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★~~Citric acid~~★

A weak organic acid found in citrus fruits, usually produced in powder form.
It exists in a variety of fruits and vegetables, but it is most concentrated in lemons and limes, where it can comprise as much as 8% of the dry weight of the fruit.
Lemons contain the highest amounts of citric acid, followed by fruits like grapefruits and oranges.
It easily mixes into liquids, making it a valuable acid.






chemical formula


Citric acid molecule. Ball-and-stick model




Properties


At room temperature, citric acid is a white crystalline powder. It can exist either in an anhydrous (water-free) form or as a monohydrate. The anhydrous form crystallizes from hot water, where as the monohydrate forms when citric acid is crystallized from cold water. When heated above 175°C, it decomposes through the loss of carbon dioxide and water. Citric acid leaves a white crystalline precipitate.



white crystalline powder

Anhydrous......... Monohydrate........




Citric acid cycle
In biochemistry, it is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of almost all living things.
Citric acid cycle, also known as the tricarboxylic acid cycle or the Krebs cycle is responsible for the final breakdown of food molecules to form carbon dioxide, water, and energy. This process requires a series of chemical reactions occurring within the cell. The citric acid cycle involves 8 distinct steps, each catalyzed by a unique enzyme.




If you are interested to know more detail on citric acid cycle, you may visit this website. They provide animation + questions.
http://www.wiley.com/college/pratt/0471393878/student/animations/citric_acid_cycle/index.html

Who discover citric acid??
The discovery of citric acid has been credited to the 8th century alchemist Jabir Ibn Hayyan (Geber). Citric acid was first discovered in 1784 by the Swedish chemist Carl Wilhelm Scheele, who crystallized it from lemon juice. In 1826, it was first produced commercially by J & E Sturge in England.
Industrial-scale citric acid production began in 1860. It is based on the Italian citrus fruit industry.
In 1880, glycerol was synthesized to produce citric acid. In 1893, C. Wehmer discovered that Penicillium mold could produce citric acid from sugar. People realized the importance of microbial production of citric acid in industrial when Italian citrus exports were disrupted by War World I. In 1917, the American food chemist James Currie discovered that certain strains of the mold Aspergillus niger could produce citric acid. Two years later, Pfizer began industrial-level production using this technique then Citrique Belge in 1929. In 1965, processes where certain yeasts were used in the production of citric acid were introduced.

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Aspergillus Niger




Medium constituents
Trace elements contain:
-Manganese: manganese deficiency leads to significantly lower lipid content in A. Niger and low mycelial lipid levels results in high yields of citric acid. Protein synthesis is also said to be inhibited by manganese deficiency
-Iron: essential for high yields of citric acid by A. Niger but excess interferes with production
-Copper: reducing the deleterious effect of iron on citric acid production
-Low concentration of zinc: plays a role in the regulation of growth and citrate accumulation





Nitrogen source: Usually ammonium sulphate or ammonium nitrate





Phosphate: key role in secondary metabolite production






Magnesium: as a cofactor in a number of enzyme reactions in the cell

Citric acid production.. HOW??


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 material 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

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 niger)
Mutagenic techniques have been successfully employed for the improvement of Aspergillus niger strains. With the help of gamma radiations several high citric acid producing strains of Aspergillus niger 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 niger
Genetic engineering of Aspergillus niger 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..

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 niger) 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..
a href="http://s824.photobucket.com/albums/zz168/citric-acid/?action=view¤t=citricacidproduction-1.jpg" target="_blank">









Places of citric acid production..

Companies that made citric acid
Major production capacity and consumption are in China, US and Western Europe so only certain companies from each of the countries are listed below:





China:
BBCA Group
Huansgi Xinghua Biochemical Co. Ltd
Shanghai Fenhe International Co.,Ltd.
Shandong Hongshide Chemical Industry Co., Ltd.
Yuhao Industry Group Co., Ltd.
Weifang Ensign Industry Co., Ltd
Jiali Bio Group
Shanxi Fenhe Biochemical Co.,Ltd
Hunan Dongting Citric Acid Chemicals Co., Ltd





US/ Western europe :
Jungbunzlauer
Tate & Lyle, Cargill
ADM
Citrique Belge
Alcan International Network U.S.A Inc.
Continental Chemical USA
Tri-Chem Industries, Inc
Thymly Products, Inc.
Coast Southwest, Inc




The annual production of citric acid is about 1,700,000 metric tons. The selling price of citric acid is increasing in the U.S which cost more than 57–58¢/lb now, due to the shortage.




Citric acid subsequently used for:


In the pharmaceutical industries, it can be metabolized as an alternate source of energy in the body and serves as a buffer. Sodium citrate can be used in blood transfusion and bacteriology.


In cosmetic industries, it is manufactured into stringent lotions due to its low pH .It is also used in hair and wig setting fluids.


Domestic uses,Citric acid is used as a greener alternative in place of phosphates in the manufacturing of detergents, as phosphates will give rise to eutrophication.


In industrial uses, it is used in electroplating, leather tanning and the removal of iron.


In food industry, use as preservatives, food acidulants and food flavourings in the manufacturing of soft drinks, jams, sweets etc.



Based on these technical and economic improvements, physiological and chemical properties, citric acid is today one of the most important organic foodstuff acids. World-wide production currently stands at 850,000 to 1,000,000 metric tons per year.






However~~~
Disadvantages??
Citric acid is commonly uses to add flavour in drink especially soft drinks. However, citric acid from the drinks eats away at the tooth’s enamel coating, causing softening and weakness causing erosive tooth. This may result in serious tooth damage or even tooth loss if not treated.


Citric acid has the ability to bond with other minerals make them useful in softening water. In shampoo, citric acid tends to remove excess minerals from the water. However, sometimes a high concentration of citric acid can damage hair by opening hair cuticles. This could strip the hair of needed minerals and bleach it.


Citric acid is a common ingredient in masks and some lotions. However, too much exposure to citric acid might cause mild skin irritation especially those people who have sensitive skin.

References:
http://www.made-in-china.com/manufacturers-exporters/c5q0nolimit/Citric_Acid_Anhydrous-1.html
http://www.alibaba.com/member/tschenhang.html
http://www.purchasing.com/article/213134-Citric_acid_pricing_pattern_due_for_upward_turn.php
http://www.mccroutons.com/products/wholegrain_ingredients_seasoned.htmlhttp://www.fao.org/docrep/w0076E/w0076ea9.jpg
http://www.vogelbusch-biocommodities.com/download/cn/vb_citricacid_technology_en.pdf
http://en.wikipedia.org/wiki/Citric_acid
http://www.wisegeek.com/what-is-citric-acid.htm
http://student.ccbcmd.edu/biotutorials/cellresp/cac.html
http://www.history.com/encyclopedia.do?articleId=205764
http://www.wiley.com/college/pratt/0471393878/student/animations/citric_acid_cycle/index.html
http://www.rossagri.ca/services/fertilizer

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