Degradation patterns and intermediates in the anaerobic digestion of glucose: experiments with 14C-labeled substrates.

A mineral salts medium containing 1% (w/v) glucose was subjected to anaerobic digestion in an upflow reactor. Performance with respect to utilization of glucose was monitored by collection of fermentation gases and calculation of carbon mass balances. Sub-samples of bacterial suspensions from the upflow reactor were incubated with (U-14C)-glucose, (U-14C)-acetate, (2-14C)-propionate, (1-14C)-butyrate or 14C-carbonate. Individual radioactive products in samples from incubation mixtures were analysed by radio gas chromatography. Quantitatively, acetate and propionate were the only important intermediates in glucose degradation by glucose-adapted sludge, with acetate accounting for the largest part of intermediary fatty acid flux.