Exopolysaccharide-Mediated Green Synthesis of Zinc Oxide Nanoparticles from Bacillus licheniformis LHG166: Antimicrobial, Antioxidant, and Anti-inflammatory Properties

Abstract

This investigation demonstrates the successful biogenic synthesis of zinc oxide nanoparticles (ZnO-NPs) using exopolysaccharide extracted from Bacillus licheniformis LHG166 as an environmentally sustainable reducing agent. Characterization confirmed ZnO formation through UV-Vis absorption at 368 nm and FT-IR Zn-O stretching vibrations at 606 –448 cm⁻¹, while TEM revealed spherical nanoparticles (10–50 nm) and XRD confirmed hexagonal wurtzite structure with 17.17 nm crystallite size. DLS analysis showed a hydrodynamic diameter of 11.5 nm and electrostatic stabilization (Z-potential: -30.47 mV). Biocompatibility assessment revealed considerable hemocompatibility, with hemolysis below 2.5% even at 1000 µg/mL. Antioxidant evaluation demonstrated radical-scavenging activity, with DPPH IC₅₀ of 30.33 µg/mL and ABTS IC₅₀ of 15.6 µg/mL. Anti-inflammatory assessment revealed COX enzyme inhibition with IC₅₀ values of 59.31 µg/mL for COX-1 and 75.58 µg/mL for COX-2. Antimicrobial evaluation demonstrated broad-spectrum activity against both Gram-positive and Gram-negative bacteria, with MIC values ranging from 15.62 to 31.25 µg/mL and MBC ratios consistently 2:1. Antifungal activity revealed considerable efficacy, particularly against P. glabrum, with MIC/MFC ratios of 1:1 for C. albicans and C. tropicalis, establishing multifunctional therapeutic potential for biomedical applications that address antimicrobial resistance with integrated antioxidant and anti-inflammatory properties.