Caracterização química e potencial antimicrobiano in vitro de extratos produzidos por fungos em cultivos submersos: uma abordagem frente a leveduras e bactérias de interesse biomédico e alimentar

Abstract

The increase in cases of microbial resistance, occurring mainly in the last 20 years, coupled with the reduction in the release of new antibiotics warn of an imminent post-antibiotic era.. In this context, the aim of this work was to select and identify isolated fungi of the Atlantic forest and Amazonian biomes that present antimicrobial potential against yeasts and bacteria of biomedical and alimentary interest, as well as to perform submerged cultures for production of metabolites that present antibiosis against the evaluated microorganisms. After the screening, fungi with antimicrobial potential were submitted to submerged cultures in both flasks (EF) and bioreactor (EB). The culture broths were filtered, concentrated by lyophilization and ressuspended (100 mg.mL-1 ) in sterile distilled water, to carry out the antimicrobial activity tests. Three fungi were selected that showed antimicrobial activity among 134 evaluated fungi. These were identified as Fusarium oxysporum, Cyclocybe cylindracea and Fomitopsis sp. The extracts prepared with the metabolites of F. oxysporum demonstrated broad-spectrum antimicrobial action with inhibition between 60% and 80%, depending on the target microorganism. The majority compounds of these extracts were identified as fusarinolic acid and its isomer (56.9% EF and 59.2% EB), dehydrofusaric acid (35.7% EF and 31.6% EB), and fusaric acid (6.5% EF and 1.1% EB). For extracts derived from C. cylindracea, antimicrobial activities superior to the amoxicillin control were observed in the assays against E. coli OP50, while for yeast the inhibition was similar to fluconazole. Fomitopsis sp. extract inhibited the growth of all microorganisms tested and showed superior antimicrobial activity to amoxicillin control against Escherichia coli OP50, Bacillus cereus, Staphylococcus epidermidis and Acinetobacter baumannii. The compounds produced by macrofungi could not be identified due to the large amount of metabolites in the samples and the limitation of information about these molecules in the databases. Although the extracts showed broad spectrum of action against the tested microorganisms, they also demonstrated toxic effects on human cells in the highest concentrations tested. The data obtained in this work indicate the potential of submerged cultures of fungi Fusarium oxysporum, Cyclocybe cylindracea and Fomitopsis sp. for the generation of metabolites and extracts, aiming the development of products that may be used in the food industry as alternative food preservatives, or even that may be studied as drugs.[resumo fornecido pelo autor]