PRODUCTION AND PARTIAL CHARACTERIZATION OF CITRIC ACID BY LOCAL ISOLATE OF ASPERGILLUS NIGER USING SORGHUM

Abstract

In the present study, the citric acid producing organisms were isolated from soil sample using serial dilution technique and the isolate were identified on the basis of their microscopic and morphological characteristics. The isolated fungal species were screened on the citric acid production using Czapek-Dox agar medium. From the isolates, fungal species Aspergillus niger were used for citric acid production, and the fungal species subculture using potato dextrose medium. The fresh culture of isolated Aspergillus niger were mixed to the fermentative medium along with the substrates, sorghum flour, corn starch and wheat flour separately and the fermentative medium was incubated 6-7 days at 30⁰C, after incubation the citric acid content was estimated by titrimetric method. Among the three substrates highest citric acid production was observed in corn starch supplemented medium than sorghum and wheat flour medium. Further characterization of citric acid was by paper chromatography, thin layer chromatography and IR. So it is highly recommended that the usage of corn starch supplemented medium with Aspergillus niger will be effective in the production of citric acid than the other substrates.