Identification, characterization, and application of a highly sensitive lactam biosensor fromPseudomonas putida

Caprolactam is an important polymer precursor to nylon traditionally derived from petroleum and produced on a scale of 5 million tons per year. Current biological pathways for the production of caprolactam are inefficient with titers not exceeding 2 mg/L, necessitating novel pathways for its production. As development of novel metabolic routes often require thousands of designs and result in low product titers, a highly sensitive biosensor for the final product has the potential to rapidly speed up development times. Here we report a highly sensitive biosensor for valerolactam and caprolactam fromPseudomonas putidaKT2440 which is >1000x more sensitive to exogenous ligand than previously reported sensors. Manipulating the expression of the sensoroplR(PP_3516) substantially altered the sensing parameters, with various vectors showing Kdvalues ranging from 700 nM (79.1 μg/L) to 1.2 mM (135.6 mg/L). Our most sensitive construct was able to detectin vivoproduction of caprolactam above background at ~6 μg/L. The high sensitivity and range of OplR is a powerful tool towards the development of novel routes to the biological synthesis of caprolactam.