Resumo

Use of the genetic analysis allows several approach forms which promote responses to some basic issues which include, whether the gene is expressed, its interactions and identification of groups of genes which imply either in the activation or repression of several regulatory pathways. As the accumulation of citric acid by Aspergillus niger is accompanied by the disappearance, reduction or increase of some tricarboxylic acid cycle enzymes, the use of molecular techniques may be a alternative viable to the characterization and identification of the gene codifying for citrate synthase in citric acid production by Aspergillus niger. The aim of the present work was verifying the expression rate of genes involved in the identification of Aspergillus niger isolates and citrate synthase with citric acid production. 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, 12 isolates were selected with best performance as to the capacity producing citric acid. The DNA extraction of the samples coming from 12 isolates of Aspergillus niger was done by means of WizardTM Genomic DNA Purification Kit (Promega). The amplification by the polymerase chain reaction (PCR) was performed by using primer for ITS region and primer specific to citrate synthase (P1/P2). The base sequencing of the ITS region was a simple, fast and efficient method to aid in identifying isolates of Aspergillus niger. The pair of P1/P2 primer was sensitive to distinguish the isolates A. niger 00116, A. niger 00104, A. niger 00098 and A. niger 00118 in the analysis of citrate synthase enzyme genes. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior(CAPES)