Methanogenic fermentation of benzoate in an enrichment culture.
Enrichment cultures inoculated with black mud fermented benzoate according to the stoichiometric equation: 4 C6H5CO2H+18 H2O → 15 CH4+13 CO2.Trans-2-hydroxycyclohexanecarboxylate, 2-oxo-cyclohexanecarboxylate, pimelate, caproate, butyrate, acetate, and molecular hydrogen were shown to be regular components of the culture fluid occurring in low concentrations. Inhibition of methanogenesis by chloroform, 4-chlorobutyrate, or 2-bromooctanoate resulted in a cessation of the benzoate breakdown after all intermediates had accumulated. It is proposed that benzoate is fermented via a direct reductive pathway to butyrate, acetate, H2, and CO2, whereafter butyrate is converted to acetate and H2, and the latter substrates are fermented to CH4 and CO2 by methane producers.
Laboratory of Veterinary Biochemistry, State University of Utrecht, Utrecht, The Netherlands.
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Shlomi
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Lankhorst
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Prins