Tuesday, May 3, 2011: 4:30 PM
Grand Ballroom B, 2nd fl (Sheraton Seattle)
Thermo-mechanical extrusion of lignocellulosic materials has been shown to decrease viscosity and improve substrate digestibility and fermentability thereby avoiding costly operations such as washing, detoxification, and nutrient supplementation. Due to the high shear, extrusion facilitates mixing, heat transfer and allows for the establishment of a high solids bioprocessing with potential for cost reductions in ethanol production. Due to the improved substrate solubility and mass transfer rates, thermostable cellulases provide greater stability and reaction rates in cellulose hydrolysis. The focus of this presentation is on thermophilic bioprocessing of corn stover to ethanol utilizing a cellulolytic extremophile, Geobacillus sp. The crude cellulase of Geobacillus sp. was most active at 75-80oC and exhibited remarkable thermostability: it retained 50% of activity after incubation at 70oC for 7 days. Enzymatic saccharification of high solids biomass (15-20% DM) at 700C partially liquefied biomass into a flowable slurry after only 36 h of hydrolysis and allowed the process to continue as SSF. This presents an opportunity to reduce the enzymatic hydrolysis time (2.5-times) with implications for reduced size of reactor vessels, increased throughput, reduced water usage, and reduced capital and operation costs. Moreover, at high solids loadings, the hydrolytic capabilities of Geobacillus cellulase were comparable to those of a commercial cellulase. It was further demonstrated that Geobacillus can ferment corn stover to ethanol in a single step as consolidated bioprocessing (CBP) with outstanding potential for cost reductions. Only a few anaerobic bacteria such as Clostridium thermocellum have been reported to have CBP capabilities utilizing lignocellulosic substrates.