Isolation and Characterization of Two Endoxylanases from Fusarium graminearum

Abstract

This paper reports the first isolation from cultures of two endoxylanases secreted by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schweinitz) Petch]. When F. graminearum is grown on wheat bran hydrated with a modified synthetic medium, high xylanase activity can be extracted. The two endoxylanases were identified by LC-MS/MS as the products of genes FGSG_6445 (Genbank gene id 2788192) (xylanase 1) and FGSG_3624 (GenBank accession no. AJ863566) (xylanase 2) with 61 and 51% sequence coverage, respectively. Both enzymes showed a pH optimum at pH 6, with xylanase 1 exhibiting a wider active pH range (5.5–9) than xlylanase 2 (5.5–7.5). Their temperature dependences were similar, >60% between 35 and 60 °C, with optimal temperatures of 45 °C for xylanase 1 and 50 °C for xylanase 2. Kinetic studies found that both enzymes had a lower K_m for linear beachwood xylan than arabinoxylan. For xylanase 2, the V_max increased with arabinoxylan, but decreased for xylanase 1.