Citric Acid Production by Aspergillus niger from Agro-Industrial By-Products: Molasses and Chicken Feather Peptone

Abstract

Citric acid is a commercially important organic acid with a wide range of applications. To reduce the cost of producing citric acid, sugar beet molasses and chicken feather peptone (CFP) were used as the sole carbon and nitrogen sources, respectively for submerged citric acid biosynthesis using Aspergillus niger. To improve the citric acid production, the parental isolate of A. niger MO-25 was improved by mutation using ethidium bromide. Citric acid production using molasses was significantly affected by CFP concentrations (1–6 g/L). The maximum citric acid concentration was determined at 4 g/L CFP and 168 h. When CFP compared to commercial peptones (casein and bacto), the highest citric acid production was obtained with CFP. Furthermore, the addition of KH2PO4 (0.15 g/L) enhanced citric acid production (68.8 g/L). These results suggested that sugar beet molasses supplemented with CFP as organic nitrogen and mineral salt sources could be utilized for the economical and efficient production of citric acid. This is the first study to investigate the influence of CFP for citric acid production.