Monitoring of dihydroxyacetone production during oxidation of glycerol by immobilized Gluconobacter oxydans cells with an enzyme biosensor

A bi-enzymatic biosensor for monitoring of dihydroxyacetone production duri ng oxidation of glycerol by bacterial cells of Gluconobacter oxydans is pre sented. Galactose oxidase oxidizes dihydroxyacetone efficiently producing h ydrogen peroxide, which reacts with co-immobilized peroxidase and ferrocene pre-adsorbed on graphite electrode. This mediator-based bi-enzymatic biose nsor possesses very high sensitivity (4.7 muA/mM in phosphate buffer), low detection limit (0.8 muM, signal/noise = 3), short response time (22 s, 95% of steady-state) and broad linear range (0.002-0.55 mM in phosphate buffer ). The effect of pH, temperature, type of buffer, as well as different stab ilizers (combinations of a polyelectrolyte and a polyol) on the sensor perf ormance were carefully optimized and discussed. Dihydroxyacetone produced d uring a batch conversion of glycerol by the pectate-immobilized bacteria in an air-lift reactor was determined by the biosensor and by reference spect rophotometric method. Both methods were compared and were in a very good co rrelation. The main advantage of the biosensor is a very short time needed for sample analysis (less than 1 min). (C) 2001 Elsevier Science Inc. All r ights reserved.