Three anaerobic lab-scale reactors R1, R2 and R3, feed respectively by secondary sludge and cow manure (95:5 ratio), secondary sludge and cow manure with addition of 20% of wheat straws and secondary sludge and cow manure with addition of 18% of wheat straws and 4% zeolite clay powder were conducted. Feeding and unloading as well as monitoring the reactor was performed daily while samples were pooled weekly. Analysis of global community composition and insight into taxonomical information was performed to (i) compare the microbial communities among the organic inputs used to feed the reactors, (ii) investigate the incidence of anaerobic digestion on these communities, (iii) compare the microbial communities among the digestate and (iv) investigate the evolution of these communities over the hydraulic retention time cycles.