Effects of Drying on the Properties and Applications of Alkaline Corn Cob Lignin

Abstract Lignins are macromolecules obtained from plant biomass with great potential for high-value industrial applications. However, gaps remain regarding how lignin processing, particularly drying, affects its valorization. This study investigated how different drying techniques affect the physicochemical and biological properties of corn cob lignin, including color, UV-blocking ability, antioxidant activity, antimicrobial potential, and toxicity. Lignin was extracted via alkaline pretreatment, and the suspension was dried using four methods: freeze-drying (L), spouted bed at 60 °C (SB), oven at 60 °C (O60), and oven at 105 °C (O105). UV analysis confirmed that air exposure and temperature increases led to condensation reactions due to the loss of phenolic hydroxyl groups. Interestingly, spouted bed drying preserved the original color and maintained a phenolic hydroxyl content similar to freeze-drying, while exhibiting the highest antimicrobial activity against Gram-positive bacteria. Oven-dried lignins (O60 and O105) showed enhanced UV-blocking capabilities and superior in vitro DPPH radical scavenging but displayed lower ABTS inhibition efficiency (∼0.02 mg/mL vs 0.012 mg/mL for L). No correlation was observed between the lignin drying method and the zebrafish survival rate within the studied range (up to 100 mg/L). These findings demonstrate that drying techniques can strategically modulate lignin functional properties, serving as a crucial processing step for developing macromolecular functional products.