Development of a transformation and selection system for the glycolipid-producing yeast Candida bombicola

Sophorolipids are surface-active compounds synthesized by the non-pathogenic yeast Candida bombicola. Over recent decades much effort has been spent to optimize culture conditions in order to improve the yield and production process. As far as we know, however, hardly any attention has been given to the genetics of the producing yeast strain itself and there are no published results available on the genetic engineering of C. bombicola. Nevertheless, this can be a useful tool for the study of the sophorolipid synthesis pathway and open up perspectives for improved production. A first step is the development of a suitable transformation and selection method. This article describes the creation and selection of an uracil auxotrophic C. bombicola mutant, which can be transformed back to prototrophy with the species' own orotidine 5'-phosphate decarboxylase or URA3 gene. Successful transformation was confirmed by a PCR-based method discriminating between the wild-type and mutated URA3 gene.