L-Lysine Fermentation

Savas      Anastassiadis

Abstract

Amino acids are the basic bioelements of proteins, which are the most important macromolecules for the functions of humans and animals. Out of the 20 L-amino acids, ecumenically found in most of living organisms, L-lysine is one of the 9 amino acids which are essential for human and animal nutrition. L-lysine is useful as medicament, chemical agent, food material (food industry) and feed additive (animal food). Its demand has been steadily increasing in recent years and several hundred thousands tones of L-lysine (about 800,000 tones/year) are annually produced worldwide almost by microbial fermentation. The stereospecificity of amino acids (the L isomer) makes the fermentation advantageous compared with synthetic processes. Mutant auxotrophic or resistant to certain chemicals strains of so-called gram positive coryneform bacteria are generally used, including the genera Brevibacterium and Corynebacterium, united to the genus. The significance of Research and Development increased rapidly since the discovery of fermentative amino acid production in the fifties (S. Kinoshita et al., Proceedings of the International Symposium on Enzyme Chemistry 2:464-468 (1957)), leading to innovative fermentation processes which replaced the classical manufacturing methods of L-lysine like acid hydrolysis. L-Lysine is separated and purified by suitable downstream processes involving classical separation or extraction methods (ultrafiltration or centrifugation, separation or ion exchange extraction, crystallization, drying) and is sold as a powder. Alternatively, spray dried pellets or liquid fermentation broth can be used as animal feed supplement. On behalf of todays strong competition in amino acid industry, Biotechnology companies are continuously aiming in innovative research developments and use complex management concepts and business strategies, towards gaining market leadership in the field of amino acid production.

Keywords: L-Lysine production, amino acids, corynebacteria, strain development, mutagenesis, fermentation, downstream process, ion exchange chromatography, recombinant DNA, feed additive