Novel Lactate Biosensor for Use in Low Oxygen Conditions

Lactate is of interest in a variety of different industrial and biotechnological applications.  In Escherichia coli, the lldPRD operon is induced in the presence of L-lactate and is involved in lactate transport and metabolism.  The BioBrick standard assembly method was used to construct a whole cell lactate biosensor which contains a gene encoding a flavin mononucleotide-based fluorescent protein (FbFP) under the control of the lldPRD operon promoter.  The biosensor also contains the lldR regulatory gene which acts as a repressor in the absence of lactate, and an inducer in the presence of lactate.  To enable the biosensor to function in anaerobic conditions, the ArcA-P binding site on the lldPRD operon was modified to prevent repression of the operon, allowing the biosensor to function in both aerobic and anaerobic conditions.  The biosensor exhibited a concentration dependent response to lactate in the range of 0.05–5 mM lactate.  This biosensor could be used in low oxygen environments to detect lactate.  Due to the growing demand for lactate, this biosensor could play a valuable role in industrial processes.