Production of citric acid in continuous culture
1993
Chaiwat Bundiphet
Production of citric acid in batch culture was carried out in cassava starch medium containing 20 % (W/V) liquefied starch with DE not more than 12.35. The optimal condition at 30 deg C 10.78 % (w/v) of citric acid was produced at the rate of 0.534 g/l/h and 2.60 unit/ml of glucoamylase enzyme with the mximum specific growth rate of 0.122 h-1. In chemostat culture, the fermentation was carried out using nitrogen as a limiting substrate, at controlled dilution rate (D) and pH between 0.02 to 0.10 h-1 and 2.0 to 5.0 respectively, it was found that citric acid production increased as D was decreased. The optimal D was 0.04 h-1 (feed rate 80 ml/h) at pH 3.5 resulting in the citric acid production was 16.75 g/l in the maxiumum specific rate 0.626 g/l/h and 1.65 unit/ml of glucoamylase enzyme activity. The results clearly show that citric acid production was dependent on up-take rate of NH++NO-. The optimal uptake rate of NH++NO- was 16.2 mg/g/h, at the higher or lower uptake rate, production rate of citric acid and glucoamylase enzyme was decreased. Increase on the uptake rate of NH4NO3 suppressed the activity of the enzyme pyruvate carboxylase (Pc) was not affected. As the uptake rate of NH4NO3 was increased to 18.8 mg/g/h, the activity of Pc was lower than of Cs and the activity of aconitate hydratase increased which resulted in reduction of citric acid production.
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This bibliographic record has been provided by Thai National AGRIS Centre, Kasetsart University
