Effect of operating temperatures on the microbial community profiles in a high cell density hybrid anaerobic bioreactor

► Correlation of performance of reactor with microbial structure. ► Temperature specific DGGE fingerprints. ► Higher richness and diversity at 37 °C leading to better reactor performance. ► Acetoclastic methanogens at 37 °C replaced by hydrogenotrophic methanogens at 55 °C. ► Self-immobilized fluidized granules developed and maintained at higher temperatures.