Otimização das condições de cultivo submerso do fungo Lasiodiplodia sp. para produção de extratos com atividade antimicrobiana

Abstract

Studies on discovering new antimicrobial agents from natural resources have great relevance. The increase in the frequency of resistant pathogens to commercial antibiotics clearly demonstrates that new drugs are necessary for current medicine. Among the compounds with therapeutic potential from nature, secondary metabolites produced by endophytic fungi have attracted a lot of attention. Literature has demonstrated that endophytic fungi have the ability to produce a plethora of compounds with various biological activities. In this study, ethyl acetate extracts (EtOAc) obtained after Lasiodiplodia endophyte cultivation, showed relevant antimicrobial activity. To determine the best fermentation conditions, Lasiodiplodia was cultivated in Czapek medium, in static and stirred mode, and broth samples were taken at different times of cultivation to evaluate the production of antimicrobial compounds from EtOAc extracts, which were evaluated against ATCC Staphylococcus aureus, Candida albicans and Escherichia coli strains, through the Minimum Inhibitory Concentration (MIC) and Minimum Microbicide Concentration (MMC). The fermentation after 12 days in static mode was selected for producing larger EtOAc mass extract (154mg/300mL). The Response Surface Methodology (RSM) was used to maximize the production of this extract, a Central Composite Rotational Design 23 was performed, with six-star points and three repetitions at the central point, totaling 17 essays, whose the independent variables were glucose, sucrose, NaNO3, and the dependent variable was EtOAc dry mass production. Regarding the experimental design, the optimum fermentation conditions were 15 g.L-1 of glucose, 24 g.L-1 of sucrose and 0.85 g.L-1 of NaNO3, yielding an improvement of 84% in EtOAc dry mass extract. The antimicrobial activity of the extracts remained satisfactory against S. aureus and C. albicans, and it is possible to suggest that under the conditions studied herein, Lasiodiplodia sp. is able to produce substances with antimicrobial properties which is biotechnologically relevant.