Fig. 4. Biomass/lignin degradation screening with the P_LC biosensor system in E. coli BL21. Different lignin sources were submitted to treatment with three feruloyl esterase enzymes (CE1) or in the absence of enzyme and the supernatants were tested with the P_LC biosensor. The relative fluorescence to cell density (RFU/OD₆₀₀) is shown for the feedstock treatments, with the phosphate buffer alone or with ferulic acid at 100 mM. (* P < 0.05, *** P < 0.001, **** P < 0.0001 analyzed by one-way ANOVA followed by Tukey's multiple comparison test).