Citric acid is produced industrially through fermentation using the fungus Aspergillus niger. The process involves: 1) Growing A. niger in large fermenters on a substrate like molasses under controlled conditions of pH, oxygen levels, and temperature. 2) After several days of fermentation, citric acid is recovered from the liquid through precipitation and crystallization. 3) Citric acid finds a wide variety of applications as a food additive, cleaning agent, in cosmetics and personal care products, and for industrial uses due to its acidity and ability to chelate metals. Worldwide production exceeds 1 million tons annually to meet demand.

1. “Industrial
Production of Citric
Acid”

2. SHRI SHIVAJI EDUCATION SOCIETY AMRAVATI
SHRI SHIVAJI COLLEGE OF ARTS COMMERCE AND SCIENCE
AKOLA(MS)
NAAC REACCREDITED WITH A GRADE(CGPA OF( 3.24)COLLEGE WITH POTENTIAL FOR EXCELLENCE(STATUS BY UGC)LEAD COLLEGE
(STATUS BY SGBAU, AMRAVATI)
DST-FIST SUPPORT

3. INTRODUCTION
Citric acid (C6H8O7 ) is a weak organic tricarboxylic acid found in citrus
fruits.
Citrus fruits (lemons, oranges, tomatoes, beets etc.) are those fruits which
contains sufficient amount citric acid and they are classified as acid fruits.
Citric acid is produced by three method fermentation, chemical synthesis
and extraction from citrus fruits.
Citric acid is the most important organic acid produced in tonnage and is
extensively used in food and pharmaceutical industries.
Citric acid is a weak organic acid found in citrus fruits.
It is good, natural preservative and is also used to add an acidic
Taste to food and soft drinks, more than million tonnes are
produced every year by fermentation.

4. HISTORY OF CITRIC ACID
PRODUCTION
1. History of Citric Acid Production 1784 by W. Scheele isolated from
the lemon juice as calcium citrate, which treated with sulphuric
acid gave citric acid in the liquid phase.
2. Zahorsky in 1913 patented a new strain - Aspergillus niger
3. Currie 1917 opened the way for industrial citric acid
fermentation using a new micro-organism.
4. In 1960’s practice of submerged fermentation gained popularity.
1 2 3 4

5. STRAINS FOR CITRIC ACID
PRODUCTION
 Many strains excrete traces of citric acid as a metabolite of primary
metabolism.
 Various strains of genera fungi, yeast and bacteria were reported such as:
Penicillium luterum, Penicillium purpurogenum, Penicillium restrictum,
Penicillium janthinellum, Penicillium citrinum, Paecilomyces divaricatum,
Mucor piriformis, Trichoderma viride, Sacharomycopsis lipolitica,
Arthrobacter paraffineus, Corynebacterium sp.,etc.
 Only mutants of Aspergillus (Aspergillus niger) and yeasts genus Candida
have almost exclusively been utilized.

6. PRODUCTION PROCESSES
 Surface or submerged fermentation technique dominated over
traditional method of preparing citric acid by extraction from various
juices.
 Promising results were obtained in fed-batch process and by
continuous fermentation.
 Citric acid fermentation using immobilized A. niger cells on various
kinds of carriers as glass, polyurethane foams, entrapment in calcium
alginate beds, polyacrylamide gels, agar, agarose , cellulose carriers,
metal screens and polyester felts.

7. Industrial Production of Citric Acid
• Microorganism: Aspergillus niger (mainly), Candida yeast (from
carbohydrates or n-alkanes)
• Citric acid production is mixed growth associated, mainly take place
under nitrogen and phosphate limitation after growth has ceased.
• Medium requirements for high production.
• Carbon source: molasses or sugar solution.
• Na-ferrocyanide is added to reduce Iron (1.3 ppm) and manganese
• - High dissolved oxygen concentration
• - High sugar concentration
• - pH<2
• - 30 °C

8. • Bioreactor: batch or fed-batch (100m 3 ) - 5-25X10 6 A. niger
spores/L may be introduced to the fermenter.
• Aeration is provided to the fermenter by air sparging (0.1-0.4
vvm)
• Temperature is controlled by cooling coil.
• Agitation: 50-100rpm to avoid shear damage on molds.
• Fed-batch is used to reduce substrate inhibition and prolong the
production phase one or two days after growth cessation.
• Volumetric yield: 130 kg/m 3

9. FLOW CHART OF CITRIC ACID
PRODUCTION

10. • Molasses substrate(15-20 % of sucrose, added nutrients) acidified with, phosphoric acid to a pH
• 6.0 - 6.5 and heated at temperature 110 ºC for 15 to 45 min.
Potassium hexacyanoferrate is added to the hot substrate, to precipitate or complex trace metals
• [Fe, Mn, Zn] and to act in excess as a metabolic inhibitor restricting growth and promoting
• acid production
• Inoculation is performed in two ways, as a suspension of conidia added to the cooled medium, or as a
• dry conidia mixed with sterile air and spread as an aerosol over the trays
• The temperature is kept constant at 30 ºC during the fermentation by means of air current
• Within 24 hours after inoculation, the germinating spores start forming a 2-3 cm cover blanket of
• mycelium floating on the surface of the substrate. As a result of the uptake of ammonium ions the pH
• of the substrate falls to 2.0
• The fully developed mycelium floats as a thick white layer on the nutrient solution. The fermentation
• process stops after 8 - 14 days.
• Recovery of mycelium to extract citric acid
SURFACE FERMENTATION PROCESS

11. SOLID STATE FERMENTATION
The solid substrate is soaked with water up to 65 - 70 % of water content. After the removal
of excess water, the mass undergoes a steaming process
Sterile starch paste is inoculated by spreading Aspergillus niger conidia in the form of
aerosol or as a liquid conidia suspension on the substrate surface
The pH of the substrate is about 5 to 5.5, and incubation temperature 28 to 30 ºC. Growth
Can be accelerated by adding α-amylase, although the fungus can hydrolyze starch with its
own αamylase. During the citric acid production pH dropped to values below 2
The solid state surface process takes 5 to 8 days at the end of which the entire is extracted
with hot water. On other cases, mechanical passes are also used to obtain more citric acid
from the cells

12. SUBMERGED FERMENTATION
Beet molasses substrate (12 - 15 %. reducing sugar content ), Nutritive salts, such as ammonium
nitrate or potassium dihydrogen phosphate are added. pH of substrate is maintained at 5.5 to
5.9.
The process can usually run in one or two stages, using hydrophilic spores suspensions or
germinated conidia from the propagator stage . Amounts of spores are 5 to 25 x 106 per liter of
Substrate
The development of the hyphae and the aggregation generally requires a period from 9 to 25
hours at temperature of 32 ºc
Mycelia aggregation and spherical pellets, the productive form can be detected after 24 hrs of
inoculation.
The change of pH in this phase is from 5.5 to 3.5, for beet molasses substrate, and to 2.2 for the
sucrose substrate
Fermentation last up to 6-8 days and later citric acid is purified from mycelium

13. FACTORS AFFECTING CITRIC ACID
PRODUCTION
 Factors affecting citric acid fermentation
i. The concentration of carbon source,
ii. Nitrogen and phosphate limitation,
iii. pH (pH>5)
iv. Aeration
v. Trace Elements
vi. Lower Alcohols

14. PRODUCT RECOVERY
The recovery of citric acid from liquid fermentation is generally accomplished by
three basic procedures :
1. Precipitation
2. Extraction
3. Adsorption and Absorption (mainly using ion exchange resins).
Separation of citric acid from the liquid :
calcium hydroxide is added to obtain calcium citrate
tetrahydrate → wash the precipitate→ dissolve it with
dilute sulfuric acid, yield citric acid and calcium
sulphate precipitate → bleach and crystallization →
anhydrous or monohydrate citric acid.

15. APPLICATIONS OF CITRIC ACID
 Powdered Citric Acid Uses
• We get a citric acid powder which is white. It helps in improving kidney
health, throat infection, get rid of acne etc. Some other citric acid uses are
• Used as a food additive
• Used in cleaning
• Used as cosmetics
• Used in water softener
• Used in Industries

16.  Food Additive
• Citric acid is used in food as a flavoring agent and preservative.
• It is used in processed food products like beverages, soft drinks etc.
• Due to its sour taste, it is used in making certain candies.
• Sometimes the sour candy is covered with white powder which is citric acid.
• To keep fat globules away some ice cream companies use it as an emulsifier.
 Cleaning Agent
• Citric acid is one of the chelating agents.
• With the help of citric acid limescale from evaporators and boilers is removed.
• It is used in soaps and laundry detergents as water are softened by the acid.
• Household cleaners used in kitchen and bathroom also contain some amount of citric
acid.
• It is not only used as a cleaner but also as a deodorizer.

17. Cosmetics
• Citric acid helps in the removal of dead skin so used for home masks.
• Improves skin tone and skin growth reducing wrinkles, acne scars etc.
• To balance the pH levels citric acid is commonly used the ingredient in cosmetics.
• It is found in hand soap, body wash, nail polish face cleansers, shampoos and some
other cosmetics products.
 Water Softener
• Citric acid is used as a water softener in detergents, because of it’s an organic acid,
chelating, and buffering properties.
• The chemical properties of citric acid as a weak organic acid make it a strong softener
for water.
• It operates by breaking down the trace quantities of metal discovered in water, making
it an optimal all-natural option for hard water treatment.

18. Separation:
• The biomass is separated by filtration
• The liquid is transferred to recovery process:
• Separation of citric acid from the liquid: precipitation
calcium hydroxide is added to obtain calcium citrate
tetrahydrate → wash the precipitate→ dissolve it with
dilute sulfuric acid, yield citric acid and calcium
sulphate precipitate → bleach and crystallization →
anhydrous or monohydrate citric acid.

19. THANK YOU