Microbial community composition and methanogens’ biodiversity during a temperature shift in a methane fermentation chamber

More information on the connection between anaerobic digestion (AD) parameters and composition of the microbial community involved in the AD process is required to gain a better understanding of how a bioreactor functions. The aim of this study was to analyse the composition of microbial communities and the dynamics of methanogens’ biodiversity changes during the shift from mesophilic (38°C) to thermophilic (55°C) conditions during biogas production. The total microbial composition was examined via the metagenomic approach based on 16S rRNA gene sequencing, whereas the methanogen communities were analysed using PCR–DGGE (Polymerase Chain Reaction–Denaturing Gradient Gel Electrophoresis) of mcrA. Even though the temperature is one of the crucial parameters affecting microorganisms involved in the AD process, the results presented here revealed that there were no statistically significant differences in bacterial community composition between the mesophilic and thermophilic phases of the process. The most abundant phyla were found to be Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. However, the methanogens’ community genotypic structure as examined by the PCR–DGGE method changed under thermophilic conditions. The temperature had the strongest impact on the archaeal methanogens in the fermentation chamber directly after implementing the temperature shift. A relatively higher biogas yield and average content of CH₄ in the produced biogas were observed under thermophilic conditions.