Insoluble wheat arabinoxylan

FT-IR measurements were performed on ball-milled samples using a Nicolet 6700 spectrometer from Thermo Fisher equipped with a PIKE Diamond ATR unit. Spectra were obtained in the spectral range of 4,000 to 600 cm⁻¹ using 64 scans, Happ-Genzel apodization, and a resolution of 4 cm⁻¹.
Oven dried wheat straw samples (50 mg) were weighed into NMR tubes and incubated at room temperature in a desiccator above liquid water for 240 h for equilibration prior to hydrogen-deuterium exchange. For vapor exchange samples were then placed over deuterated water (99.9 atom% D) in another desiccator and measured by FT-IR after 20 h and 240 h.
Chemicals used in vapor exchange experiments on cell wall model compounds were commercial products. Avicel® PH-101 (11365 FLUKA) was purchased from Sigma-Aldrich, Denmark ApS. Insoluble wheat arabinoxylan was purchased from Megazyme, Bray, Ireland. Chemical composition includes arabinose, 36%; xylose, 51%; glucose, 6.5%; mannose, 4.4% and galactose, 1.6%. Alkali lignin (370959) was purchased from Sigma-Aldrich, Denmark ApS. OriginPro 9 software was applied to calculate the peak IR and peak AR.

T. reesei CICC 41,495 used in this study was purchased from the China Centre of Industrial Culture Collection (Beijing, China). Commercial malted barley (Hordeum vulgare L. cv. Dan’er, Chinese harvest 2017), with low β-glucan content (96 mg/L) and poor filtration efficiency, was obtained from a commercial malting company in the Jiangsu province of China.
Oat-spelt xylan, birchwood xylan, beechwood xylan, and 4-Nitrophenyl-α-L-arabinofuranoside (p-NPAF) were from Sigma-Aldrich (St Louis, MO, USA). Arabinoxylo-oligosaccharide was from Hualan Chemical (Shanghai, China). Soluble wheat arabinoxylan (medium viscosity) and inSoluble wheat arabinoxylan were from Megazyme (Wicklow, Ireland). Sephadex G-25, DEAE-Sepharose Fast Flow and Sephacryl S-100 were from GE Healthcare (Uppsala, Sweden). The protein molar-mass marker was from Bio-Rad Laboratories (Shanghai, China). All other chemicals used were from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China), and were analytical grade.

Soluble wheat arabinoxylan with medium viscosity, inSoluble wheat arabinoxylan, xylose, and arabinose were obtained from Megazyme (Bray, Ireland). Preparation of the de-starched wheat bran (DWB) was done as described in our earlier report [7 (link)]. Briefly, the DWB was prepared by milling 60 g of wheat bran (WB) to pass through a sieve of diameter < 0.5 mm, followed by suspension in 600 mL of phosphate buffer (80 mM, pH 6.2). We then added 4.5 mL of the starch-degrading thermostable alpha-amylase (Termamyl 120 L, EC 3.2.1.1, from Bacillus licheniformis, 20,000–60,000 U/mL) to the mixture, followed by incubation at 92 °C for 20 min. The insoluble fraction, i.e., the DWB, was obtained by centrifugation at 4000× g rpm for 10 min, followed by washing twice with water, twice with acetone, and finally drying at 40 °C.