Oil production by the marine microalgae Nannochloropsis sp. F&M-M24 and Tetraselmis suecica F&M-M33 Paolo Bondioli a , Laura Della Bella a , Gabriele Rivolta a , Graziella Chini Zittelli b , Niccolò Bassi c , Liliana Rodolfi c,d,⇑ , David Casini e , Matteo Prussi e , David Chiaramonti e , Mario R. Tredici d a INNOVHUB–Stazioni Sperimentali per l’Industria - SSOG Division, Milan, Italy b Istituto per lo Studio degli Ecosistemi, CNR, Florence, Italy c Fotosintetica & Microbiologica S.r.l., Florence, Italy d Dipartimento di Biotecnologie Agrarie, University of Florence, Italy e CREAR, Dipartimento di Energetica ‘‘Sergio Stecco’’, University of Florence, Italy article info Article history: Received 12 December 2011 Received in revised form 23 February 2012 Accepted 24 February 2012 Available online 10 March 2012 Keywords: Biodiesel GWP Microalgae Nannochloropsis Tetraselmis abstract Nannochloropsis sp. F&M-M24 and Tetraselmis suecica F&M-M33 were cultivated outdoors in Green Wall Panels under nutrient deficiency to stimulate oil synthesis. Under nitrogen deprivation, Nannochloropsis attained average biomass and lipid productivities of 9.9 and 6.5 g m À2 day À1 , respectively. Starved Tetra- selmis cultures achieved a biomass productivity of about 7.6 g m À2 day À1 and a lipid productivity of 1.7 g m À2 day À1 . Lipids represented 39.1% and 68.5% of non-starved and starved Nannochloropsis biomass, respectively. Starvation did not increase lipid content in Tetraselmis biomass. Important differences in lipid classes and in fatty acid composition were observed under the different cultivation conditions for both microalgae. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Biodiesel is currently produced from oils and fats of vegetable or animal origin. Biodiesel is constituted of fatty acid methylesters (FAMEs) that are normally obtained by means of a simple alkali catalyzed chemical reaction, from triglycerides and methanol, with parallel production of glycerol as a by-product. The general balance of this process, starting from 100 kg of neutral fat, is approximately 100 kg of biodiesel and 10 kg of glycerol, with a parallel consump- tion of 10 kg of methanol. The demand of natural oils for biodiesel production is constantly raising in Europe and worldwide (Subr- amaniam et al., 2010). For this reason and in order to avoid the competition with the food market, research is today focusing on alternative renewable feedstocks for biodiesel production. Microalgal biodiesel is technically feasible. However, algal biomass is, at present, largely too expensive to compete with petrodiesel. Besides, the energy balance of algae biomass produc- tion is still not sufficiently positive (Tredici, 2010). Microalgae have been identified as a possible source of new generation biofuels since they do not compete with food and feed crops, attain higher oil yields than currently available agricultural crops, and can be cultivated in seawater on non-arable land (Greenwell et al., 2010; Tredici, 2010). During last years several re- search projects have been launched and numerous papers have been published on this subject (Amaro et al., 2011; Gouveia and Oliveira, 2009; Griffiths and Harrison, 2009; Huerlimann et al., 2010; Mutanda et al., 2011; Scott et al., 2010). Oil-rich algae (the so-called oleaginous species) can be grown either autotrophically or heterotrophically. In the first mode, carbon dioxide (or bicarbon- ate) is used as the sole carbon source, which is incorporated by means of the photosynthetic process, while in the second mainly organic molecules are used for growth. The photosynthetic process needs light to take place and hence algal cultivation must be car- ried out with artificial light or under sunlight, while the heterotro- phic process can take place in classical fermenters. Despite the metabolic flexibility of microalgae and the impressive progress achieved in these years by algal biotechnology, a long way must still be run before microalgae might be exploited for commercial biofuel production (Tredici, 2010). A first crucial point to be cleared is the maximum oil yield attainable with microalgae cultures. This is strictly dependent on the selected microorganism, the geographical location of the production plant and the culture conditions (Hu et al., 2008). According to Rodolfi et al. (2009) and Studt (2010), the potential oil yield of microalgae cultures is from 5 to 20 times that of oil 0960-8524/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2012.02.123 ⇑ Corresponding author. Address: Dipartimento di Biotecnologie Agrarie, Univer- sity of Florence, Piazzale delle Cascine 24 - 50144 Firenze, Italy. Tel.: +39 0553288304; fax: +39 0553288272. E-mail address: liliana.rodolfi@unifi.it (L. Rodolfi). Bioresource Technology 114 (2012) 567–572 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech