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Abstract

Staphylococcus aureus is a major Gram-positive pathogen that is increasingly resistant to antibiotics, significantly contributing to antimicrobial resistance (AMR)-related deaths. Therefore, this study aimed to examine the antibacterial activity of calcined chicken eggshell powder (CCEP), a waste-derived material rich in calcium compounds. CCEP was prepared by calcining eggshell powder at 900 °C for 3 hours. Its antibacterial potential was evaluated using in vitro assays, including agar disc diffusion and broth microdilution, as well as in silico molecular docking against penicillin-binding protein 4 (PBP4, PDB ID: 3HUM). The in vitro results showed that a 20% (w/v) CCEP solution in glycerol produced the largest inhibition zone, while the minimum inhibitory concentration (MIC) was 1,562.5 µg/mL, suggesting weak antibacterial activity, likely limited by poor solubility. The docking of calcium diglyceroxide from CCEP and glycerol produced a binding affinity of -5.9 kcal/mol, forming hydrogen bonds and hydrophobic interactions with PBP4 active site residues. Spearman correlation analysis showed a strong negative correlation (rs = -0.943, p < 0.001) between the docking affinities and inhibition zone diameters. These results suggest that CCEP exhibit antibacterial activity through both physicochemical and molecular-level mechanisms but require optimization to improve its solubility.

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