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Low-pressure steam explosion (LPSE) combined with alkaline peroxide (AP) pretreatment was first employed to separate hemicellulose from Lespedeza stalks. The monosaccharide composition and molecular weight distribution of the obtained hemicellulose fractions were characterized in this study. The results show that the hemicellulose extracted from Lespedeza stalks consisted of xylose, glucose, galactose, and mannose, which was a mixture of arabinoxylans and xyloglucans or β-glucans. The yield of hemicellulose fractions after AP pretreatment ranged from 11.2% (2.5% hydrogen peroxide (H2O2), w/v for 12 h) to 12.2% (3.3% H2O2, w/v for 72 h). The molecular weight of hemicellulose decreased from 2,458 g/mol to 1,984 g/mol after AP pretreatment, indicating its degradation reaction. The structure of hemicellulose was analyzed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and heteronuclear single quantum coherence. The AP pretreatment partially cleaved the backbone and the ether linkage between lignin and hemicelluloses. Also, branched-chain α-Darabinofuranosyl in which β-D-xylose substituted at the C-3 position (monosubstituted) was removed, illustrating a partial debranching reaction. Therefore, the combination of low-pressure steam explosion and alkaline peroxide pretreatment (LPSE-AP) is an effective pretreatment method to separate hemicellulose from Lespedeza stalk. [ABSTRACT FROM AUTHOR]

A combination of steam explosion (SE) and alkaline peroxide (AP) used to pretreat bamboo was investigated. Steam explosion at 224 °C for 4 min was applied to bamboo, and the pretreated bamboo was delignified by alkaline peroxide. Enzymatic hydrolysis was compared in the pretreated samples. Steam pretreatment led to remarkable hemicellulose solubilization (63.2%). Lignin solubilization (93.1%) was achieved by alkaline peroxide treatment of steam-pretreated bamboo at 80 °C for 1 h in 0.88% (v/v) H2O2, whereas only 33.4% of lignin was solubilized when using raw bamboo. Pretreatment methods resulted in a low degree of polymerization and increased hydrolysis of cellulose. A maximum glucose yield of 90.5% was achieved with a combined steam explosion and alkaline peroxide pretreatment. The surface structure of treated bamboo and the adsorption of enzyme on the substrate were characterized by X-ray photoelectron spectroscopy. Delignification decreased enzyme adsorption and increased enzymatic conversion. SEM analyses indicated that SE-AP pretreatment disrupted lignin networks and exposed crystalline cellulose in bamboo more effectively than SE or AP pretreatment alone. [ABSTRACT FROM AUTHOR]