Use of NMR Spectroscopy to Characterize AFEX Treated Corn Stover Hydrolysates

An important contemporary issue facing our planet is the search for clean, renewable energy. Bioenergy, especially that from cellulosic biomass has the potential to reduce carbon dioxide emissions and develop a green economy. The treatment of cellulosic biomass using ammonia fiber expansion (AFEX), followed by enzymatic hydrolysis, results in a liquid mixture rich in fermentable monosaccharides. This hydrolysate mixture is a suitable medium in which an organism such as Saccharomyces cerevisiae can be cultured and used to produce ethanol. However, analysis of the chemical composition of AFEX treated corn stover hydrolysates indicates that a range of metabolites from various compound classes is present in varying degrees of concentration. The Great Lakes Bioenergy Research Center (GLBRC) has been developing strains of S. cerevisiae that are capable of efficiently converting glucose and xylose into ethanol using AFEX treated corn stover hydrolysates as a culturing medium. Furthermore, the GLBRC is interested in understanding how the chemical composition of the hydrolysate affects microbial growth and fermentation potential. To that end, our experiment aimed to identify and quantify metabolites that were used or produced by four different strains of S. cerevisiae developed by the GLBRC. To accomplish this goal we analyzed hydrolysate samples by two-dimensional nuclear magnetic resonance spectroscopy. Resulting changes or lack thereof between strains gives researchers valuable information in their endeavor to find a sensible means of energy production.