Lipid Peroxidation in Dunaliella Salina IPPAS-294 Cells Modified by Ionol at High Salinity in Optimal and Low-Temperature Cultivation Conditions

As a result of various factors such as ultraviolet radiation exposure, low and high temperatures, the presence of additives, pollutants in nutritional supplements and drinking water influencing the environment, lead to the formation of radicals. In every living organism constantly occur active forms of exogenous, peroxide, hydro peroxide and other radicals [1]. Simultaneously with the formation of these radicals, happens their destruction with the help of antioxidant enzyme system. Excess accumulation of forming concentrations over cancelled radicals leads to development of oxidative stress, which accompanies with injure of biological molecule, lipid oxidation, protein and DNA modification [2-4]. Influence of adverse temperatures on plants is one of most common stressors. So, most part of plants, during a year, is exposed to low positive temperatures, frost [5,6].

ROS has a special place among stress metabolites. The important role of ROS in the launch of protective reactions to abiogenists causes no doubt. In the cultivation of seeds, at the presence of ionol, both ROS formation and especially, superoxide are strongly depressed [7]. It is clear that, as well as formation and inactivity of ROS, the antioxidant ionol can inhibit ROS-induced exit from mitochondria to cytoplasm cytochrome [8]. Significantly, reducing of oxidative stress and its consequences allows addition of synthetic antioxidants, such as ionol and its derivatives belonging to a class of hundred phenols in mineral medium. The purpose of the work is the investigation of lipid peroxidation in Dunaliella cells cultivated in optimal and low-temperature cultivation conditions at high salinity and modified by various concentrations of ionol.

As investigation object was used green algae Dunaliella Salina IPPAS-294, taken from the saline lake Masazir located on the north eastern part of Baku. The algae were grown at 27 °C temperature in glass photo reactors (250ml), in the installation for growing unicellular algae. Mineral medium contained (g/l): NaCl-175.5 (30M), KNO₃-50; KH₂PO₄-125; MgSO₄-50; FeSO₄-0.009 and microelement solutions(1mg/l). The cell suspension in photo reactors was irradiated by white light (16Wt/m²) within 24 hours and permanently purged with mixture (air+1.5% CO₂) at 25 °C temperature in optimal and blowing of air mixture 50 (low temperature stress) to photoreactors. The culture growth rate was determined by periodically counting cell number in Qoryayev chamber under the microscope or by nephelometric measurement of optic suspension density in photoelectrocolorimeter.

The cell suspension prepared for measuring MDA content was led to 106 cells/ml (optic density OD=0.8).

The evaluation degree of lipid peroxidation (POL) was carried out by the method of determining MDA content in Dunaliella Salina cells-method based on the reactions with thibarbituric acids. The cell suspension (35ml) was centrifuged 30000rev/min. within 10 minutes. The resulting sediment was homogenized in 20ml 0.1% TCA. Homogenate was centrifuged at 30000rev/min. within 10 minutes. To the 1ml supernatant was added 4ml 20% TCA, containing 0.5% TBA. The mixture was heated in water bath at 95 ⁰C within 30 minutes and immediately cooled in running water. After centrifugation of mixture at 30000rev/min within 10 minutes was determined optic density of supernatant at 532nm [3]. The content of MDA was calculated with extinction coefficient equal to 1.36×10^-5sm^-1, after subtraction of non-specific absorption at 532.

Figure 1: The growth dynamics of population in Dunaliella Salina IPPAS-294 cells in optimal 1. Low temperature 2. Cultivation regimes Temperature 40%, light intensity 100Wt/m2