In order to minimize the environmental impacts of agricultural activities, reducing the use of agrochemical products is mandatory. However, because there is usually a need to supplement the soil with phosphate for the good development of several agricultural crops, an alternative that has shown to be promissing is the use of biological agents capable of acting as biofertilizers, promoting biological solubilization of the mineral from phosphate-containing rocks in the form of stable complexes that need to be broken down for the mineral to become available to the plants.The main mechanism of phosphate solubilization by microorganisms is associated with the production of organic acids, but it can also be associated with the adhesion of the filamentous fungi hyphae to the rock particles. In this context, in this project, it is proposed to perform the solid state cultivation of the fungus Aspergillus niger C, already known for its ability to produce citric acid in a solid medium and for solubilizing phosphate from commercial rocks.The work will be divided into two steps: in the first stage, the production of organic acids through the cultivation of the fungus in a matrix containing sugarcane bagasse and wheat bran as substrates will be evaluated, as substrates, with or without glucose and sucrose as carbon and peptone and yeast extract as nitrogen addittional sources. In this step, it will be tried to define the substrate composition that provides greater production of organic acids.In the second stage of the work, once the composition of the nutrient solution to be impregnated in the solid matrix has been defined, the substrate will be added with powdered phosphate rock. In this phase, phosphate solubilization will be evaluated, seeking to establish a relationship with the production of citric acid and proteins throughout the culture, with the help of kinetic studies. It is expected that, at the end of the project, it will be possible to obtain a cultivated material that can be used in the field as a biofertilizer, which should be activated in high humidity, provided by rain or irrigation of crops.
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