Xylan from bambara and cowpea biomass and their structural elucidation

This work is the first report on the isolation and structural elucidation of xylan from bambara and cowpea biomass. The xylans, isolated using acidic delignification followed by NaOH extraction method gave 12.3% and 13.6% yield, respectively. ¹H NMR analyses revealed that both the xylans were glucuronoxylan. The presence of xylose and glucuronic acid was confirmed by monosaccharide analysis and uronic acid assay. Further, xylooligosaccharide production from bambara and cowpea xylans was carried out using xylanase from three different glycoside hydrolase families, and the products were analyzed by TLC and MALDI-ToF MS. The hydrolysis products of both xylans resembled hardwood glucuronoxylan fragments, generated under similar conditions. The most common oligosaccharides observed in the hydrolysates were Xyl₂, Xyl₃, MeGlcA³Xyl₃, MeGlcAXyl₄ and MeGlcAXyl₅. A series of computational approaches were also used to study the interactions of the three different xylanases with xylan. Thus, untapped biomass such as bambara and cowpea could serve as a potential source for xylan which could further be converted to xylooligosaccharides and many other value-added chemicals.