(76e) Comparative Study On Enzymatic Digestibility of Upland and Lowland Switchgrass Varieties Processed by Leading Pretreatment Technologies

Switchgrass (Panicum virgatum L.) is a promising dedicated bioenergy feedstock with numerous environmental benefits, due to its low fertility requirements, tolerance of poor soils and drought, and high biomass yield. Switchgrass varieties can be categorized into two different ecotypes primarily based on latitude of origin: upland and lowland. Upland varieties are more adapted to cold temperature and semi-arid climates and tend to grow shorter and less coarse than low land types. Southern-origin lowland curtivars tend to grow taller and be more bunchy and thicker-stemmed, producing more biomass than upland types. In this study, we report comparative saccharification yields of three different varieties of switchgrass, two upland types (Dacotah and Shawnee) and one lowland type (Alamo) switchgrass, pretreated by controlled pH, liquid hot water (LHW) pretreatment. Hydrolysis of LHW pretreated switchgrass at 15% w/v dry solids loading resulted in 80% glucose yield and 90% xylose yield at a total protein loading of 11 mg protein/g dry biomass where the total protein consists of cellulase combined with supplementary xylanase. Comparisons were also made among the types of switchgrass processed by other pretreatment technologies as part of the CAFI project (ammonia fiber expansion, aqueous ammonia recycle, dilute sulfuric acid, lime, and neutral pH liquid hot water). These comparisons are of data obtained through identical experimental protocols and data analysis techniques using common supplies of switchgrass. The key features of different types of switchgrass and the effects these differences had on hydrolysis performance for the applied pretreatment methods are briefly discussed.