Extraction and preliminary study of antibacterial compounds of three species of Aspergillus genus

Abstract

In the interest of discovering new antibiotic molecules, the antibacterial activity of three fungal strains namely: Aspergillus quadrilineatus, Aspergillus niveus, and Aspergillus wentii isolated from particular ecosystems was sought against six bacterial strains including three with Gram-positive staining (Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis) and three with Gram-negative staining (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae). The results of the agar cylinder technique highlighted that the three fungal strains showed a considerable antibacterial activity. In order to optimize the extraction conditions of the bioactive molecules, five solvents in different polarities were tested, of which chloroform turned out to be the best one. After the selection of this solvent, four culture media of different compositions were used in order to determine the most adequate medium for the production of antibacterial substances. The results revealed that Czapek-dox medium supplemented with yeast extract turned out to be the most favorable one for the production of bioactive molecules from both strains: A. quadrilineatus and A. niveus, while the most suitable medium for the A. wentii strain was Sabouraud. In addition, a study of the antibacterial effect of organic extracts by the Biolog micro-culture system was performed using a range of concentrations. The obtained results revealed that the extracts of the three fungal strains presented a remarkable activity with different concentrations and this, against all the tested bacterial strains. It was recorded only for the three used fungal species, the antibacterial activity was studied for the first time by the Biolog system.