Denitrifying anaerobic methane oxidation process responses to the addition of growth factor betaine in the MFC-granular sludge coupling system: Enhancing mechanism and metagenomic analysis.

To solve the problem of the slow growth of denitrifying anaerobic methane oxidation (DAMO) bacteria during the enrichment process, betaine was added as a growth factor and its influence on the mechanism of DAMO process along with the metagenomic analysis of the process in a MFC-granular sludge coupling system was explored. When the addition of betaine was increased to 0.5 g/L and 1.0 g/L, the NO3--N removal increased to 210 mg/L. Also, the increasing betaine dosage in 1st to 4th chambers resulted in a significant increase in dissolved methane concentration which reached a maximum value of 16.6 ± 1.19 mg/L. When the dosage of betaine was increased from 0 g/L to 1.0 g/L, the dominant bacterial phyla in the 1st to 4th chambers changed to Proteobacteria (20.8-50.7%) from Euryarchaeota (42.0-54.1%) and Methanothrix which was significantly decreased by 17.9-37.4%. There was a slight decline in the DAMO microorganism abundance, possibly due to the increased methyl donors limiting the DAMO microorganism growth. Denitrification metabolism pathway module (increased from 0.10% to 0.15%) of Nitrogen metabolism and Formaldehyde assimilation, and serine pathway of Methane metabolism presented an ascendant trend with the increased betaine dosage as determined by the metagenomics analysis of KEGG metabolism pathway.