Comparison of pH-controlled lactic acid hydrolysis and xylanase hydrolysis for xylo-oligosaccharides production from delignified poplar

Abstract

Previously, lactic acid (LA) hydrolysis has been applied in xylo-oligosaccharides (XOS) production from poplar. However, the impact of the pH value of LA on the production of XOS was unclear. In this study, the delignified poplar was prepared by hydrogen peroxide-acetic acid pretreatment of poplar, and lignin removal reached 84.1%. LA with different pH values (2.0–5.0) was applied in XOS and monosaccharides production from delignified poplar, and the xylanase hydrolysis of delignified poplar for XOS production was used for comparison. Results demonstrated that a XOS yield of 18.5% was acquired from delignified poplar by xylanase hydrolysis. However, a high XOS yield of 44.1% was acquired from delignified poplar by LA hydrolysis at pH 2.5, an increase of 20.2% when compared with LA hydrolysis with original pH value (2.0). Xylanase hydrolysis of the LA hydrolysates increased the XOS yield by 38.3% and finally, a total XOS yield of 61.0% was obtained, which was the highest XOS yield from poplar in the previous reports. Additionally, a satisfied glucose yield of 89.4% was acquired from poplar residue by cellulase. This work confirmed the high efficiency of the combination of pH-controlled LA hydrolysis and xylanase hydrolysis in XOS production from poplar.