Survival and growth of Spirulina platensis cells and thermodynamic stability of their main proteins after recultivation following irradiation with Cs137 γ doses of 0 to 400 kGy

Using the optical and DSC studies, for the first time, it was shown that Spirulina platensis irradiated with Cs137 γ 400 kGy and then stored under anaerobic conditions in dark at 4 °C remained viable despite 96.9 % denaturation of its whole biomass. After preliminary irradiation with Cs137 γ 10 kGy to 400 kGy doses, the recultivated Spirulina platensis suspension restored its biomass, the cell growth increased by 10 %, chlorophyll increased by 27 %, and the phycobilisome complexes (PBPc) increased by 17 % compared to the normal values. The DSC data showed that PBSc in the recultivated samples, which were preliminarily irradiated with 10–400 kGy doses, melted cooperatively with the following parameters: ∆Hm = 39.39 J/g, Tm = 57.5 ± 0.3 °C, and ∆T = 3.3 ± 0.5 °C. These values were close to the freshly cultivated Spirulina platensis parameters. The PBPc weight percent of the total dry biomass W/W% calculated from the DSC data equaled 59.3 %. We demonstrated that storing native/fresh and/or recultivated Spirulina platensis under conditions close to ones under which it was irradiated caused a decrease in W/W% PBPc in a time-dependent manner, and a sharp increase in proteins that melt within the temperature range of 75–100 °C. We suggested that the observed redistribution of the biomass was caused by blockage of the light-harvesting proteins and initiation of the dark protein synthesis. •Sp. pl. is resistant to high radiation in both aerobic and anaerobic conditions.•Thermostability of Spirulina platensis main proteins in different conditions•Differential scanning calorimetry (DSC) and optical methods•Light harvesting phycobilisome complex (PBPc), C-phycocyanin (C-PC), dark proteins•In vivo DSC measurements of native, irradiated and recultivated Spirulina platensis