Produção e caracterização de biossurfactantes por novas espécies de leveduras do gênero starmerella.

Abstract

Biosurfactants are surface-active molecules produced by microorganisms, with the potential to replace petroleum-derived surfactants, which generate significant ecological damage to the environment. Biosurfactants have advantages over synthetic surfactants as they are biodegradable, less toxic and more stable under varying conditions of temperature, pH and salinity. Among the various existing types of biosurfactants, sophorolipids are among the best known and studied, belonging to the class of glycolipids. An obstacle faced in the production of biosurfactants is that the production costs are still high compared to synthetic surfactants, since the substrates used are expensive and the recovery methods are still inefficient. In view of this, the success of producing biosurfactants on an industrial scale depends on the use of alternative and low-cost substrates, as well as the choice of microorganisms. Therefore, the present study aimed to evaluate and characterize the production of sophorolipids from new species of yeasts of the genus Starmerella using low-cost substrates. For the development of this work, 10 new species of yeasts of the genus Starmerella isolated from Brazilian and Ecuadorian ecosystems were selected. These yeasts were submitted to a screening process, using the Emulsification Index test (E24) as a criterion for selecting the best producers. The yeasts with the highest emulsification indexes were selected for the next fermentation step, using a medium containing 50g/L of glucose, 50g/L of glycerol and 40g/L of rice bran. To confirm the production of glycolipids, the blue agar test was performed and the biosurfactants produced were subjected to tests to evaluate the stability in different conditions of pH, salinity and temperature. In addition, the surfactant property was also analyzed in a digital tensiometer using the maximum bubble pressure method, with values expressed in mN/M. The extraction of the produced sophorolipids was carried out with ethyl acetate (1:1) and the values expressed in g/L. From the data sets obtained, it was identified that the isolates TMY12.2 and TOC03_80.2 analyzed in the present study were able to produce sophorolipids with excellent emulsifying properties, stable at pH values between 6-10 and at temperatures of 0ºC, 25ºC and 40ºC. Regarding the concentration of NaCl, the isolate TMY12.2 obtained stable emulsions at concentrations of 2% and 6% and the isolate TOC03_80.2 at a concentration of 2%, thus having great potential for biotechnological applications