Acid-insoluble lignin (Klason lignin) was determined. Carbohydrate
contamination was measured by analyzing the hydrolyzate
using high performance liquid chromatography [Jasco LC Net II/ADC
with a ROA organic acid (00H-0138-K0) column (Phenomenex)
equipped with a refractive index detector (RI-2031Plus) and a
photodiode array detector (MD-2018Plus)]; 0.005M H2SO4 prepared
with 100% deionized and degassed water was used as mobile
phase (0.35 mL/min flow, 40 ◦C, and injection volume of 40mL).
High purity standards of d-(+)-glucose, d-(−)-xylose, and d-(−)-
arabinose (provided by Fluka, with 99% of purity) were used for
calibration.