Academia and Society Sowmya Kuppusamy 12 1 2025 https://doi.org/10.6025/aas/2025/12/1/1-20 https://www.dline.info/aas/fulltext/v12n1/aasv12n1_1.pdf This study investigates the biosoftening of lignin in sugarcane bagasse using the white-rot fungus Pleurotus sajor-caju through solid-substrate fermentation. Bagasse, a ligno cellulosic waste rich in lignin (21%), was inoculated with fungal spawns and incubated for five weeks. Lignin was extracted weekly via alkaline delignification and analyzed using UV spectroscopy and FT-IR to assess structural changes. Results showed a progressive decline in lignin yield-from 62.2% at week 0 to 15.38% by week 5-indicating effective fungal degradation. UV scans revealed reduced absorbance at 260-280 nm and shifts in max, suggesting cleavage of aromatic rings and demethoxylation. FT-IR analysis confirmed the breakdown of key lignin structures, including aromatic skeletal vibrations (1600-1510 cm-1), O-H stretching (~3420 cm-1), and ether linkages (1120-1030 cm-1), alongside the emergence of carbonyl groups (~1720 cm-1), signaling oxidative depolymerization. These modifications enhance lignin's reactivity, making it more suitable for resin synthesis, particularly lignin-phenol-formaldehyde (LPF) resins. The study demonstrates that P. sajor-caju offers an eco-friendly, cost-effective alternative to chemical softening methods, reducing environmental impact while valorizing agricultural waste. The findings support the use of white-rot fungi in sustainable bioprocesses for industrial lignin modification and the production of bio-based polymers.