Estimation physiological state and carotenoid content of Dunaliella salina (Teod.) using flow cytometry and variable fluorescence methods

Production characteristics of the microalgal Dunaliella salina were studied. The maximum rate of carotenoid synthesis was observed at high light intensity and nitrogen deficiency. The applicability of cytometric and fluorescent indicators to assess the degree of β-carotene accumulation and to estimate the D. salina functional state was studied. The shift in growth conditions, which stimulated carotenoid accumulation, affected the algae photosynthetic apparatus and weakly affected cell enzyme activity and cell viability. Fluorescein diacetate (FDA) fluorescence and the ratio of live cells can be used to assess the degree of lethal effect of an external factor on the physiological state of microalgal. The measurement of cell autofluorescence at a wavelength of 575 nm was a highly effective approach to the rapid assessment of β-carotene content in D. salina and to the prediction of β-carotene formation. The correlations were obtained between cell autofluorescence ratios in the orange (575 nm) and red (680 nm) spectrum areas and the ratio content of carotenoid and chlorophyll in algae cells. A linear relationship was established between the Fm/D 750 ratio (the ratio of the maximum chlorophyll fluorescence at closed PS II reaction centers to the suspension optical density at 750 nm) and intracellular chlorophyll content in microalgal. These relationships allow assessing pigment content in the cells as well as predicting β-carotene formation in D. salina .