CITRIC-ACID PRODUCTION BY ASPERGILLUS-FOETIDUS IN BATCH AND FED-BATCH CULTURES

Sucrose and ammonium nitrate, respectively, were the preferred carbon and nitrogen sources for citric acid production by Aspergillis foetidus CCRC 30206. For a 7-day fermentation, the maximal citric acid production of 7.2 similar to 28.4 g/l appeared at an initial sucrose concentration of 12% under various initial levels of nitrogen and phosphorous sources. Citric acid production commenced and ceased earlier in either the nitrogen-limited (NH4NO3, 0.5g/l) or the phosphorous-limited (KH2PO4, 0.2 g/l) medium. The richer media delayed the onset of citric acid production. Nonetheless, 48.3 g/l of citric acid was produced in the medium rich in nitrogen (NH4NO3, 2.0 g/l) and phosphorous (KH2PO4, 1.4 g/l) when the batch culture was extended to 16 days. The cultivation time of this rich medium was reduced to 12 days in a fed-batch culture under dual limitation of both nitrogen and phosphorous.