Comparação de métodos de preservação de linhagens de Aspergillus da Coleção DPUA na produção de metabólitos secundários com potencial antimicrobiano

Abstract

Fungi remain one of the most important sources of bioactive compounds, among which, the genus Aspergillus predominates as an alternative for the production of secondary metabolites of industrial interest, especially as source of antimicrobials, enzymes and antioxidants. This work aimed to verify the influence of the preservation method on the activity of secondary metabolites and to select a species of Aspergillus as a source of compounds with antimicrobial activity. The antimicrobial activity against Gram-positive (Staphylococcus aureus), Gram-negative (Escherichia coli) and Candida albicans yeast was determined by agar diffusion and bioautography techniques. The viability of the fungi was performed based on the morphological characteristics and reproduction structures of the Aspergillus species. The production of the bioactive compounds was carried out in yeast extract agarose extract (YES). The organic extracts, ethanolic, ethyl acetate and hexane obtained from the cultures were tested by agar diffusion method against Staphylococcus aureus (Gram-positive bacteria), Escherichia coli (Gram-negative) and Candida albicans (unicellular fungus). The results showed that filamentous fungi continue to be one of the most important sources of bioactive compounds, among which, the genus Aspergillus predominates as an alternative for the production of metabolites of industrial interest, such as Lovastatin and other antimicrobials. The extracts that demonstrated antibiosis by agar diffusion were analyzed by agar immunoassay and subsequent determination of the minimum inhibitory concentration (MIC) using the multiwell plate dilution method. The viability of Aspergillus species predominated in cultures preserved in distilled water, the phenomenon of pleomorphism was observed in 2.5% and 7.5% of the Aspergillus species preserved in water and mineral oil, respectively. Contamination by other filamentous fungi was observed in 2.5% in both water and mineral oil preserves. The profile of the antimicrobial activity by diffusion in agar showed the activity of one to three extracts of Aspergillus cultures predominantly against S. aureus. Growth of E. coli and C. albicans was inhibited only by ethyl acetate extract of A. japonicus DPUA 613 and ethanolic extract of A. flavo furcatis DPUA 1451, respectively. In bioautography, antimicrobial activity was detected in different compounds against S. aureus, ranging from one to three zones of inhibition, in the Rf range of 0.70 to 0.81. In this test, A. flavo furcatis DPUA 1451 was the only growth inhibitory species of C. albicans, composed of Rf 0.75 constituent of the hexane extract. The data presented here showed that Aspergillus species, although preserved for different periods under in vitro conditions, synthesize compounds with antibacterial and antifungal activity capable of inhibiting the growth of S. aureus, E. coli and C. albicans.