Production and characterization of novel/chimeric sophorose–rhamnose biosurfactants by introducing heterologous rhamnosyltransferase genes into Starmerella bombicola.

Glycolipid biosurfactant, sophorolipids (SLs) and rhamnolipids (RLs) can be widely used in agriculture, food and chemical industries. The different physicochemical properties of SLs and RLs, such as hydrophilic lipophilic value (HLB) and critical micelle concentration (CMC), determine they have different application focus. Researchers are still hoping to obtain new glycolipid surfactants with unique surface activities. In this study, we successfully transformed two rhamnosyltransferase genes rhlA and rhlB from Pseudomonas aeruginosa to the sophorolipid-producing Starmerella bombicola CGMGG 1576 to obtain a recombinant strain was SbrhlAB. Two novel components with molecular weight of 554 (C26H50O12) and 536 (C26H48O11) were identified with the ASB C18 column from the fermentation broth of SbrhlAB, the former was a non-acetylated acidic C14:0 glycolipid containing one glucose and one rhamnose, and the latter was an acidic C14:1 glycolipid containing two rhamnoses. With the Venusil MP C18 column, one new glycolipid component was identified as an acidic C18:3 glycolipid with one rhamnose (C24H40O7), which has not been reported before. Our present study demonstrated that novel glycolipids can be synthesized in vivo by reasonable genetic engineering. The results will be helpful to engineer sophorolipid-producing yeast to produce some specific SLs or their derivatives in more rational and controllable way. [ABSTRACT FROM AUTHOR]