ACCUMULATION OF α-TOCOPHEROL IN MICROALGAE CELLS

Abstract

To date, the main natural source of vitamin E is vegetable oils. Among the compounds of the vitamin E group, α-tocopherol has the higher biological activity, the relative content of which in vegetable oils is comparatively small. Significantly higher concentrations of α-tocopherol (up to 4-6 mg / g dry weight) accumulate some microalgae, such as Euglena gracilis, Dunaliella tertiolecta, Nannochloropsis oculata, Tetraselmis suecica and others. Due to this, there has been a growing interest in biotechnology of microalgae as a raw material for the production of vitamins. The largest amount of tocopherols is synthesized in Euglena gracilis cells by myxorotrophic cultivation.Lipid-soluble α-tocopherol is a component of the non-enzymatic antioxidant system and performs the function of protecting cell membranes from reactive oxygen species and free radicals. As a result of many studies, the dependence of the level of α-tocopherol accumulation on the conditions of cultivation of microalgae, including light intensity, photoperiod, nitrogen level, temperature, type of carbon nutrition, etc. At the same time, stressful conditions stimulate the accumulation of antioxidants in photosynthetic organisms, but limit the normal rate of their growth. The problem of increasing the yield of tocopherols is solved in systems of two-stage cultivation through the separation in time of the stage of biomass accumulation and the stage of stimulation of α-tocopherol biosynthesis. The increase in tocopherol content is achieved due to the introduction of exogenous carbon sources at the stage of biomass accumulation and limiting the nutrient medium for some nutrients at the stage of stimulating the synthesis of antioxidants. The review presents data on the effects of the composition of the nutrient medium, type of nutrition, temperature, light intensity, cultivation technique on the accumulation of vitamin E by microalgae cells.