Changes in the Archaea microbial community when the biogas fermenters are fed with protein-rich substrates

► Laboratory-scale CSTR AD was done with casein or pig blood as sole substrate. ► The mesophilic methanogenic microbial community acclimated to these substrates. ► T-RFLP and sequencing of mcrA and 16S rRNA gene identified methanogenic Archea. ► The methanogens responded to the change in substrate.