Citric acid, a key metabolic intermediate found in many fruits, is primarily produced through fungal fermentation, particularly using the organism Aspergillus niger due to its high yield and economic efficiency. Various fermentation methods include surface culture, submerged fermentation, and solid-state fermentation, each requiring specific environmental conditions. The recovery of citric acid involves filtration and concentration of the fermented liquid to obtain the final product.

1. Production of Citric Acid
by Fermentation
BY- SANCHIT DHANKHAR

2. Citric Acid
It is an intermediate in the metabolism of carbohydrates occuring in many fruits
such as limes & lemons.
These are obtained by fermentation of crude sugar or corn sugar.
Formulae: C6H8O7

3. Citric Acid in Pharmaceuticals:
 Citric acid found as natural constituent of a variety of fruits.
 It was first isolated in lemon juice by Sheele in 1784.
 Chemical synthesis of citric acid is also possible.
 It can also be produced by yeast and bacteria in shorter period of time.
 Today most of citric acid is produced from fungal fermentation because
this process is most competitive and economic.

4. Test Organism:
First time in 1917 Curie used Aspergillus Niger, a
fungus which is the organism of choice even today.
Advantages:
# it is an efficient strain.
# it can utilize cheaper raw material.
# it gives consistent and high yield.
# easy to handle.

5. Types of Fermentation:
1): The Surface Culture Method:
 In this sterile nutrient medium containing sugar
is allowed to flow into trays.
 The medium is then inoculated with spores of
A.niger.
Conditions: temp. = 28c to 30c
relative humidity: 40% to 60%
time period = 8 to 12 days.
After the completion of fermentation the fermented
liquid is drained off & further processed for
recovery of citric acid.

6. 2): SUBMERGED FERMENTATION METHOD:
it involves
a growth and production stage.
3): SOLID STATE FERMENTATION METHOD:
The medium is first impregnated on porous solid
material such as sugarcane, potato etc.
And then sterilize it after that fungal spores are
introduced in it.
Conditions: temp. = 25 to 30C
time period = 6 to 7 days
Glucose + A.niger Citric Acid

7. Sugar or
Molasses
Mixer
(Water + Acid)
Sterilization
Mold spores Fermenter
Citric Acid
Separator
Drier
Filter
Crystallizer
Purifier

8. Media:
The basal media with following composition is
normally used for production of citric acid by
A.niger
INGREDIENTS QUANTITY
Sugar or molasses 14 – 15 %
Nitrogen source 0.25%
Potassium dihydrogen phosphate .10 - .15 %
Magnesium sulphate .02%
pH( sucrose medium) 2.0- 3.0
pH( molassess medium ) 5-6

9. Inoculum development:
Fungal strains are maintained on standard media & the
inoculum is either the pregrown mycelia.
Spores inoculum is prepared freshly as suspension in
water with or without tween 80.
Aeration:
Citric acid fermentation is aerobic fermentation.
It can be ensured through surface cultivation ,
submerged aeration and shake culture.
Incubation Period:
A shorter incubation period of 4-5 days is adequate for
submerged fermentation but surface culture method
requires 7-10 days. Under solid state fermantation a
period of 6-7 days is considered.

10. RECOVERY METHODS:
The fermened liquid is free from mycelia and other
impurities by filtration.
It is then heated to 80-90C by addition of
hydrated lime.
The liquid is conc. in vacuum and finally passed
through low temperature crystalliser.

11. THANKYOU