Encyclopedia of Amino Acids : Production methods of amino acids

Fermentation method

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Other production methods


	Currently, the amino acids used in amino acid products are mainly manufactured by the fermentation method using natural materials, similar to yogurt, beer, vinegar, miso(bean paste), soy sauce,etc.

The amino acid fermentation method is a method for the production of amino acids utilizing the phenomenon that microorganisms convert nutrients to various vital components necessary to themselves.
With the fermentation method, raw materials such as syrups are added to microorganism culture media, and the proliferating microorganisms are allowed to produce amino acids. It is enzymes that play an important role here. Enzymes, which are proteins to catalyze chemical reactions in the living body, are indispensable to degrade and synthesize substances. Consecutive reactions by 10 to 30 kinds of enzymes are involved in the process of fermentation, and various amino acids are produced as a result of these reactions.

In order to produce amino acids using microorganisms, it is important to find a microorganism with a high potential for producing amino acids. One gram of natural soil contains about 100 million microorganisms. From these a useful one can be picked out.
Once a microorganism suitable for the fermentation method has been selected, it is necessary to enhance its potential, that is, to make improvements to take full advantage of the potential of the organism.
Generally, microorganisms produce the 20 kinds of amino acids only in the amounts necessary to themselves. They have a mechanism for regulating the quantities and qualities of enzymes to yield amino acids only in the needed amounts. Therefore, it is necessary to release this regulatory mechanism in order to manufacture the target amino acid in large amounts.
The yield of an amino acid depends on the quantities and qualities of the enzymes. The yield increases if the enzymes involved in the production of the target amino acid are present in large quantities under workable conditions, while it decreases if the enzymes are present in small quantities. Suppose that a microorganism has a metabolic pathway A (a) B (b) C (c) D (a, b, and c are enzymes). In order to produce only amino acid C in large amounts, you have to enhance the actions only of enzymes a and b and to get rid of the action of enzyme c. Strains are improved using various techniques to make this process possible.
A fermentation tank is filled with syrups/sugars derived from sugar cane, corn, and cassava, and then fermentation conditions are set so that the stirring conditions, air supply, temperature, and pH are optimum. Finally, only the target amino acid is obtained from this fermented broth in high purity.

In addition to the fermentation method, the enzymatic reaction and extraction methods are used for producing amino acids.
With the enzymatic reaction method, an amino acid precursor is converted to the target amino acid using 1 or 2 enzymes. This enzyme method allows the conversion to a specific amino acid without microbial growth, thus eliminating the long process from glucose. This method comes into its own when the amino acid precursor is supplied at low prices.
With the extraction method, natural proteins are degraded to various amino acids, but the amount of each amino acid contained in the raw material proteins naturally restricts the yield.
The fermentation method has the advantage of mass production at low cost, which was the great impetus for expanding the amino acid market. The manufacturing method of glutamate shifted from the extraction method to the fermentation method in the 1960s. Subsequently, a similar shift to the fermentation method took place for the other amino acids in rapid succession.

Glutamate is produced the most.
Generally, amino acids can not be manufactured in quantities without deactivating the regulatory mechanism that microorganisms possess. However, the glutamate-producing microorganism has such a rare characteristic that glutamate can be produced solely by setting special fermentation conditions without improving the strain.
A fermentation tank is fed with raw materials such as syrup derived from sugar cane, and glutamate-producing micoroorganisms are fermented under the appropriate conditions. During this fermentation process, glutamate is excreted from the micoroorganisms into the fermented broth. This is how glutamate is obtained in large amounts.