Current biotechnological applications of L-amino acid deaminases for keto acids production

There is a growing interest in the pharmaceutical and agrochemicals industries for the use of enantiomerically-pure amino acids. α-keto acids are commonly used in feeds, food additives, pharmaceuticals, and chemical manufacturing. Commonly, most α-keto acids are manufactured by chemical synthesis, but due to the increasing concern for environment-friendly approaches, microbial fermentation and enzymatic transformation are alternative processes for the production of keto acids. Regarding this, L-amino acid deaminase (LAAD), is a major enzyme for α-keto acids production and is only found in Proteus bacteria. In this review, we discussed the recent biological applications of the enzyme LAAD in the production of keto acids, and summarized the recent advancements in the biological production of six important a-keto acids; specifically, phenylpyruvate, α-ketoglutaric acid, pyruvate, α-ketoisocaproate, α-keto-γ-methylthiobutyric acid and α, -ketoisovaleric acid.