A simple Koji fermentation process was followed which is quite similar to solid-state fermentation. The collected fresh peels were washed twice with sterile distilled water to remove adhering dust. Then their finger stalk and black base regions were removed. Thereafter, one kg of peels was steamed with one liter of water in order to get the desired moisture content. The steamed peels were homogenized for five minutes under aseptic conditions. After homogenization, the pH of the steamed peels was 5.12. It was adjusted to different pH ranges using 1 N HCl/NaOH. From the pasty fibrous material, 2 cm thick Koji beds were prepared in a clean sterilized glass trough having 30 cm diameter. The glass trough was used as a fermentation vessel. After inoculation with A. niger the Koji bed was covered with cheesecloth. The cloth cover allowed adequate gas exchange. The troughs were placed in a sterile chamber and fermented at different experimental conditions. Citric