Effect of sulfate on carbon monoxide conversion by a thermophilic syngas-fermenting culture dominated by a Desulfofundulus species.

Enrichments were promoted with syngas and resulted in a culture (named T-Syn) highly enriched in bacteria related to Desulfofundulus australicus strain AB33T (98 % 16S rRNA gene sequence identity). Being identified as sulfate reducers, follow up studies on the performance of this culture with and without sulfate were performed. Although in the absence of sulfate, a higher H2/acetate ratio was observed in the products profile, no significant differences in CO conversion rates were observed. The Desulfofundulus australicus strain AB33T ability for CO utilization in the presence and in the absence of sulfate as final electron acceptor was also investigated in this work. D. australicus strain AB33T uses up to 40 % CO (pCO = 68 kPa) with sulfate and up to 20 % CO (pCO = 34 kPa) without sulfate. A genomic comparison between Desulfofundulus species within T-Syn culture and D. australicus strain AB33T revealed an ANI value of 99 % and only 32 genes in the genome of the Desulfofundulus species from T-Syn culture, that were not present in the D. australicus strain AB33T genome. This work proves that Desulfofundulus australicum strain (from T-Syn culture) is able to convert high carbon monoxide concentrations (from pCO = 34 kPa to pCO = 170 kPa), both in the presence and absence of sulfate. So far, only Desulfofundulus nigrificans strain CO-1-SRB is described to have this same capacity, which gives insights on the carboxydotrophic potential of Desulfofundulus genus.