Isolation and Screening of Citric Acid Producing Aspergillus Spp and Optimisation of Citric Acid Production by Aspergillus Niger S-6

Abstract

The present study was aimed to isolate and screen the ability of citric acid producing Aspergillus spp from soil. Citric acid is the most important organic acid, used as a natural preservative and conservative. It is also used to add an acidic or sour taste to foods and soft drinks. In this study, fungal samples were isolated from soil samples, using serial dilution agar plating method and the isolates were identified based on their microscopic and morphological characteristics. From the isolates, the dominant fungal species, Aspergillus niger and Aspergillus fumigatus were sub-cultured using Potato Dextrose Agar (PDA) medium and the fungal species were used for citric acid production. The spores were mixed in the fermentative medium for 72 hours at 30±1° C. After incubation, the citric acid content was estimated by titrimetric method. Among the two species, higher citric acid production was shown by Aspergillus niger S-6. Then it was undertaken for optimisation under various pH, temperature, Carbon and Nitrogen sources. In this assay, the maximum production of citric acid was observed in Aspergillus niger S-6 at pH 6.0, temperature 30±1° C, Carbon source Glucose and Nitrogen source Ammonium sulphate.