Utilization of sugarcane bagasse waste by Aspergillus welwitchiae SVUAw9 for production, purification, and characterization of cold-active xylanase under solid-state fermentation conditions

Abstract Aspergillus welwitschiae strain SVUAw9 was isolated from sugarcane bagasse and identified by the sequencing of the calmodulin (CaM) gene, was found to exhibit substantial cold-active xylanase activity in this study. Under solid-state fermentation conditions, the strain can utilize a range of agro-industrial residues as substrates to produce cold-active xylanase. After 14 days at pH 7 and 10 °C using ammonium chloride as the nitrogen source, sugarcane bagasse was the most productive substrate, generating 106.93 ± 12.1 U/gram dry substrate (gds), followed by bean straw, corn cob, and date palm leaves which produced 57.82 ± 8.27, 57.75 ± 7.44, and 38.87 ± 6.15 U/gds, respectively. Conversely, the substrate exhibiting the lowest production was rice husk, producing 29.32 ± 4.88 U/gds. Using Trilite MC 08 and Sephacryl S-200 columns, the xylanase was purified 75.87 times, yielding a single band at approximately 71 kDa. At pH 4.0 and 30 °C, the maximum activity of 156.46 ± 12 U/mg was achieved. Co(NO₃)₂, MnSO₄, and NiSO₄ markedly enhanced enzyme activity, resulting in residual activity increases of 152.94 ± 11.54%, 152.94 ± 9.58%, and 134.12 ± ठर 7.66%, respectively, with specific activities of 239.3 ± 18, 239.3 ± 15, and 209.84 ± 12 U/mg. Km and Vmax for the pure xylanase were determined as 0.1 ± 0.005 mg/mL and 144.9 ± 7.14 µmol/min, respectively. The purified xylanase could degrade oat spelt xylan, corn cob xylan, xylan, Birchwood xylan, maize stalk xylan, carboxymethyl cellulose (CMC), beechwood and microcrystalline cellulose (MCC), resulting in activities of 156 ± 12, 108 ± 7, 82 ± 6, 79 ± 5, 62 ± 4, 22 ± 1.5, and 38 ± 3 U/mg, respectively.