Work

Microalgae are widely used as additives for animal feed and in healthy food as feedstock for the manufacture of pharmaceuticals. Especially great interest is in the use of algae as a potential source of renewable fuels such as biodiesel, biogas, and Biohydrogen. Productivity and biochemical composition of microalgae depends on the method of cultivation. Although microalgae are photosynthetic organisms, the growth rate of many of them increases in mixotrophic culture, with the use of light energy and organic carbon source. The aim of our work was to study the influence of the simple sources of organic carbon – methanol, ethanol and glutamate on the overall performance and yield of valuable substances such as photosynthetic pigments and tocopherols for Euglena gracilis var. bacillaris, Biohydrogen and free amino acids for Chlamydomonas reinhardtii Dangeard. These species are chosen because they are the most studied and due to the variety of nutrition pathways are model organisms in biology. The study was performed using conventional microbiological, biochemical, biophysical, cytological methods. It was established that for C. reinhardtii single addition of methanol to a concentration of 50 mM was optimal, and stimulated growth by 34%. Thus, significant restructuring of metabolism occurs: the content of glutamic acid derivatives is increased, serine and tyrosine and methionine content is reduced, mitochondrial respiration is activated, and protein content temporarily increases. In the presence of 150 mM methanol hydrogen evolution was stimulated by 2.9 times, that exceeds the result of a leading lab of A.Melis. Stimulating effect of organic substrates is based not only on being sources of carbon and energy, but also on their regulatory effect. Adding ethanol and glutamate intensifies the growth of E. gracilis by 6 times and changes photosynthesis, respiration and biochemical composition of cells. β-carotene content increased 3-fold compared with the control. Tocopherols yield in autotrophic cells is the highest, however, due to high rates of biomass accumulation, in mixotrophic culture its total yield was 2.7 times higher than in autotrophic culture, that opens new perspectives for creating two-stage technology of tocopherols production of E. gracilis.