Abstract
Aspergillus niger strains were isolated from various sources like soil,
floor, window glass and Microbiology lab. These strains were screened
for the production of citric acid and the strain that produced maximum
amount of citric acid was selected and identified based on its cultural
characteristics, employing slide culture method. A basal medium made
of Oat bran was employed for the production of citric acid (using SSF).
Optimization studies were conducted by varying some nutritional and
physiological parameters. Fructose concentration of 20% in the basal
media enhanced citric acid production. A concentration of 0.25 (%w/v)
NH4NO3 was found optimum. Likewise, an incubation temperature of
280C, pH 4.5 and incubation period of 72h were found optimum for the
production of citric acid using oat bran as substrate. Maximum amount
of citric acid produced was 62g/kg of oat bran.