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. 2022 Mar 18;10:838732. doi: 10.3389/fbioe.2022.838732

FIGURE 4.

FIGURE 4

Optimization of biosensor’s sensitivity and operational range. (A) Schematic presentation of strategies employed to optimize the biosensor. The ABC transporter Pdr12p is known to regulate the intracellular level of weak organic acids by export. To improve the biosensor’s sensitivity, an ABC transporter gene PDR12 was deleted to increase the intracellular SBCFA level (TDL-SLCA), which will increase the fluorescence. To extend the biosensor’s operational range, PDR12 was over-expressed under the control of a strong constitutive promoter pTEF1 to reduce the intracellular SBCFA level (TOE-SLCA) through SBCFA export, which will enhance the SBCFA saturation level. (B) Dose-dependent responses of biosensors against IVA fed at 0.5, 2, 5, 10, and 25 mM. Their responses (fold change) were compared to control BY4741-SLCA. Fluorescence was measured after a 5-h incubation with IVA. Values are the means of three independent experiments, and an error bar represents a standard deviation of three independent experiments.