Spirulina platensisis used as a feed and food source, which contains 50-70% of protein, up to 8% of fat, carbohydrates (20%), has a balanced amino acid composition, vitamins A – 29 mcg/100g, E – 5 mg/100g, K – 25.5 mcg/100g, B1 – 2.4 mg/100g, B2 – 3.7 mg/100g, as well as iron – 28.5 mg/100g, magnesium – 195 mg/100g, sodium – 1048 mg/100g, copper – 6.1 mg/100g, manganese – 1.9 mg/100g. Spirulina production is a waste-free and environmentally friendly process. Only photosynthetic oxygen is released during the production process. In Ukraine, spirulina cultivation is limited due to the imperfection of technological approaches. It has been established that one of the main technological parameters of the operation of spirulina cultivation plants is the dilution rate, which aff ects the productivity of the plant. Therefore, improving the process parameters of the biotechnology of spirulina cultivation using a cascade-type installation is relevant. A photoreactor for growing spirulina of the cascade type was developed. The installation consists of a tank, cascade surfaces, phytoirradiators, a pump, a compressor, mixers, a bubbler, a heat exchanger, inlet and outlet pipes for medium and suspension, a pipe for removing the gasair mixture, a carbon dioxide cylinder. Its main parameters: - temperature regime of the installation – 20-30°C; - volumetric pump fl ow – up to 12 m 3 /h; 2- operating mode – continuous; - number of cascades – 14; - illuminated working surface of the photoreactor – 8.82 m; - total area of the illuminated working surface of the photoreactor – 124 m 2; - volume of suspension in one cascade – 0.529 m; - volume of suspension in the cascades of the photoreactor – 7.42 m 3 3; - volume of suspension in the photo reactor – 8.52 m 3; - installed capacity – 17.1 kW; - overall dimensions: height – 5.8 m, width – 2.1 m, length – 4.2 m. The culture was grown in continuous mode at di lution rates of 0.02 h-1 and 0.04 h-1. At a dilution rate of 0.02 h-1, an increase in the concentration of abso lutely dry biomass was observed from 1.4 to 2.9 g/l. The culture remained in a steady state. Increasing the dilution rate to 0.04 h-1 leads to a decrease in the concentration of absolutely dry spirulina biomass in the culture medium from 2.6 to 1.1 g/l during cultivation due to cell washout from the system. At a dilution rate of 0.02 h-1, the pH value was stable within 9.1. Stable pH is a sign of an optimal cultivation regime. The slow inflow of fresh nutrient medium ensures a balance between CO₂ uptake by cells and the buffering capacity of the medium, which leads to the system entering a quasi-steady state. At a dilution rate of 0.04 h-1, the pH value increased from 9.1 to 10.2, which indicates a violation of the physiological and biochemical balance of the culture, since during the growth process it reduces the concentration of carbonic acid, as a result of which the medium becomes more alkaline (pH increases). Based on the conducted research, the technical regulation for growing spirulina in a cascade-type photoreactor were improved.

Keywords: spirulina, photoreactor, biotechnology, biomass, algae, nutrient medium.