Production Process

Production Process - Citric Acid
Production Process - Citric Acid


Strain of Aspergillus niger , type of raw material fermented, the initial moisture content of the substrate, the amount of methyl alcohol present, and the fermentation time and temperature could affect the yield of citric acid.



Step 1: Upstream Process..
Raw materials processing
All substrates containing glucose, saccharose or starch are well-suited for the manufacture of citric acid.
Low impurity substrates use decationization and subsequent continuous sterilization while substrate with a high degree of impurity especially molasses, the raw material is subjected to hexacyanoferrate clarification with simultaneous boiling and decontamination.

The scheme of inoculation material production for mutant Aspergillus Niger
6.jpg picture by citric-acid
6.jpg picture by citric-acid


1. Initial culture
2. Inoculation on the culture medium of agar
3. Selection of active colonies
4. Multiplication
5. Collection of colonies
6. Mixing with active carbon
7. Inoculation material
8. Multiplication of colonies in trays
9. Spore material prepared for production

Strain improvement
1. Genetic improvement of industrial microorganisms (Aspergillus *)
Mutagenic techniques have been successfully employed for the improvement of Aspergillus * strains. With the help of gamma radiations several high citric acid producing strains of Aspergillus * were induced at the laboratory. These strains were found to yield 3-5 times more of citric acid than their parent strain.

2. Metabolic engineering of the glycolytic pathway in Aspergillus *
Genetic engineering of Aspergillus * primary metabolism is employed to improve citric acid production by fungus. The aim is to increase the metabolic flux through the pathway leading to citric acid formation. One way to do is to decrease the fluxes through branches of the main pathway resulting in decreased formation of by-products. Another way is to use direct increase of the flux through the main pathway, for example, by overproduction of the enzymes involved


Step 2: Fermentation Process..
Production Process - Citric Acid
Production Process - Citric Acid

Fermentation section
All of the commercial citric acid is produced by fermentation.
Bubble column fermenter is chosen in the production of citric acid based on its energy consumption and design consideration.
Processes employed are surface or submerged fermentation by mold (Aspergillus *) and submerged fermentation by yeast (Candida guilliermondii, C. lipolytica), using a variety of substrates including sucrose, molasses, corn syrup, enzyme-treated starch, and normal paraffins.

Step 3: Downstream Process..
Citric acid is recovered from the fermentation broth by solvent extraction or more commonly by calcium citrate precipitation and separation, followed by treatment with sulfuric acid to convert the calcium citrate to calcium sulfate and citric acid. The calcium sulfate is removed by filtration. This is to obtain a largely pre-purified citric acid solution.
The final purification of the citric acid is carried out by treating the isolated citric acid solution with activated carbon, cation and anion exchange resins in fixed bed reactors
The final processing of the crystalline end product involves the following process stages:
• Evaporation
• Crystallization (using a hot aqueous solution of above the transition temperature of 36.6°C or 97.9°F to yields anhydrous citric acid; crystallization from a cold solution yields the monohydrate)
• Centrifuging
• Fluidized bed drying and Classification


Overview of process..


Production Process - Citric Acid
Production Process - Citric Acid




Places for citric acid production.
Production Process - Citric Acid
Production Process - Citric Acid
Production Process - Citric Acid
Production Process - Citric Acid
Production Process - Citric Acid
Production Process - Citric Acid