Size-exclusion chromatography of xylan derivatives—the critical evaluation of macromolecular data

Structural characterization of pure xylan from corncob and its effect on xylooligosaccharides yield after enzymatic hydrolysis

The structure of xylan plays a significant role in the degradation rate by xylanase to product xylooligosaccharides (XOS). In this study, xylan was extracted and purified from corncob, yielding two xylan fractions (WUAX-2, WUAX-3) with purities exceeding 90 %. The structures of WUAX-2 and WUAX-3 were characterized and hydrolysis efficiency was studied in relation to their structures. FT-IR results indicated that although xylan fractions had the same types of functional groups, WUAX-3 exhibited a higher level of -OH, CH, and CO groups compared to WUAX-2. NMR, the vibration signal of WUAX-2 and WUAX-3 was β-(1 → 4) -linked D-lignin unit β-D-xylopyran. X-ray diffraction results confirmed that WUAX-2 was a stable single-crystal structure. Meanwhile, the number of side-chains of WUAX-2 in the liquid was smaller than that of WUAX-3. WUAX-2 and WUAX-3 were hydrolyzed by a high-temperature-resistant xylanase (XynA) and yielded primarily xylohexaose (X6), xylotriose (X3), and xylobiose (X2). The XOS yield of WUAX-2 was 4.25 times higher than that of WUAX-3. These results indicate that the fewer xylan side-chains and substituent groups of xylan, the higher the enzymatic hydrolysis efficiency. The findings provide a deep understanding of the effect of xylan structure on the enzymatic behavior.

Molecular modification, structural characterization, and biological activity of xylans

The differences in the source and structure of xylans make them have various biological activities. However, due to their inherent structural limitations, the various biological activities of xylans are far lower than those of commercial drugs. Currently, several types of molecular modification methods have been developed to address these limitations, and many derivatives with specific biological activity have been obtained. Further research on structural characteristics, structure-activity relationship and mechanism of action is of great significance for the development of xylan derivatives. Therefore, the major molecular modification methods of xylans are introduced in this paper, and the primary structure and conformation characteristics of xylans and their derivatives are summarized. In addition, the biological activity and structure-activity relationship of the modified xylans are also discussed.