Tuesday, May 3, 2011
Reed canary grass is a temperate perennial grass cultivated widely in the northern hemisphere that has been historically grown for forage. It has been proposed as a candidate bioenergy crop because of its high productivity and its ability to grow on marginal farmlands. The goal of this study was to identify processing options for its enzymatic and fermentative conversion to ethanol. Reed canary grass, which was field grown and harvested at early and late maturities, was extensively analyzed for composition in a previous study. Samples were pretreated either using dilute sulfuric acid, liquid hot-water, or dilute ammonium hydroxide. The pretreatments were assessed on the basis of minimal furan production, associated with monosaccharide dehydration, and maximum monosaccharide yields following enzymatic treatment. Reed canary grass contains fructan, which led to the formation of excess hydroxy-methyl furfural when pretreated with dilute-acid. Subsequently, ammonium hydroxide was selected as the preferred pretreatment. Samples were pretreated at various ammonia loadings (2, 3, and 4%), reaction temperatures (130, 140, and 150°C), and times (10 or 20 min) and evaluated for enzymatic conversion to sugars and simultaneous saccharification and fermentation to ethanol using Saccharomyces cerevisiae. The optimal pretreatment condition for ethanol formation was determined to be 150°C for 20 min with 2% ammonia catalyst. We are currently seeking to improve our conversion yields by using a recombinant S. cerevisiae strain engineered for xylose fermentation.