Hello,
The microplate reader and the chi.bio fluorescence work in different ways. In short, the Chi.Bio one has an array of photodiodes with various filters each of which admits something like a ~30nm band of light. Consequently if there is lots of background fluorescence / media autofluorescence it can leak into this band and wash out your measurement. In contrast plate readers usually have a diffraction grating type spectrometer which allows you to look at narrower wavelength bands.
The answer to this is, as in the manual, you should use non-fluorescencent media (e.g. M9) rather than LB which is massively autofluorescence. If you do use such media then you should be able to detect fairly small fluorescence signals, particularly if they are time changing. But if not, it will be very difficult to distinguish small fluorescence signals in LB.
I should also say, the whole point of the turbidostat system is that you can measure time changing fluorescence, and it is MUCH better at this than trying to compare various batch growth curves (e.g. without pumping) in which the dynamics of growth mess with your fluorescence. Doing batch growth is difficult in such a large volume since it inevitably leads to larger inter-experiement variation (e.g. due to media/growth/optics inhomogeneity) than small volumes, and this is why we recommend inducing things DURING experiments rather than before with Chi.Bio, as you then get much higher quality data. I.e. you put your biosensor in, grow it to exponential phase for a while, then add inducer chemical, then see how it responds over time – gives you great data w.r.t dynamic and absolute response levels.
Another note in this direction is that the system is designed to return fluorescence per cell, rather than absolute fluorescence (as in a plate reader). So, the output it gives in the UI is more like a plate reader if you calculate fluorescence/OD.
.
