[Directed evolution of maltose induced promoters with expanded gradient intensity]

Promoters with different sensitivity and response intensity are useful tools in gene expression regulation and metabolic engineering. Maltose induced promoter P_glvc was engineered to obtain promoters with different induced expression intensities. A promoter P_glvc mutant library was built by error-prone PCR, and screened by a growth-associated method using tetracycline resistance as an indicator. A library of promoter mutants with different sensitivity and intensity was obtained, and the maltose-induced response threshold range of promoter mutants (MT2, MT3, MT4, MT6) was extended from 0-3 g/L to 0-15 g/L. Among them, the highest induced expression intensity (MT8) was about 3.15 times higher than that of the original promoter for eGFP expression, which would be useful for its application in metabolic engineering and synthetic biology.