Diacetylated lactonic sophorolipids

Diacetylated lactonic sophorolipids have both esteric and glycosidic bonds which exhibit different sensitivities to either acid or alkaline hydrolysis. The latter will only hydrolyse the esters whereas acid hydrolysis at first cleaves the esters and, under more harsh reaction conditions, removes the sophorose moiety to yield a hydroxy fatty acid. In performing alkaline hydrolysis, the gradual removal of the esters transforms the solid... 

Figure 11.6 Alkaline (first step) and acid (both steps) hydrolysis of a diacetylated lactonic sophorolipid.

Treatment of the diacetylated lactonic sophorolipid with an alcohol will result in removing both acetyl groups and opening the lactone ring to the concurrent alcohol ester. Figure 11.8 depicts the transesterification of a sophorolipid with methanol. 

Native sophorolipids are understood to be produced by the wild-type organism and contain a C16-C18 hydroxy fatty acid. Two types of variations occur the nature of the lipophilic moiety and the amount of esterification. For the lipophilic moiety, predominantly hydroxy stearic acid is observed in the case of de novo synthesis [23] and when feeding a fatty acid of a suitable length, the concurrent hydroxy fatty acid is found. The extent of the esterification, either acetylation or lactonization, determines the solubility of the final product and is influenced by the pH. A value of 3-3.5 predominantly yields the poorly soluble diacetyl lactone and biosynthesis using a pH of 2 results in a more soluble and thus less esterified product. It is this last parameter that most influences the emulsifying properties of the sophorolipids. Adapting these properties to specific applications is further explored in Section 11.2. 

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