The average
decrease in CH4 in batch cultures was of 0.037 mol/
mol of added fumarate, which is considerably lower
than 0.25 mol/mol, the decrease predicted from the
stoichiometry of the reactions involved. One reason that
fumarate was not effective at decreasing CH4 in batch
cultures was that only an average of 48% of added fumarate
appeared to be converted to propionate. Secondly,
the incorporation of reducing equivalents in the
conversion of fumarate to propionate was almost entirely
offset by their release from an average of 20% of
added fumarate that appeared to be converted to ace-tate