Effect of preferential delignification on xylooligosaccharides production from poplar by acetic acid/sodium acetate hydrolysis

Abstract

Acid/base conjugate of acetic acid/sodium acetate solution (AC/SA) can efficiently produce xylooligosaccharides (XOS) with relatively high purity from poplar. The lignin in poplar is an important factor limiting the hydrolysis of xylan using enzymes and dilute acids. Until now, the effect of lignin content of poplar on XOS production by AC/SA hydrolysis is not clear. This work examined the relationship between lignin removal and XOS production from poplar by AC/SA hydrolysis. It was revealed that lignin removal of poplar enhanced XOS yield almost linearly (R2 = 0.95) in AC/SA hydrolysis. Under the optimal conditions (0.15 M AC/SA at a molar ratio of 3.0, 170 °C, 60 min), the highest XOS yield of 55.7% with a low xylose yield of 4.1% was obtained from poplar at a preferential lignin removal of 84.0%. Compared to the optimal XOS production from raw poplar, the XOS yield was increased by 32.3% and xylose production was decreased by 41.4%. Cellulase hydrolysis of the poplar residue produced a satisfying glucose yield of 92.8% and a xylose yield of 88.4%. This work proved that preferential delignification of poplar was vital in XOS and monosaccharides production by AC/SA hydrolysis combined with enzymatic hydrolysis.