Patent ID: 8642302

Claim:
A continuous method for producing ethanol comprising: culturing in a fermentation bioreactor a strain of Clostridium ljungdahlii bacteria in a continuously fed liquid nutrient medium to provide a fermentation broth; supplying vitamin solution to fermentation broth, supplying to said fermentation bioreactor a gaseous substrate comprising carbon monoxide; maintaining a specific rate of CO uptake in said fermentation bioreactor at an amount of 0.3 to 2 mmol CO/gram dry cells weight of bacteria per minute in the fermentation broth after the bacteria achieve a stable cell concentration in the fermentation bioreactor; and removing the fermentation broth from the fermentation bioreactor, distilling ethanol from the broth, and recovering the ethanol; wherein the bacteria produce both ethanol and acetate in a ratio of ethanol to acetate ranging from 1:1 to 20:1; and wherein the ratio of acetic acid to ethanol is less than 0.8:1; and wherein said liquid nutrient medium comprises one or more of the following: Fe, PO 4 , Zn, Mn, B, Co, Cu, Ni, Mo, Se, W, K, Na, Mg, Cl, and S.