Characterization of Yarrowia lipolytica and related species for citric acid production from glycerol

Twenty-seven Yarrowia lipolytica strains as well as five strains from three other species of the Yarrowia clade (Aciculoconidium aculeatum, andida hispaniensis and Candida bentonensis) were screened for citric acid production with pure glycerol as the carbon source. The cultures were rown under nitrogen-limited conditions. None of the non-Yarrowia strains produced citric acid, although they were able to grow on glycerol. All f the Y. lipolytica strains were able to produce citric acid in varying concentrations and, under the screening conditions used, the yields obtained ormed a continuum from very low to among the highest reported for this substrate. The highest yielding strain, Y. lipolytica NRRL YB-423, roduced 21.6 g/L citric acid from 40 g/L glycerol (54% yield). The citric acid to isocitric acid ratio produced by this strain in the initial screen was 1.3, while most of the strains produced ratios of between 2 and 6. Further work on medium optimization with this strain showed that the optimum arbon to nitrogen ratio for the rate of citric acid production was 172 while the best combination of rate and yield was obtained at a C/N ratio of 43. The citric acid to isocitric acid ratios produced reached an optimum at C/N ratios of 343–686. ublished by Elsevier Inc.