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Characterization of a new propionic acid bacterium that ferments ethanol and displays a growth factor-dependent association with a Gram-negative homoacetogen

1982; Oxford University Press; Volume: 15; Issue: 1 Linguagem: Inglês

10.1111/j.1574-6968.1982.tb00040.x

1574-6968

Eric Samain, Guy Albagnac, H.C. Dubourguier, J.P. Touzel,

Anaerobic Digestion and Biogas Production

During mesophilic methanogenesis of sugars, lactate and ethanol are commonly found as intermediates produced by hydrolytic and fermentative bacteria [1]. Under anaerobiosis, various bacterial species utilize ethanol as sole energy source for their growth concurrently with volatile fatty acid production. According to this production, several patterns of fermentation were distinguished inc!uding (a) the production of butyric, valeric and caproic acids which is characteristic of Clostridium kluyveri. This micro-organism utilizes ethanol and condenses it with short volatile fatty acids (C 2 to C4) into acids with two more carbons [2]; (b) the ethanol oxidation to acetate with concurrent reduction of CO 2 to methane which was first described by Barker [3]. The responsible microorganism, Methanobaeillus omelianskii , has later been shown to be a syntrophic association of two strains [4]: the 'S organism' which oxidizes ethanol to acetate and reduces protons to H 2, and a H 2utilizing methanogenic bacter ium Methanobacterium strain Moll , i.e. Methanobacterium bryantii. Growth of the acetogenic bacterium was inhibited by low partial pressure of hydrogen and occurred only when an H 2 utilizer was present. In low sulfate media, hydrogenase-forming strains of Desulfovibrio or Desulfotomaculum performed the same type of syntrophic association with methanogens [5]. In this report, we provide the first documentation for the fermentation of ethanol into propionate and acetate and show that the responsible anaerobe requires a growth factor produced by a H2-oxidizing species. These findings were presented in preliminary form at the 2nd International Symposium on Anaerobic Digestion (poster session, Travemunde, Germany, Sept. 81).