An improved method for the quantitative evaluation of the potential for methane production of mixed microbial communities in digestion mixed liquors through the determination of the content in coenzyme F 420

Abstract

The potential for methane production in anaerobic digestion mixed liquors can be estimated from their content of the specific coenzyme F 420. This can be determined spectrofluorimetrically by its emission at 470 nm when excited at 420 nm. With most methane digestion mixed liquors, however, severe interferences hamper the spectrofluorimetric measurements. The determination of coenzyme F 420 can be substantially improved by performing the extraction at pH 8·5 after a centrifugation step. It was found that a large portion of the spectrofluorimetric interferences was associated with soluble matter whereas only particulate-bound coenzyme F 420 is of significance as a measure of the potential for methane production. A further substantial portion of the spectrofluorimetric interferences could be eliminated by oxidation of the aqueous extract with KMnO 4. The success of the latter step depended on the pH of oxidation, the duration of oxidation and the amount of KMnO 4 added, but not on the temperature of oxidation nor on the amount of H 2O 2 added to destroy the excess KMnO 4. A small part of the coenzyme F 420 was destroyed in the oxidation process but in a sufficiently reproducible way as not to hamper proper determination.