High-level expression of a sweet protein, monellin, in the food yeast Candida utilis

We describe the heterologous expression of monellin in the yeast Candida utilis. A single-chain monellin gene was expressed under the control of the glyceraldehyde-3-phosphate dehydrogenase [correction of decarboxylase] gene promoter from C. utilis. A promoter-deficient marker gene allowed high-copy-number integration of vectors into either the rDNA locus or the URA3 gene locus. Monellin was produced at a high level, accounting for > 50% of the soluble protein. No significant decrease in the production level of monellin was detected in transformants after 50 generations of nonselective growth.