Methanogenic community during the anaerobic digestion of different substrates and organic loading rates

Three anaerobic reactors using pig manure ( PM ), maize straw ( MS ), and a mixture of the two as substrates were compared for archaeal community structure and diversity, and for methanogens response to increased organic loading rate ( OLR , expressed in the mass of volatile solid ( VS )). Methanogenic archaeal richness during codigestion of pig manure with maize straw ( ACE : 2412) was greater than that during the others ( ACE : 1225, 1467) at an OLR of 4 g L −1 day −1 , accompanied by high specific methane yield. Euryarchaeota and Crenarchaeota predominated during overall digestion of different substrates; with relative abundances of 63.5%–99.0% and 1.0%–36.3%, respectively. Methanosarcina was the predominant genus that accounted for 33.7%–79.8% of the archaeal community. The diversity in the PM digester decreased with increase in OLR , but increased in the MS digester. The diversity was stable during the codigestion with increased OLR . The relative abundances of hydrogenotrophic methanogens increased by 2.6 and 2.1 folds; the methanogenic community shifted from acetoclastic to hydrogenotrophic methanogens during digestion of MS , and of the mixture of MS and PM . Canonical correspondence analysis revealed a strong relationship between reactor parameters and methanogenic community.