Bioactive coating using Aspergillus niger: a strategy to improve the efficiency of multi nutrients fertilizers

Full text: Aspergillus niger is a fungus which can be used to increase the solubilization of minerals such as phosphate, potassium or oxides, which can be used as source of nutrients to plants. The direct use of oxide mineral as source of micronutrients would be desirable in order to reduce environmental impacts and costs. However, the challenges is to obtain a system that allows the interaction of mineral oxides particles with the simultaneous encapsulation of microorganisms. Therefore, we proposed a development of a biocoating based in a starch matrix gel. Starch is a cheap, abundant, biodegradable and natural polymer that can be metabolized by microorganisms to support its growth. This biocoating can be used for coated granular fertilizer as monoammonium phosphate (MAP), producing a multinutrient fertilizer. The starch matrix was prepared from dispersion of ZnO, MnO and CuO and A. niger spores [1] The starch gel was dispersed over the MAP granules using a metal turntable coater. The MAP granules coated were characterized and evaluated in a liquid medium bioactivation experiment. Scanning electron microscopy and X-ray tomography showed that the biocoating had a good adhesion on the surface of the fertilizer and the oxides particles presenting a high dispersion. The bioactivation experiments showed that A. niger spores germinated and proliferated around the fertilizer granule, promoting an increase in the solubilization of oxides when compared with the control experiment (without A. niger). This provides a basis for the development of a new class of biocoating for application of different microorganisms of agronomic interest. References: [1] Klaic R.; Giroto A.S.; Guimarães G.G.F.; Plotegher F.; Ribeiro C.; Zangirolami T.C.; Farinas S.C. Nanocomposite of starch-phosphate rock bioactivated for environmentally-friendly fertilization. Minerals Engineering, 2018; 128: 230-237. (author)