Commercial Production of Citric Acid

Citric acid is a weak organic acid with the chemical formula of C6H8O7, which is produced annually by more than two million tons in the world.

The production of organic acids due to their wide uses in various industries has long been studied. Among the organic acids used is citric acid, which due to its nontoxicity, good acidity, and buffer ability, has several uses in cosmetics, pharmaceuticals, food, and other industries.

How is Citric Acid Produced:

One way to the Production of citric acid is to extract it from citrus and sour fruits. But this method has no economic and time justification and is not used at the macro level.

Microbial Production of Citric Acid:

Solid State:

This method was used for the first time in 1920, but with the use of the immersion method (due to the method of executive and more suitable production efficiency), the method of surface culture is typically second.

The discovery of citrate accumulation by Aspergillus niger led to the rapid development of the fermentation process, and today a large part of the global production of citric acid is done using this process. The most important characteristics of this process are the use of cheap raw materials and high efficiency.

Submerged:

In this method, a substrate or liquid culture medium is used for the growth and development of the fungus under controlled conditions. Since 1940, the immersion culture method for the production of citric acid in industrialized countries has developed a lot. For reasons such as higher yields than surface culture, less time for microbial growth, ease of operation due to the presence of automatic devices and continuous and precise controllers, and as a result more convenience in the entry and exit of substrate and product, this the method has become more popular.

Production of Citric Acid through Chemical Reactions:

Citric acid was first synthesized by Grimaux and Adam in 1880 using glycerol as a chemical starting material, but this method was not economically viable compared to other production routes such as fermentation.

Production through Natural:

The method of extracting citric acid from lemon juice was done in 1784 by a Swedish chemist, Karl Wilhelm Shell. This method maintained its monopoly as the only commercial source for citric acid production until the late nineteenth century.

Effective Parameters in the Production of Citric Acid:

PH:

pH is an important factor in the synthesis of chemicals that varies according to metabolic microbial activity. The most obvious reason for these fluctuations in the production of organic acids such as citric, acetic, or lactic acids, which lower the pH during the process. In addition, changes in pH are highly dependent on the activity of microorganisms.

Aeration:

It has been shown that aeration has a special effect on citric acid fermentation. Increasing aeration rate leads to an increase in yield and reduced fermentation time. As a result, this factor should always be controlled during synthesis. It is important to maintain oxygen concentration over 25% saturation. An interruption in oxygenation for synthesis is very harmful.

Aeration is performed during the entire fermentation process with 0.5 to 1.5 volts. However, for economic reasons, it is usually preferred to start with a low aeration speed (0.1 to 0.4 volts). High aeration speed, especially in phase formation, leads to large amounts of floors. Therefore, to deal with this problem, adding foaming agents is essential.

The Share of Citric Acid Production in the World:

It is not bad to know that the largest share of citric acid production belongs to European countries.  After Europe, the largest producers of citric acid in the world are the United States and China.

Given the low price of citric acid supplied to the world market by China, it can be said that China has been able to compete very well with other producers of this acid, and by eliminating some competitors, a significant share in this field to allocate.