Comparison of antifungal activities of scallop shell, oyster shell and their pyrolyzed products

Waste shells create several serious problems, however, only parts of them are being utilized now. Therefore, the ideal solution would be to convert the waste shells into a product that is both environmentally beneficial and economically viable. Scallop and oyster shells were exposed to heat treatment at 1050 °C. SEM and XRD analysis results showed that the resultant powder turned completely into CaO after the treatment. The antifungal activities of non-treated and heat-treated scallop and oyster shell powder slurry were investigated. Non- treated oyster shell powder exhibited a significant antifungal activity at 25,000 ppm. Its antifungal activities against Physalospora piricola Nose (P. piricola) and Rhizoctonia solani Kühn (R. solany) were even up to 100%. Moreover, increasing culture time did not alter the antifungal activities. Heat-treated scallop and oyster shell powder exhibited obvious antifungal activity at 500 ppm, at which concentration 100% inhibition of R. solany was observed. The possible antifungal mechanism of the oyster shell and its heat-treated counterpart was studied using R. solani Kuhn as model. The results illustrated that oyster shell is able to affect the membrane permeability of the fungus. The above-mentioned results showed that it is possible for oyster shell to be an agriculture fungicide.