Astaxanthin induction in Chromochloris zofingiensis by transition of nutritional modes
摘要
Chromochloris zofingiensis is a natural astaxanthin producing oleaginous green microalga, known as an emerging model for studying carotenogenesis. In this study, we investigated the effect of transition of autotrophic and heterotrophic nutritional modes (preculture) into two different astaxanthin induction phase, namely autotrophic (300 µmol photons m−2 s−1 light intensity with nitrogen depletion) and heterotrophic (dark with 10 g L−1 glucose). In the nitrogen depleted autotrophic astaxanthin induction phase, the growth and carotenoid production were different between the cells transitioned from autotrophic and heterotrophic precultures. The heterotrophically precultured cells showed the highest astaxanthin content (1.50 mg g−1) due to transition into nitrogen depleted autotrophic astaxanthin induction phase, while the autotrophically precultured cells reached < 0.51 mg g−1 astaxanthin content with inhibited cell growth due to continuous cultivation of C. zofingiensis cells into light (two consecutive precultures to astaxanthin induction phase). The heterotrophic astaxanthin induction phase, on the other hand, with different precultures showed higher accumulation of primary carotenoids than the secondary carotenoids, where the heterotrophically precultured cells had 0.32 mg g−1 lutein content and about 0.09 mg g−1 astaxanthin content possibly due to prolonged cultivation of C. zofingiensis cells in the dark phase. The autotrophically precultured cells, however, reached 0.24 mg g−1 astaxanthin content possibly due to presence of light in the preculture phase. Our study reveals that alternation of light condition between preculture and astaxanthin induction phase can enhance the cell growth and astaxanthin accumulation than repeating the same preculture condition into the latter phase.