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Figure 2. Structure of maize stover glucuronoarabinoxylan (GAX). Abbreviations: Ace, acetate; Araf, arabinofuranose; Fer, ferulate; GlcA, glucuronate; Xyl, xylose. Arabinose/xylose ratio is 
0.1, glucuronate/xylose 0.2, and ferulate ester/arabinose 0.4 in a corn stalk (Jung and Casler, 2006a,b). All of arabinose and most of glucuronate in stover are assumed to occur as GAX, with the remainder of glucuronate present as potentially in other forms, e.g., trace amounts of pectin. Acetate concentration in maize stover has been reported to be 30 to 50 g kg–1 of dry matter (McAloon et al., 2000; Wooley et al., 1999). Assuming that all of it occurs in GAX and adjusting for molarity, approximately one-third to half of the xylosyl residues on GAX are expected to be acetylated.
