Citric acid production by agricultural wastes with Aspergillus niger using solid state fermentation and process optimization

Citric acid is one the most commonly used organic acid in the food and pharmacntical which is produced mainly by submerged or surface fermentation by Aspergillus niger. As the most important of commereial producer. Recent works showed successful citric acid production through solied state fermentation. Under our experimental conditions, four important factor each one in four levels including substracte type (wheat straw, rice straw, rice bran, peanut skin) and pH (4,5,6,7) substrate treatment tempretures (45,60,75,90,.c) and substracte treatment time (30,60,90,120min) on citric acid production by Aspergillus niger were assayed. Maximum amount of citric acid production was pH =5, treatment time and temperature of 60(min) and 60 (.c) respectively also the wheat straw was the best substrate for citric acid production. The results of this study showed that Aspergillus niger is a suitable microorganism for citric acid production and wheat straw is a good base for economical production of citric acid due to its low price. All of four understudied factors had significant effect on citric acid production in solid state fermentation (P < 0.05).