Methods and systems using ionophores to control contamination in fermentation of gaseous substrates

A fermentation system for anaerobically fermenting a syngas to form a liquid product, the system comprising:

• a. a fermentation vessel;
• b. a syngas supply conduit for introducing the syngas into the fermentation vessel;
• c. an aqueous fermentation broth disposed in the fermentation vessel, the fermentation broth containing at least two types of microorganisms, one type comprising at least one fermenting species, and the other type comprising at least one competing species;
• d. an ionophore supply conduit in communication with the fermentation vessel for introducing at least one type of ionophore into the vessel, the ionophore having selectivity for preferentially inhibiting the at least one competing species from growing and/or producing an undesired product;
• and
• e. a liquid recovery conduit for collecting the liquid product after the syngas is allowed to ferment by exposure to the at least one fermenting species;
• the fermenting species is Clostridium autoethanogenum;
• and
• the competing species is Acetobacterium woodii.