Laboratory-scale reactors, in which the pH could be auto-adjusted, were employed to investigate the
mesophilic methane fermentation with pig manure (7.8% total solids) at pH 6.0, 7.0, and 8.0. Results
showed that the performance of anaerobic digestion was strongly dependent on pH value. Biogas produc-
tion and methane content at neutral pH 7.0 were significantly higher (16,607 mL, 51.81%) than those at
pH 6.0 (6916 mL, 42.9%) and 8.0 (9739 mL, 35.6%). Denaturing gradient gel electrophoresis fingerprinting
and Shannon’s index indicated that the samples contained highly diverse microbial communities. The
major genus at pH 7.0 was
Methanocorpusculum
, compared with that was
Methanosarcina
at both pH
6.0 and 8.0. Our research revealed that cultures maintained at pH 7.0 could support increased biogas
production, which has significant implications for the scale-up biogas engineering.