Ways of increasing the efficiency of technologies for the synthesis of microbial exopolysaccharides. Part 2. Improvement of producer strains by methods of metabolic and genetic engineering

Abstract

In recent decades, methods of metabolic and genetic engineering have been used to increase synthesis indicators, as well as to regulate the composition and functional characteristics of microbial exopolysaccharides. Metabolic engineering techniques are used to analyze the producer’s metabolic pathways, determine potential limiting reactions ("bottlenecks" of metabolism) and their impact on the synthesis of the final product, followed by the use of genetic engineering tools to eliminate these limitations. One of the strategies to increase exopolysaccharides synthesis indicators is to direct metabolism to the biosynthesis of the final product by eliminating competing metabolic pathways. Quite often, the "bottleneck" of polysaccharides synthesis is an insufficient level of nucleoside diphosphate saccharides. That’s why another approach to intensifying biosynthesis is to increase the pool of nucleoside diphosphate derivatives in producer cells. Increasing the expression of key genes of polysaccharide biosynthesis allows to increase exopolysaccharides synthesis indicators several times. The use of genetic engineering methods also makes it possible to design producers with a full cycle of synthesis of practically valuable biopolymers that are not characteristic of them. The analyzed literature data on the improvement of microbial polysaccharides producers by methods of metabolic and genetic engineering indicate that the synthesis indicators of the final product by recombinant microorganisms are 2—20 times higher than the original strains. In addition, recombinant producers are able to synthesize polysaccharides of different composition and molecular weight, which allow to regulate their rheological properties depending on the field of practical application.