2-28: Characterization of Four Clostridium species for Ethanol Production

This research aims to address a piece of the energy crisis by looking for more efficient methods of ethanol production from lignocellulose.  Four Clostridium species were characterized: C. phytofermentans, C. cellulolyticum, C. cellulovorans, and C. thermocellum.   These bacteria are capable of breaking down cellulosic substrates and fermenting them into a variety of products, including ethanol. Six substrates were used: cellobiose, crystalline cellulose, fibrous cellulose, xylan and rice straw (both raw and pretreated).  Both celluloses were combined with xylan for a total of 8 treatments per bacterium.  Each bacterium was grown on each substrate in triplicate.  Gas production and products were measured using a pressure transducer and high performance liquid chromatography (HPLC), respectively. Products that were measured are ethanol, formic acid, acetic acid, propionic acid, butyric acid and lactic acid, as well as residual soluble carbohydrates.  Pressure was measured daily and products were measured after gas production had ceased. Preliminary data has shown that C. phytofermentans and C. cellulolyticum can produce ethanol yields up to 0.4 g/g on cellobiose.  These two bacteria have shown a preference for xylan over both types of cellulose while C. cellulovorans has the highest preference for crystalline cellulose of the four Clostridium species.