Application of electrochemical optical waveguide lightmode spectroscopy for studying the effect of different stress factors on lactic acid bacteria

Electrochemical optical waveguide lightmode spectroscopy (EC-OWLS) has been developed to combine evanescent-field optical sensing with electrochemical control of surface adsorption processes. For bioanalytical sensing, a layer of indium tin oxide (ITO) served as both a high-refractive index waveguide and a conductive electrode. In addition, an electrochemical flow-through fluid cuvette was applied, which incorporated working, reference, and counter electrodes, and was compatible with the constraints of optical sensing. The subject of our study was to monitor how the different stress factors (lactic acid, acetic acid and hydrogen peroxide) influence the survival of lactic acid bacteria. The advantage of EC-OWLS technique is that we could carry out kinetic studies on the behaviour of bacteria under stress conditions, and after exposure of lactobacilli to acid and oxidative stress we get faster results about the status of bacteria compared to the traditional quantitative methods. After optimization of the polarization potential used, calibration curve was determined and the sensor response of different rate of living and damaged cells was studied. The bacterial cells were adsorbed in native form on the surface of the sensor by ensuring polarizing potential (I V) and were exposed to different concentration of acetic acid and hydrogen peroxide solution to 1h, respectively and the behaviour of bacteria was monitored. Results were compared to traditional micro-assay method. (c) 2006 Elsevier B.V. All rights reserved.