Quorum Sensing Systems Engineering for Enhanced iso-Butylamine Production in Escherichia coli

Quorum sensing (QS), characterized by pathway-independence and autonomous control, has been applied in bio-manufacturing, while the lack of versatile and functional regulatory components limits its broader applications. To address this issue, a series of efficient QS systems with diverse properties were established in Escherichia coli. Firstly, combinatorial optimization, including element selection and promoter replacement, led to an improvement of 8.82- and 3.03-fold in output range and response threshold, respectively. Then, a library of LuxR mutants was constructed for screening novel variants with decreased sensitivity to acyl-homoserine lactone through the high-throughput screening technique. Notably, the optimal variant V36E/H89L/P97L exhibited a decrease of 266-fold in the sensitivity. As a proof-of-concept, iso-butylamine biosynthesis was tested by re-directing pyruvate catabolism using QS circuits, and in particular, a total of 15.4 g/L iso-butylamine was generated in strain IB21 during the fed-batch culture, marking a 2.96-fold increase over the static control. Finally, the generated bioproduct reached 44.23 g/L in a bioreactor, representing the highest reported titer so far. In summary, this study not only enriches the genetic toolbox of QS systems, but also facilitates industrial applications in value-added chemical production.