In this study, an E. coli biosensor based on modular green fluorescent protein and luxI/IuxR cycle amplification circuit was constructed for sensitive detection of bioavailable lysine. The results indicated that the luxI/IuxR positive feedback circuit based on quorum sensing can be used as a signal amplifier to improve the sensitivity to lysine detection with the detection limit of 256 nM. The presented method was more sensitive than the previously reported whole-cell fluorescent microbial biosensors. In addition, the developed E. coli biosensor was specific for lysine detection, and other amino acids and proteins did not cause any interference. The constructed genetic engineered biosensor was accurate for lysine detection, the lysine content of 6.87 ± 0.36% in tryptone was successfully measured, and after adding 10, 30, and 50 μM lysine in tryptone, the recoveries of 109.98 ± 10.44%, 103.88 ± 7.66%, and 105.89 ± 6.34% were obtained, respectively. Furthermore, as the design of the genetic engineered biosensor is modular, it can conceivably be utilized as a component in the design of more complex synthetic gene circuits without any changes to the amplifier and reporter system.

Graphical abstract