“…For example, online monitoring of green fluorescence protein (GFP) fluorescence to determine recombinant product concentration (Randers-Eichhorn et al, 1997), and online monitoring of firefly luciferase to track intracellular ATP concentration (Lasko and Wang, 1996) have been reported. In the case of GFP, green fluorescence could be monitored online and/or in vivo during fermentation to indicate product level (Albano et al, 1996(Albano et al, , 1998Cha et al, 1997Cha et al, , 1999aDeLisa et al, 1999c;Randers-Eichhorn et al, 1997). Because GFP fluorescence was used to monitor production of a model recombinant protein (CAT) during both low-and high-celldensity cultivations of E. coli (DeLisa et al, 1999c), it was suggested that GFP fluorescence could serve as a sensor for taking a process control action.…”