Analysis of microbial community structure and diversity in the thermophilic anaerobic digestion of waste activated sludge

The microbial community structures in the thermophilic anaerobic digestion (TAD) of waste activated sludge (WAS) and WAS were analyzed with molecular biological techniques including real-time polymerase chain reaction (PCR) and cloning. The microbial community of TAD had less diversity than that of WAS, and the sequences obtained in WAS were not present in TAD by the cloning analysis. In the TAD bacterial clone library, 97.5% of total clones were affiliated with the phylum Firmicutes and 73.1% with the genus Coprothermobacter. Real-time PCR and cloning analysis revealed that the number of Methanosarcina thermophila, which is an acetoclastic methanogen, is larger than that of Methanoculleus thermophilus, which is a hydrogenotrophic methanogen, in terms of the numbers of copies of 16S ribosomal DNA (rDNA).