Zusammenfassung
The green microalga Chromochloris zofingiensis can accumulate significant amounts of
valuable carotenoids, mainly natural astaxanthin, a product with applications in functional food,
cosmetics, nutraceuticals, and with potential therapeutic value in cardiovascular and neurological
diseases. To optimize the production of astaxanthin, it is essential to monitor the content of astaxanthin
in algal cells during cultivation. The widely used HPLC (high-performance liquid chromatography)
method for quantitative astaxanthin determination is time-consuming and laborious. In the present
work, we present a method using flow cytometry (FCM) for in vivo determination of the astaxanthin
content and the carotenoid-to-chlorophyll ratio (Car/Chl) in mixotrophic C. zofingiensis. The method
is based on the assessment of fluorescent characteristics of cellular pigments. The mean fluorescence
intensity (MFI) of living cells was determined by FCM to monitor pigment formation based on the
correlation between MFI detected in particular channels (FL1: 533 15 nm; FL2: 585 20 nm;
FL3: >670 nm) and pigment content in algal cells. Through correlation and regression analysis,
a linear relationship was observed between MFI in FL2 (band-pass filter, emission at 585 nm in FCM)
and astaxanthin content (in HPLC) and applied for predicting astaxanthin content. With similar
procedures, the relationships between MFI in different channels and Car/Chl ratio in mixotrophic
C. zofingiensis were also determined. Car/Chl ratios could be estimated by the ratios of MFI (FL1/FL3,
FL2/FL3). FCM is thus a highly efficient and feasible method for rapid estimation of astaxanthin
content in the green microalga C. zofingiensis. The rapid FCM method is complementary to the
current HPLC method, especially for rapid evaluation and prediction of astaxanthin formation as it is
required during the high-throughput culture in the laboratory and mass cultivation in industry.
