| dc.description.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 | |
