Evaluation of Fusarium sp. PSA-3 Xylanolytic Enzymes for Xylose and Xylo-oligosaccharide Production from Pretreated Plant Biomass

Lignocellulosic biomass, particularly forest residues and agricultural wastes, has been recognized as a promising renewable feedstock for biofuel and bioenergy production because it is rich in fermentable sugars. In plant cell walls, glucose is present mainly as crystalline cellulose, which is embedded in a hemicellulosic matrix, including xylose-rich xylan, and further protected by lignin. However, xylans vary structurally depending on plant species and biomass type, and these structural differences can limit xylanase activity, thereby reducing xylan conversion to xylose. This limitation can also impair cellulose degradation because portions of cellulose remain covered by xylan, preventing cellulase enzymes from effectively accessing and hydrolyzing cellulose. Therefore, it is important to identify robust enzymes capable of degrading diverse xylan structures, particularly complex arabinoxylans, in plant biomass. In this study, the xylanolytic activity of crude enzymes from Fusarium sp. PSA-3 was evaluated against alkaline-pretreated plant biomass, including rice straw, Napier grass, and corn leaves. The results showed that the crude enzyme degraded xylan in all pretreated substrates, releasing reducing sugars at concentrations ranging from 0.5 to 1.2 mg/mL after incubation at pH 5.5 and 50 °C for 24 h. The released sugars were qualitatively analyzed by thin-layer chromatography, which revealed a series of xylo-oligosaccharides with degrees of polymerization (DP) of 2–6. Oligomers with DP 2–4 were dominant, together with a small amount of xylose. These findings demonstrate that crude enzymes from Fusarium sp. PSA-3 possess xylanolytic activity against xylans from different plant materials, highlighting their potential application in the biomass saccharification step for biofuel production. Further studies will integrate β-xylosidase into the reaction system, based on the hypothesis that this enzyme will act synergistically with the Fusarium sp. PSA-3 xylanolytic enzyme system to enhance the conversion of short-chain xylo-oligosaccharides into xylose.