Seleção de cepas do grupo Bacillus subtilis para produção de biossurfactantes com potencial antimicrobiano

Abstract

Brazil has an economy strongly attributed to agriculture and this results in the large production of agro-industrial waste. The reuse of these residues as nutritional sources in bioprocesses contributes to the reduction of environmental damage, as well as reducing the costs of producing high added value metabolites, such as biosurfactants. In order to make the microbial production of biosurfactants less costly and more sustainable, it is appropriate to use the residual glycerol from biodiesel production as a substrate for microorganisms. Biosurfactants, amphipathic molecules synthesized by plants and microorganisms, have several applications in the agro-industry, in the pharmaceutical, food and oil industries, in addition to their potential in the bioremediation of soils contaminated with hydrocarbons. The objective of this study was to produce biosurfactants by the Bacillus subtilis group in residual glycerol and to verify the antimicrobial potential and phytotoxicity of these bioproducts. The tests of Emulsification Index (E24), Oil spreading assay and Thin Layer Chromatography indicated the production of lipopeptide biosurfactants by the strains tested and, among these, Bacillus subtilis group CCMA 87 stood out for its antibacterial and bactericidal activity against E.coli. In addition, it was verified that the crude biosurfactant of the strain Bacillus subtilis group BAL 0081 presented the highest inhibition rates against the species of Fusarium and Aspergillus among the tested Bacillus strains. Furthermore, the crude extracts of Bacillus subtilis group BAL 0081 and CCMA 0087 were not phytotoxic to Lactuca sativa var. “Veronica” at a concentration of 50mg/mL. These results demonstrated that the crude biosurfactants of Bacillus subtilis group BAL 0081 and 0087 exerted antimicrobial activity against pathogenic bacteria, phytopathogenic fungi and were not phytotoxic at a concentration of 50mg/mL, which indicates the potential of these metabolites as biocontrol agents.