Abstract
The urgency of the problem is to determine the parameters of the external factor, the effect of which on Chlorella vulgaris cells increases the biosynthesis of triacylglycerols – feedstock for biodiesel production without reducing the biomass growth rate. The purpose of the paper is to determine the impact of sound irradiation on Chlorella vulgaris metabolism and biomass growth. Cultivation was carried out in the Gromov 6 medium at a temperature of 18 ± 2 0 С . The effect of sound irradiation with frequencies of 5, 10, 15 and 20 kHz, power of 5 W/cm 2 on the yield of lipids and biomass is investigated. It is shown that ultrasound irradiation with a frequency of 20 kHz increases the growth of biomass by 10% and lipids by 3 times compared to non–irradiated cells. This irradiation frequency is optimum among the studied frequencies to be used as a factor of influence for biodiesel production from Chlorella vulgaris microalgae. Irradiation with sound spectrum frequencies affects the cell metabolism towards increased biosynthesis of lipids. The specific content of the lipid fraction exceeds its content in non–irradiated cells by 1.5, 2.1 and 2 times for frequencies of 15, 10 and 5 kHz, respectively. At the same time, irradiation of microalgae cells with frequencies of 10 and 15 kHz reduces the biomass growth by 10±1 % compared to the control sample.
Highlights
Ukraine and other countries face the problem of substituting traditional energy resources with alternative clean fuel
Cultivation of Chlorella vulgaris microalgae under irradiation with different frequencies leads to changes in the cell metabolism and increase in the lipid fraction biosynthesis
Under the influence of any frequency, cells begin to increase the biosynthesis and accumulate triacylglycerols – feedstock for biodiesel production. It means that irradiation is a stress factor for cells, resulting in the raised biosynthesis of substances that serve as energy reserves, for Chlorella vulgaris cells these are lipids (Fig. 3, 4)
Summary
Ukraine and other countries face the problem of substituting traditional energy resources with alternative clean fuel. One of these sources is biodiesel, which is produced from the microalgae lipid fraction. The problem of microalgae cultivation for biodiesel production is that the maximum biomass growth occurs under optimum cultivation conditions while the accumulation of cell lipids, namely triacylglycerols – under stress conditions. These conditions are created mostly by changing the culture medium structure (lack of nitrogen or sulfur), or process parameters (light, pH, etc.) [1]. The actual problem is to study the stress factors, which lead to a simultaneous increase in the rate of microalgae biomass growth and lipid fraction accumulation
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