Induction of canthaxanthin production in a Dactylococcus microalga isolated from the Algerian Sahara Borhane Samir Grama a,b , Samira Chader c , Douadi Khelifi a , Spiros N. Agathos b , Clayton Jeffryes b,d,⇑ a Laboratory of Genetic Biochemistry and Plant Biotechnology, Faculty of Nature and Life Sciences, Université Constantine 1, Constantine, Algeria b Earth & Life Institute – Bioengineering Laboratory, Université Catholique de Louvain, Place Croix du Sud 2, bte. L07.05.19, B-1348 Louvain-la-Neuve, Belgium c Algerian Center of Renewable Energy (Centre de Développement des Energies Renouvelables), Unité de Recherche Appliquée en Energies Renouvelables (U.R.A.E.R.), Ghardaïa, Algeria d Fonds de la Recherche – FNRS, Place Croix du Sud 2, bte. L07.05.19, B-1348 Louvain-la-Neuve, Belgium highlights  A Dactylococcus from the Sahara was characterized for carotenoids production.  Carotenoid production was a function of light intensity and enhanced by salinity.  Nitrate depletion enhanced lipids production but not carotenoids production.  Production of lipids and carotenoids was greatest when stresses were combined.  Canthaxanthin was the main secondary carotenoid. article info Article history: Received 26 July 2013 Received in revised form 21 October 2013 Accepted 23 October 2013 Available online 1 November 2013 Keywords: Dactylococcus Carotenoid Canthaxanthin Fatty acids Photosynthetic biorefinery abstract Secondary carotenoids are high-valued anti-oxidants which can be produced by some algae when exposed to an environmental stress (e.g. nutrient deprivation, high light intensities). To this end, we char- acterized the stress-induced carotenoid production of a new microalgal strain, Dactylococcus dissociatus MT1, which was isolated from the Sahara Desert of Algeria. Nitrate starvation, oxidative stress and vary- ing light intensities were applied to determine the effect of illumination on carotenogenesis. Canthaxan- thin was the main secondary carotenoid and light intensity had an important influence on the rate of its accumulation. The addition of NaCl also enhanced canthaxanthin production while nitrate depletion had more of an effect on lipid production. However, these two stresses in combination synergistically increased the production of both. Our results represent a step toward the development of strains suitable for secondary carotenoid production at the industrial scale. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The primary and secondary carotenoids of microalgal origin are bioactive compounds with antioxidant activities which may have diverse applications in human or animal nutrition and pharmacol- ogy (Plaza et al., 2010). They are used as additives and colorants in the food industry and aquaculture, in cosmetics and as active ingredients in pharmaceutical products (Higuera-Ciapara et al., 2006). Secondary carotenoids, such as astaxanthin and canthaxan- thin, can be produced in algal cell cultures and are considered to be stronger antioxidants than primary carotenoids (Jin et al., 2006). While the primary, or photosynthetic, carotenoids are localized exclusively in the thylakoid membranes of chloroplasts, secondary carotenoids do not participate in photosynthesis and are character- ized by extra-thylakoid localization. Secondary carotenoids are accumulated in specialized structures which can be localized in both the chloroplast stroma and outside the plastids (Solovchenko, 2013). The study of secondary carotenoids biosynthesis pathways, the factors of their induction and the mechanisms of their synthe- sis regulation are less studied in comparison with those of primary carotenoids, although progress has been made in recent years (Takaichi, 2011). The carotenogenesis process in algae is induced by various stressors and especially their combinations. Combinations of os- motic stress, nitrogen and phosphorus deficiency and oxidative stress from high light intensities are particularly effective (Solovchenko, 2013). Under high light intensities which oversatu- rate the photosystem, photons are absorbed in excess and a consid- erable part of the incident light energy cannot be utilized in photochemical reactions (Solovchenko, 2010). As a result, the excess energy leads to the formation of highly active oxygen 0960-8524/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2013.10.073 ⇑ Corresponding author at: Earth & Life Institute – Bioengineering Laboratory, Université Catholique de Louvain, Place Croix du Sud 2, bte. L07.05.19, B-1348 Louvain-la-Neuve, Belgium. Tel.: +32 1047 3149; fax: +32 1047 3062. E-mail address: clayton.jeffryes@uclouvain.be (C. Jeffryes). Bioresource Technology 151 (2014) 297–305 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech