Protein accumulation and expression of the nitrate reductase gene in Spirulina platensiscells depending on the spectral composition of led radiation

The effect of LED lighting of different spectral composition on the productivity of Spirulina platensis, an accumulation of protein in alga cells and an expression of the nitrate reductase gene has been studied. It was shown that LED lighting with a predominance of the red component in the emission spectrum allows achieving 9–29 % higher alga productivity compared to using fluorescent lamp illumination. Illumination with single blue light resulted in significant (83 %) decrease in the productivity of Spirulina platensiswhich apparently was due to the absence of the yellow and red components in the illuminator spectral composition, which are most effectively absorbed by phycocyanin. A positive correlation between an increase in the productivity of alga and the accumulation of protein in its cells was found. So, by using an illuminator with red LEDs, the protein content increased by 21 % calculated per gram of dry weight and 47 % calculated per liter of suspension relative to the control. Analysis of the expression of the Nar gene encoding nitrate reductase in Spirulina platensiscells did not reveal a direct dependence between an increasing protein accumulation and an expression level of the Nar gene in the most promising in terms of biomass and protein yield sample of alga, growing under red LEDs. This indicates the crucial role of the photosynthetic activity of Spirulina platensiscells in increasing productivity and protein synthesis.