Growth Study Arthrospira platensis Gomont Culture in a Two-Stage Luminostat

The work is devoted to the experimental study of Arthrospira platensis culture growth in a two-stage luminostat. A new method of flow culture is presented, which allows to increase the efficiency of light energy assimilation, as well as to control the content of photosynthetic pigments in algal biomass. In the first stage, the growth of A. platensis culture in the first stage of luminostat in batch mode was investigated. Due to high surface and spatial irradiance, a prolonged exponential phase is present on the growth curve. The maximum specific growth rate of the culture was 0.96 1/day and the chlorophyll a and C-phycocyanin content was low – 1.37 and 2.3% respectively. The light energy passing through the first stage varied from 2.23 to 33.24% depending on the maintained density of the quasi-continuous culture. The reduction in light flux affected the maximum productivity of A. platensis in the second stage of luminostat, which was 0.08 g/(l·day). In the second experiment, cultivation was carried out in a two-stage luminostat regime, in which the nutrient medium was sequentially flowed through both stages. It was shown that in the second stage, due to a decrease in irradiance, photoadaptation of A. platensis cells occurred, consisting in a slight increase in the proportion of chlorophyll a and a significant increase in C-phycocyanin – 13.6 %. The pigment content was directly influenced by the uniformity of cell irradiation, which for the second stage was only 8 %, which led to a decrease in productivity and an increase in the content of C-phycocyanin. The obtained results allow us to recommend the two-stage luminostat for optimisation problems solving on obtaining microalgae biomass of a given pigment composition.