L-tryptophan is an essential amino acid for human body, which is widely used in food, medicine, feed production and other industries. At present, most of the engineering strains for the production of L-tryptophan by biological fermentation are Escherichia coli and Corynebacterium glutamate, which are mainly obtained by rational methods such as metabolic engineering and synthetic biology. However, due to the long metabolic pathway, complex and unclear regulation mechanism of L-tryptophan in microbial cells, the production efficiency of the production strain is still low, so it is necessary to improve the production capacity of the strain by means of adaptive evolution.

In order to construct a strain for efficient production of L-tryptophan, the researchers adopted traditional mutation breeding and a variety of metabolic engineering strategies to optimize the strain according to the main factors restricting the synthesis of L-tryptophan. At present, a series of fruitful results have been achieved.

Adaptive evolution improves the performance of L-tryptophan producing strains

At present, an important factor limiting the production level of L-tryptophan by direct fermentation is that the excessive accumulation of L-tryptophan in cells will produce physiological toxicity to cells. therefore, improving the tolerance of the strain to high concentration of L-tryptophan is of great significance to the fermentation production of L-tryptophan.

Traditional adaptive evolution

Adaptive evolution is a method that combines artificial selection pressure and simulates the compilation and selection process in natural evolution to achieve directional evolution of microorganisms under laboratory conditions to select individuals with excellent traits from the evolved population.

Biosensor binding

Biosensor is a widely used element in synthetic biology, which can adjust the expression of downstream genes by sensing the concentration of the corresponding substances. By combining the original parts of synthetic biology with adaptive evolution, it is beneficial for cells to express specific traits of different intensity according to the difference of intracellular tryptophan concentration, so as to provide conditions for efficient screening.

At present, a large number of attempts have been made to transform tryptophan-producing strains of Escherichia coli and Corynebacterium glutamicum, and certain results have been achieved. However, due to the unclear tolerance mechanism of strains to high concentrations of L-tryptophan, it is still not possible to better Relieving the physiological toxicity of L-tryptophan to strains, resulting in low production intensity and poor robustness of production strains, is the main difficulty encountered in the industrial large-scale production of L-tryptophan today. Although adaptive evolution is highly practical, it suffers from problems such as long time required and large labor force. Therefore, the method of combining biosensors with adaptive evolution can effectively improve the efficiency of evolution, thereby conducting in-depth research on the L-tryptophan tolerance mechanism of the production strain, reducing the toxic effects of L-tryptophan, and finding ways to use L-tryptophan Methods to efficiently expel bacterial cells will promote the further development of rational metabolic transformation.