FT-IR spectra of cell wall polysaccharides
The characteristic spectra of pectin, hemicellulose, and cellulose exhibit a strong absorption band in the 1800-800 cm-1region (Yapo & Koffi, 2008). To reveal the effect of enzyme hydrolysis parameters on the main components in the cell wall of peanut, the characteristic wave numbers of cell wall polysaccharides under different extraction conditions were measured within two specific regions, 1800-1200 cm-1 and 1200-800 cm-1. FT-IR spectra are shown in Figs. 2-5, and the main characteristic wave numbers measured in the present study and infrared spectral wave numbers of cell wall polysaccharides in available literature are listed in Table 2.
Cellulose is a linear homopolymer composed of 1,4-linkedβ -D-Glcp units (1,4-linked β -D-glucan), while hemicellulose is a polymer composed of different types of monosaccharides such as pentose and hexose (e.g. xylose, arabinose, and galactose). Cellulose and hemicellulose are combined by hydrogen bond forming the network structure of cell wall which is filled with pectin (Frankova & Fry, 2013). In the case of plant cell wall, polysaccharides are bonded with each other, which may cause the slight shift of characteristic bands (Szymanska-Chargot & Zdunek, 2013). Slight differences were observed in the characteristic wave numbers of cell wall polysaccharides measured herein and those reported in previous studies (Kačuráková, Smith, & Gidley, 2002; Fellah, Anjukandi, & Waterland, 2009; Chatjigakis, 1998; Mccann, Defernez, & Urbanowicz, 2007; Synytsya, J Čopı́ková, & P Matějka, 2003) (Table 2).