Hydrolysis of Tifton 85 bermudagrass in a pressurized batch hot water reactor.

BACKGROUND: Ethanol production from grass is desirable due to the large amount of biomass it produces. However, a pretreatment is necessary before fermentation to increase ethanol yield. Tifton 85 bermudagrass was treated with a newly designed pressurized batch hot water reactor. Multiple temperatures, pressures, and reaction times were evaluated, and reducing sugars liberated during enzymatic hydrolysis were determined. RESULTS: Pressure had a negligible effect on digestibility of the grass, and a reaction temperature of 230 °C for 2 min was the most effective in releasing reducing sugars. Fermentations were conducted with untreated grass and with grass treated for 2 min at 200 °C or 230 °C to confirm that the increase in reducing sugar concentration resulted in an increased ethanol yield. Following hydrolysis with 2 filter paper units (FPU) of a mixed cellulase enzyme cocktail per gram dry weight of grass, fermentations were performed with engineered Escherichia coli strain LY01. Grass treated at 230 °C produced 14.7 g L−1 of ethanol, which was significantly higher than 200 °C treated grass (11.0 g L−1) and untreated grass (9.0 g L−1). Ferulic and para-coumaric acids were also released during the fermentations. CONCLUSION: Pressurized batch hot water reactor pretreatment is effective in increasing ethanol yield of grass in fermentations. Copyright © 2008 Society of Chemical Industry