## 2 Materials and Methods
### Analytical Methods  
The analysis of the hydrothermal hydrolysate was conducted using HPLC (Agilent 1260 II, Germany). Firstly, the hydrolysate was subjected to hydrolysis with dilute sulfuric acid (4% H\({}_{2}\)SO\({}_{4}\)) at 121 \({}^{\circ}\)C for 60 min to convert xylo-oligosaccharides to xylose, and the quantity of xylo-oligosaccharides was expressed as monosaccharides equivalents [17]. The post-hydrolysate was then filtered through syringe filters (0.22 \(\mu\)m) and analyzed using HPLC with a refractive index detector using a ZORBAX carbohydrate analysis column at 25 \({}^{\circ}\)C. A volume of 15 \(\mu\)L filtrate was injected by an autosampler and the mobile phase was a mixture of acetonitrile and water (90:10, \(v/v\)), with a flow rate of 1.1 mL/min. The deashing guard column was placed ahead of the analysis column. It should be noted that these procedures were also employed to determine the purity of as-obtained xylo-oligosaccharides. The yield of xylo-oligosaccharides from bamboo hemicellulose was determined to be 50.9% with a purity of 81.6%. In addition, the quantitative analysis of glucose content during enzymatic saccharification was also analyzed using HPLC with a refractive index detector using a ZORBAX carbohydrate analysis column at 30 \({}^{\circ}\)C. A volume of 20 \(\mu\)L filtrate was injected by an autosampler and the mobile phase was a mixture of acetonitrile and water (75:25, \(v/v\)), with a flow rate of 1.0 mL/min.  
The surface morphology of samples was observed using FE-SEM (S-4800, Hitachi, Tokyo, Japan). The samples were coated with gold and photographed at 5.0 kV, 10 \(\mu\)A.  
The measurement of FTIR spectroscopy was performed on an FTIR spectrophotometer (Nicolet iS50, ThermoFisher, MA, USA) with a scanning range of 4000-400 cm\({}^{-1}\) and an accumulation of 32 scans.  
X-ray diffraction was conducted on an X-ray powder diffractometer (X'Pert Pro, Panalytical, Almelo, Holland) with Cu-K\(\alpha\) radiation. The spectra were collected at 20 of 5-60\({}^{\circ}\) with a scan speed of 0.2\({}^{\circ}\)/s and a step size of 0.02\({}^{\circ}\). The acceleration voltage and current were 40 kV and 40 mA, respectively. The crystallinity index (_CrI_) was determined according to Equation (4) reported by [PERSON] et al. [36]:  
\[CrI=\frac{I_{002}-I_{\mathrm{am}}}{I_{002}}\times 100\%, \tag{4}\]  
where _CrI_ represents the relative degree of crystallinity, \(I_{002}\) is the intensity of (002) lattice diffraction at 2\(\theta\) = 22.8\({}^{\circ}\), and \(I_{\mathrm{am}}\) is the diffraction intensity of amorphous scattering at 2\(\theta\) = 18.0\({}^{\circ}\).  
The specific surface area of untreated bamboo, HTB, and CR were determined using N\({}_{2}\) adsorption/desorption isotherms using the Brunauer-Emmett-Teller (BET) equation on an automated physisorption analyzer (3 Flex, Micromerities, GA, USA) at 77 K. Results showed that there was no significant difference among untreated bamboo, HTB, and CR with respect to BET surface area (around 1.0 m\({}^{2}\)/g).  
HSQC-NMR spectra were recorded on a Bruker AVANCE III 500 MHz NMR spectrometer (Bruker, Zurich, Switzerland). For HSQC spectroscopy, around 80 mg of lignin was dissolved in 0.5 mL deuterated dimethylsulfoxide (DMSO-\(d_{6}\)). The spectral widths were 12-0 and 160-0 ppm for \({}^{1}\)H and \({}^{13}\)C dimensions, respectively. The chemical shift of DMSO-\(d_{6}\) at \(\delta_{\mathrm{C}}\)/\(\delta_{\mathrm{H}}\) 39.5/2.49 ppm was treated as an internal reference. Data of spectra were processed using Bruker Topspin 3.6.2 (Bruker, Karlsruhe, Germany)