title: Simultaneous increases in specific growth rate and specific lipid content of Chlorella vulgaris through UV-induced reactive species.
abstract: A challenge in algae-based bio-oil production is to simultaneously enhance specific growth rates and specific lipid content. We have demonstrated simultaneous increases in both the above in Chlorella vulgaris through reactive species (RS) induced under ultraviolet (UV) A and UVB light treatments. We postulated that the changes in photosystem (PS) stoichiometry and antenna size were responsible for the increases in specific growth rate. UVB treatment excited PSII, which resulted in a twofold to sevenfold increase in PSII/PSI ratio compared to control. An excited PSII caused a 2.7-fold increase in the specific levels of superoxide and a twofold increase in the specific levels of hydroxyl radicals. We have established that the increased specific intracellular RS (si-RS) levels increased the PSII antenna size by a significant 10-fold as compared to control. In addition, the 8.2-fold increase in specific lipid content was directly related to the si-RS levels. We have also demonstrated that the RS induced under UVA treatment led to a 3.2-fold increase in the saturated to unsaturated fatty acid ratio. Based on the findings, we have proposed and demonstrated a UV-based strategy, which achieved an 8.8-fold increase in volumetric lipid productivity.
authors.affiliation: Dept. of Biotechnology, Indian Inst. of Technology Madras, Chennai, 600036, Tamil Nadu, India.
authors.forename: Ranjini
authors.initials: R
authors.lastname: Balan
authors.forename: G K
authors.initials: GK
authors.lastname: Suraishkumar
mesh_terms: D048408:Chlorella vulgaris / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology / Q000528:radiation effects*; D050356:Lipid Metabolism / Q000528:radiation effects*; D008055:Lipids / Q000032:analysis; D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D008055:Lipids; D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species
keywords: PSII; UV; antenna size; lipid productivity; microalgae growth; reactive species