Pretreatment of Corn Stover by Extremely Low-Liquid Ammonia (ELLA) Method for Improved Enzymatic Digestibility

For an effective bioconversion of lignocellulosic biomass into biofuels, the pretreatment is one of the most important steps because plant cell walls in lignocelluloses are highly resistance to chemical, physical and enzymatic degradations. Therefore, an efficient pretreatment process should be designed to open up the rigid structure of lignocellulosic biomass. Corn stover is one of the most promising renewable feedstocks for biological conversion to biofuel (ethanol). In our lab, a low-liquid pretreatment method of corn stover using aqueous ammonia, designated the extremely low-liquid ammonia (ELLA) process, were studied to improve the enzymatic saccharification of corn stover with low severity and liquid throughput associated with the pretreatment step. In this process, ammonium hydroxide is applied to the corn stover using a drum mixer, and ammoniated solid was then treated at elevated temperatures (~150ºC). This method enhanced the enzymatic saccharification of corn stover (>80% for glucan and >75% for xylan after 72-h hydrolysis). There are a number of factors that influence the effectiveness of pretreatment process, i.e., chemical and water loadings, reaction temperature, reaction time, and so on. These factors determining the effectiveness of pretreatment were evaluated via the compositional change and enzyme digestibility of pretreated corn stover. Fermentation of pretreated material is also tested in order to evaluate the suitability of ELLA-treated corn stover as a substrate for ethanol fermentation.