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Biological production of citric acid in solid state cultures ofAspergillus niger

Ifeanyi Ezea, Nneka Virginia Chiejina, James C.Ogbon

The effects of nutrient supplementation, initial pH and alcohol addition on citric acid production by Aspergillus niger under solid-state culture was studied, using cassava flour, corn four or rice grain as the carbon source. Citric acid concentrations (g/kg) of 31.5, 17, and 20.5 were obtained from cassava flour, rice grain and corn flour, respectively. The highest concentration of citric acid (58.5g/kg)was accumulatedwhen 2mLofmethanol and 0.02 g of NH4NO3were added to 100 g of cassava flour. Simultaneous alcohol fermentation and invescitric acid production from cassava flour by co-inoculation of Aspergilius niger and Saccharomyces cerevisiae gave citric acid concentration of (53.5 g/ kg) which was comparable to the value (54 g/kg) obtained when ethanol was added to a monoculture of Aspergillus niger under the same culture conditions.