RESPONSE SURFACE METHODOLOGY FOR OPTIMIZATION OF SORGHUM MALT MEDIA FOR CITRIC ACID PRODUCTION BY IMPROVED STRAINS OF Aspergillus niger

Citric acid is a tri carboxylic organic acid is the most important acid produced by fermentation used in the food and pharmaceutical industries. The present work deals with determination of optimum growth conditions for citric acid production by submerged fermentation by using strain of A.niger MTCC662 respectively. Isolation, screening and mutated the A.niger strain induced by UV irradiation, diethylsulphate and Co60 by providing different types of media and the submerged fermentation was carried out under various growth parameters like temperature, pH and media of Sorghum malt as substrate. Strain improvement studies for maximum production of citric acid obtained after the fermentation. By using the response surface methodology has been optimized the production of citric acid. These variables were further optimized using a 24 full factorial CCD (Central Composite Design) and a second order polynomial model equation was obtained. In the present study the value of the regression coefficient R2 = 0.6238 which indicates that 62.38% of the variability in the response could be explained by the model. The adjusted R2 value is 0.6238 which is also very high to advocate the significance of the model. Maximum yield was obtained from mutant type of A. niger MTCC 662 than wild strains were about 12.0g/100ml and 8.2g/100ml. It could be concluded that the A.niger MTCC662 mutant strains have produced high yield than wild strain of A.niger MTCC662 cultures.