Resumo

Citric acid is an important organic acid, multifunctional with a wide array of uses, versatile in domestic and industrial applications as an acidulant, flavoring, antioxidant, buffering and sequestering. In spite of a great deal of microorganisms being able to be used to produce citric acid, Aspergillus niger continues being the main industrial producer. Despite the extensive research conducted, the understanding of the events relevant to citric acid production is not completely understood. Several microorganisms, including both bacteria and fungi, possess a capacity to solubilize phosphates by means of different mechanisms. Therefore, this work was intended both to isolate and select strains of the genus Aspergillus producing citric acid and investigate the phosphate solubilization from these isolates. By the direct plating method, samples of soil, fruits, grains and breads were utilized for selection of Aspergillus niger for further purification. The characterization and the identification of the species of the genus Aspergillus was conducted on the basis of the taxonomy, From these, twelve isolates were selected with best performance as to the capacity of solubilizing phosphate and producing citric acid. To verify the mechanisms of microorganisms to solubilize phosphate to the medium in the citric acid production, Araxá phosphate was utilized. Further, citric acid in two culture media Potato Dextrose(BD) and Sabouraud(SA) was evaluated. The isolates of Aspergillus niger were efficient to solubilize Araxá phosphate. The isolate of A. niger 00118 stood out in the solubilization efficiency with increase of up to five times the amount of soluble phosphorus when compared with the control treatment. The results of citric acid production stressed a better influence of the conditions of the culture SA medium upon its production. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior(CAPES)