Biosurfactantproduction by Bacillus spp. for use in dairy industry effluents

Abstract

Biosurfactants are surface-active compounds produced by the secondary metabolism of different groups of microorganisms, such as bacteria, filamentous fungi and yeasts. Bacteria of the genus Bacillus are recognized as good producers of lipopeptide biosurfactants for producing compounds that have characteristic properties such as; emulsifying, antimicrobial, antibiotic action, inhibition of biofilm formation and hydrocarbon degradation, which allows its use in different industrial sectors and environmental applications. Considering the need to use environmentally friendly compounds in fatty effluent treatment plants, the use of microbial biosurfactants is an alternative. Thus, the objective of the present work was to produce biosurfactant by inoculating strains of Bacillus ssp in soybean oil used as a carbon source and subsequently applying it to effluent treatment plants in the dairy industry. Three bacteria of the genus Bacillus, identified as belonging to the species Bacillus subtilis strains CCMA 0658 and CCMA 2031 and Bacillus velezensis strain CCMA 0087, were selected using the droplet collapse test and β-hemolysis. The biosurfactant-producing strains were inoculated in a medium containing soybean oil used as a carbon source. To evaluate the biosurfactants produced, the following tests were performed: (i) emulsification (IE24), (ii) oil scattering tests and (iii) surface tension analysis. The crude biosurfactants produced by the three strains of Bacillus showed emulsifying and surface-active properties. Emulsification (IE24) was equal to or greater than 40%, oil scattering values were greater than 50% of the Petri dish diameter and surface tension less than 35 mN m-1 for all three strains. When applied to the dairy effluent, the biosurfactants produced by the strains B. velezensis CCMA 0087 and B. subtilis CCMA 2031 presented values of 25% in the emulsification test. The results obtained suggest that, in adequate volumes, the biosurfactants produced could promote greater solubility of the fats present in these effluents.