*Correspondence: kitsak.yok@mahidol.edu (Received: 17 January 2019; accepted: 07 February 2019) Citaton: Tassnapa Wongsnansilp, Kitsak Yokthongwatana, Sitruk Roytrakul and Niran Juntawong, β-carotene Producton of UV-C Induced Dunaliella salina Under Salt Stress, J Pure Appl Microbiol., 2019; 13(1):193-200 doi: 10.22207/JPAM.13.1.20 © The Author(s) 2019. Open Access. This artcle is distributed under the terms of the Creatve Commons Atributon 4.0 Internatonal License which permits unrestricted use, sharing, distributon, and reproducton in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creatve Commons license, and indicate if changes were made. Wongsnansilp et al. J Pure Appl Microbiol, 13(1), 193-200 | March 2019 Artcle 5408 | htps://dx.doi.org/10.22207/JPAM.13.1.20 Print ISSN: 0973-7510; E-ISSN: 2581-690X ReseARCh ARtiCle www.microbiologyjournal.org 193 Journal of Pure and Applied Microbiology β-carotene Producton of UV-C Induced Dunaliella salina Under Salt Stress Tassnapa Wongsnansilp 1,2 , Kitsak Yokthongwatana 3 *, Sitruk Roytrakul 4 and Niran Juntawong 5 1 Interdisciplinary Graduate Program in Bioscience, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand. 2 Department of Bioscience, Faculty of Science and Fisheries Technology, Rajamangala University of Technology, Srivijaya, Trang Campus, Trang 92150, Thailand. 3 Department of Biochemistry, Faculty of Science, Mahidol University, 272 Rama 6 Rd., Bangkok 10400, Thailand. 4 Natonal Center for Genetc Engineering and Biotechnology (BIOTEC), Natonal Science and Technology Development Agency, Pathum Thani, Thailand. 5 Department of Botany, Faculty of Science, Kasetsart University, Thailand. Abstract Dunaliella salina is an important microalga for β-carotene producton. In Thailand, the D. salina has not been commercially cultvated. Aim of this study was to screen high β-carotene producing mutants. D. salina KU11 cells were radiated with 0.4 mmol photons m -2 ·s -1 UV-C for 22 min. Afer 3 weeks, colonies which survived afer radiaton were allowed to grow on agar plates; ffy colonies out of 19,720 UV-mutagenized strains turned to orange. These colonies were picked up and transfer to modifed Johnson medium. Four mutants out of ffy were KU5, KU18, KU20 and KU37 signifcantly produced high β-carotene at the statonary phase approximately up to 1.62, 2.03, 1.32 and 1.21 folds, respectvely, compared to the wild type strain. In all three consecutve cycles of cultvaton, the mutant KU18 accumulated 2.4-8.5 folds β-carotene (µg/ml) and 2.1-4.8 folds β-carotene (pg/cell) higher than the wild type, whereas cell density of the mutant KU18 was not diferent from the wild type. This is the new record of b-carotene producing mutant isolated from saline soil in Thailand. Keywords: Dunaliella salina; UV-C radiaton; β-carotene; high salinity.