FIG. 3.

Protocol for the GFP fluorescence assay for nisin with the indicator strain L. lactis LAC240. A LAC240 inoculum is supplemented with a sample and grown overnight at 30°C on a microplate. Prior to measurement the supernatant is removed, and the cells are frozen and thawed. The fluorescence is expressed in RFU as determined with a fluorometer; the excitation light is red (λ = 485 nm), and the emission light is green (λ = 538 nm).