Av 3 400 m spectrometer

Using a Bruker AV-III 400 M spectrometer (Avance; Bruker, Billerica, MA, USA), solid-state cross-polarization/magic angle spinning (CP/MAS) ¹³C NMR spectra of cellulose fractions were acquired at 100.6 Hz. Using a CP pulse program with a 1 ms match time and a 2 s delay between transients, measurements were carried out on dry cellulose fractions packed onto a 4 mm zirconia (ZrO₂) rotor. At a spinning rate of 5 kHz, a total of 5000 scans were recorded.

The chemical compositions (%, w/w) of the substrates were measured by the NREL standard analytical method [13 ]. Analyses of the carbohydrates of the substrates were assessed by HPLC under the same conditions as enzymatic hydrolysates. CP/MAS ¹³C-NMR spectra of the substrates were conducted using a Bruker AV-III 400 M spectrometer (Germany) [19 (link)]. XRD analysis of the substrates was recorded by a D/MAX 2500PC diffractometer (Rigaku Corporation, Japan). The crystallinity indexes (CrIs) of the substrates were determined from the ratio of the crystalline peak area to the total area of crystalline and amorphous peaks. SEM images of the substrates were performed with a Phenom XL (Phenom-World, Netherlands) instrument at 10 kV. BET surface areas of the substrates were measure by analyzing of the nitrogen adsorption using an SSA-7000 surface area analyzer (Beijing Bi’aode Electronic Technology Co., Ltd., Beijing, China) after 8 h of degassing at 120 °C and 1 h of degassing at 150 °C. The measurements (chemical compositions and BET surface areas) were conducted in triplicate, and the relative standard deviation was below 5.0%. The data represented are the averages obtained from experiments.