Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Pretreatment of lignocellulosic biomass can produce fermentation inhibitors such as furfural, 5-HMF, and acetic acid. These compounds can decrease the xylitol and ethanol yields from sugars derived from lignocellulose. Most yeasts, including industrial strains, are susceptible to these inhibitory compounds, especially when multiple inhibitors are present. A variety of physico-chemical treatments has been used for improving fermentation. These detoxification steps add cost and complexity to the process and generate additional waste products. In this paper, we report a novel approach of improving fermentation yields by optimizing the steam pretreatment conditions to obtain low concentration of common fermentation inhibitors. A systematic study of the effects of low concentrations of fermentation inhibitors on the fermentation of xylose to xylitol and hexoses to ethanol by C. guilliermondii and R. mucilaginosa in the steam pretreated hydrolysates from sugarcane bagasse, hybrid poplar, switchgrass, yard waste and giant reed was conducted.
We showed improved xylitol yields and as well as ethanol yields compared to the controls for hydrolysates from steam pretreated ward waste and sugarcane bagasse by C. guilliermondii and R. mucilaginosa. Ethanol yield from hexoses was 100% and xylitol from xylose was ~ 90% of theoretical yield for both hydrolysates. Xylitol yields in the hydrolysates were about 20% higher compared to controls (theoretical xylitol yield was ~ 66% for mixed synthetic sugars fermentation).
In this study we present a novel approach of optimizing the steam pretreatment conditions to generate a low concentration of fermentation inhibitors to improve hexoses to ethanol and xylose to xylitol yields.