Production of citric acid by mutants of Aspergillus niger.

Development of methodology for the recovery of citric acid from the fermented broth involves standardization of the various parameters to achieve maximum performance in terms of recovery and optimum conditions. The present investigation was carried out to study the purification of citric acid from fermented broth by calcium carbonate precipitation and subsequent acid hydrolysis. The parameters affecting the recovery were identified and empirical equation proposed to predict the recovery by precipitation method. Citric acid is the principal organic acid found in citrus fruits. To meet increasing demands it is produced from carbohydrate feedstock by fermentation with the fungus Aspergillus niger and the yeasts of Candida sp. Effect of various fermentation conditions and the biochemistry of citric acid formation by A. niger have been discussed. Commercially citric acid is produced by surface, submerged and solid state fermentation techniques. Recovery of pure acid from fermentation broth is done primarily by precipitation with lime and also by solvent extraction