Effect of light level and salinity on the composition and accumulation of free and ester-type carotenoids in the aerial microalga Scenedesmus sp. (Chlorophyceae)

Abstract

Composition and accumulation of stress-induced carotenoids were characterized in the aerial microalga Scenedesmus sp. KGU-Y002. The specific growth rate was 0.27d−1, in the logarithmic growth phase. Nitrate starvation and varying light levels were applied to determine the effect of stress on the carotenogenesis of the algal cells. Under 200μmolphotonsm−2s−1, the alga accumulated 34.2±3.8mgg−1dryweightcells (dwc) of total carotenoids and 2.5±0.6mgg−1dwc of total chlorophyll content after 13days of culture. Astaxanthin and adonixanthin were the main xanthophylls in the algal cells. These xanthophylls existed as fatty acid esters in the algal cells under the culture conditions. Light level had an important influence on the rate of accumulation. The addition of NaCl was also found to promote the synthesis of these free and ester-type xanthophylls. Higher light and salt stresses synergistically activated carotenogenesis in the algal cells. These results imply that the esterification of astaxanthin and adonixanthin of algal strain KGU-Y002 is modulated by culture conditions such as light level and salinity.