PRODUCTION OF BIOSURFACTANTS FROM YEASTS ISOLATED FROM BRAZILIAN ECOSYSTEMS FOR APPLICATION IN THE FOOD INDUSTRY

Biosurfactants are amphiphilic molecules of microbial origin with wide application in the food, cosmetic, pharmaceutical, agricultural, and bioremediation industries. In the food industry, they act as emulsifiers and stabilizers in bakery, dairy products, and sauces, replacing synthetic additives. Yeasts capable of metabolizing lignocellulosic pentoses stand out as promising candidates for their production. This study evaluated the growth and surfactant activity of Scheffersomyces stipitis and Meyerozyma guilliermondii cultivated in xylose or sucrose. The cultures were carried out in triplicate for 120 h (30 °C, 200 rpm), in a medium containing 50 g/L of xylose or sucrose, 5 g/L of yeast extract, and 5% (v/v) of soybean oil, with an initial inoculum of 1 g/L. Growth was monitored by optical density (OD₆₀₀), and the supernatants, obtained by centrifugation, were subjected to the drop collapse test, foam height evaluation, and determination of the emulsification index (E₂₄ and E₄₈) against sunflower oil, hexane, and toluene. When cultivated in xylose, S. stipitis stabilized its growth at 36 h (maximum of 1.27 g/L), whereas in sucrose it reached 2.08 g/L. In contrast, M. guilliermondii showed similar behavior in both carbon sources (1.55 g/L in xylose and 1.48 g/L in sucrose). The E₂₄ index against sunflower oil ranged from 59% to 60% in all conditions. However, hexane emulsification distinguished the species: S. stipitis in sucrose reached an E₂₄ of 67.4% and an E₄₈ of 64.2%, whereas M. guilliermondii showed no significant activity (0–6.5%). Foam activity was low (4.7% to 6.0%). The drop collapse test revealed positivity in more than 96% of the measurements from 12 h onward, with more evident reactions between 60 and 72 h. The early stabilization of S. stipitis in xylose signals lower efficiency in pentose utilization. The specificity in hexane emulsification, restricted to S. stipitis in sucrose, evidences metabolic differences between the microorganisms. Furthermore, the peak of drop collapse activity between 60 and 72 h, dissociated from the biomass peak, suggests that biosurfactant synthesis occurs, in part, in a non-growth-associated manner. In short, both yeasts synthesized compounds that were stable against oil, with the performance of S. stipitis in sucrose standing out in hydrocarbon emulsification.

Acknowledgments: The authors thank FAPEMIG, CAPES, CNPq, and UFSJ for their financial support and infrastructure.