Estudio de surfactantes biológicos producidos por Streptococcus thermophilus, usando suero de queso como fuente de carbono para remediación de aguas contaminadas con aceite de motor

In this research work, it was studied the obtaining of a biological surfactant produced from the fermentation of cheese whey as a carbon source, using Streptococcus thermophilus bacteria. The fermentation process was carried out for 72 h at 37 °C. Then, it was centrifuged at 4000 rpm for 30 minutes to remove waste. The separation of the biosurfactant was carried out by the acid precipitation method and it was dried in an oven at 40o C. A weight of 0.1 g of biosurfactant was obtained for every 100 ml of cheese whey used. To optimize the production of the biosurfactant, a complete factorial design of three levels and two factors was carried out, with the response variable being the amount of surfactant obtained. The main effects of temperature (38, 40 and 42 oC), time (24, 48 and 72 hours) and their combination were evaluated. It was found that the main effects of temperature and time were significant, in addition to their interaction. It was found that the highest performance with respect to biosurfactant production was obtained at a temperature of 40oC and a time of 48 hours. The characterization confirmed the presence of the biosurfactant, several qualitative and quantitative tests were performed: hemolytic activity, Parafilm, oil dispersion, emulsification index (63.64%) and surface tension (52.7 mN/m). In addition, an ecotoxicity test was carried out with Daphnia magna and after carrying out the bioremediation test to corroborate that the biosurfactants are environmentally friendly. Finally, during the 45 days of the bioremediation process, the biosurfactant combined with microorganism achieve a motor oil removal of more than 50%.