Anais do Congresso Paranaense de Microbiologia
IV Congress of Microbiology in Paraná

Foodborne diseases are an important cause of morbidity and mortality worldwide. In many countries, over the past two decades, they have emerged as a growing economic and public health problem. Numerous outbreaks of foodborne diseases attract media attention and an increase consumer concern. These diseases involve bacteria like Salmonella sp., Escherichia coli, and Staphylococcus sp. Therefore, several studies are directed to the search of antimicrobial molecules to avoid and control bacterial diseases from contaminated food. Sophorolipids are biosurfactants glycolipids mostly produced by the yeast Starmerella bombicola and presents antioxidant and antimicrobial activities, representing a promising industrial potential. Thus, the aim of this study was to produce sophorolipids by S. bombicola and evaluate its antimicrobial properties against the bacteria Staphylococcus aureus coagulase positive and Escherichia coli ATCC 8739. Sophorolipids production was conducted on a 5 L bioreactor, with 3.5 L of working volume for 288 h, 30 °C at 450 rpm. The production medium contained (g/L): oleic acid, 220; glucose, 200; and yeast extract, 6, with initial pH at 6.0. Samples were taken every 24 h to quantify the consumption of substrates, growth of biomass and sophorolipid production. The medium was centrifugated at 3500 rpm for 15 min and the cell pellet was collected, washed with distilled water and dried for determining the biomass concentration. From the supernatant, a solvent extraction with ethyl acetate (1:1), hexane and methanol (4:1) was performed. The crude sophorolipids were collected from the methanol phase, while the remaining hydrophobic substances were collected from the hexane phase, being both quantified gravimetrically. Glucose consumption was determined by the Somogyi-Nelson method. The antioxidant activity was performed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and the antimicrobial activity by the disk diffusion test and broth microdilution technique, to determine the minimum inhibitory concentration (MIC). Sophorolipids production reached 131.91 g/L in 288 h, with a productivity of 9.42 g/L/d and a substrate conversion efficiency of 51.7%. The produced sophorolipids presented a 98% antioxidant activity at 5% concentration and it also showed effectiveness in inhibiting both bacteria at a MIC concentration of 30 µg/mL. Therefore, the results presented here demonstrate the great industrial potential that sophorolipid possess, both for its high production yield, and for its antioxidant and antimicrobial properties, which could be exploited in the most diverse industrial sectors, such as the food industry.