Application of Novel Sensors for Bioprocess On-Line Monitoring to Dextran Fermentation

An on-line monitoring system was developed for the measurement of various parameters such as cell concentration, viscosity of broth and sucrose concentration in dextran fermentation. This system was constructed from a piezoelectric gum sensor, a quartz crystal viscous sensor, a sucrose sensor, a bioreactor and a personal computer. A piezoelectric gum sensor for the determination of biomass was prepared with two piezoelectric gums, a pulse generator and an amplifier. The calibration curve for L. mesenteroides was linear in the range of 1.0-4.8 g dry cell mass·l^-1. A quartz crystal viscous sensor was prepared with AT-cut quartz crystal, an oscillating circuit and a peak level meter. A linear relationship was obtained between resonant resistance (R₁) of the quartz crystal and (ρη)^1/2 of dextran solution, where ρ and η were density and viscosity respectively. A sucrose sensor was prepared with three immobilized enzyme layers (glucose oxidase, mutarotase and invertase) and a gold working electrode. The calibration curve for sucrose was linear up to 1000 mg·l^-1. An on-line monitoring system was applied to dextran fermentation, and these paramenters were measured. Good correlation was obtained between the sensor signals and the values determined by conventional methods.