Question

How inoculum is prepared during industrial production of citric acid by surface culture method ?

Answer 1

In the industrial production of citric acid by surface culture method, the inoculum is prepared as follows:

1. Pure culture of Aspergillus niger is obtained from a reliable source.
2. The spore suspension is prepared by growing the fungus on a sterile nutrient agar medium for 7 to 10 days at 30°C.
3. The spores are then harvested by washing the agar surface with sterile distilled water and collecting the spores in a sterile flask.
4. The spore concentration is determined using a haemocytometer and adjusted to a desired level, usually 10^7 to 10^8 spores per ml.
5. The inoculum is then added to the sterilized medium containing glucose and other nutrients in a fermenter.
6. The fermenter is maintained at an optimal temperature (usually 30°C) and pH (usually 4.5 to 5.0) and aerated with sterile air.
7. The fungus grows on the surface of the medium and produces citric acid, which is collected and purified.
8. Inoculum preparation is a crucial step in the industrial production of citric acid, as it ensures the uniform growth of the fungus and the production of high-quality citric acid.