|BRANDON, SARAH - UNIV OF GA
|EITEMAN, MARK - UNIV OF GA
|PATEL, KRISHNA - UNIV OF GA
|RICHBOURG, MICHELE - UNIV OF GA
|MILLER, DAVID - UNIV OF GA
|Anderson, William - Bill
|PETERSON, JOY - UNIV OF GA
Submitted to: Journal of Chemical Technology & Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2007
Publication Date: 4/15/2008
Citation: Brandon, S.K., Eiteman, M.A., Patel, K., Richbourg, M.M., Miller, D.J., Anderson, W.F., Peterson, J.D. 2008. Hydrolysis of Tifton 85 bermudagrass in a pressurized batch hot water reactor. Journal of Chemical Technology & Biotechnology. 83:505-512.
Interpretive Summary: Among the many aspects that need to be improved for commercialization of ethanol production from plant biomass is the refinement of techniques to make more of the cell wall available for conversion. In this study a liquid hot water pre-treatment of Tifton 85 bermudagrass was used to help break apart the cell wall to allow for greater conversion of the cellulose and hemicellulose to sugars used in fermentation. Three reaction times, three temperature treatments and two pressure treatments were tried in different combinations. Pressure differences had little effect. It was concluded that the optimal conditions for hot water pretreatment is two minutes at a temperature of 230°C. This released the optimum amount of sugars for fermentation.
Technical Abstract: 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. Pressure had a negligible effect on digestibility of the grass, and a reaction temperature of 230°C for two minutes was the most effective in releasing reducing sugars. Fermentations were conducted with untreated grass and with grass treated for two minutes at 200°C or 230°C to confirm that the increase in reducing sugar concentration resulted in an increased ethanol yield. Following a hydrolysis with 2 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 of ethanol, which was significantly higher than 200°C treated grass (11.0 g/L) and untreated grass (9.0 g/L). Ferulic and para-coumaric acids were also released during the fermentations. Pressurized batch hot water reactor pretreatment is effective in increasing ethanol yield of grass in fermentations.