Characterization and antibacterial activity of synthesized zeolite from natural kaolinite loaded with streptomycin

Abstract

The escalating problems of antibiotic resistance coupled with its growing environmental pollution as a result of rapid release of antibiotics demands the development of new and efficient antibacterial agents. To overcome this problem, antibacterial compounds are immobilized on a carrier system such as zeolite. In this study, zeolite A was successfully synthesized from natural kaolinite using alkaline hydrothermal method with sizes ranging from 0.5 to 0.9 µm. The product was used as a carrier system by loading it with three concentrations of streptomycin (50 mg/L, 100 mg/L and 200 mg/L). To characterize and validate the production of the zeolite A, the samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy with energy dispersive X-ray (FESEM-EDX), transmission electron microscope (TEM) and dispersion behaviour. The XRD and FTIR results proved that zeolite A framework was maintained even after loading with streptomycin denoting its successful adsorption with minimal release. FESEM-EDX micrographs clearly indicated the presence of streptomycin particles on the cubic surface of zeolite A. In term of its dispersion behaviour, streptomycin-zeolite showed hydrophobic as compared to hydrophilic parent zeolite and thus, could attract bacterial cell wall. The antibacterial assay of the samples was conducted against Gram-negative bacteria (Escherichia coli ATCC 11229) and Gram-positive bacteria (Staphylococcus aureus ATCC 6538) through disk diffusion technique (DDT) and minimum inhibition concentration (MIC). The DDT results indicated that the streptomycin released into the media because the inhibition zone values increased proportional to the increasing amount of streptomycin adsorbed onto zeolite A. Both types of bacteria were susceptible to the modified zeolite with the lowest MIC value for Gram negative bacteria at 3.0 g/L in distilled water. In conclusion, the synthesized zeolite A from raw kaolinite is a good adsorbent for antibiotic streptomycin, generating a broad spectrum antibacterial activity.