(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.