Abstract: A bacterial pure culture of Alcaligenos eutrophus KT02 was immobilized and integrated as a sensor in an amperometrical flow-through system ('dynamic microbial sensor'). The sensor showed characteristic time dependent responses in oxygen consumption for different pure organic analytes. Chemometrical data analysis revealed that the responses are additive and linear concerning single analytes and mixtures, Simultaneous multicomponent analysis of a binary mixture of acetate and gluconate was realized by using only a single dynamic microbial sensor.

Abstract: An amperometric biosensor based on immobilized bacterial cells of Alcaligenes eutrophus KT02 and an oxygen electrode was integrated in a now-through system. Because microorganisms metabolize various organic analytes in a specific manner, the sensor shows for different pure analytes distinct time-dependent oxygen consumption rates that can be treated as characteristic patterns. This behavior is conserved also when the biosensor is exposed to a mixture of these organic analytes; the sensor with a particular type of microorganisms responds with a total signal. The respiration curves as time-dependent amplitudes were subdivided into several time channels. This procedure creates an additional data dimension and makes the single sensor dynamic. Using multivariate calibration models with only one single biosensor, simultaneous quantitative analysis of ternary mixtures of acetate, L-lactate, and succinate was realized. A nonlinear algorithm that compensated for conceivable interactions of the analytes was superior to a partial least-squares algorithm. Each analyte was predicted more precisely by the nonlinear approach resulting in root-mean-square errors of prediction of 0.20 mg/L for acetate, 0.43 mg/L for L-lactate, and 0.73 mg/L for succinate.

Abstract: A biosensor consisting of Alcaligenes eutrophus micro-organisms immobilized on to a Clark-type O2 sensor was used in a FIA system for the analysis of binary mixture of gluconate/acetate and L-serine/L-threonine. The determination was based on the increased respiratory activity of the microbial cells in the presence of the analytes. The biosensor was fabricated by immobilizing the microbial cells within a polyurethane hydrogel and sandwiching this material between an inner polyethylene membrane and an outer capillary pore membrane (0.6 µm pore diameter; 10 µm thick) attached to the O2 electrode. The FIA system was operated with an alternating flow (100 ml/h) of 50 mM Tris-hydrochloride buffer of pH 7.2 and the sample in the same buffer. The O2 electrode vs. Pt cathode and Ag/AgCl reference electrode was polarized at -800 mV. Transient signals for the analyte mixtures were obtained by allowing the sample streams to flow for 25 or 30 s. The experimental data was analyzed by partial least squares using the software package ICB-PLS. The system was calibrated using a standard containing up to 40 mg/l gluconate/10 mg/l acetate and 10 mg/l L-serine/15 mg/l L-threonine. The root mean square errors of prediction for gluconate, acetate, L-serine and L-threonine were 1.67, 0.51, 0.85 and 1.31 mg/l, respectively.