Abstract
Microbial surfactants are surface-active metabolites, produced by microorganisms, which have low toxicity, are biodegradable and biocompatible. Furthermore, these molecules are stable in extreme environmental conditions, such as pH, temperature, and salinity changes. The maim factor for the ever increasing biosurfactant use by industries is its capacity to reduce surface tension and interfacial tension of immiscible solutions. The selection of microorganisms capable to produce biosurfactants has been investigated in the last years, and the Antarctic environment has become of great interest due to its extraordinary diversity. The present work reports the evaluation of biosurfactant production by Antarctic isolated yeasts. Four yeasts isolated in the Antarctic environment were evaluated, coded as L69, L87, L104, and L106, and the biosurfactant production was accessed by the emulsification index in kerosene, diesel oil, engine oil and soybean and surface tension. The biosurfactant containing solution was obtained from a five day old fermentation broth, composed by 3 g L-1 yeast extract, 5 g L-1 peptone, and 20 g L-1 glucose, and incubated at 15 °C and 30 °C. The emulsification index was accessed by mixing with the oils and the cell free aqueous solution of the fermented broth, in a 1:1 ratio, and the surface tension was obtained using a Tensiometer. The L69 and L104 yeast showed the best results at the tested conditions, whereas the L69 yeast showed 96, 0, 92 and 50% of emulsification index in kerosene, diesel oil, engine oil and soybean, respectively, while L104 showed 100 and 93 % of emulsification index in engine oil and soybean, and zero for the other tested oils. The results showed that these yeasts were capable to produce biosurfactants, however further tests should be performed to characterize these biomolecules.
