Microbial biosensor array with transport mutants of Escherichia coli K12 for the simultaneous determination of mono-and disaccharides.

An automated flow-injection system with an integrated biosensor array using bacterial cells for the selective and simultaneous determination various mono- and disaccharides is described. The selectivity of the individually addressable sensors of the array was achieved by the combination of the metabolic response, measured as the O(2) consumption, of bacterial mutants of Escherichia coli K12 lacking different transport systems for individual carbohydrates. Kappa-carrageenan was used as immobilization matrix for entrapment of the bacterial cells in front of 6 individually addressable working electrodes of a screen-printed sensor array. The local consumption of molecular oxygen caused by the metabolic activity of the immobilized cells was amperometrically determined at the underlying screen-printed gold electrodes at a working potential of -600 mV vs. Ag/AgCl. Addition of mono- or disaccharides for which functional transport systems exist in the used transport mutant strains of E. coli K12 leads to an enhanced metabolic activity of the immobilized bacterial cells and to a concomitant depletion of oxygen at the electrode. Parallel determination of fructose, glucose, and sucrose was performed demonstrating the high selectivity of the proposed analytical system.