(481e) Enhancing Antimicrobial Potency of Lignin through Phenolation

The battle against antibiotic resistance and the pursuit of waste valorization are driving the advancement of bio-renewable antimicrobial materials. Utilizing a cost-effective polymer precursor like lignin, equipped with cationic functionalities, presents a promising strategy to combat antibiotic-resistant bacterial strains and create highly potent antimicrobials. However, the complex, heterogeneous composition of lignin poses challenges for large-scale production of these antimicrobials. Thus, this study investigated the potential of lignin pre-treatment, specifically phenolation, to enhance the structural homogeneity and reactivity of lignin for grafting cationic moieties. Our research focused on optimizing phenolation parameters to maximize lignin phenolation. The resulting phenolated lignin (PAL) samples were then cationized with glycidyl trimethyl ammonium chloride (GTMAC) to produce cationized phenolated lignin, QPAL. Remarkably, QPAL demonstrated a 100% reduction in colony-forming units (CFU) and exhibited bactericidal effects against wild-type, kanamycin-resistant, and ampicillin-resistant E. coli at a concentration of only 40 µg/mL, whereas it took ~150 to 300 µg/mL of cationic non-phenolated lignin to achieve similar antimicrobial efficacy. Phenolation and subsequent cationization of lignin did not only boost the antimicrobial potency significantly but also exhibited minimal cytotoxicity against human embryonic kidney cells. These findings highlight a promising avenue for improving the effectiveness of cationic lignin as an antimicrobial agent, while also offering a more efficient approach to valorizing lignin and addressing antibiotic resistance.