(264c) Enhanced Alcohols, Ketones and Organic Acids Production Via Co-Fermentation of Sugars and Gases

Butanol is a better fuel than ethanol due to its compatibility with gasoline and existing fuel infrastructure. Butanol can also be converted into drop-in diesel and jet fuel by a simple hydrogenation step. Butanol has been produced biologically by the traditional acetone-butanol-ethanol (ABE) fermentation using molasses, starches and, recently, lignocellulosic biomass. The ABE process suffers from low conversion yields that hinder its commercialization. More than 50% of the carbon in sugars is wasted in producing H₂ and CO₂.Increasedconversion efficiency of renewable raw materials to butanol could make this butanol production viable. The present study reports on a novel process for biological production of alcohols, organic acids and ketone. This process consists of a co-fermentation of sugars and gaseous substrates for ABE production in a single fermentation system while converting the off gases containing H₂ and CO₂ to produce ethanol and acetic acid. Depending on the microorganism and reactor configuration used, the novel process can enhance alcohol yield by more than 25%. Media containing pure sugar and redcedar hydrolyzate were used in this study. The use of two-stage reactors resulted in a 19% improvement in ABE yield from sugar by Clostridium acetobutylicum ATCC 824 in the first stage with 60 g/L glucose and the conversion of generated H₂ and CO₂ by Clostridium ragsdalei to ethanol and acetic acid in the second reactor. The efficiency of H₂ and CO₂ conversion by C. ragsdalei was 72% and 16%, respectively. The total organic acid production in the co-fermentation process in the two-stage reactors was also increased by 141%. In addition to reducing CO₂ emissions, the co-fermentation of sugars and gases has the potential to enhance the feasibility of ABE fermentation by producing more alcohols from an otherwise waste gas stream. The results demonstrate that co-fermentation of sugars and gases to various products is feasible, and can be exploited to enhance a bioprocessing economy.