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Objective : Gamma radiation induces free radicals with a corresponding alteration in the cell’s antioxidant defense system. The present study thus aimed at determining the role of gamma irradiation in improving the cosmeceutical potential of CEK in terms of antioxidants. Methods : C.emersonii KJ725233 was subjected to low (100 Gy) and high (1000 Gy) gamma irradiation doses and its effect on the chlorophyll content was evaluated. The quantitative alterations in the antioxidant content of CEK were evaluated by phosphomolybdenum assay (TAC), ferric reducing antioxidant potential (FRAP), 2, 2 - Dipheny-1-picryl hydrazyl radical scavenging assay (DPPH), total phenolic (TPC) and total flavonoid content (TFC). Also, the corresponding qualitative alterations in the bioactives of CEK were determined by GC-HRMS analysis. Results : A 179.57±2.55% increase in the total chlorophyll content alongwith a 71.76±2.96%, 32.08±2.16%, 11.67±0.89%, 42.85±8.0% and 31.37±3.18% increase was observed in the TAC, FRAP, DPPH radical scavenging, TPC and TFC was observed in CEK irradiated at 1000 Gy. GC-HRMS analysis revealed the induction of Vitamin E on irradiation at both the doses with a corresponding decrease in the phytol content whereas 100 Gy stimulated the induction of phytosterols. Conclusion : The potent intrinsic antioxidant activity of cosmeceutically significant CEK can be elevated with the induction of the most sought after antioxidant in cosmetology – Vitamin E on irradiation.

Microalgae are promising species with high potential for biodiesel production. Large-scale cultivation of oleaginous microalgae in industrial effluents and municipal wastewater provides dual benefits of biodiesel production and wastewater treatment. Such approach to biodiesel production does not interfere with conventional agricultural resources and practices. Microalgae can accumulate lipid under various stress conditions. In this study, gamma irradiation was used for the first time as a stressor to trigger lipid accumulation in two strains of Chlorella sorokiniana. Gamma irradiation enhanced the lipid content of more than 40% of biomass. Intracellular reactive oxygen species generated by gamma ray exposure was measured by 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) staining under flow cytometry. Cytoplasmic lipid droplets were observed by Nile red staining using fluorescence microscopy. Expression patterns of regulatory genes involved in lipid biosynthesis, namely acetyl-CoA carboxylase and diacylglycerol acyl transferase, were upregulated immediately after irradiation and were highest 3 days post irradiation. This novel strategy of using gamma radiation as a faster and extremely potent stressor for triggering lipid biosynthesis in microalgae has immense potential in industrial biodiesel production.