Cultivo de Aspergillus niger C em estado sólido em biorreator de leito empacotado para a produção de ácido cítrico e biofertilização de solos

Abstract

To minimize the environmental impact of agricultural activities, it is imperative to replace the use of agrochemicals produced from fossil sources with fertilizers from renewable sources. With regard to phosphate fertilizers, which are generally necessary as a supplement in the initial stages of cultivation, a sustainable alternative is the use of microorganisms capable of promoting the biological solubilization of the mineral from phosphate rocks, in which phosphorus is present in the form of stable complexes that need to be broken down in order to make the mineral available to plants. The main mechanism of phosphate solubilization by microorganisms is related to the production of organic acids. In this scenario, the fungus Aspergillus niger C stands out for its already known ability to produce citric acid and solubilize phosphate from commercial rocks. The production of acid and the solubilization of phosphate by this fungus can be carried out by solid-state fermentation (FES), a bioprocess that allows the use of agro-industrial solid wastes as substrates. In this context, this work aimed to contribute to the development of an industrial process for the production of biofertilizer capable of solubilizing the phosphate present in Brazilian commercial phosphate rock, using the filamentous fungus Aspergillus niger in a packed bed bioreactor (BLE), batch cultivations were carried out and in continuous mode in BLE, in order to compare the results of the scale-up with those obtained previously in bottle scale experiments. The parameters analyzed in the scale-up were: concentration of organic acids, quantified as citric acid using the titration method, concentration of soluble phosphate, quantified by the Murphy and Riley method, concentration of soluble proteins, quantified by the Bradford method, and temperature profiles. Finally, results were obtained that showed that there is a great challenge in controlling the temperature of the fermentative modules during the scale expansion, both in batch cultivation and in continuous cultivation, which resulted in a low metabolization of organic acids, with direct consequence in the solubilization of the commercial phosphate rock.