Development of a Dunaliella tertiolecta Strain with Increased Zeaxanthin Content Using Random Mutagenesis

Zeaxanthin is a xanthophyll pigment that is regarded as one of the best carotenoids for the prevention and treatment of degenerative diseases. In the worldwide natural products market, consumers prefer pigments that have been produced from biological sources. In this study, a Dunaliella tertiolecta strain that has 10-15% higher cellular zeaxanthin content than the parent strain (zea1), was obtained by random mutagenesis using ethyl methanesulfonate (EMS) as a mutagen. This mutant, mp3, was grown under various salinities and light intensities to optimize culture conditions for zeaxanthin production. The highest cellular zeaxanthin content was observed at 1.5 M NaCl and 65-85 μmol photons·m^-2·s^-1, and the highest daily zeaxanthin productivity was observed at 0.6 M NaCl and 140-160 μmol photons·m^-2·s^-1. The maximal yield of zeaxanthin from mp3 in fed-batch culture was 8 mg·L^-1, which was obtained at 0.6 M NaCl and 140-160 μmol photons·m^-2·s^-1. These results suggest that random mutagenesis with EMS is useful for generating D. tertiolecta strains with increased zeaxanthin content, and also suggest optimal culture conditions for the enhancement of biomass and zeaxanthin production by the zeaxanthin accumulating mutant strains.