From Corncob By-Product to Functional Lignins: Comparative Analysis of Alkaline and Organosolv Extraction Followed by Laccase Treatment

Corncobs, produced globally at over 200 million tons annually with 11-18% lignin content, represent an abundant and underexploited lignocellulosic resource for sustainable lignin valorization. In this study, two distinct extraction methodologies, alkaline treatment using sodium hydroxide and an organosolv process with a 50:50 ethanol/water mixture, were systematically compared for their efficiency in isolating lignin from corncobs. Both protocols achieved high yields, up to 82% for alkaline and 84% for organosolv extraction under optimized conditions. The resulting lignins displayed notable differences in chemical structure and physical properties, as revealed by spectroscopic and thermal analyses, highlighting their divergent potential for downstream applications. To evaluate the suitability of these lignins to biocatalytic upgrading, post-extraction enzymatic treatment was performed using <i>Pycnoporus cinnabarinus</i> laccase (EC 1.10.3.2). Significant structural modifications were observed in alkaline-extracted lignin, as determined by FTIR spectroscopy, while organosolv lignin remained largely unaltered, a difference attributed to its lower aqueous solubility at the enzyme's optimal pH. These results demonstrate the critical impact of extraction conditions on lignin reactivity and suitability for enzymatic tailoring. This work underscores the potential for holistic corncob valorization within integrated biorefinery frameworks. Selective extraction and targeted enzymatic modification not only facilitate efficient by-product utilization but also expand the prospects for producing versatile bio-based materials, thereby advancing the transition toward a sustainable, circular bioeconomy.