Biohydrogenation of Sterols by Eubacterium ATCC 21,408—Nova Species

Abstract

Biohydrogenation of A5-steroids was studied in vitro by incubating various steroids with a pure culture of Eubacterium 21,408 in a brain-thioglycollat<e medium under anaerobic conditions.1. Eubacterium 21,408, a strictly anaerobic bacterium, was isolated from rat cecal contents. It differed from any previously described Eubacteriuwz species by its requirements for a A5-3/lhydroxy steroid.2. Eubaeterium 21,408 reduced the 5,6-double bond of cholesterol, campesterol, j3-sitosterol and stigmasterol, exclusively yielding the corresponding 5p-saturated derivatives. Similarly, the 4,5-double bond of allocholesterol was reduced to yield coprostanol. Neither the 7,8-double bond in 7-dehydrocholesterol or in lathosterol, nor the 22,23-double bond in the side chain of stigmasterol were reduced.3. In the absence of a 3-hydroxyl function (e.g. in cholest-5-ene), when the 3-hydroxyl function was in the 3a-position (e.g. in epicholesterol) or was substituted (e.g. in 3~-chloro-cholest-5-enc and in cholesteryl esters), no saturation of the 5,6-double bond was observed.4. When incubated with Eubacterium 21,408, the carbonyl group of 4-cholesten-3-one, was reduced to the corresponding 3p-hydroxyl group along with saturation of the 4,5-double bond. The bacterium also reduced the 3-0x0 group of cholestanone and coprostanone to a 3B-hydroxyl group.During their passage through the intestine, cholesterol avd plant sterols such as 8-sitosterol and campsterol are converted into the respective 5b-cholcstan of 58-stigmastan derivatives by microbial 58-H reduction I I' the 5,6-double bond in the steroid nuclrw. Clopro3tanol is not, found in the feces of gcrm-free animals [ 1 -31. In conventional animals, copro,&nol formation can be abolished by the A preliminary communication on this subject has been presented a t the NATO Advanced Study Institute The Germ-jrrr. Anirnals as a Tool in Research, September 14-21, 1969, at Leuven, Belgium.Trivial names. Cholesterol, 5-choIesten-3,9-01; coprostanol, Sp-cholestan-3/?-01; cholestanol, 5a-cholestan-3B-ol; eoprostanone, @-choleutan-%one; cholestanone, 5a-cholestan-3-one; cholesteryl chloride, 3B-chloro-cholest-5-ene; cholesteryl bromide, 3,3-bromo-cholest-B-ene ; epicholesterol, 5-cholesten3a-01; epicoprostanol, 5/l-cholestan-3a-o1; allocholesterol, 4-cholesten-3fl-ol; 7-dehydro-cholesterol, 5,7-cholestadien-38-01; lathosterol, Sa-cholest-7-en-3B-01; cholesteryl stearate, 5-cholesten-3~-yl-stearate; cholesteryl acetate, 5-cholesten-3B-yl-acetate; cholesteryl heptadecanoate, 5-cholesten-3,9-ylheptadecanoate ; campesterol, (24 R)-24-methyl-5-cholesten3p-01; 5/3-campestanol, (24 R)-24-methyl-5/l-cholestan-3~-ol; 5a-campestano1, (24 R)-24-methyl-5a-cholestan-3~-ol; B-sitosterol, (24 R)-24-ethyl-5-cholesten-3/?-ol; 5/?-stigmastanol, (24 R)-24-ethyI-5B-eholestan-3~-ol; 5a-stigmastanol, (24 Rf-24-ethyl-5a-cholestan-3~-ol; stigmasterol, (24 R)-24-ethyl-5,22-cholestadien-3p-ol. [S-lO]. However, all attempts to isolate a pure culture of a As-steroid-reducing microorganism were unsuccessful.Biohydrogenatio...

Bacteroides sp. Strain D8, the First Cholesterol-Reducing Bacterium Isolated from Human Feces

“…Only a few cholesterolreducing strains have been isolated from rat or baboon feces (7,12). All these strains exhibited similar properties and have tentatively been assigned to the genus Eubacterium.…”

“…This bacterial metabolism proceeds according to two pathways (4,31), one involving the intermediate formation of 4-cholesten-3-one and coprostanone and the other involving the direct conversion of cholesterol into coprostanol through reduction of the 5-6 double bond. Surprisingly, the organisms responsible for this bioconversion in humans are still unknown, and only a few cholesterol-reducing strains have been isolated from the rat cecum (12), baboon feces (7), and a hog sewage lagoon (13). Isolation and characterization of cholesterol-reducing bacteria of human origin are nevertheless a prerequisite for understanding microbial cholesterol metabolism and its true impact on human health.…”

Sterols in decomposing Spartina alterniflora and the use of ergosterol in estimating the contribution of fungi to detrital nitrogen1

“…The conversion of sten01s (sterols with unsaturated ring structure) to stanols (sterols with saturated ring structure) is a well known microbial reduction process (Eyssen et al 1973). The conversion of cholesterol to cholestanol has been documented jn sediments (Gaskell and Eglinton 1975;Nishimura 1978 (Table 1).…”

Role of the gut microflora in metabolism of lipids and sterols

“…Recently, a micro-organism responsible for 5 P-H reduction of 5,6-unsaturated sterols in the rat has been isolated in pure culture (Eyssen, Parmentier, Compernolle, De Pauw & Piessens-Denef, 1973). It is a strictly anaerobic bacterium tentatively classified into the genus Eubacterium.…”