Production of Citric Acid by Aspergillus niger Using Sugarcane Molasses as Substrate

Citric acid (CH2COOH.COH.COOH.CH2COOH) is a tricarboxylic acid, soluble in water with a pleasant taste; it is an important acid used in food Industries. It exists in nature when carbohydrates are oxidized to carbon dioxide. Because of its high solubility, palatability and low toxicity it can be used in food, biochemical, and pharmaceutical industries. The aims of this study are citric acid production from fungi (Aspergillus niger) using by-product of sugar (sugarcane molasses) and to evaluate its concentration. Indigenous strains of A. niger were isolated from soil (depth 15cm), air and bread and identified using ordinary medium Sabouraud s dextrose agar medium supplemented with Rose Bengal. A pure culture of tested microorganisms were inoculated into different flasks containing different concentrations of molasses and incubated for 144 hrs at 28°C. The production of citric acid determined by the appearance of air bubble and colour s change; the mixtures were distilled at 175ºC for one and half hr. After the distillation process; the citric acid was detected and titrated to determine its percentage by adding bromocryesol green and NaOH (N 0.1), respectively. Citric acid production from the soil sample was of high amount, when compared with air, and bread. The soil sample produced 9.6 % of citric acid compared with air 6.7% and bread 7.7 %. The maximum citric acid production was produced on the 6th day of fermentation in all samples. By recycling and reusing waste material from cane molasses citric acid production can be easily achieved by using microorganisms that have the ability to produce citric acid efficiency such as Aspergillus niger.