MATERIALS AND METHODS

The present project was done in the Industrial Biotechnology Lab in the Department of Chemistry & Biochemistry.


3.1 Production of citric acid from Aspergillus niger

3.1.1Fermentative Organism



Pure wild type culture of Aspergillus niger was obtained from Industrial Biotechnology Lab (IBL). The stock culture was raised on Potato dextrose agar (PDA). The pH of the medium was adjusted to 4 with 1 M HCl/ 1M NaOH and autoclaved for 15 min at 121 oC under the pressure of 15 lb/in2. Fungal culture was transferred aseptically to PDA medium in Laminar airflow. The slants will be incubated at 28oC for 7 day and preserved at 4oC for two months.

Composition of PDA medium for sporulation of Aspergillus niger

S. no Components Quantity g/100ml


1 Potato Starch 2.0

2 Glucose 2.0

3 Urea 0.3

4 ZnSO4.7H2O 0.001

5 KH2PO4 0.008

6 KCl 0.015

7 Agar 2.0

8 MgSO4.7H2O 0.05

9 Distilled water 100ml

PH, 5.5; temperature, 37oC.


pH of the medium was adjusted to 5.5 with 1 M HCl/ 1M NaOH and autoclaved for 15 min at 121oC under the pressure of 15 lb/in2. The media was poured into the autoclave test tubes and the test tubes were left undisturbed in slanting position at 250C for solidification. Fungal culture was transferred aseptically to PDA medium slants in laminar airflow. The slants were incubated at 28oC for 3 days for sporulation and preserved at 4oC for subsequent use for citric acid production.