Construction of nisin whole-cell biosensors

Abstract:

[Background] Nisin is a small antibacterial peptide mainly produced by Lactococcus lactis. It is the only natural food preservative approved for wide applications. However, its low biosynthesis yield, and lack of simple and efficient detection methods limit its research and applications. [Objective] To develop a simple and efficient method to detect nisin, the nisin controlled gene expression (NICE) system and a visible red fluorescent protein were adopted for construction of a whole-cell nisin biosensor. The biosensor was used to quickly screen for nisin-producing candidate strains. [Methods] A Golden-Gate cloning method was used to construct a vector which contains a nisin-inducible promoter (Pnis) for regulating a red fluorescent protein gene (rfp). Two rfp genes, identical in protein sequences but different in DNA sequences, were tested. The constructed biosensor plasmids were transferred into Lactococcus lactis, generating the whole-cell nisin biosensors and further used for the screening. [Results] Both of the two whole-cell nisin biosensors could specifically and quantitatively respond to nisin varied from 2 to 200 ng/mL. Moreover, the biosensor was applied to screen candidate strains and identified a nisin-producing strain Lactococcus lactis ATCC 11454. [Conclusion] The developed whole-cell nisin biosensor can specifically respond to nisin, and can be used to simply and quickly identify nisin-producing strains.