Cofermentation of rutin and hesperidin during two-stage anaerobic pre-treatment of high-loaded brewery wastewater.

In a lab-scale two-stage digester (consisting of an acidification and a methane reactor) operated continuously with high-loaded brewers wastewater (psiCOD 9.000 mg1(-1)) as the primary substrate, the cofermentation of two commonly found flavonoids (rutin and hesperidin) was studied. At overall hydraulic retention times of 48-50 h and organic loading rates in the methane reactor ranging from 8 to 10 g COD 1R(-1) d(-1) the addition of up to (0.71 g 1R(-1) d(-1) of either rutin or hesperidin did not cause adverse effects on the reactor performance, in terms of VFA pattern, COD removal efficiency, and specific biogas production. The added flavonoid glycosides were rapidly converted in the acidification reactor yielding several hydroxyaromatic metabolites. With hesperidin as the cosubstrate, all of the formed metabolites were completely removed during passage through the methane reactor whereas in case of rutin, substantial amounts of m-cresol and 4-hydroxyphenylacetate were built up in the medium and remained in the effluent of the methane reactor.