egWebsite : Effect of Gamma Irradiation on Growth and Lipid Productivity of Green Microalgae [ 78 ]

In the present research, the impact of exposing Scenedesmus ecornis, S. communis, and Chlamydomonas sp. cultures to doses of gamma irradiation on their growth and productivity of lipids was investigated. Biomass concentration (g/L) of each microalga was periodically determined after exposure to a range of gamma irradiation doses of 0, 25, 50, 75, 100, 200, and 300 Gray (Gy) through 20 days of cultivation. Subsequently, the lipid content (%), and lipid productivity (mg/L day) of each species were evaluated. Results showed that the S. ecornis growth was positively affected by gamma irradiation, that the maximum concentration of biomass was obtained after 15 days at 1.3 g/L by the irradiated S. ecornis exposed to a dose of 300 Gy, while the non˗irradiated culture achieved up to 1.1 g/L. On the other hand, the growths of Chlamydomonas sp. and S. communis were reduced significantly by the radiation treatment. Significant variations have been also observed in the content of lipid and lipid productivity of each microalga. Irradiated S. ecornis at a dose of 300 Gy exhibited the highest content of lipid and lipid productivity to reach 28.4% and 24.9 mg/L day, respectively. Conversely, the best yields of lipid content and lipid productivity were achieved by the non˗irradiated culture of S. communis (24.4% and 16.6 mg/L day, respectively), compared to irradiated culture, regardless of the irradiation dose. The highest lipid content and lipid productivity gained by Chlamydomonas sp. were obtained by the cultures exposed to 25 Gy, being 27.3% and 21.3 mg/L day, respectively. In conclusion, results indicated that exposing cells of S. ecornis and Chlamydomonas sp. to specific doses of gamma˗rays has significantly stimulated lipid accumulation into cells, unlike S. communis which was negatively affected by gamma irradiation.