Enzymatic preprocessing of lignocellulosic biomass within the supply chain has potential to improve feedstock characteristics and reduce ethanol production costs at the biorefinery. While endo-β-1,4-xylanases improve fermentable sugar yields when used during enzymatic pretreatment in water-saturated systems, there are potential benefits to their application in low moisture environments such as dry storage where low water activity improves feedstock stability. To assess the feasibility of endoxylanase treatment in dry storage, endoxylanase activity was tested using wheat arabinoxylan and three commercial endoxylanases at various fixed water activities. Unbuffered solutions of a fixed enzyme to substrate ratio were prepared, flash-frozen, lyophilized, and incubated in chambers at 21% to 100% relative humidity (t=35±0.5° C). Replicates were sacrificed periodically and endoxylanase activity was quantified as an increase in reducing sugar relative to desiccant-stored controls. Endoxylanase activity was observed at water activities over 0.91 in all enzyme preparations in under four days, and at a water activity of 0.59 in under one week in two preparations. Endoxylanase activity after storage was confirmed for selected desiccant-stored controls by incubation at 100% relative humidity. Water content to water activity relationships were determined for three lignocellulosic substrates and results indicate that two endoxylanase preparations retained limited activity as low as 7 to 14 % water content (wet basis), which is well within the range of water contents representative of dry biomass storage. Future work will examine the effects of endoxylanase activity toward substrates such as corn stover, wheat straw and switchgrass in low-water content environments.