A Microbial Sensor Based on Pseudomonas putida for Phenol, Benzoic Acid and Their Monochlorinated Derivatives Which Can Be Used in Water and n-Hexane

Abstract

A microbial sensor for the detection of phenol, benzoic acid and their monochlorinated derivatives was developed. Detection was based on oxygen consumption in relation to analyte oxidation. To this end, induced cells of Pseudomonas putida DSM 548 were immobilized on Clark-type oxygen electrodes. The sensors were linear in their current signal up to a phenol concentration of 50 μM and had a detection limit of 0.1μM. Monochlorophenols could be detected at a concentration of 8 μM with a strong dependency on the growth substrate used for cell cultivation. Further variations in cell induction protocols resulted in microbial sensors with different selectivities. Using sensors equipped with cells grown on benzoic acid, this substance was detectable in the range of 2–16 μM, whereas 3- and 4-chlorobenzoic acid were detected at concentrations of 7 μM. The sensors were found to be stable under storage at 4°C for over 21 days. The use of n-hexane as a solvent increased the sensitivity for phenol five fold, the measurement frequency six fold, and operational stability was 7 hrs. Preliminary experiments using screen-printed thick film electrodes as disposable oxygen sensors resulted in a wider detection range from 6.3 μM to 90 μM phenol.