of purified water. Both solutions were mixed, without sterilization, in a 5-liter bench jar fermenter to give a medium (pH 10.4). 40 ml of a culture broth of Bacillus sp. TTUR 2-M5 was inoculated therein which had been obtained by culturing the strain with shaking at 30 °C for 20 hours in 20 ml of a medium in a test tube having the same composition as in the above medium except that chenodeoxycholic acid and sodium hydroxide were excluded. Thereafter, culture was carried out at 30 °C for 3 days with an aeration of 2 L/min and stirring (300rpm). After the culture, the cells were removed by centrifugation (3500 rpm ×15min) and the culture supernatant was adjusted to pH 2.5 with sulfuric acid to form a precipitate. This precipitate was filtered and washed with water, and the resultant crystalls were dried at 50 °C to give 99.2g of white powder. Part of this was taken and subjected to high performance liquid chromatography. The thereby determined production ratio was 0% of chenodeoxycholic acid and 100% of 3α-hydroxy-7-keto-5β-cholanic acid ( recovery 99.1% ). Example 29 The procedure of Example 28 was repeated except that Bacillus sp. TTUR 2-M4-250 was used as a strain. The production ratio was 0.5% of chenodeoxycholic acid and 99.5% of 3α-hydroxy-7-keto-5β-cholanic acid ( recovery 99.0% ). [ Effect of the Invention ] By using novel microorganisms of the genus Bacillus according to this invention, a substrate chenodeoxycholic acid or cholic acid in a high concentration can be converted, in a high yield, to 3α-hydroxy-7-keto-5β-cholanic acid, or 3α-hydroxy-7,12-diketo- 5β-cholanic acid or 3α, 12α-dihydroxy-7-keto-5β-cholanic acid, each of which is a preparation intermediate for ursodeoxycholic acid. (1) Morphology Microorganism Bacillus sp. TTUR 2-2 Bacillus sp. TTUR 4-1 Bacillus sp. TTUR 4-2 Morphology rod rod rod Size (µm) 0.4∿0.7 ×1.5∿4.5 0.4∿0.7 ×1.5∿4.5 0.4∿0.7 ×1.5∿4.5 Cellular polymorphism None (partially chained) None (partially chained) None (partially chained) Flagellum Peritrichous flagella Peritrichous flagella Peritrichous flagella Spore oval oval oval Formation position Slightly at the end of the cell Slightly at the end of the cell Slightly at the end of the cell Sporangium Slightly swelling Slightly swelling Slightly swelling Size (µm) 0.3 ∿0.7 ×0.6 ∿1.2 0.3 ∿0.6 ×0.6 ∿1.2 0.3 ∿0.6 ×0.6 ∿1.2 Gram staining Variable Variable Variable Acid fastness None None None (2) Growth in various media (All of the TTUR 2-2, TTUR 4-1 and TTUR 4-2 strains exhibited the following growth states) Growth state Kind of medium pH 7.0 pH 10.0 1 ○ Nutrient agar plate culture Poor growth Irregular, convex, and auriculate or lobate; milky-white and glistening 2 ○ Nutrient agar slant culture Poor growth Grows in a spreading state. Pigment is not formed. 3 ○ Nutrient broth culture Slight growth Grows, slightly turbid. Sediment is observed. 4 ○ Gelatin stab culture Not liquefied because of poor growth Liquefies it stratiformly. 5 ○ Litmus milk Change is scarcely observed Grows and liquefies it. Litmus is not changed because of the alkaline environment. Physical characteristics of the TTUR 2-2 strain (Part 1) (1) Reduction of nitrate salt Not or very weakly reduced (2)Denitrification Not observed (3)MR test Discoloration of methyl red is not observed because of the medium being alkaline (4) VP test Negative (5)Formation of indole Not formed (6)Formation of hydrogen sulfide Not formed (7) Hydrolysis of starch Hydrolized (8)Utilization of citric acid Koser citrate medium Not utilized Christensen agar Excellently utilized (9)Utilization of inorganic nitrogen source Ammonium salt Scarcely utilized Nitrate salt Scarcely utilized (10)Formation of pigment Not formed (11)Urease (pH9) Negative (12)Oxidase Positive (13)Catalase Positive (14) Range of growth Growth pH pH 7∿11(optimum pH9∿10) Growth temperature 15∿43°C(optimum temperature 30∿ 37°C) (15) Attitude to oxygen Aerobic (16)0-F test The strain grows in an aerobic condition, a slight amount of acid is formed, and formation of gas is not observed (17)Resistance to sodium chloride The strain grows in the presence of 10 % sodium chloride but does not grow in the presence of 15% sodium chloride. Physical characteristics of the TTUR 2-2 strain (Part 2) (18)Formation of acid or gas from saccharides (pH 9) Formation of acid Formation of gas L-arabinose ± - D-xylose ± - D-glucose ± - D-mannose - - D-fructose + - D-galactose - - Maltose + - Sucrose + - Lactose - - Trehalose + - D-sorbitol - - D-mannitol + - Inositol - - Glycerol - - Starch + - Physical characteristics of the TTUR 4-1 strain (Part 1) (1) Reduction of nitrate salt Reduced (2)Denitrification Not observed (3)MR test Discoloration of methyl red is not observed because of the medium being alkaline (4) VP test Negative (5)Formation of indole Not formed (6)Formation of hydrogen sulfide Not formed (7) Hydrolysis of starch Hydrolized (8)Utilization of citric acid Koser citrate medium Not utilized Christensen agar Excellently utilized (9)Utilization of inorganic nitrogen source Ammonium salt Not utilized Nitrate salt Not utilized (10)Formation of pigment Not formed (11)Urease (pH9) Negative (12)Oxidase Positive (13)Catalase Positive (14) Range of growth Growth pH pH 7∿11(optimum pH9∿10) Growth temperature 15∿40°C(optimum temperature 30∿ 37°C) (15) Attitude to oxygen Aerobic (16)0-F test The strain grows in an aerobic condition, a slight amount of acid is formed, and formation of gas is not observed (17)Resistance to sodium chloride The strain slightly grows in the presence of 15% sodium chloride. Physical characteristics of the TTUR 4-1 strain (Part 2) (18)Formation of acid or gas from saccharides (pH 9) Formation of acid Formation of gas L-arabinose - - D-xylose + - D-glucose - - D-mannose - - D-fructose + - D-galactose - - Maltose + - Sucrose ± - Lactose - - Trehalose + - D-sorbitol - - D-mannitol + - Inositol - - Glycerol - - Starch + - Physical characteristics of the TTUR 4-2 strain (Part 1) (1) Reduction of nitrate salt Reduced (2)Denitrification Not observed (3)MR test Discoloration of methyl red is not observed because of the medium being alkaline (4) VP test Negative (5)Formation of indole Not formed (6)Formation of hydrogen sulfide Not formed (7) Hydrolysis of starch Hydrolized (8)Utilization of citric acid Koser citrate medium Not utilized Christensen agar Excellently utilized (9)Utilization of inorganic nitrogen source Ammonium salt Not utilized Nitrate salt Scarcely utilized (10)Formation of pigment Not formed (11)Urease (pH9) Negative (12)Oxidase Positive (13)Catalase Positive (14) Range of growth Growth pH pH 7∿11(optimum pH9∿10) Growth temperature 15∿40°C(optimum temperature 30∿ 37°C) (15) Attitude to oxygen Aerobic (16)0-F test The strain grows in an aerobic condition, a slight amount of acid is formed, and formation of gas is not observed (17)Resistance to sodium chloride The strain slightly grows in the presence of 15% sodium chloride. Physical characteristics of the TTUR 4-2 strain (Part 2) (18)Formation of acid or gas from saccharides (pH 9) Formation of acid Formation of gas L-arabinose ± - D-xylose - - D-glucose - - D-mannose - - D-fructose + - D-galactose - - Maltose + - Sucrose - - Lactose - - Trehalose + - D-sorbitol - - D-mannitol + - Inositol - - Glycerol - - Starch + - Main characteristics of each strain Microorganism TTUR 2-2 TTUR 4-1 TTUR 4-2 Shape of colonies irregular irregular irregular Periphery of colonies auriculate auriculate auriculate Color of colonies milky-white milky-white milky-white Liquefaction of gelatin stratiform stratiform stratiform Growth under an anaerobic environment - - - Growth temperature °C 15∿43 15∿40 15∿40 Optimum growth temperature °C 30∿37 30∿37 30∿37 Resistance to NaCl 15% - ± ± Utilization of NH 4 salt - - ± Reduction of nitrate salt - + + Utilization of citrate salt (Koser) - - - Formation of acid from saccharides L-arabinose ± - ± D-xylose ± + - D-glucose ± - - Sucrose + ± - Main characteristics of comparative strains Comparative strain Bacillus alcalophilus Bacillus alcalophilus subsp. halodurans Bacillus cereus 8-1 (FERM P-2885) Bacillus alcalophilus (FERM P-2674) Shape of colonies circular circular irregular irregular Periphery of colonies entire entire lobate lobate Color of colonies milky-white milky-white pale yellow milky-white Liquefaction of gelatin stratiform crateriform stratiform Growth under an anaerobic environment - + - + Growth temperature °C ∿46 ∿54 ∿45 ∿50 Optimum growth temperature °C 33∿35 around 48 40∿45 40∿43 Resistance to NaCl 15% - + Utilization of NH 4 salt - ± Reduction of nitrate salt - + Utilization of citrate salt (Koser) - ± + Formation of acid from saccharides L-arabinose + + + + D-xylose + + + + D-glucose + + + + Sucrose + + + + (1) Morphology (All of the TTUR 2-2, TTUR 2-M4, TTUR 2-M5, TTUR 2-M4-250 and TTUR 2-M4-294 strains exhibited the following characteristics) Morphology rod Size (µm) 0.4∿0.7 ×1.5 ∿4.5 Cellular polymorphism None (partially chained) Flagellum Peritrichous flagella Spore oval Formatin position Slightly at the end of the cell Sporangium Slightly swelling Size (µm) 0.3 ∿0.7 ×0.6 ∿1.2 Gram staining Variable Acid fastness None (2) Growth in various media Growth state Kind of medium pH 7.0 pH 10.0 TTUR 2-2, TTUR 2-M4, TTUR 2-M5 TTUR 2-M4-250 TTUR 2-M4-294 TTUR 2-2, TTUR 2-M4, TTUR 2-M5, TTUR 2-M4-250, TTUR 2-M4-294 Nutrient agar plate culture Poor growth No growth Irregular, convex, and auriculate or lobate; milky-white and glistening Nutrient agar slant culture Poor growth No growth Grows in a spreading state Pigment is not formed. Nutrient broth culture Slight growth No growth Grows, slightly turbid. Sediment is observed. Gelatin stab culture Not liquefied because of poor growth No growth Liquefies it stratiformly. Litmus milk Change is scarcely observed No growth Grows and liquefies it. Litmus is not changed because of the alkaline environment. Formation of acid or gas from saccharides (pH 9) Bacillus sp. TTUR 2-2 Saccharide Formation of acid Formation of gas L-arabinose ± - D-xylose ± - D-glucose ± - D-mannose - - D-fructose + - D-galactose - - Maltose + - Sucrose + - Lactose - - Trehalose + - D-sorbitol - - D-mannitol + - Inositol - - Glycerol - - Starch + - Formation of acid or gas from saccharides (pH 9) Bacillus sp. TTUR 2-M4 Saccharide Formation of acid Formation of gas L-arabinose ± - D-xylose - - D-glucose ± - D-mannose - - D-fructose + - D-galactose - - Maltose + - Sucrose + - Lactose - - Trehalose + - D-sorbitol - - D-mannitol + - Inositol - - Glycerol - - Starch + - Formation of acid or gas from saccharides (pH 9) Bacillus sp. TTUR 2-M5 Saccharide Formation of acid Formation of gas L-arabinose + - D-xylose + - D-glucose + - D-mannose - - D-fructose + - D-galactose - - Maltose ± - Sucrose ± - Lactose - - Trehalose + - D-sorbitol - - D-mannitol + - Inositol - - Glycerol - - Starch ± - Formation of acid or gas from saccharides (pH 9) Bacillus sp. TTUR 2-M4-250 Saccharide Formation of acid Formation of gas L-arabinose ± - D-xylose - - D-glucose + - D-mannose - - D-fructose + - D-galactose - - Maltose + - Sucrose ± - Lactose - - Trehalose + - D-sorbitol - - D-mannitol - - Inositol - - Glycerol - - Starch ± - Formation of acid or gas from saccharides (pH 9) Bacillus sp. TTUR 2-M4-294 Saccharide Formation of acid Formation of gas L-arabinose ± - D-xylose - - D-glucose + - D-mannose - - D-fructose + - D-galactose - - Maltose + - Sucrose ± - Lactose - - Trehalose + - D-sorbitol - - D-mannitol + - Inositol - - Glycerol - - Starch + - Main characteristics of each strain (Part 1) Microorganism Bacillus sp. TTUR 2-2 Bacillus sp. TTUR 2-M4 Bacillus sp.TTUR 2-M5 Shape of colonies irregular irregular irregular Periphery of colonies auriculate auriculate auriculate Color of colonies milky-white milky-white milky-white Liquefaction of gelatin stratiform stratiform stratiform Growth under an anaerobic environment - - - Growth temperature °C 15∿43°C 15∿43°C 15∿43°C Optimum growth temperature °C 30∿37°C 30∿37°C 30∿37°C Resistance to NaCl 15% - - - Utilization of NH 4 salt - - - Reduction of nitrate salt - - - Utilization of citrate salt (Koser) - - - Formation of acid from saccharides L-arabinose ± ± + D-xylose ± - + D-glucose ± ± + Sucrose + + ± Main characteristics of each strain (Part 2) Microorganism Bacillus sp. TTUR 2-M4-250 Bacillus sp. TTUR 2-M4-294 Shape of colonies irregular irregular Periphery of colonies auriculate auriculate Color of colonies milky-white milky-white Liquefaction of gelatin stratiform stratiform Growth under an anaerobic environment - - Growth temperature °C 15∿40°C 15∿40°C Optimum growth temperature °C 30∿37°C 30∿37°C Resistance to NaCl 15% - - Utilization of NH 4 salt - - Reduction of nitrate salt - - Utilization of citrate salt (Koser) - - Formation of acid from saccharides L-arabinose ± ± D-xylose - - D-glucose + + Sucrose ± ±

Claims: A microorganism of the genus Bacillus capable of selectively oxidising a 7α hydroxy group of chenodeoxycholic acid, wherein said microorganism is other than Bacillus sp. TTUR 2-M4 (accession No. Ferm BP-3393 at the Fermentation Research Institute, Japan). A microorganism as claimed in Claim 1 which is capable of converting chenodeoxycholic acid to 3α-hydroxy-7-keto-5β-cholanic acid. A microorganism selected from Bacillus sp. TTUR2-2 (deposited at the Fermentation Research Institute, Japan under the accession No. Ferm BP-3651), Bacillus sp. TTUR 2-M5 (accession No. Ferm, Bacillus sp. TTUR 2-M4- 250 (accession No. Ferm BP-3395), Bacillus sp. TTUR 2-M4- 294 (accession No, Ferm BP-3396) and mutant strains thereof capable of selectively oxidising a 7α hydroxy group of chenodeoxycholic acid. A process for selectively oxidising a 7α hydroxy group of chenodeoxycholic acid, comprising culturing, in a culture medium containing chenodeoxycholic acid, a microorganism of the genus Bacillus capable of selectively oxidising said 7α-hydroxy group of a chenodeoxycholic acid. A process as claimed in claim 4 wherein said microorganism is capable of converting chenodeoxycholic acid to 3α-hydroxy-7-keto-5β-cholanic acid. A process as claimed in claim 4 or claim 5, wherein said microorganism is selected from Bacillus sp. TTUR2-2 (deposited at the Fermentation Research Institute, Japan under the accession No. Ferm BP-3651), Bacillus sp. TTUR2-M4 (accession No. Ferm BP-3393), Bacillus sp. TTUR 2-M5 (accession No. Ferm BP-3398), Bacillus sp. TTUR 2-M4-250 (accession No. Ferm BP-3395), Bacillus sp. TTUR 2-M4-298 (accession No, Ferm BP-3396) and mutant strains thereof capable of selectively oxidising the 7α hydroxy group of chenodeoxycholic acid. A process as claimed in any one of claims 4 to 6 wherein the pH of the culture medium is pH7 to 11.

Inventors: KAWAIDE HIROSHI, KIMURA HIROMI, OKAMURA AKIO, YAMAURA TAKUROU, KAWAIDE, HIROSHI, KIMURA, HIROMI, OKAMURA, AKIO, YAMAURA, TAKUROU, KIMURA, HIROMI, B-403, SYARUMU-KITAKOSHIGAYA
Applicants: TOKYO TANABE CO, TOKYO TANABE COMPANY LIMITED
Application year: 1992
Main classification: C12P33
IPC codes: C12P33