The effect of temperature on the microbial communities of peak biogas production in batch biogas reactors

In this study, changes in the microbial communities and the metabolic pathway involved in anaerobic digestion were examined as the temperature was changed from 9 to 55 °C. The results from six batch biogas reactors, which were designed to ferment at 9, 15, 21, 35, 45 and 55 °C, showed that: 1) The components of the microbial communities and metabolic pathways were found to be very similar but the metabolic activities increased significantly when the temperature grew from 15 to 35 °C. 2) Hydrogenotrophic metabolism was almost exclusively observed when the temperature was lowered to 9 °C, whereas greater bacterial diversity involving hydrolisis, acidogenesis, and acetogenesis was observed when the temperature was raised to 45 °C. Finally, these dominant bacteria involved in hydrolisis, acidogenesis, and acetogenesis decreased in number when the temperature was raised to 55 °C and acetotrophic-type metabolism became the major metabolic pathway. That means the turning point for microbial community composition and metabolic pathway from mesophilic to thermophilic was at 45 °C and the metabolic pathway at 9 °C was somewhat different to those observed at 15-35 °C.