Isolation of Phaffia rhodozyma auxotrophic mutants by enrichment methods.

Abstract

To establish the optimal conditions for mutagenesis in the astaxanthin-producing yeast Phaffia rhodozyma when different mutagens are used, dose-response curves for UV radiation, ethyl methanosulfonate and N-methyl-N′-nitro-N-nitrosoguanidine were constructed. An enrichment scheme using the polyene antibiotic nystatin for the isolation of auxotrophic mutants was designed. This treatment resulted in auxotrophic isolates at a frequency of 1×10-3. Uracil-requiring mutants were obtained by 5-fluoro-orotic acids selection at a frequency of 1.67×10-7.