1439 Research Article Received: 21 February 2011 Revised: 28 April 2011 Accepted: 28 April 2011 Published online in Wiley Online Library: 6 July 2011 (wileyonlinelibrary.com) DOI 10.1002/jctb.2658 Citric acid, biomass and cellular lipid pro- duction by Yarrowia lipolytica strains cultivated on olive mill wastewater-based media Dimitris Sarris, Maria Galiotou-Panayotou, Apostolis A. Koutinas, Michael Komaitis and Seraphim Papanikolaou * Abstract BACKGROUND: Olive mill wastewaters (OMWs) are an important residue and several physico-chemical and/or biotechnological methods have been proposed for their treatment. RESULTS: The ability of three Yarrowia lipolytica strains to grow on and convert glucose-enriched OMWs into added-value compounds in carbon- and nitrogen-limited shake-flask cultures was assessed. Remarkable decolorization (up to 63%) and non-negligible removal of phenolic compounds (up to 34%, w/w) occurred. In nitrogen-limited cultures, the accumulation of cellular lipids was favored by OMW addition into the medium. In contrast, although remarkable quantities of citric acid (Cit) were produced in control experiments (cultures without OMW addition), in which Cit up to 18.9 g L -1 was produced with yield of Cit synthesized per sugar consumed ∼0.73 g g -1 ), adaptation of cultures to media supplemented with OMWs reduced the final Cit quantity and conversion yield values achieved. In OMW-based media, the highest concentration of citric acid produced was 18.1 g L -1 , with conversion yield ∼0.51 g g -1 . In carbon-limited cultures, despite the presence of inhibitory compounds in the medium (e.g. phenols), biomass production was enhanced with the addition of OMWs. The highest biomass concentration achieved was 12.7 g L -1 , with biomass conversion yield per sugar consumed ∼0.45 g g -1 . Fatty acid analysis of cellular lipid produced demonstrated that adaptation of all strains in OMW-based media favored the synthesis of cellular lipids that contained increased concentrations of cellular oleic acid. CONCLUSIONS: The Y. lipolytica strains tested can be regarded as possible candidates for simultaneous OMWs remediation and production of added-value compounds. c  2011 Society of Chemical Industry Keywords: Yarrowia lipolytica; olive mill wastewaters; citric acid; cellular lipids; waste bioremediation NOTATIONS (UNITS) X – biomass (g L −1 ) Glc – glucose (g L −1 ) Cit – citric acid (citric plus iso-citric acid) (g L −1 ) L – total lipid (g L −1 ) Y X/Glc – biomass yield on glucose consumed (g formed g −1 glucose consumed) Y Cit/Glc – total citric acid yield on glucose (g formed g −1 glucose consumed) Y L/X – total lipid yield on biomass (g formed g −1 biomass formed). Subscripts 0, cons and max indicate the initial, consumed and maximum quantity, respectively, of the components in the kinetics performed. INTRODUCTION Olive mill wastewaters (OMWs) are the principal residues derived from olive oil mills and are considered one of the strongest and most difficult to treat industrial effluents. 1 OMW composition is variable and depends on several factors such as the variety of olives, the conditions and the technology used for the extraction of oil. 2–4 In these residues, biological oxygen demand (BOD) and chemical oxygen demand (COD) concentration values 200–400 times higher than in typical municipal sewage usually occur, 1 with OMW organic fraction principally composed of sugars, (poly)-phenolic compounds, organic acids and residual oil. 3,5 In addition, the OMW dark color and phytotoxic and antimicrobial effects have been attributed to the phenolic compounds that are found in various concentrations in the residue. 4,6–9 In some cases OMWs derived from press extraction systems, besides ∗ Correspondence to: Seraphim Papanikolaou, Laboratory of Food Microbiology and Biotechnology, Department of Food Science and Technology, Agricultural University of Athens, Iera Odos 75-Athens, Greece. E-mail: spapanik@aua.gr Department of Food Science and Technology, Agricultural University of Athens, 75 Iera Odos, 11855- Athens, Greece J Chem Technol Biotechnol 2011; 86: 1439–1448 www.soci.org c  2011 Society of Chemical Industry