Citrate production from n-alkane by Candida lipolytica in reference to carbon fluxes in vivo

Summary Citrate production by Candida lipolytica from n-alkane as sole carbon source was studied with a NH₄⁺-limited chemostat culture. This organism produced citrate and isocitrate simultaneously, the ratio of these acids remaining nearly unchanged within the range of dilution rates used. However, the specific production rates of these acids were maximal around a particular dilution rate. For each steady-state culture, specific activities of some key enzymes in tricarboxylate and glyoxylate cycles were measured in vitro. In order to correlate the enzyme activites with the change in specific production rate of each acid, the intracellular carbon fluxes were assessed by solving algebraic equations derived from carbon balance with respect to a simplified metabolic map of n-alkane metabolism. By comparing the fluxes assessed in vivo with the enzyme activities measured in vitro, the metabolic pathway(s) most likely to control the production of acids and cell material were investigated.