Characterization of three tissue fractions in corn (Zea mays) cob

Corn (Zea mays) cob is composed of three tissue fractions, chaff, woody ring, and pith, with dry weight percentages of 21.1%, 77.5%, and 1.4%, respectively. In this study, the cell wall components in these tissue fractions were characterized to examine their tissue morphology. The chemical compositions in the three fractions were relatively similar, and hemicellulose was the main component. Through sugar composition analysis, hemicellulose was mainly composed of xylan in all fractions, whereas the proportion of arabinose and galactose was different in the woody ring. From the alkaline nitrobenzene oxidation analysis, lignin in all fractions was composed of guaiacyl, syringyl, and p-hydroxyphenyl lignins, whereas their ratios varied in the three fractions. Furthermore, the amounts of cinnamic acids such as ferulic and p-coumaric acids, which are associated with corn lignin, were also different among the three fractions. With respect to the tissue morphology, the component cells in the three fractions were totally different each other. Furthermore, from the ultraviolet microspectrophotometry of each morphological region in the three tissue fractions, lignin concentration and distribution of cinnamic acids were different from one morphological region to another. The differences in chemical composition and lignin structures influence the decomposition behaviors in various treatments; thus, this information provides a clue to promote efficient utilization of corn cob into value-added chemicals.