Abstract
Surfactants are amphipathic molecules that reduce surface and interfacial tension, conferring properties such as detergency, emulsification and phase dispersion, making them versatile chemicals. Most of the surfactants in use are derived from petroleum; however, interest in microbiological surfactants has increased because of its biodegradability and reduced toxicity. The objective of this work was to evaluate the production of a biosurfactant by the bacterium Bacillus invictae UCP 1617 using a complete 23 factorial design as a tool to optimize the variables agitation, temperature and inoculum size in 5 L bioreactor in mineral medium containing 2 % unconventional raw material. In the factorial tests, the surface tension and the yield in isolated biosurfactant were evaluated. The best condition of the experimental design was transferred to a 50 L bioreactor, being evaluated the kinetics of biosurfactant production. The biosurfactant formulation was carried out with the addition of 0.2 % of potassium sorbate. The formulation was then subjected to stability evaluation under different environmental conditions. The oil surface wash test with the biosurfactant was performed with motor oil. The best result obtained from the 2³ complete factorial design was the cultivation condition test number 5 (175 rpm at 28 ° C and 2 % inoculum), considering the best yield (1 g/L) in 72 hours of cultivation. The transfer of biosurfactant production to the 50 L bioreactor showed a surfactant productivity corresponding to 2.42 ± 1.1 g/L in 72 hours. The surface tension of the medium was reduced from 69.5 to 30.2 mN/m after 60 hours of fermentation, demonstrating the presence of surfactants. The chemical composition of the biosurfactant suggested the presence of 65 % of lipids and 32 % of carbohydrates, meaning its glycolipidic nature. The formulation produced with the addition of potassium sorbate proved to be a promising product because of its stability at various pH, temperature and NaCl concentrations. The biosurfactant removed 95.42 % of the oil adhered to the glass surface. Therefore, the biosurfactant presents potential application in remediation processes for the reduction of environmental impacts on ecosystems.
