Development of a composite graphene-Prussian blue-chitosan sensor for monitoring peroxide within Lactobacillus johnsonii DSM 10533 cultures

The design and application of a composite sensor for monitoring bacterial peroxide originating from Lactobacillus johnsonii DSM 10533 is described. The sensor format is based on the co-deposition of Prussian blue and chitosan onto a laser-induced graphene substrate to yield a highly sensitive system capable of monitoring peroxide with bacterial culture over the range 20 µM to 1 mM with a sensitivity of 122 mA/mM and detection limit of 30 mM. Amperometric detection of H2O2 at − 0.036 V vs Ag/AgCl was achieved allowing selectivity in complex media. The miniature nature of the sensor enabled a detection volume of 200 µL and gave a response in 20 s, and the samples required no dilution or reagent addition. The ability to rapidly prototype LIG-PB-CS integrated electrode assemblies provides a facile route for the production of sensors capable of monitoring lactobacilli interactions at small scales and within batch-level fermentation reactors.