Amino acids are important biomaterials for the food, chemical, pharmaceutical, and cosmetic industries. The world market for amino acids is steadily growing and predicted to go over US$ 10 billion within a few years. Of the twenty proteogenic amino acids, essential amino acids, such as lysine, methionine, threonine, and tryptophan which are not synthesized in animals, constitute a major end-use market as feed additives with the largest share of the total amino acid market. Glutamic acid, a sodium salt of which (mono-sodium glutamate) is extensively used in food as a flavour-enhancer, has the largest production amounting to approximately two million tons per year. Amino acid fermentation was triggered in 1957 by the discovery of the soil bacterium, Corynebacterium glutamicum, which produces large amounts of glutamic acid in culture medium. Since then, efforts to produce various amino acids by microbial fermentation resulted in the development of cost-effective strains with extremely high productivity. The early strategies for obtaining such a high producer strain were based on mutagenesis and screening, called metabolic engineering, which lead to changes in metabolic flow toward a certain amino acid of interest mainly by deregulation of the amino acid biosynthetic pathway. As a next step, genetic engineering has been employed recombinant DNA techniques to improve productivity by cloning a gene that encodes a rate-limiting enzyme along the biosynthetic pathway of the amino acid, or by introducing beneficial mutant alleles into the chromosome of a wild-type background strain.[Seryoung K, Yoneyama H (2013) Amino Acid Exporter: A Tool for the Next-Generation Microbial Fermentation]
Last date updated on March, 2024