Background: Citric acid is produced in insignificant quantities in Iran. Despite its great range of utilizations, and from another aspect, high level of production of sugarcane bagasse, the related problems arising from maintenance of this acid require thinking of a measure in the direction of its optimal usage and production. Objectives: The objective of the present study is to obtain effectual variables in producing citric acid from sugarcane bagasse through Solid State Fermentation (SSF) method using Aspergillus niger mold and to optimize its mass production by employing Taguchi method. Materials and Methods:The effective parameters such as spore inoculation level, methanol percentage, solvent type, spore age, humidity percentage, initial pH of substrate, fermentation period and temperature, initial sugar percentage, autoclaving duration, nitrogen source and etc. were studied for producing citric acid from sugarcane bagasse with respect to Tagouchi method. Results: By considering the findings obtained from the tests, the highest production rate of citric acid g/kg out of untreated sugarcane bagasse is 75.45 based on the consumed sugar and a yield of 15.1 g/kg of sugarcane was achieved per day. Application of sodium hydroxide and acid pretreated sugarcane bagasse increased the production of citric acid in such a fashion that the production rates were 97.81 g/kg and 87.32 g/kg of sugarcane bagasse, respectively, compared to sodium hydroxide and acid untreated sugarcane bagasse. Conclusions:The obtained findings in the present study indicated that sugarcane bagasse is an ideal substrate in producing citric acid and the aforementioned process could be considered as a beneficial and cost-effective method in citric acid production.

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