Oxygen and temperature effect on continuous citric acid secretion in Candida oleophila

• Savas Anastassiadis ^[1] ; Hans-Jürgen Rehm ^[2]
  1. [1] Democritus University of Thrace

     Democritus University of Thrace

     Dimos Komotini, Grecia

     
  2. [2] University of Münster

     University of Münster

     Kreisfreie Stadt Münster, Alemania

     
• Localización: Electronic Journal of Biotechnology, ISSN-e 0717-3458, Vol. 9, Nº. 4, 2006
• Idioma: inglés
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• Resumen

  • The influence of air saturation and temperature on continuous citric acid secretion was studied in chemostat cultures of Candida oleophila ATCC 20177 (var.). Simultaneous measurements of intra- and extracellular concentration of glucose, citric and isocitric acid confirmed the involvement of a specific active transport system in citrate secretion, favouring citric acid over isocitrate. An optimum air oxygen saturation of 20% and temperature of 30-31ºC were determined for the continuous citric acid secretion. The highest values of citric acid concentration (98 g/L), citrate to isocitrate ratio (33.3:1), volumetric citric productivity (1.8 g/(L x h)), and specific citric acid productivity (0.1 g/(g x h)), were reached at 20% air saturation at a residence time of 54 hrs by the experiment's lowest biomass of 18 g/L. The highest isocitic acid volumetric productivity (55.6 mg/(L x h)) and specific productivity (0.99 mg/(g x h)) were identified at 50%, instead. The fastest citrate excretion rate of the generic product of 0.046 g/(g*h) was found at 30-31ºC. A concentration ratio between extra- and intracellular concentration of citrate of up to 9 was identified. The highest extra-/intracellular ratio of citrate and lowest intracellular concentrations of glucose, citric and isocitric acid were determined at optimum air saturation as a consequence of active citrate export.