Abstract:
The present study was conducted to study the effect of different incubation periods on the production of citric acid from fruit and vegetable wastes obtained from the local market in Khartoum State. Ten samples of fruit and vegetable wastes were screened i.e. mangoes, oranges, bananas, lemon, grapefruits, beets, carrots, pumpkin, potatoes, and sweet potatoes. The solid state fermentation method was adopted in this study to produce citric acid using Aspergillus niger which isolated from rotten onion and cultured on Potato Dextrose Agar (PDA) and incubated at 25ºC. Three different incubation periods were used in this study (seven, ten and thirteen days) at 25ºC for acid production. The produced citric acid concentration was determined and in parallel, the sugar concentration in the substrates was also determined before and after fermentation. The results showed that the highest production of citric acid was obtained through incubation period of seven days especially, by fermentation of mango wastes (130.50 mg/ml) followed by the grapefruit wastes (99.80 mg/ml)while, the lowest acid production was obtained by banana wastes fermentation (40.42mg/ml). It was also shown that citric acid concentration decreased by increasing incubation period in all the tested wastes substrates. This study also showed that the production of citric acid was accompanied with the reduction in the concentration of sugar content in manner depends on the type of the substrate used.
