ABSTRACT
Aims: Citric acid is a commercially important acid that has many applications in varying sectors of industries. It is produced by various substrates through solid state or submerged fermentation. The capabilities of potato and rice as substrates for citric acid production using Aspergillus niger were tested in this experiment under submerged fermentation. Methodology and results: Potato and rice extract media were prepared and inoculated with A. niger and titrations were carried out to determine the amount of citric acid produced. It was shown that rice extract media proved more useful than potato extract media as it produced the highest citric acid production. Rice extract media was supplemented with varying concentrations of glucose and sucrose and 5% sucrose (w/v) proved to be the best as it produced the highest amount of citric acid. The rice extract media with 5% sucrose (w/v) were supplemented with varying concentrations of ammonium nitrate and ammonium sulphate and 0.25% ammonium nitrate proved more effective in citric acid production. A low pH (1.9-2.3) was found during the maximum production of citric acid. Conclusion, significance and impact of study: The results depict that potato and rice extract media can produce citric acid, hence providing an alternate substrate for citric acid production.