Lysine Industrial Uses and Production

Abstract

l-Lysine belongs to the essential amino acids that cannot be synthesized by higher animals and humans. It is an essential ingredient for growth of animals and must therefore be available in animal feed to meet the nutritional requirements and to ensure a balanced diet. l-Lysine is widely used as feed supplement for poultry, swine, and other livestock and is also used in pharmaceuticals, dietary supplements, and cosmetics. Therefore, l-lysine is a biotechnological product of considerable economic importance, and the worldwide production was recently estimated to be above 2 million tons per year. Most bacteria can synthesize l-lysine, and industrial production of l-lysine is almost entirely by microbial fermentation. The most important industrial l-lysine producer is the bacterium Corynebacterium glutamicum, and several decades of extensive research has resulted in a detailed insight into its physiology, biochemistry, and genetics. This knowledge has been used to generate efficient l-lysine-overproducing strains by systems-level metabolic engineering. Along with these metabolic engineering strategies, fermentation technology and downstream processes are constantly being optimized. The carbon sources for C. glutamicum fermentations are sugars from agricultural crops. In recent years, alternatives to sugars, such as lignocelluloses and methanol, have gained increased interest. Alternative approaches including extending the substrate range by genetic engineering, as well as adopting methylotrophic bacteria for l-lysine production, will be discussed.