Hydrogen is foreseen as a viable CO2-neutral alternative to fossil fuels for generation of energy.
Production of H2 from wastes/wastewaters is possible as this is one of the main products resulting from
anaerobic fermentation of organic compounds. If hydrogenotrophic methanogens are suppressed, H2-rich
biogas can be recovered from anaerobic reactors. In order to optimize and improve H2 production, it is
essential to get more insight into the composition and structure of the microbial communities involved in
the process. In this study microbial community shifts in expanded granular sludge blanket (EGSB)
reactors producing H2 at different temperatures and organic loading rates (OLR) were studied using PCRDGGE
fingerprinting analysis. The aim was to get more insight into the microbiology of dark
fermentative hydrogen production at mesophilic, thermophilic and hyperthermophilic temperatures. Three
EGSB reactors were inoculated with granular biomass previously treated with heat to suppress
methanogens. Reactors were operated at 37, 55 and 70 ºC with 5gCOD L-1of a mixture containing glucose
and L-arabinose (1:1); pH was kept at 5.5. OLR applied varied from 5 to 16. PCR amplification of the
16S rRNA gene and subsequent DGGE analysis of sludge samples collected from the reactors at different
operational times showed different profiling, mainly correlated with differences in temperature. Bacterial
diversity (measured as the number of bands) in sludge samples from reactors operating at 55 ºC and 70ºC
was remarkably lower than in sludges growing at 37ºC. No significant changes on DGGE profiles
diversity were observed with the increase of OLR over time
