[Development of biosensors highly responsive to -acetylneuraminic acid in ].

is recognized as a generally-regarded-as-safe strain, and has been widely used in the biosynthesis of high value-added products, including -acetylneuraminic acid (NeuAc) which is widely used as a nutraceutical and a pharmaceutical intermediate. Biosensors responding to target products are widely used in dynamic regulation and high-throughput screening in metabolic engineering to improve the efficiency of biosynthesis. However, . lacks biosensors that can efficiently respond to NeuAc. This study first tested and optimized the transport capacity of NeuAc transporters, and obtained a series of strains with different transport capacities for testing NeuAc-responsive biosensors. Subsequently, the binding site sequence of Bbr_NanR responding to NeuAc was inserted into different sites of the constitutive promoter of . , and active hybrid promoters were obtained. Next, by introducing and optimizing the expression of Bbr_NanR in . with NeuAc transport capacity, we obtained an NeuAc-responsive biosensor with wide dynamic range and higher activation fold. Among them, P535-N2 can sensitively respond to changes in intracellular NeuAc concentration, with the largest dynamic range (180-20 245) AU/. P566-N2 shows a 122-fold of activation, which is 2 times of the reported NeuAc-responsive biosensor in . . The NeuAc-responsive biosensor developed in this study can be used to screen enzyme mutants and . strains with high NeuAc production efficiency, providing an efficient and sensitive analysis and regulation tool for biosynthesis of NeuAc in . .