Two-step continuous alkali pretreatment for fractionation of the carbohydrates from bamboo and cotton stalk

Alkaline pretreatment has great potential for the separation of biomass components. In this study, taking bamboo and cotton stalk as raw materials, two-stage alkaline pretreatment was designed for evaluating the components fractionation. The chemical structure of isolated xylan from bamboo and cotton stalk have a backbone of (1 → 4)-β- D -Xylp units attached with 4-O-Me-α- D -GlcpA and/or α-L-Araf units as the branched chain, characterized by Fourier transform infrared spectroscopy and Heteronuclear Single Quantum Coherence Nuclear Magnetic Resonance. Its excellent pretreatment performance was mainly due to the alkali solution weakening the hydrogen bond between cellulose and hemicellulose and saponifying the ester bond between hemicellulose and lignin, thus increasing the fiber porosity. The cellulose enzymatic hydrolysis yield of two-stage alkaline pretreatments cotton stalks and bamboo could reach to 74.2% and 82.1%. The recovery of xylan and lignin of two-stage alkaline pretreatments cotton stalks and bamboo was 85.4% and 84.5%, and 85.1% and 85.1%. This technology was a great potential to promote the efficiency of the component separation of nonwood biomass.