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Biosurfactants are surface active biomolecules, mostly produced by microorganisms, with a wide range of industrial applications. Biosurfactants are usually designed with a hydrophilic moiety composed of amino acids or peptides, anions, or cations; mono-, di-, or polysaccharides; and a hydrophobic moiety consisting of unsaturated, saturated, or fatty acids (Banat et al. 2010).

Since biosurfactants are a wide group of biocompounds, there are different methods of classification. The most usual is classification according to the nature, chemical composition and microbial origin of the biosurfactants. They can be divided into five major categories: glycolipids, fatty acid/phospholipid, lipopeptide/lipoprotein, polymeric and surfactant particles (Cortés-Sánchez et al. 2013).

Among the biosurfactants, glycolipids have been intensively studied and are one of the most promising categories for commercial production and utilization (Warnecke and Heinz 2010). Glycolipids with one or two sugar residues attached to different lipid backbones can be found in cell membranes of bacteria, fungi, plants and animals in the form of sterylglycosides, glycosylceramides, and diacylglycerolglycosides (Warnecke and Heinz 2010). The most well-known glycolipids are sophorolipids (Bogaert et al. 2007; Oliveira et al. 2015), mannosylerythritol lipids (Im et al. 2001), rhamnolipids and trehalose lipids (Figure 1.1). The glycolipods that this chapter will focus on is a case study of trehalose lipids, also known as trehalolipids.

Figure 1.1 The chemical structures of the most common glycolipids.

The amphiphilic character triggers them to aggregate at liquid interfaces with different degrees of polarity and hydrogen bridges, giving them the ability to reduce surface- and interfacial-tension between solids, liquids and gases.

Furthermore most biosurfactants exhibit characteristics such as tolerance to pH, temperature and ionic strength, biodegradability, low toxicity, detergency, emulsification, de-emulsification and foaming. There is considerable interest in potential applications, due to their environmental friendly character and sustainability (Geys et al. 2014; Makkar et al. 2011; Santos et al. 2016; Smyth et al. 2010). Nowadays the preservation of the Earth as a sustainable planet is one of humanities greatest concerns. In line with this concern about the environment, many industries are changing to a global viewpoint on the future of manufacturing. In fact, they have recognized the potential of living cells in the pre-treatment of raw materials, processing operations, product modifications, selective waste management, energy recycling and conservation.

Biosurfactants are quite adaptable, their performance is versatile in a wide range of applications, in different areas, such as pharmaceutics, cosmetics, agronomy, food, beverages, metallurgy, agrochemicals, organic chemicals, petrochemicals, fertilizers, and others (Abdel-Mawgoud and Stephanopoulos 2018). The main applications in the pharmaceutical field are as anti-microbial, anti-cancer, anti-viral and anti-adhesive agents, immunological adjuvants, and in drug and gene delivery (Abdel-Mawgoud and Stephanopoulos 2018).