Accepted_test

The presented study is devoted to the analysis of the reasons for the instability of the level of L-valine production in a superproducer of this amino acid, constructed on the basis of Corynebacteruim glutamicum. It has been established that the decrease in production occurs due to spontaneous mutations leading to complete or partial inactivation of the key enzyme of valine biosynthesis – acetolactate synthase. The influence of these mutations on the structure of the enzyme and the properties of cells was analyzed. It is assumed that inactivation of acetolactate synthase leads to the redirection of metabolic flows from the biosynthesis of L-valine to other processes. As a result, the rate of cell growth and their accumulation in culture increases. It was concluded that a necessary measure to maintain the productivity of the strain at a high level is to control the activity of acetolactate synthase in the inoculum.