ANTIMICROBIAL ACTIVITY OF METABOLITES PRODUCED BY Brevibacillus sp. LABIM 17 UNDER DIFFERENT CULTURE CONDITIONS

There has been a growing interest in researching and developing new antimicrobial agents from various sources to combat microbial resistance. Prokaryotic organisms are highlighted in the production of bioactive compounds during their secondary metabolism,especially because ofthe low molecular weight of those compoundsand their antimicrobial potential, which gives their producer a native advantage, making them a promising alternative for the development of new compounds with antimicrobial activity. In view of the need for both the discovery and the production optimization of molecules with antimicrobial power, the present study had as objective evaluating the potential antagonistic of 31 isolates of Gram positive bacteria and optimizing the production conditions of the antimicrobial metabolites from the best antagonist. In order to evaluate the antagonist potential of the 31 isolates, an dual culture methodwas performed in Nutrient agar for the bacteria and Saboraund for the yeast strain, using as indicator the bacteria Staphylococcus aureusATCC,29213, Escherichia coli ATCC 8739 and Candida albicans ATCC 26790, having each microorganism a duplicate of itself. The strain selected was LABIM 17, isolated from a soil fragment of the Atlantic Forest and, according to preliminary studies of the genome, it belongs to the genus Brevibacillus. Luria Bertani Broth (LBB), Luria Bertani supplemented with micronutrients (LBm) and Mueller Hinton Broth (MHB) were tested for the production and maintained at temperature of 28 °C for 72 hours in orbital shaker at 150rpm. At the end of the production, the antagonist activity of the cell-free supernatant was tested against the indicator microorganisms Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 8739 and Candida albicans ATCC 26790 throughwell diffusion method using 200µl of a cell-free supernatant that was sterilized by membrane filtration (0,22µm). All tests were performed in triplicate. The MHB production was the one that presented the best performance (p <0.001) against the three indicatormicroorganisms tested, while no antimicrobial activity was observed in production fromLBm. Considering the results obtained, we conclude that the strain Brevibacillussp LABIM 17 showed the best antagonist potential when it was cultured in MHB, meaning that Brevibacillussp LABIM 17 could be an alternative to the development of natural product with antimicrobial activity.