Chapter 19 *Corresponding Author: Galba M. Campos-Takaki—Nucleus of Research in Environmental Sciences, Center of Sciences and Technology, Catholic University of Pernambuco, 50.050-900 Recife, Pernambuco, Brazil. Email: gmctakaki@pesquisador.cnpq.br Biosurfactants, edited by Ramkrishna Sen. ©2010 Landes Bioscience and Springer Science+Business Media. Environmentally Friendly Biosurfactants Produced by Yeasts Galba M. Campos-Takaki,* Leonie Asfora Sarubbo and Clarissa Daisy C. Albuquerque Abstract Some yeasts are preferred to bacteria as sources for biosurfactants, mainly due to their GRAS status for environmental and health safety reasons. his chapter thus focuses on the production of biosurfactants by some yeast cultures using renewable resources like fatty wastes from household and vegetable oil reineries as major substrates. he chapter also emphasizes on the importance of the application of response surface methodology and artiicial neural network techniques for the optimization of biosurfactant production by yeasts. Introduction Biosurfactants are amphipathic molecules with both hydrophilic and hydrophobic (generally hydrocarbon) moieties, a structurally diverse group of surface active molecules synthesized by a variety of microorganism bacteria, ilamentous fungi and yeasts. 27,34 hese molecules reduce surface and interfacial tensions in both aqueous solutions and hydrocarbon mixtures, which make them potential candidates for enhancing oil recovery and emulsiication processes. 9,18,55 Biosurfactants have several advantages over chemical surfactants, such as lower toxicity; higher biodegradability; 82 better environmental compatibility; 28 higher foaming; 47,50,61 high selectivity and speciic activity at extreme temperatures, pH and salinity; and the ability to be synthesized from renewable feedstock. 47,50,81,82 Information concerning the studies of yeast and the biodegradation of hydrocarbons and oil is described in the literature. 9,10,24‑27 Studies on emulsiier production by yeasts have been undertaken by Cirigliano and Carman, 15 Cirigliano and Carman 16 and Singh and Desai. 75 Table 1 shows the biosurfactant produced by diferent yeast strains, according to the literature. For the last ten years, our research group has been working on the biosurfactant molecules produced by yeasts, given that the criteria for advantage is the low risk associated with the prod‑ ucts obtained from the metabolism of yeast i.e., that all molecules are generally regarded as safe (GRAS). his is a concept used in some countries to identify substances that have been assessed as ingredients in many products and found in all cases to be safe. his simpliies the assessment process by eliminating those substances from extensive and repetitive assessment. Most of the substances that have been classiied as GRAS are very common ingredients, such as sodium chloride, but also include substances such as emulsiiers, surfactants and wetting or sticking agents. In addition, the production of biosurfactants has been steadily increasing. his is due to their diversity of action, their environmentally friendly nature, the possibility of their production through fermentation,