Enhanced Production of β-Glucosidase in Aspergillus niger Induced by Corncob Powder through Regulatory Modification

β-Glucosidase (BGL), a pivotal enzyme in lignocellulosic saccharification, has been increasingly recognized as an “emerging green biocatalyst” in modern biorefinery processes. Here, Aspergillus niger An-BGL was rationally engineered to achieve high-level production of BGL under low-cost inducers. Corncob powder served as a cost-effective alternative inducer, enhancing BGL production to 14.2 U/mL. The knockout of CreA and the overexpression of Xln R increased the BGL yield by 75% and 27%, respectively. Combinatorial engineering of CreA and Xln R generated the XO–CK strain, which exhibited a derepression effect at high glucose concentrations. Supplementation with 1% glucose alleviated the delayed enzyme production in the engineered XO–CK strain, resulting in a BGL activity of 31.54 U/mL. Furthermore, integration of the bglA gene into the high-expression amyA site enhanced BGL to 40.68 U/mL. The rational modification strategy for A. niger strain established in this study offers an efficient and sustainable approach for transforming corncob agricultural waste into high-value enzymatic preparations.