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muzzaffar zaidi

on 16 December 2013

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Transcript of CITRIC ACID

How to synthesis citric acid??

It can be synthesized by using Aspergillus niger strain.

What you need??

A culture of Aspergillus niger

Citric acid is a weak organic acid that is an important intermediate in the Krebs cycle.

It breaks down glucose to citric acid and carbon dioxide with the presence of oxygen.

Due to its branching structure of white septate hypha

It the capabilities to utilize varieties of substrates

Why Aspergillus Niger?

The process starts with the glycolysis of glucose. In this stage, glucose is splitted into two 3-carbon molecule known as pyruvate @pyruvic acid. As pyruvic acid enter the mitochondrion, carbon is removed, forming carbon dioxide,CO2, and electrons are removed, changing the NAD+ to NADH. Co-enzyme A joins the 2-carbon molecule, forming Acetyl-CoA. Acetyl-CoA then adds the 2 carbon acetyl group to a 4-carbon compound, forming the citric acid.
However, the citric acids need to be extracted. Below are few stages where the extraction process took place.
A. Cell growth in each phases

Log of growth with time
ln⁡xt = ln⁡xo +μt

Cube root of growth linear with time

〖xt^(1/3) =〖xo^(1/3)+kc t
Linear with time

xt=xo+kc t

Where xt=biomass concentration of time, t
μ=specific growth rate

B. Product formation
It is related to the growth rate
rp = (a.rx )+(b.x)
Where x=biomass concentration
rx=rate of biomass accumulation

Rate of product formation is proportional to the rate at which the cells entered the maturation state,
rpt=krx (t-tm)
Where (t-t_m )=rate of biomass growth at time,t

Primarily, the production of citric acid starts with the reaction of sugar and Aspergillus niger as shown below
Addition of sulphuric acid

(C6H507)2.Ca3.4H2O + 3H2SO4
Calcium nitrate sulphuric acid citric acid

calcium sulphate water

C6H12O6+A.niger C6H806+CO2

Sugar citric acid carbon dioxide
Addition of calcium hydroxide
2C6H807 + 3Ca(OH)2 (C6H507)2.〖Ca3.4H2O+2H2O

The solution is then centrifuged at 3000rev/min for 10minutes then dried overnight at room temperature to get a crystallized product of citric acid.
However, there is a problem in this equation as the k is not constant. It kept increasing. So we resolve the problem by assuming that there were at least two different types of cells within the mycelium and both have different productivity. This equation is modified and become
rpt=k1 rx (t-tm )+k2 x(t-tm)

K1=growth associated constant
K2= non growth associated constant


a weak organic acid

important intermediate in Krebs Cycle


Breaks down glucose

With the presence of Oxygen

Citric Acid + CO2

to form

Citrus fruits




All living things


Artificial flavouring

For chemical-processed food


Mostly by using Aspergillus niger

by utilizing starchy and sugar substrate

It can be found in citrus fruits such as grapefruits, orange, lemon and etc as well as in all living things.

Citric acid has been widely used as an antioxidant and as an artificial flavouring in chemical-processed food. It is usually produced by Aspergillus niger by utilizing starchy and sugar substrate.

Table Sugar

Calcium hydroxide

Sulphuric acid

Add sugar into Aspergillus niger

Fungus will recycle sugar into citric acid and carbon dioxide

Filter and extract the citric acid by adding calcium hydroxide

Calcium hydroxide react with acid to form salt that is calcium nitrate that will precipitate.

Scoop the salt and add sulphuric acid into it

Crystallized precipitate will form but you do not need it.. you will only require the liquid solution which is the pure citric acid.

Citric acid calcium hydroxide calcium nitrate water
The reactor selected in the production of citric acid is batch reactor as shown in the schematic diagram below
A bioreactor is a vessel in which an organism is cultivated and grown in

control manner to form byproduct.
consist of ;

• agitation system which will mix the organism completely
• control panel which regulates pumps cooling water , pump air supply and acid/base supply
• sensors-check medium temperature, medium aeration and medium pH value

• There is steam supply to the system
• Thermal jacket
• Tedium air supply and cooling water
supply to control the temperature in the reactor

selection of reactor

Batch reactor

It is a strirred fermenter

Size of bioreactor

For laboratories scale 2-100litre

Sources of sugar &pH plays a major role in Citric Acid production

Process involved

Anaerobic process

It used strain Aspergillus niger

For industrial scale up to 100m3
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