NOVELTY - NOVELTY u Fermentation of syngas, comprises (a) introducing the syngas into a reactor vessel (100) through a gas sparger (120), which is located below a liquid level in the reactor vessel, and (b) providing an agitation energy of 0.01-12 k Watts/m3 into the reactor vessel, where the syngas is introduced at a flow rate effective for maintaining pressure of at least 1 psig inside the reactor vessel , the syngas has a carbon monoxide/carbon dioxide molar ratio of 0.75, and the process is effective for providing a volumetric carbon monoxide mass transfer coefficient of 100-1500 per hour.    USE - The process is useful for fermenting syngas, which is useful as a fuel source or as an intermediate for the production of other chemicals.    ADVANTAGE - The process allows effective fermentation of syngas with high quality and improved volumetric carbon monoxide mass transfer coefficient.    DETAILED DESCRIPTION - Fermentation of syngas, comprises: either (a) introducing the syngas into a reactor vessel (100) through a gas sparger (120), which is located below a liquid level in the reactor vessel, and (b) providing an agitation energy of 0.01-12 k Watts/m3 medium into the reactor vessel, where the syngas is introduced at a flow rate effective for maintaining a pressure of at least 1 psig inside the reactor vessel, the syngas has a carbon monoxide/carbon dioxide molar ratio of at least 0.75, and providing a volumetric carbon monoxide mass transfer coefficient of 100-1500 per hour; or step (a) as above per se, (bb) contacting the syngas with at least one gas dispersion impeller located above the gas sparger, (c) mixing the syngas with acetogenic bacteria with at least one mixing impeller (220) located above the gas dispersion impeller (225), where the gas dispersion impeller and mixing impeller are operably connected to an agitator through a drive shaft (200), and (b) as above per se; or inoculating acetogenic bacteria into a medium contained in a boot portion of a reactor vessel, where the medium is effective for filling at least 75% of a total volume of the boot, contacting the acetogenic bacteria with syngas for a time effective for providing a cell density of at least 5 g/l, adding medium to the reactor vessel to provide a liquid level in the reactor vessel, and step (a), (bb) and (c) as above per se. INDEPENDENT CLAIMS are included for:    (1) a process for improving a volumetric carbon monoxide mass transfer coefficient, comprising introducing a syngas into a reactor vessel containing a liquid at a flow rate effective for maintaining a pressure inside the reactor vessel of at least 1 psig, contacting the syngas with at least one gas dispersion impeller and at least one mixing impeller; and    (2) a bioreactor comprising either a housing defining a reactor vessel, where the reactor vessel effective for maintains a pressure of at least 1 psig, an agitator disposed at least partially in the reactor vessel and at least partially below a liquid level in the reactor vessel, the agitator operably connected to a drive shaft, at least one mixing impeller operably connected to the drive shaft and disposed below the liquid level of the medium, at least one gas dispersion impeller operably connected to the drive shaft and disposed below the mixing impeller, and a gas sparger disposed below the gas dispersion impeller, where the gas sparger includes holes having a diameter of 10 mm or less which are effective for providing a gas velocity of 25 m/sec or greater at the exit of the holes, and a boot disposed at a lower end of the reactor vessel, the boot including a boot sparger and boot mixer.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a bioreactor.    Reactor vessel (100)    Sparger (120)    Drive shaft (200)    Mixing impeller (220)    Dispersion impeller. (225)