Purification and biochemical characterization of an extracellular endo xylanase from Phlebia acerina SF23754

Efficient lignocellulose conversion requires xylan-degrading enzymes that function without energy-intensive pretreatment. Although many xylanases have been reported, the biochemical diversity of Basidiomycota-derived enzymes remains unclear. Here, we purified and characterized the extracellular xylanase secreted by Phlebia acerina SF23754. The enzyme is a 44-kDa protein with an acidic pH optimum (pH 4.0) and an optimal temperature of 50 °C. It retained over 80% activity after 24 h at pH 3-9, showed moderate thermal stability, and was strongly inhibited by heavy metals, whereas EDTA had no effect. Tryptic peptides mapped to conserved GH10 motifs, identifying the enzyme as a basidiomycete GH10 xylanase. It hydrolyzed glucuronoxylans and arabinoxylans to produce short xylooligosaccharides without releasing xylose. Removal of arabinose substituents markedly enhanced arabinoxylan degradation, indicating a preference for less substituted xylan regions. These features highlight a GH10-type catalytic strategy in Basidiomycota and broaden the understanding of fungal xylan degradation mechanisms.