Butanol Production from Corn Residue Using the Simultaneous Saccharification and Fermentation Method with Genetically Modified Clostridium Cellulovorans

Butanol production by fermentation of biomass, rather than by petrochemical routes, has regained interest due to butanol’s strong potential as a biofuel which would not require modifications to current infrastructure. However, production by fermentation of glucose is not cost-effective. The use of lignocellulosic agricultural residue from corn, rather than nutritious corn product, would reduce substrate cost, as well as greenhouse gas emissions. Clostridium cellulovorans, genetically modified for overexpression of adhE2, was examined for use in the saccharification and fermentation of corn cob, corn fiber, corn bran, and corn husk. Pretreatment methods for the corn substrate were also examined, with each substrate being treated with sulfuric acid, calcium hydroxide, and sodium hydroxide. Bacterial growth was measured daily, and the composition of the supernatant, including butanol, ethanol, acetate, and butyrate, was tested using HPLC. It was determined that, for both bacterial growth and butanol yield, sodium hydroxide is the most effective pretreatment for lignocellulosic corn agricultural residue. For certain substrates and pretreatment methods, a butanol titer >2g/L was achieved in serum bottles in a ten-day fermentation.