NOVELTY - Restricting carbon monoxide dissolution into a syngas fermentation liquid in a vessel during the feed phases of production of biofuels, comprises: either (a) passing a feed gas stream comprising carbon oxide, hydrogen gas, and carbon dioxide through the syngas fermentation liquid, (b) monitoring the cell density level of the syngas fermentation liquid, and (c) inoculating the fermentation liquid with a surface tension active compound at a concentration of 20-800 mg per liter of syngas fermentation liquid, when the cell density level is 0.05-0.5 optical density (OD).    USE - The process is useful for restricting carbon monoxide dissolution into a syngas fermentation liquid for producing biofuel including ethanol or n-butanol (all claimed), where the biofuel is useful as liquid motor fuels or for blending with conventional gasoline or diesel motor fuels.    ADVANTAGE - The improved process provides biofuels without affecting cell growth and overall efficiency of syngas to biofuel conversion process.    DETAILED DESCRIPTION - Restricting carbon monoxide dissolution into a syngas fermentation liquid in a vessel during the feed phases of production of biofuels, where at least 2 mg of carbon monoxide per liter of syngas fermentation liquid are present, comprises: either (a) passing a feed gas stream comprising carbon oxide, hydrogen gas, and carbon dioxide through the syngas fermentation liquid, (b) monitoring the cell density level of the syngas fermentation liquid, and (c) inoculating the fermentation liquid with a surface tension active compound at a concentration of 20-800 mg per liter of syngas fermentation liquid, when the cell density level is 0.05-0.5 OD; or the step (a), (b1) monitoring the level of hydrogenase activity of cells in the fermentation liquid, either via measurement of hydrogen gas uptake in mmol/l/hour or via measurement of hydrogen gas conversion as a percentage of mass, and (c1) inoculating the fermentation liquid to a concentration of 20-800 mg per liter of fermentation liquid with a surface tension active compound when either the hydrogen gas uptake level decreases by 30% or more over a 48 hour period or the hydrogen gas conversion as a percent of mass is 0-25.    An INDEPENDENT CLAIM is included for process-I for restricting carbon monoxide dissolution into a syngas fermentation liquid in a vessel during recovery from a process upset where at least 2 mg of carbon monoxide per liter of fermentation liquid are present, comprising the step (a), the step (b1), and inoculating the broth fraction of the syngas fermentation liquid with 10-400 mg per liter of broth per day of a surface tension active compound when either the hydrogen gas uptake level decreases by 30% or more over a 48 hour period or the hydrogen gas conversion as a percent of mass is 0-25.