Effect of amino acids on microbial production of citric acid by Aspergillus niger.

The effect of different concentrations of cysteine, serine, lysine, aspartic acid, and glutamic acid on the growth and fermenting activity of Aspergillus niger AL 29 was studied at different incubation periods. It was observed that the presence of glutamic acid and aspartic acid stimulated the citric acid production to the extent of 79.6% and 76.7%, respectively. Lysine was effective in producing citric acid by 62%. However, serine could not influence the yield (50.4%) to a greater extent, while the effect of cysteine was found to be detrimental. The yield of citric acid was determined on sugar consumption basis.