Citric acid, a key organic acid with the formula C6H8O7, is commercially produced mainly via fermentation methods using microorganisms like A. niger and S. cerevisiae. The production process involves various steps, including raw material selection, medium formulation, fermentation, and purification techniques such as precipitation and filtration. Citric acid has wide-ranging applications in food, pharmaceuticals, and other industries as an acidifying agent, preservative, and flavoring agent.

1. PRODUCTION OF ORGANIC ACIDS
- Citric acid
BOOMIKA. S
M. Sc Microbiology

2. INTRODUCTION
Citric acid is the most important commercial product
which is found in almost all plant and animal tissues.
The molecular formula of citric acid is C6H8O7, 2-
hydroxy-1,2,3-propane tricarboxylic acid.
It is widely used organic acid in the field of food
(60%) and pharmaceuticals (10%).
In 1784 W.SCHEELE’s first time isolated from
lemon juice as calcium citrate, which treated with
sulphuric acid gave citric acid in the liquid phase.

3. Microorganism and advantages
A. niger and Saccharomyces sp. are employed
for commercial production because it has
several advantages.
Advantages of using this micro-organism
Its ease of handling.
Its ability to ferment a variety of cheap raw
materials.
It provides high yields

4. • There are three types of
fermentation in the production of
citric acid
Surface fermentation
Submerged fermentation
Solid-state fermentation

5. Steps of Citric Acid Cycle
CITRIC ACID CYCLE
• The citric acid cycle is also called the tricarboxylic acid cycle (TCA).
• The steps include in the citric acid cycle are:
1.Formation of Citrate
2.Formation of Isocitrate via cis-Aconitate
3.Oxidation of Isocitrate to a-Ketoglutarate and CO2
4.Oxidation of a-Ketoglutarate to Succinyl-CoA and CO2
5.Oxidation of Succinate to Fumarate
6.Hydration of Fumarate to Malate
7.Oxidation of Malate to Oxaloacetate
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6. Others organisms
yeasts
•candida tropicalis
•c. oleophila
•c. guilliermondii
•c. citroformans
•hansenula anamola
•yarrowia lipolytica
bacteria:
Bacillus licheniformis
Arthrobacter paraffinens
corynebacterium species
Fungi:
•Aspergillus niger
•A. aculeatus
•A. awamori
•A. carbonarius
•Penicillium luteum
•P. citrinum
•Mucor piriformis
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7. Medium for fermentation
RAW MATERIALS THAT ARE USED FOR CITRIC ACID PRODUCTION ARE
DIVIDED INTO TWO GROUPS:
GROUP 1:
• Substances with low ash content: e.g. cane or beet sugar, dextrose syrups,
and crystallized dextrose
GROUP 2:
• Materials which have high ash content: e.g. cane and beet molasses, crude
unfiltered starch hydro-lysates.
pH 6.0-6.5, temperature is kept constant at 30 degrees during the fermentation
by means of air current.
The fermentation process stop after 8-14 days.

8. Medium formulation
Components grams/litre
1. Sucrose - 125-150
2.NH4NO3 - 2.0-2.5
3.KH2PO4 - 0.75-1.0
4.MgSO4.7H2O - 0.20-0.25
5.HCl to pH 3.4 to 5.5
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9. Purification and product recovery
• Recovery of mycelium to extract citric acid
• Purification is a simple way of getting pure citric acid
followed by two simple techniques.
1.Precipitation
2.Filtration
• Precipitation is the most commonly used technique.
• The biomass is separated by filtration.
• Then the liquid broth is transferred to the recovery
process.

10.  It is performed by the addition of calcium oxide hydrate (milk of lime) to form the
slightly soluble tri-calcium citrate tetrahydrate.
 The precipitated tri-calcium citrate is removed by filtration and washed several
times with water.
 It is then treated with sulphuric acid forming calcium sulfate, which is filtered off.
 Mother liquor containing citric acid is treated with active carbon and passed
through cation and anion exchangers.
 Several anion-exchange resins are commercially available.
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11. Applications
• Acidifying agent and pharmaceutical industries
• Chelating and sequestering agent (tanning of skin)
• It is used in the detergent industry as a phosphate substitute.
• Used as a preservative and flavoring agent.
• Production of carbonated beverages.
• Emulsifying agent in ice cream.
• Also used as an antioxidant.
• Plasticizers.
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12. thank you