(200b) Variations of Acetone Butanol Ethanol (ABE) Yield Among Solventogenic Clostridium Species

A major limitation of the biomass conversion to acetone-butanol-ethanol (ABE) is the toxicity of butanol to microbes resulting in reduced ABE titer, productivity, and fermentation time during ABE fermentation. The second major limitation of biomass conversion to ABE is poor ABE yields because significant amounts of substrate are used by solventogenic Clostridium species for the production of un-captured CO2. Carbon dioxide and H2 evolved from ABE fermentation can be as much as 1.5 times the mass of ABE produced. Typically, ABE fermentation gas is composed of 60% CO2 and 40% H2 (v/v). Yield values of ABE ranging from 33% to 41% produced by solventogenic Clostridium species have been reported by different investigators and often a subject of controversy. Some investigators have even reported ABE yield values ranging from 19% to 31%. To study ABE yields variability among solventogenic Clostridium species, we cultivated C. beijerinckii 8052, C. beijerinckii 592, and C. acetobutylicum 824 in P2 medium containing glucose or xylose as carbon source followed by analyses of ABE, acetic and butyric acid, and fermentation gases produced. Progress has been made in these efforts and details will be presented.