EVIDENCE FOR H-2 AND FORMATE FORMATION DURING SYNTROPHIC BUTYRATE AND PROPIONATE DEGRADATION

Both H-2 and formate were formed during butyrate oxidation by Syntrophospora bryantii with pentenoate as electron acceptor and during propionate oxidation by a mesophilic propionate oxidizing bacterium (MPOB) with fumarate as electron acceptor. H-2 and formate levels were affected by the bicarbonate concentration. S bryantii and MPOB were also able to interconvert formate and H-2+HCO3-; the apparent K-M values for formate were of 2.9 mM and 1.8 mM, respectively. The conversion of H-2+HCO3- to formate was detected only when the H-2 partial pressure was above 80 kPa. This interconversion seems to be rather unimportant under conditions prevailing during syntrophic propionate and butyrate oxidation.