Biological production of citric acid in solid state cultures ofAspergillus niger

Author(s): 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.

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