OPTIMIZATION OF CITRIC ACID FERMENTATION BY ASPERGILLUS NIGER USING CHEMICALLY PRETREATED BLACKSTRAP SUGARCANE MOLASSES

Abstract

The present study deals with the pre-treatment of sugar cane molasses for the enhanced
production of citric acid by Aspergillus niger NG-4. The maximum production of citric acid
(36.4 g/l) was achieved in the medium pre-treated with 250 ppm potassium ferrocyanide. In a
parallel study, the acids and metal complexing agents were added in the molasses medium,
alternatively prior to heating at 90°C for 1 h. Sugar concentration (150 g/l), intial pH (6) and
incubation period (168 h) were also optimized. The kinetic parameters such as growth yield
coefficients (Yp/s, Yp/x, Yx/s in g/g), volumetric rates (Qp, Qs, Qx in g/l/h) and specific substrate
rates (qp, qs in g/g cells/h) of the research work were also undertaken. The value of Qp (0.134
g/l/h) is highly encouraging (p≤0.05).