Sustainable Production and Optimization of α-Amylase from Aspergillus niger Using Agro-Wastes via Solid-State Fermentation

Abstract

Alpha (α)-amylase is an industrially significant enzyme with extensive applications across the food, textile, detergent, and biofuel sectors. In the context of sustainable biotechnology, this study explores the use of agro-industrial residues—wheat straw, wheat bran, sugarcane bagasse, and spoiled bread—as alternative carbon sources for α-amylase production via solid-state fermentation (SSF) using A. niger. Among all tested substrates, wheat straw yielded the highest enzyme activity (1481 U/mL), confirming its suitability for low-cost bioconversion systems. A central composite design within the Response Surface Methodology (RSM) framework was applied to optimize four critical fermentation parameters: pH, substrate concentration, moisture content, and inoculum size. Statistical modeling revealed that pH 6.0, 6 g substrate, 55% moisture, and 6 mL inoculum size produced the highest α-amylase yield, validating the robustness of the predictive model (R² > 0.95). Interaction effects were visualized through contour and 3D response surface plots, which demonstrated synergistic parameter dependencies. This study not only advances scalable enzyme production from underutilized lignocellulosic biomass but also aligns with global sustainable development objectives, namely SDG 9 (Industry and Innovation), SDG 12 (Responsible Production), and SDG 13 (Climate Action) by promoting resource-efficient, waste-derived biomanufacturing platforms.