Cultivation of Chlorella sorokiniana in natural open air conditions of the Volga region and in a laboratory experiment under the effect of a constant magnetic field

• Main Authors: O.A. Aref’eva, L.N. Ol’shanskaya, R.Sh. Valiev
• Format: Article
• Language: English
• Published: Penza State University Publishing House 2021-03-01
• Series: Известия высших учебных заведений. Поволжский регион: Естественные науки
• Subjects: microalgae; chlorella; chlorella sorokiniana; cultivation; biomass; constant magnetic field

Background. Chlorella sorokiniana is used for the production of biofuels and the release of biologically active substances. Biomass can be grown in low-energy and economical conditions. The purpose of this work is to assess the influence of the cultivation’s conditions of microalgae Ch. sorokiniana in the open air and the effect of a constant magnetic field in laboratory conditions on the reproduction, growth and development of microalgae. Materials and methods. Population growth was assessed by the optical density of the chlorella suspension and further counting in the Goryaev chamber for the number of million cells per ml. For statistical analysis of the experimental results, we used the R version 3.4.0 software environment. In this work, we compared the quantitative indicators of reproduction, as well as the sizes of chlorella cells after and without the effects of constant magnetic field (CMF). Regression analysis was carried out to assess the dependence of the growth rate of chlorella on the air temperature. Results. Visually (under a microscope), it was revealed that the growing population in a bioreactor placed in the open air has a larger proportion of elongated cells (young cells) and a smaller proportion of rounded cells (old cells). Intensive growth and development of cells occurs in July and August with a minimum of cloudy days. The optimal temperature regime for constant renewal of chlorella cells was reached at 27–30 ºС. When analyzing the influence of CMF with a strength of 2 kA/m on the growth and reproduction of chlorella in laboratory conditions, an intensive growth of cells was revealed during the first 3 days of cultivation. The increase in biomass increased 3–4 times and reached 7,5 million cells/ml. When exposed to CMF with a strength of 0,5 and 1,0 kA/m, no increase in cell concentration was observed during the entire cultivation period. Conclusions. As a result of the work done, it was found that exposure to constantly high temperatures (30–36 ºС) in open air without additional aeration is an unfavorable factor for the development of Ch. sorokiniana. The optimal temperature regime for constant renewal, growth and development of chlorella cells in natural conditions was achieved at 27–30 ºС. In the course of studies carried out in laboratory conditions, the maximum increase in chlorella cells was revealed when exposed to CMF with a voltage of 2 kA/m during the first 3 days of cultivation, after which a stabilization phase was observed. It has been shown that the use of a magnetic field promotes cell aggregation.