Citric acid is one of the most remarkable industrial goods fabricated by industrial fermentation using filamentous fungus. When Aspergillus niger, a filamentous fungus, is produced under suitable conditions, high amounts of citric acid are obtained. This study aims to explain the citric acid synthesis studied in a biodisc reactor using A. niger. Various physiological parameters have been investigated in order to determine the optimum citric acid synthesis in biodisc reactor. Optimum incubation time was found to be as 168 hours in the study. The optimum value of the incubation temperature was determined to be 30°C. The optimum value of the initial pH was found to be 3.8. Optimum citric acid synthesis occurred when the disc rotation speed was 2 rpm. In addition, the optimum value of the initial sugar (sucrose) concentration was determined to be 20%. In a semi-continuous production study with the renewal of the medium after a certain incubation period, it was determined that the citric acid yield increased approximately 3 times compared to the batch system. As a result, the highest value of citric acid was determined as 67.65 g/L.