Methanotroph and methanogen coupling in granular biofilm under O2-limited conditions

The co-culture between Methylosinus sporium, a strictly aerobic methanotroph, and strictly anaerobic methanogens was studied in 5 L aerobic/anaerobic coupled granular sludge reactors under O2-limited conditions. The methanogenic bacteria maintained very good metabolic activities and were able to produce sufficient methane which serviced as substrate for methanotrophic growth. Although other strictly aerobic population proliferated by two orders of magnitude after the granular sludge had been operated under O2-limited conditions for one month, only a limited amount of the added methanotroph remained in the sludge. This result may indicate that M. sporium lacks sufficient O2 affinity to compete with facultative bacteria for the dissolved O2 for their growth.