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The exact synthetic pathways of the majority of glycolipids are not yet fully known. Various pathways are involved in the biosynthesis of precursors for biosurfactant production, depending on the main carbon source used in the fermentation medium.

Generally the last step of the glycolipid-synthesis implicates the linking of glycosyl and lipid precursors. The linking is mostly via o-glycosidic or ester bonds formed by glycosyltransferases or acyltransferases. Glycosyltransferases are highly valuable glycosylation catalysts, inducing the transfer of the glycosyl residue from an activated glycosyl donor (mostly sugar nucleotides or phosphates) to a lipid acceptor, by making glycosidic bonds between the nucleophilic hydroxyl groups of the acceptor and the anomeric carbon of the sugar donor (Abdel-Mawgoud and Stephanopoulos 2018; Bungaruang et al. 2013).

Acyltransferases catalyze the transfer of the lipid residue from an activated acyl donor, such as acyl-coA, to a glycosyl acceptor, by forming an ester bond between the nucleophilic hydroxyl group of the glycosyl residue (acceptor) and the donor’s carbonyl group (Abdel-Mawgoud and Stephanopoulos 2018).

Glycolipids could also be theoretically hydrolyzed, as is shown in Figures 1.2 and 1.3. Glycoside hydrolase can hydrolyze the sugar–lipid or sugar–sugar glycosidic bonds (Figure 1.2), while carbohydrate esterase can hydrolyze the sugar–lipid ester bonds (Figure 1.3) (Abdel-Mawgoud and Stephanopoulos 2018).

Figure 1.2 Hydrolysis of the sugar–lipid or sugar–sugar glycosidic bonds from glycolipids. R₁: Nucleotides or phosphates groups of the glycosyl residue; R₂: any substitution that could be glycosyl, lipid, or glycolipid units.

Figure 1.3 Hydrolysis of sugar–lipid ester bonds from glycolipids. R₁: Coenzyme A or Acyl Carrier Protein groups of the acyl donor; R₂: any substitution that could be glycosyl, lipid, or glycolipid units.