Abstract:
This study was conducted to produce citric acid from fruit and vegetable wastes from the local market in Khartoum state .Ten samples of fruit and vegetable wastes were collected: mangoes, oranges, bananas, lemon, grapefruits, beets, carrots, pumpkin, potatoes, and sweet potatoes. The solid state fermentation method was used to produce citric acid using Aspergillus niger whichwas isolated from rotten onion and cultured on potato dextrose agar medium and incubated in fungi incubator at 25ºC for five days. The fungus isolated was identified by viewing under the microscope for its morphological characteristics, features then it was cultured on the fermentation media. The fermentation media were incubated for incubation periods of seven days, ten days, and thirteen days at 25 º C and then sugar and pH concentration of citric acid were determined. The result showed that the incubation period of seven days at 25ºC gave the highest production of citric acid by the fermentation medium of mango wastes which yielded (130.50 mg/ml) then followed by the grapefruit wastes which yielded (99.80 mg/ml) and lower acid production was yielded by banana wastes which was (40.42mg/ml). On the fermentation period on ten days at 25ºC yielded the highest acid production by mango wastes (111.36mg/ml) then followed by grapefruit which yielded(72.96 mg/ml) and lowest acid production yield on ten days at 25ºC was recorded by carrot (23.16 mg/ml of citric acid). On fermentation period of thirteen days at 25ºC yielded the highest acid production by mango wastes (97.92 mg/ml) followed by the grapefruit waste which yielded (58.52 mg/ml) of citric acid and the lowest yield of acid was recorded by carrot which was (16.00mg/ml). It was also shown that citric acid concentration decreased after maximum yield by increasing incubation period in all the tested wastes substrates. This study also showed that the production of citric acid was accompanied by reduction in the concentration of
sugar content in manner depends on the types substrate used. Therefore mango and grapefruit wastes showed the best medium for the production of citric acid. However banana and carrot were the lowest.
