The PCR-DGGE technique was used to determine the microbial community in the
activated sludge samples obtained from three different biogas plants using livestock including
cows, chickens, and pigs as the substrates. Fourteen dominant bands of bacteria and eight
bands of the archaea were observed. Most of the dominant bacterial groups were related to
the uncultured bacteria collected from an anaerobic digester. The bacterial phyla in the activated
sludge were Proteobacteria, Acidobacteria, Synergistetes and Bacteroidetes. Additionally, it was
shown that three bands associated with the uncultured Acidobacteria clone, uncultured
Aminanaerobia clone, and Geobacter sp. Methanogenic bacteria identified were found mainly in
the orders (and genera) Methanobacteriales (Methanobacterium, Methanobrevibacter), Methanomicrobiales
(Methanolinea) and Methanosarcinales (Methanoseata). The archaeal community showed that
Methanoseata sp. dominated in the activated sludge sample from the biogas plant supplied with
chicken and cow manure as the substrate, while Methanobacterium sp. and Methanobrevibacter sp.
dominated in the activated sludge sample from pig manure. These results supported the
approach of using PCR-based DGGE method to analyze the microbial community in the
activated sludges. An understanding of these microorganisms will lead to management
and improvement in biogas plant efficiencies.
Keywords
anaerobic activated sludge, biogas plant, PCR-DGGE, microbial community