A D,L-lactate biosensor based on allosteric transcription factor LldR and amplified luminescent proximity homogeneous assay

Lactate, a hydroxycarboxylic acid commercially produced by microbial fermentation, is widely applied in diverse industrial fields. Lactate exists in two stereoisomeric forms (D-lactate and L-lactate). D-Lactate and L-lactate are often simultaneously present in many biological samples. Therefore, a biosensor able to detect both D- and Llactate is required but previously unavailable. Herein, an allosteric transcription factor LldR from Pseudomonas aeruginosa PAO1, which responds to both D-lactate and L-lactate, was combined with amplified luminescent proximity homogeneous assay technology to develop a D,L-lactate biosensor. The proposed biosensor was optimized by mutation of DNA sequence in binding site of LldR. The optimized biosensor BLac-6 can accurately detect the concentration of lactate independent on ratio of the two isomers in pending test samples. The biosensor was also tentatively used in quantitative analysis of D-lactate, L-lactate, or D,L-lactate in fermentation samples produced by three recombinant strains of Klebsiella oxytoca. With its desirable properties, the biosensor BLac-6 may be a potential choice for monitoring the concentration of lactate during industrial fermentation.

Automated summary

A biosensor capable of detecting both D-lactate and L-lactate was developed in this study, using an allosteric transcription factor LldR and amplified luminescent proximity homogeneous assay technology. The optimized biosensor, BLac-6, showed high accuracy in lactate concentration detection and was tentatively applied in industrial fermentation.