Thermo- and photoisomerization of astaxanthin was investigated in a model system (solutions in methanol and chloroform), and the dynamics of astaxanthin isomers and esters content was analyzed in Haematococcus pluvialis green algal cells exposed to factors inducing astaxanthin accumulation. In both systems, the astaxanthin isomerization process seems to be defined by a) the action of light (or heat), and b) the dielectric constant of the surrounding medium. Upon heating, the accumulation of Z-isomers occurred in a model system during the entire incubation period. For the first 5 h of illumination, both Z-isomers accumulated in the solutions up to 5%, and then their content decreased. The accumulated amount of the Z-isomers in the cells of H. pluvialis was found to reach 42% of the total content of astaxanthin initially, and then it decreased during the experiment. The results lead to a conclusion that both cultivation of H. pluvialis culture in specific conditions and heat treatment of the resulting extracts from it might be efficient for obtaining large amounts of economically useful astaxanthin Z-isomer.
Spirulina (Arthrospira) platensis biomass has a wide range of applications in several industries. One of the key issues for its production is the reduction of the culture medium cost. Here we have shown the possibility of a single recycling (repeated usage) of the modified Zarrouk nutrient medium (MZM; which contains 8.4 g/l of NaHCO3and 0.1 g/l of NaOH instead of 16.8 g/l of NaHCO3) for spirulina cultivation without altering culture productivity, photosynthetic pigments and protein contents in its biomass given that technological approach consisting in application of a mixture of a freshly prepared and once recycled modified Zarrouk medium in a ratio of 1:1 by volume is used. The obtained results can be applied for further reduction of costs of spirulina biomass production compared to methods described in previous studies.
The content of astaxanthin, including its mono- and diesters, and photosynthetic pigments, has been analyzed in cells of H. pluvialis strain IBCE-H17 under the combined prolonged action of several inducers of astaxanthin accumulation. The effective induction of the astaxanthin accumulation, mainly in the form of monoesters of fatty acids, was shown after a 20-day cultivation under high-intensity light and with the addition of 1-2 g/l of sodium acetate to the culture medium. A simultaneous decrease in the content of chlorophylls and lutein in the H. pluvialis cells was observed under these conditions. The use of sodium acetate in combination with sodium chloride did not lead to noticeable changes in the content of astaxanthin compared with the use of sodium acetate alone. The obtained data can be helpful in the biotechnological production of Haematococcus biomass enriched with economically valuable compounds.
astaxanthin, Haematococcus pluvialis, pigments, sodium acetate, sodium chloride, high-intensity light.
This work was supported by Grant no. Б19РМ-010 of the Belarusian Republican Foundation for Fundamental Research and Grant no. 19-54-04003 of the Russian Foundation for Basic Research.
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