ORIGINAL PAPER Single cell oil production by Gordonia sp. DG using agro-industrial wastes Mona K. Gouda Sanaa H. Omar Linda M. Aouad Received: 22 November 2007 / Accepted: 7 January 2008 / Published online: 22 January 2008 Ó Springer Science+Business Media B.V. 2008 Abstract Lipid accumulation by Gordonia sp. DG using sodium gluconate as carbon source in comparison with Rhodococcus opacus PD630 was studied. Maximum lipid content 80% was observed at the beginning of the sta- tionary phase for R. opacus and 72% at the end of stationary phase for Gordonia sp. Different agro-industrial wastes were used as carbon source. The cells of the two organism accumulated lipid more than 50% of the biomass with most tested agro-industrial wastes. The maximum value was in presence of sugar cane molasses (93 and 96%) for R. opacus and Gordonia sp. respectively. Maximum triacyglycerols (TAGs), 88.9 and 57.8 mg/l, was obtained using carob and orange waste by R. opacus and Gordonia sp. respectively. The use of orange waste as carbon source by R. opacus, increased lipid unsaturation with C18:3 as the major unsaturated fatty acid. On the other hand, C22:0 and C6:0 were the dominant fatty acids (54.5% of the total identified fatty acids) produced by Gordonia sp. in pres- ence of orange waste as carbon source. Statistical optimization of the medium revealed that maximum lipid content was achieved with 60% orange waste, 0.05 g/l ammonium chloride and 0.2 g/l magnesium sulphate. Keywords Single cell oil Á Agro-industrial wastes Á Gordonia Á Central composite design Introduction Natural sources of oils and fatty acids include plants, ani- mals and microorganisms. Plant oils have some advantages over animal oils on one hand for the production methods which are relatively cheap, and on another hand for the productivity of plants that have been increased by the agricultural methods optimized over history. Prokaryotic microorganisms should now also consider as a source of lipid with potential application in the oil industry. Microbial triacylglycerol (TAG) share some properties with those from plants and animals but exhibit their own unique features. In addition, the use of micro- organisms for lipid production provides some advantage over agriculture sources with regards to the enormous variability of fatty acid composition depending on the carbon source used for the cultivation of cells (Alvarez and Steinbu ¨chel 2002). Another interesting aspect of bacterial oils is the potential production of oleochemicals that are currently produced from petrochemicals or from plant lipids (Alvarez and Steinbu ¨chel 2002). Microbial lipid (single cell oil, SCO) production has been an object of research and industrial interest for more than 60 years (Ratledge 1982; Woodbine 1959) and the current status of lipid biotechnology has been reviewed by Rattary (1984) and Ratledge (1984). Most of the work has, so far, been performed on yeasts mainly because of their ability to accumulate high amounts of lipid intracellularly, their relatively high growth rates and the resemblance of their TAG fraction to plant oils (Ratledge 1982). Microorganisms can store TAG as intracellular oil droplets. In the 1990s the structure of lipid-bodies was revealed in Streptomyces sp. (Packter and Olukoshi 1995). The authors described TAG as insoluble inclusions sur- rounded by a membrane, which occurred in the late stationary growth phase. The occurrence of TAG as reserve compounds is wide- spread among eukaryotic organisms such as yeast, fungi, plants and animals, whereas occurrence of TAG in bacteria M. K. Gouda (&) Á S. H. Omar Á L. M. Aouad Botany Department, Faculty of Science, Alexandria University, 21511 Moharram Bey, Alexandria, Egypt e-mail: monagouda@yahoo.com 123 World J Microbiol Biotechnol (2008) 24:1703–1711 DOI 10.1007/s11274-008-9664-z