One of our PhD students, Marta Salgado, won the Jerry King Poster Award to the best poster presented by a graduate student, sponsored by Critical Fluid Symposia, in the recent 14th European Meeting on Supercritical Fluids. All presented posters were evaluated by the Poster Judging Committee, chaired by Jerry King and composed of members of the International Society for Advancement of Supercritical Fluids (ISASF) board. The awarded work contained information about our research on developing a formulation of a powder fungicide that improves the absorption of the active compound by the fungi. For that purpose, the fungicide is encapsulated on β-glucans, which are one of the constituents of the cell wall of the fungi.
Botrytis cinerea is a pathogenic fungus that affects several fruits and plants. In order to reduce the use of toxic substances against fungus, new formulation methods are being developed. In this work, β-glucans are used as encapsulating material for conventional fungicides. Taking into account that the cell wall of Botrytis cinerea contains β-glucans in its structure, this novel formulation may provide an improvement on the absorption of the fungicide in the fungus, which results in more effectiveness and less quantity of product required to control the infection.
Tebuconazole is one of the compounds commonly employed in plant protection, and it is the fungicide used in this work. First, an oil-in-water emulsion is formed, with tebuconazole dissolved in ethyl acetate as organic phase, whereas the aqueous phase contains the different matrixes used: β-glucans, soybean lecithin (for comparison) or a mixture of both of them. Then, the organic solvent is removed by vacuum evaporation, and finally the suspensions are dried either by particles from gas-saturated solutions (PGSS-drying) or conventional spray-drying. The main advantage of the PGSS in comparison to spray-drying is that the formation of particles is due to the sudden decompression of the fluid, so lower process temperature is required in the spray tower, preventing thermal degradation of the product.
Besides, particles are obtained also by supercritical anti-solvent technique (SAS), by dissolving β-glucans on dimethyl-sulfoxide (DMSO).
Once the particles are produced by any of the above mentioned methods, the encapsulation efficiency of tebuconazole in the different matrixes and drying processes is evaluated. The morphology of the particles is analyzed by scanning electron microscopy (SEM). Also the antifungal activity of the particles against Botrytis cinerea is studied through in-vitro culture techniques, and compared to that of pure tebuconazole powder and commercial emulsion of tebuconazole.
a) High Pressure Processes Group, Department of Chemical Engineering and Environmental Technology, University of Valladolid, Doctor Mergelina s/n, 47011 Valladolid, Spain
b) Sustainable Forest Management Research Institute, University of Valladolid- INIA, Department of Plant Production and Forest Resources, Avda. Madrid, 57. Campus “La Yutera”, 34004 Palencia, Spain