Microorganism
The conidiospore suspension of A. oryzae RIB 128 was prepared by washing a slant with 0.9% NaCl solution, as described previously (8). The suspension was then added to the wheat bran moistened by distilled water (50%, w/w) and incubated at 30 °C with 95% humidity for 4 days.
Purification of enzymes
A crude extract from an A. oryzae solid culture was prepared as follows. Five hundred ml of 40 mM acetate buffer (pH 5.0) containing 150 mM NaCl was added to the solid-state culture and kept at 4 °C overnight. The mixture was filtered with the cheesecloth and centrifuged at 8000 rpm for 20 min. The supernatant was filtered with a membrane (45 μm) and concentrated by ultrafiltration. The extract was applied to a HiPrep-DEAE column (16 × 100 mm) equilibrated with 40 mM acetate buffer (pH 5.0). The column was eluted with a linear gradient of NaCl (0–1 M) in the same buffer. The eluate was monitored by the absorbance at 280 nm and the xylanase activity, and the active fraction was pooled. After concentrated by ultrafiltration, the active fraction was applied to TSKgel Phenyl-5PW column (21.5 × 150 mm) equilibrated with 40 mM acetate buffer (pH 5.0) containing 0.5 M (NH4)2SO4. The column was eluted with a linear gradient of (NH4)2SO4 (0–0.5 M).