Abstract
High-added value inputs and inefficient means of production using the already known microorganisms make it even more difficult the industrial application of biosurfactants. Therefore, this work aimed to optimize the fermentation parameters for biosurfactant production by the Antarctic yeast Candida sake, since to the best of our knowledge it was not investigated for this purpose yet. First, the optimized condition for the production of biosurfactant using the yeast Candida globosa was adopted, being as follows: residual soybean oil (72 g/L), ammonium nitrate, NH4NO3 (1.4 g/L), monobasic potassium phosphate, KH2PO4 (0.2 g/L), yeast extract from brewing industry or residual yeast extract (0.4 g/L), and fermentation time (72 h). However, no biosurfactant production was observed. So, the further fermentation assays were performed using the production medium known as Czapek, which was prepared as follows: sodium nitrate, NaNO3 (2 g/L), magnesium sulfate, MgSO4 (0.5 g/L), potassium chloride, KCl (0.5 g/L), iron(II) sulfate, FeSO4 (0.01 g/L), monobasic potassium phosphate, KH2PO4 (1 g/L), and residual yeast extract (1.2 g/L). Secondly, the biosurfactant production by the yeast Candida sake was evaluated as regard to the fermentation time (24, 48, 60, 72, and 84 h), residual soybean oil concentration (40, 60, 80, and 90 g/L), KCl concentration (0.3, 0.4, and 0.5 g/L), and how necessary would be the use of FeSO4, MgSO4 and yeast extract. According to the results, the greater biosurfactant yield was obtained for 60 h of fermentation, coupled with 80 g/L of residual soybean oil and 0.4 g/L of KCl. The results also revealed that the process demanded yeast extract, but did not need FeSO4 and MgSO4, providing a biosurfactant yield of 13.8 g/L. Finally, Candida sake showed a better performance in relation to Candida globosa and Candida lipolytica (mostly explored in the literature), proving to be quite effective and promising in producing biosurfactant.
