NOVELTY - Bioconverting carbon monoxide, hydrogen and carbon dioxide to oxygenated organic compound comprises: e.g. passing a gas feed comprising carbon monoxide, hydrogen and carbon dioxide into a primary reactor containing aqueous fermentation broth under aerobic fermentation conditions; maintaining in the reactor a depth of the broth; maintaining in the reactor a head space above the upper portion of the broth; continuously supplying the feed to the aqueous menstruum; and bioconverting carbon monoxide, hydrogen and carbon dioxide to the compound and providing off-gas from the menstruum in the space.    USE - The process is useful for bioconverting carbon monoxide, hydrogen and carbon dioxide to oxygenated organic compound (claimed) which is alcohols e.g. n-butanol, ethanol and propanol.    ADVANTAGE - The process recovers essential compounds for the fermentation and recycles the compounds to the fermentation; is economically; maintains the aqueous fermentation broth as an anaerobic medium and avoids discarding the entire volume of aqueous fermentation broth; attenuates loss of downtime and lost production of product oxygenated organic compound; does not require the loss or removal of a significant mass of nutrients from the broth; and removes adverse component by degradation (where the primary degradation products are gaseous and are readily eliminated from the broth being treated).    DETAILED DESCRIPTION - Bioconverting carbon monoxide, hydrogen and carbon dioxide to oxygenated organic compound comprises: (a) passing a gas feed comprising carbon monoxide, hydrogen and carbon dioxide into a primary reactor containing aqueous fermentation broth under aerobic fermentation conditions, where the fermentation broth contains microorganisms adapted for bioconverting the gas feed to oxygenated organic compound, to produce oxygenated organic compound dissolved in the fermentation broth and an off gas; (b) maintaining in the primary reactor a depth of fermentation broth of at least 10 m; (c) maintaining in the reactor a head space above the upper portion of the fermentation broth; (d) continuously supplying the gas feed to the aqueous menstruum through an injector that uses a motive liquid to form a stable gas-in-liquid dispersion in the fermentation broth; (e) bioconverting carbon monoxide and hydrogen and carbon dioxide to an oxygenated organic compound and providing off-gas from the aqueous menstruum in the head space; (f) withdrawing from the head space of the reactor at least a portion of the off-gas; (g) removing from the syngas reactor at least an aliquot portion of the fermentation broth containing oxygenated organic compound and containing biosolids; (h) separating from the aliquot portion of the fermentation broth an aqueous biosolids-containing phase containing biosolids having a higher solids content and a reduced oxygenated organic compound concentration than the aliquot portion; (i) recovering at least a portion of the oxygenated organic compound; (j) recovering from the biosolids-containing phase an essential compound for the bioconversion of the gas feed to the oxygenated organic compound; and (k) returning the essential compound to the aqueous fermentation broth in the primary reactor.