Preparation, Characterization, and Antimicrobial Evaluation of Olive Stone Biochar

Antimicrobial resistance (AMR) is a major public health threat that requires new, low-cost strategies to control microbial growth. In this study, Olive stone biochar was prepared by slow pyrolysis at 500 °c for 3 h, followed by sterilization and ethanol/HCl treatment. The prepared OBC was characterized using Brunauer-Emmett-Teller (BET), SEM-EDX and Fourier transform infrared spectroscopy (FTIR) techniques. The BET surface area of OBC was 75.09 m2/g, the total pore volume was 0.7 cm3/g, and the average pore diameter was 6.5 nm, placing it in the mesoporous range, FTIR analysis confirmed presence hydroxyl, aliphatic, C-H, aromatic C = C, and carbonyl functional groups. Antimicrobial activity was evaluated using the well dissuasion assay against selected American Type Culture Collection (ATCC) strains, including Gram – positive bacteria Staphylococcus aureus ATCC 25,923 and Staphylococcus epidermidis ATCC 12,228. And gram – negative bacteria: Klebsiella pneumonia ATCC 43,816 and Escherichia coli ATCC 25,922; and fungal strain Candida albicans ATCC 10,231. Measurable inhibition zones were observed, with the largest zone recorded against Klebsiella pneumoniae ATCC 43,816 (26 mm ± 1.26), and Staphylococcus aureus ATCC 25,923 (24 mm ± 2.53). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of olive stone biochar (OBC) against a wastewater isolate of Escherichia coli were both determined to be 2.5 mg/mL under the tested conditions. These findings indicate that OBC exhibits measurable antimicrobial and bactericidal activity. However, further investigations incorporating stronger experimental controls and viable cell count confirmation are recommended to better validate and explain its antibacterial effects.