Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
The conventional process for cellulosic biofuels production involves six distinct steps: pretreatment, cellulase production, enzymatic hydrolysis, hexose fermentation, pentose fermentation, and product recovery. Herein, a novel configuration for cellulosic biofuels production- Integrated bioconversion and separation (IBS) , which combines five of the six unit operations (all except pretreatment) into one step, was proposed. The IBS configuration is achieved by a mixed culture composed of a hydrolysis enzyme producer such as a lignocellulolytic fungus and a fermentative microorganism such as a bacterium. The lignocellulolytic fungus produces hydrolysis enzymes under ATP-plentiful conditions in an aerobic environment. The hydrolysis enzymes produced by the fungus will hydrolyze the cellulose and hemicellulose to resulting hydrolysis products. A strain engineering strategy was adopted to divert most of the hydrolysis product to the fermentative microorganism for biofuel production while maintaining a robust fungus and bacterium co-culture. A cell immobilization technology was applied to entrap the fermentative microorganism inside gel beads to create a local micro-aerobic and anaerobic environment which is favorable for high yield biofuel production. The air supplied to the system for aeration can strip out the volatile biofuel products so that they will not accumulate to high concentrations that are inhibitory to the fungus or to the fermentative microorganism. Therefore, IBS is able to achieve cellulase production, enzymatic hydrolysis, fermentation, and product separation in one single reactor. Our preliminary results showed that such a configuration is able to achieve the production of ethanol directly from cellulose by a microorganism consortium without the addition of cellulase.