Fig. 4.

Quantification of OC15 binding to the surface of untreated and xylanase-treated UBKP papers. Pulps were incubated with or without the xylanase (500 U/g of pulp) for 1 h (pH 6) at room temperature under continuous agitation (150 rpm). Untreated UBKP and xylanase-treated UBKP paper discs were incubated with OC15 probe (0.5 µg/µL) for 1 h at room temperature under agitation. Three percent (w/v) milk (20 mM Tris–HCl, pH 7.5 with 20 mM NaCl and 5 mM CaCl₂) was used to minimize paper auto-fluorescence and the non-specific binding of the OC15 probe. The fluorescence values were converted to OC15 (µg/mm²) using a standard curve (Additional file 9). The inset above each histogram columns represents the fluorescence intensity acquired by area scanning of the surface of each paper disc