Methanogenic potential activity of mixed liquors: Fluorimetric monitoring

Summary Fluorimetric monitoring of potential methanogenic activity (coenzyme F₄₂₀) of bacterial community from methane digesters is until now resstricted to a few particular cases because severe interference frequnetly occurs, or the concentration is too low when digesting highly diluted wastes. A method of purification and/or concentration, based on purification of the cellular fraction of the sample by centrifugation and washing, is proposed. In biomethanation of spent liquor from citric acid fermentation, a typical case where interference largely obscures the F₄₂₀ fluorescence signal, precision is shown to be better than ± 5% (confidence interval [t.05 (3)]) for F₄₂₀ concentration down to 200 nM, and the detection limit is below 10 nM.