Thermodynamic calculations indicated that the
conversion of added fumarate to both propionate and
acetate was feasible. Fumarate appears to be more effective
in decreasing CH4 production and increasing
propionate in continuous culture than in batch culture.
This suggests that microbial adaptation to fumarate
metabolism can be important. Variation in populations
of fumarate-reducers, methanogens, and protozoa could
all be involved. Fumarate supplementation for an extended
period may result in the amplification of otherwise
small populations of fumarate-reducers. Addition
of some of these organisms may be helpful to improve
fumarate conversion to propionate.