In this article we will discuss about:- 1. History of Glutamic Acid 2. Commercial Production of Glutamic Acid 3. Uses.
History of Glutamic Acid:
The history of the first amino acid production dates back to 1908 when Dr. K. Ikeda, a chemist in Japan, isolated glutamic acid from kelp, a marine alga, after acid hydrolysis and fractionation. He also discovered that glutamic acid, after neutralization with castic soda, developed an entirely new, delicious taste.
This was the birth of the use of monosodium glutamate (MSG) as a flavour-enhancing compound. The breakthrough in the production of MSG was the isolation of a specific soil-inhabiting gram-positive bacterium, Corynebacterium glutamicum, by Dr. S. Ukada and Dr. S. Kinoshita in 1957. The successful commercialization of monosodium glutamate (MSG) with this bacterium provided a big boost for amino acid production and later with other bacteria like E. coli as well.
Commercial Production of Glutamic Acid:
Glutamic acid commercial production (Fig. 40.6) by microbial fermentation provides 90% of world’s total demand, and remaining 10% is met through chemical methods. For the actual fermentation the microbial strains are grown in fermentors as large as 500 m3. The raw materials used include carbohydrate (glucose, molasses, sucrose, etc.), peptone, inorganic salts and biotin.
Biotin concentration in the fermentation medium has a significant influence on the yield of glutamic acid. Fermentation completes within 2-4 days and, at the end of the fermentation, the broth contains glutamic acid in the form of its ammonium salt.
In a typical downstream process, the bacterial cells are separated and the broth is passed through a basic anion exchange resin. Glutamic acid anions get bound to the resin and ammonia is released. This ammonia can be recovered via distillation and reused in the fermentation.
Elution is performed with NaOH to directly form monosodium glutamate (MSG) in the solution and to regenerate the basic anion exchanger. From the elute, MSG may be crystallized directly followed by further conditioning steps like decolourization and serving to yield a food-grade quality of MSG.
α-ketoglutaric acid serves as the precursor of glutamic acid and the conversion of the α- ketoglutaric acid to glutamic acid occurs in presence of enzyme glutamic acid dehydrogenase. It has been found that if penicillin is added in he medium, the glutamic acid production can be increased manifold.
Uses of Glutamic Acid:
As stated earlier, glutamic acid is widely used in the production of monosodium glutamate (MSG) which is commonly known as the ‘seasoning salt’. The world production of glutamic acid is to the tune of 800,000 tonnes/year. Monosodium glutamate is condiment and flavour-enhancing agent, it finds its greatest use as a common ingredient in convenient food-stuffs.
Lysine:
In recent years, a ‘single state’ fermentation process is being used for the commercial production of lysine. This process has replaced the “two-stage” fermentation process of lysine production in which Escherichia coli was used to produce diammopimelic acid (DAP) in the first stage, and Enterobacter aerogenes was used for the formation of lysine from diaminopimelic acid through decarboxylation by an enzyme called diaminopimelic decarboxylase (DAP-decarboxylasc) in the second stage.
The ‘single-stage’ process of fermentation of lysine involves mutants of Carynebacterium, Brevibacterium, etc. These bacteria are grown in a synthetic medium containing carbohydrate (glucose), an inorganic nitrogen source, small concentration of homoserine or methionine, and small concentration of biotin. The process of fermentation is completed within 48-70 hours and the yield of the amino acid is as high as 30 gm/litre.
Use:
Lysine is a vital amino acid for humans. Since cereal proteins are often deficient in lysine, it is generally used as a supplement for nutritional requirement such as bread and other food stuffs for human being.
