Citric acid is an organic acid with numerous industrial application. It is extensively used in the food and beverage industry as it combines a pleasant taste with low toxicity and sweetness. It can be produced from different materials like molasses that has sucrose content of 32%. In Ethiopia, some of the molasses were used for ethanol production and other purposes, but the remaining has been exported to abroad. This study investigated that the utilization of molasses to use as a raw material

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... r citric acid production under different fermentation conditions with submerged fermentation method in the laboratory using 250mL Erlenmeyer flask as the small scale laboratory fermentor by using Aspergillus niger. The effect of temperature (25, 30, and 35℃), fermentation time (96, 144, 196h) and pH (2, 4, and 6) of fermentation condition for citric acid yield test result were investigated. The experimental design was done by using Design Expert 6.0.8 software for three factors and Response Surface with 3- level factorial design type in optimization study. The minimum citric acid yield was found to be 20.23 g/L after the fermentation time of 96h, temperature 25℃ and pH 2. A maximum citric acid yield of 40.08 g/L was achieved under selected optimal condition of (fermentation time 156h, temperature 30℃ and pH 3.89) with high value of combined desirability. From the model regression equation developed, the linear terms of temperature, and time had a positive effect and a pH had a negative effect on response yield. The quadratic terms (pure and interaction quadratic terms) had a negative effect on extraction yield except fermentation time and pH interaction. Incubation time had a more weighty linear effect on yield as compared to fermentation temperature and pH. The quality of the product obtained under optimized condition was assessed with Atomic Absorption Spectroscopy (Buck of Scientific 210 VGP AAS, USA) and UV visible Spectrophotometer. The results revealed that the heavy metal content of the sample was below detection li [...]