anaerobic digester metagenome

The goal of the study was to assess the influence of substrate (D-glucose versus crude-glycerol) on the microbial community structure and diversity, and whether this in-turn influenced the type and concentrations of fermentation end-products synthesized by the microbial community selected. 16S rRNA gene sequence data and statistical analyses were used to provide detail information about the diversity of microbial communities selected by growth of heat pre-treated Dairy Manure Digestate (DMD) on D-glucose versus crude-glycerol, and the fermentation end-products generated by each microbial community were quantified. We observed that the diversity of the microbial communities selected, and the fermentation end-products synthesized by each, were very different. The microbial community selected by growth of DMD on glucose produced high concentrations of H2 and CO2 gas, as well as high concentrations of acetate, butyrate, lactate, and ethanol, with low concentrations of propionate. In contrast, the microbial community selected by growth of DMD on crude-glycerol produced low concentrations of H2, CO2, acetate, butyrate, lactate, and ethanol, and high concentrations of propionate. The major conclusions that may be drawn from these observations are that: 1) the microbial community structure was determined by the carbon source used for growth of the cultures; and 2) the fermentation end-products (H2, CO2, organic acids, and alcohols) synthesized, and their concentrations, were determined by the diversity of the microbial community selected.