Search Results (3)

Oyster shells, though rich in calcium, are mostly discarded and contribute to environmental issues. Developing calcium-based materials with antimicrobial functionality offers a promising solution. However, their low bioavailability limits their direct use, requiring processing to enhance their applicability. Therefore, this study aims to evaluate the physicochemical properties and antimicrobial activity of thermally processed pulverized oyster shells (TPOS) and citric acid-treated TPOS (TPOSc) compared with those of fibrous calcium carbonate (FCC) and coral-derived calcium product (CCP), which are used as reference materials. The solubility values were 0.7 mg/g for FCC, 0.5 mg/g for TPOS, 0.4 mg/g for TPOSc, and 0.05 mg/g for CCP. The average particle sizes were 476 (FCC), 1000 (TPOS and TPOSc), and 1981 nm (CCP). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses revealed calcium ion release and structural changes in TPOS and TPOSc. Antibacterial testing further confirmed that these samples exhibited significant antimicrobial activity. Furthermore, to assess their practical applicability, TPOS and TPOSc samples with antimicrobial properties were incorporated into rice cakes. All samples retained antimicrobial activity at 0.3 wt%, while higher concentrations led to deterioration in their textural properties. These findings support the potential of thermally processed oyster shell powders for food applications that require microbial control with minimal impact on product quality. Full article

Recent studies on utilizing biological functions of natural substances that mimic the mesoscopic structures (nanoparticles of about 50 to 500 nm) found in plant growth points and coral skeletons have been reported. After the calcium hydrogen carbonate contained in materials derived from plants and coral are separated, the crystals of the mesoscopic structure can be reformed by applying a high voltage under a specific set of conditions. A suspension of these mesoscopic crystals in water (CAC-717) can be used as an effective disinfectant. CAC-717 exhibits universal virucidal activity against both enveloped and non-enveloped viruses as well as bactericidal and anti-prion activity. Moreover, in comparison to sodium hypochlorite, the potency of CAC-717 as a disinfectant is less susceptible to organic substances such as albumin. The disinfection activity of CAC-717 is maintained for at least 6 years and 4 months after storage at room temperature. CAC-717 is non-irritating and harmless to humans and animals, making it a promising biosafe disinfectant. This review explores the disinfection activity of CAC-717 as well as the potential and future uses of this material. Full article

This study investigates the development of epoxy–resin composites reinforced with coral-derived calcium carbonate (CaCO₃) fillers for enhanced radiation shielding and mechanical properties. Leveraging the high calcium content and density of coral, composites were prepared with filler weight fractions of 0%, 25%, and 50%. SEM and EDS analyses revealed that higher filler concentrations (50%) increased particle agglomeration, affecting matrix uniformity. Mechanical testing showed that while the tensile and flexural strengths decreased with the increased filler content, the compressive strength significantly improved, reaching 135 MPa at a 50% coral content. Radiation shielding evaluations demonstrated enhanced attenuation with a higher filler content, achieving 39.63% absorption at 60 kVp for the 50% coral composite. However, the shielding efficiency was notably lower compared to lead, which achieves over 99% absorption at similar energy levels. These quantitative comparisons highlight the material’s limitations in high-radiation environments but emphasize its suitability for moderate shielding applications. Despite their lower shielding efficiency, the composites provide an environmentally friendly and non-toxic alternative to lead, aligning with sustainability goals. Future work should focus on optimizing filler dispersion, mitigating agglomeration, and exploring hybrid systems to enhance the shielding efficiency and mechanical properties. The further quantitative evaluation of parameters such as Zeff and cross-sections is recommended to comprehensively assess the material’s performance. Full article