Self-assembled β-galactosidase on T4 phage capsid through affinity binding with enhanced activity and stability for rapid bacteria detection

Due to the highly efficient and specific catalysis, enzymes have been extensively applied in various fields. In the development of enzyme-based sensing devices, the immobilization of enzyme is critical for achieving superior performance which is drastically dependent on enzyme stability and activity. In this study, we construct and assemble the beta-galactosidase( β -gal)-Soc fusion proteins onto biologically produced nanoparticle – T4 phage in vitro as a specific sensing probe for the rapid colorimetric detection of Escherichia coli K12. The stability and substrate affinity of β -gal assembled on T4 phage were largely enhanced in comparison with that of free β -gal due to this affinity-based immobilization, and the assay based on this β -gal T4 phage was able to quantify bacteria at concentration of 10 3 cfu mL −1 in drink water within 2 h. This affinity binding based enzyme immobilization strategy employed T4 bacteriophage capsid as the supporting nanoparticle and exhibited enhanced enzyme activity and stability which are highly favored for the future development of sensing applications. • Bacteriophage T4 with assembled β -gal-Soc fusion protein on its capsid was designed and developed for bacteria detection. • The stability and substrate affinity of the β -gal T4 phage were significantly enhanced in comparison with that of free β -gal. • The detection system we developed can efficiently and specially capture E. coli K12 from complex background.