Abstract: A process to temporarily and selectively control the dissolved concentration of CO in the feed medium portion of a fermentation liquid by addition of a surface tension active compound (STAC), particularly during seed train scale-up operations and during recovery from process upsets, to support improved production of biofuels from a syngas fermentation. The process inoculates the fermentation liquid when the cell density level is from 0.05 to 0.5 OD with the surface tension active compound at a concentration of from 20 to 800 mg per liter of syngas fermentation liquid. The surface tension active compound may be a polyol or glycol.