For complete degradation of hemicellulose into its monomers from lignocellulose biomass, the synergistic action of a broad range of hydrolytic enzymes is needed. Therefore, production of enzymes from their natural producer is desirable. To obtain a powerful β-1,4-endoxylanase producing fungus, 304 environmental samples were collected from various locations in Singapore, leading to 603 isolates. Among them, 71 exhibiting β-1,4-endoxylanase activity were identified belonging mainly to the genera of Aspergillus, Penicillium, and Trichoderma. Further analysis revealed Aspergillus niger DSM 26641 as a potential and stable β-1,4-endoxylanase producer, being able to grow in hydrothermal lignocellulose hydrolysate exhibiting its maximal β-1,4-endoxylanase activity at pH 4 and 60 °C. This strain is thought to be very suitable for lactic acid production in a simultaneous saccharification and fermentation at pH values below 5.