JJBS Volume 4, Number 1, January 2011 ISSN 1995-6673 Pages 29- 36 Jordan Journal of Biological Sciences The Effect of Certain Environmental Factors on Growth and β- Carotene Production by Dunaliella sp. Isolated from the Dead Sea Nader Fareid AbuSara a , Sadeq Emeish b and Abdul-Karim Jaber Sallal a, * a Department of Applied Biology, Jordan University of Science and Technology, Irbid; b Department of Chemical Engineering, Faculty of Engineering Technology, Al Balqa’a University, Amman, Jordan. Received: 22 November 2010; accepted in revised form 2 January 2011 Abstract اﻟﻤﻠﺨﺺ Microalga Dunaliella sp. was isolated and identified from ponds of the south-east shores of the Dead Sea. The most suitable media for the isolated Dunaliella sp. was found to be M1 (modified BG-11) which gave the highest growth and β-carotene production. The effects of different physical (temperature and light intensity) and chemical (different nitrogenous and sulfate compounds) factors were tested. The best salinity for Dunaliella growth was 2.5 % NaCl, while the maximum β-carotene to chlorophyll a (Chl. a) ratio was found in high salinities: Dead Sea water- M1 (DSw-M1) dilution (1:1), 10% NaCl and DSw-M1 (3:1). By using NaNO 3 at 40 mg N l -1 concentration as a nitrogen source and MgSO 4 at 25 mg l -1 concentration as a sulfate source, the maximum growth and β-carotene production was obtained. In response to different light intensities, the maximum growth was obtained at 61 μmol s -1 m -2 , and the maximum β-carotene production was at 200 μmol s -1 m -2 , while the maximum β-carotene to chlorophyll a ratio was recorded in cells grown at 1000 μmol s -1 m -2 . ﻟﻠﻤﻠﻮﺣﺔ اﻟﻤﺤﺒﺔ اﻟﺪﻗﻴﻘﺔ اﻟﻄﺤﺎﻟﺐ ﻋﺰل اﻟﺪراﺳﺔ هﺬﻩ ﻓﻲ ﺗﻢ " دوﻧﺎﻟﻴﻼ" اﻟﺠﻨﻮﺑﻲ اﻟﺠﺰء ﻓﻲ واﻟﻤﺘﻨﺎﺛﺮة اﻟﻤﺎﻟﺤﺔ اﻟﻤﺎﺋﻴﺔ اﻟﺴﺒﺨﺎت ﻣﻦ اﻟﻤﻴﺖ اﻟﺒﺤﺮ ﻣﻦ. اﻟﻼﻋﻀﻮﻳﺔ اﻟﻤﻮاد ﻣﻦ ﻏﺬاﺋﻲ وﺳﻂ أﻓﻀﻞ آﺎن ﺣﻴﺚ هﻮ اﻟﻄﺤﺎﻟﺐ ﻟﻬﺬﻩM1 (BG-11) . ﻋﻨﺪ ﻟﻠﻄﺤﺎﻟﺐ ﻧﻤﻮ أﻓﻀﻞ وآﺎن ﺣﺮارة درﺟﺔ20 C ، م ﺣﺮارة درﺟﺔ ﻋﻨﺪ اﻟﺨﻼﻳﺎ ﻣﻌﻈﻢ ﻣﺎﺗﺖ ﺑﻴﻨﻤﺎ 40 و50 C م. ﻓﻴﺰﻳﺎﺋﻴﺔ وﻇﺮوف ﻋﻮاﻣﻞ ﺗﺄﺛﻴﺮ دراﺳﺔ ﺗﻢ وﻗﺪ هﺬ ﻧﻤﻮ ﻋﻠﻰ ﻣﺨﺘﻠﻔﺔ وآﻴﻤﻴﺎﺋﻴﺔ اﻟﺒﻴﺘﺎآﺮوﺗﻴﻦ ﻟﻤﺎدﺗﻲ واﻧﺘﺎﺟﻬﺎ اﻟﻄﺤﺎﻟﺐ ﻩ واﻟﻜﻠﻮروﻓﻴﻞ. اﺳﺘﺨﺪام ﻋﻨﺪ اﻟﻄﺤﺎﻟﺐ ﻟﻬﺬﻩ ﻧﻤﻮ أﻋﻠﻰ ﺳﺠﻞ وﻗﺪ ﺑﻨﺴﺒﺔ اﻟﺼﻮدﻳﻮم آﻠﻮرﻳﺪ2.5 % ﻧﺴﺒﺔ أﻋﻠﻰ آﺎﻧﺖ ﺑﻴﻨﻤﺎ، ﺑﻴﺘﺎآﺎروﺗﻴﻦ/ اﻟﻌﺎﻟﻴﺔ اﻟﻤﻠﻮﺣﺔ ﺗﺮاآﻴﺰ ﻋﻨﺪ أ آﻠﻮروﻓﻴﻞ10 % , DSw- M1 (1:1), DSw-M1 (3:1) . ﻧﻤ أﻋﻠﻰ ﻋﻠﻰ اﻟﺤﺼﻮل ﺗﻢ وﻧﺴﺒﺔ ﻮ اﻟﺼﻮدﻳﻮم ﻧﺘﺮات اﺳﺘﻌﻤﺎل ﻋﻨﺪ اﻟﺒﻴﺘﺎآﺎروﺗﻴﻦ اﻧﺘﺎج) آﻤﺼﺪر ﻟﻠﻨﻴﺘﺮوﺟﻴﻦ( ﺑﺘﺮآﻴﺰ40 ﻧﻴﺘﺮوﺟﻴﻦ ﻣﻠﻎ/ اﻟﻤﻐﻨﻴﺴﻴﻮم وآﺒﺮﻳﺘﺎت، ﻟﺘﺮ ) ﻟﻠﻜﺒﺮﻳﺖ آﻤﺼﺪر( ﺑﺘﺮآﻴﺰ25 ﻣﻠﻎ/ ل. اﻟﻀﻮء ﺷﺪة ﺗﺄﺛﻴﺮ دراﺳﺔ وﺑﻌﺪ اﺿﺎءة ﺷﺪة ﻋﻨﺪ ﺗﺴﺠﻴﻠﻪ ﺗﻢ ﻧﻤﻮ أﻋﻠﻰ أن وﺟﺪ61 ) ﻣﺎﻳﻜﺮوﻣﻮل/ ث. م2 ( ﻟ اﻧﺘﺎج وأﻋﻠﻰ اﺿﺎءة ﺷﺪة ﻋﻨﺪ آﺎن ﻠﺒﻴﺘﺎآﺎروﺗﻴﻦ200 ) ﻣﺎﻳﻜﺮوﻣﻮل/ ث. م2 ( ﺑﻴﺘﺎآﺎروﺗﻴﻦ ﻧﺴﺒﺔ أﻋﻠﻰ آﺎﻧﺖ ﺑﻴﻨﻤﺎ/ أ آﻠﻮروﻓﻴﻞ اﺿﺎءة ﺷﺪة ﻋﻨﺪ1000 ) ﻣﺎﻳﻜﺮوﻣﻮل/ ث. م2 .( © 2011 Jordan Journal of Biological Sciences. All rights reserved Keywords: Dunaliella, β - Carotene, Dead Sea, Halophiles 1. Introduction * The Dead Sea is the lowest exposed surface on earth (416 m below sea level) and is one of the world's saltiest lakes, with a total dissolved salt concentration of 340 gl - 1 . It is considered sterile and, therefore, unsuitable for fishery (Gavrieli et al., 1999). The eukaryotic algae Dunaliella was first described by Teodoresco in 1905, and first reported to be present in the Dead Sea by Elazari-Volcani in 1940 (Oren, 1999). Dunaliella is a unicellular, motile, green microalgae which lacks a rigid cell wall and has a single large cup- shaped chloroplast that fills the posterior part of the cell (Butcher, 1959; Javor, 1989). Great interest in Dunaliella has arisen because of its ability to withstand various environment stresses, * Corresponding author. sallal5@just.edu.jo. especially those associated with hypersaline conditions. Its halotolerance is predominantly mediated by an accumulation of glycerol as an osmoregulator (AL-Hasan et al., 1987; Ginzburg, 1987). A number of studies have revealed that growth (Ben- Amotz and Avron, 1983; Ginzburg, 1987) and pigment compositions (Ben-Amotz et al., 1989) of this algae are affected by halostress conditions. It was found that the β- carotene to chlorophyll a ratio gradually increased with an increase in NaCl concentration, and, as a result, the algae changed its appearance from green to deep orange (Ben-Amotz and Avron, 1983; AL-Hasan et al., 1987). Overproduction of β-carotene is induced by high light intensity (Kleinegris et al., 2010) and by other environmental factors such as nutrient deprivation, or high salt concentration (Ben-Amotz and Avron, 1983; Raja et al., 2007; Macias-Sa’nchez et al., 2009). β- Carotene was found to be accumulated in oil globules in the interthylakoid space of the chloroplast and it is composed of two major stereoisomers: all-trans and 9-cis