Biomass increase of Spirulina platensis as a feed additive with different doses of sulfur in the nutrient environment

Spirulina biomass is a renewable resource that can be cultivated on cheap nutrient media and used as a feed supplement for animal and poultry diets. It contains many complete proteins, vitamins, trace elements, and other biologically active substances. The nutrient medium for growing spirulina contains many macro-elements and micro-elements. Sulfur is essential for algae. This element is very important in nitrogen anabolism and protein and chlorophyll synthesis. The issue of the effectiveness of using increased doses of Sulfur and its various sources as part of the nutrient medium for spirulina remains insufficiently researched. The work aimed to study different doses of Sulfur in purified, alimentary form and in the form of Glauber's salt to increase spirulina biomass and the total protein and chlorophyll content in its biomass. Four groups of phytoreactors were formed for research. Zarruk nutrient medium with standard sulfur content was placed in the phytoreactors in the control room. Additional purified alimentary Sulfur was added to the nutrient medium from the I, II, and III research groups to bring the level of the element in the medium, respectively, to the level of 250.0; 300.0 and 350.0 mg/dm3 (I series of experiments). In the II series of experiments in the I, II, and III experimental groups, the Sulfur content in the nutrient medium was brought to the level of 250.0, 300.0, and 350.0 mg/dm3 using Glauber's salt. During the experiment, the optical density of the nutrient medium with spirulina and the content of total protein and chlorophyll in the biomass of spirulina were determined. During the first series of studies, it was established that the intensity of the increase in spirulina biomass depended on the concentration of Sulfur in the nutrient medium. The lowest optical density of the nutrient medium was found in the control group and the highest in the medium containing 350.0 mg/dm3 of Sulfur. The difference between the optical density index in the III experimental group and the control one was 16.7%. Using Glauber's salt as an additional source of Sulfur, the tendency was maintained that the higher the element's content in the nutrient medium, the higher its optical density. It has been proven that the cultivation of spirulina on a nutrient medium with a sulfur content of 350.0 mg/dm3 in alimentary form and the form of Glauber's salt leads to an increase in the content of total protein and chlorophyll in the spirulina biomass, respectively, by 4.2 and 5.7 % and 11.4 and 13.4 % relatively to the control group.