Citric acid, biomass and cellular lipid production by Yarrowia lipolytica strains cultivated on olive mill wastewater‐based media

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. Copyright © 2011 Society of Chemical Industry