Abstract

Xylanases (EC 3.2.1.8) are key enzymes that hydrolyze β-1,4-glycosidic linkages in xylan, facilitating its depolymerization. Microorganisms like bacteria, fungi, and actinomycetes are capable of producing enzymes that withstand high temperatures. This study focused on improving xylanase production by screening mutant strains of Aspergillus niger GCBT-35 (wild-type) that were resistant to 2-deoxy D-glucose following exposure to N-methyl N-nitro N-nitroso guanidine (MNNG) for 15–45 min. To maximize enzyme yield, various culture conditions were optimized in a solid-state fermentation system. Different agricultural by-products, including wheat straw, wheat bran, sunflower meal, soybean meal, newspaper, rice husk, rice straw, and bagasse, were tested as substrates. Wheat bran, at a 1:1 ratio (w/v), was identified as the most effective substrate for xylanase production. The highest enzyme activity (94.9 U/mg/min) was achieved 48 h after inoculation when the moistening agent had a pH of 5.0, controlled incubation temperature of 30°C and the nitrogen source was optimized to 0.2% ammonium sulfate [(NH4)2SO4]. Xylanase production was boosted by 2.3 times compared to the wild-type strain. These findings revealed that mutagenesis significantly enhanced xylanase yield, highlighting its potential for industrial-scale enzyme production. The study highlighted the importance of strain improvement and fermentation optimization in developing cost-effective biotechnological applications for xylanase production.