Substrate influence on the structure of methanogenic Archaea communities during anaerobic digestion

This study compares the diversity of methanogenic Archaeal communities that developed during biogas production in reactors fed with different substrates. Reactor I was fed with silages of maize and of alfalfa and timothy; and Reactor II was fed with these silages plus pig slurry and glycerol as co substrates. The Archaeal community structure was studied using polymerase chain reaction––denaturing gradient gel electrophoresis based on the 16S rRNA gene. In both reactors, Methanosphaerula palustris was most abundant, and species belonging to Methanolinea, Methanoculleus, and Methanotorris were present. Only Reactor I, where the ammonia concentration was lower, had species belonging to Methanospirillum and Methanosarcina. Thus, it appears that addition of pig slurry increased the ammonia concentration, which inhibited the growth of Methanospirillum and Methanosarcina.