Study of enzyme sensors with wide, adjustable measurement ranges for in-situ monitoring of biotechnological processes

We report on a study of enzymatic glucose and lactate sensors for measurements of wide concentration ranges from 1 mM up to 600 mM and 900 mM, respectively, in biotechnological processes. Diffusion-limiting polyurethane membranes were used to extend the linear measurement range and the influence of two fabrication parameters on membrane properties and sensor performance evaluated. The polymer concentration was varied between 4% and 10% and the ratio of the solvents tetrahydrofuran and dimethylformamide between 9:1 and 1:9. Surface morphology and permeability of the membranes and the linear measurement range of membrane-covered enzyme sensors were determined. A distinct relationship between the different results was found. The sensors retained their functionality after being sterilized using gamma and electron beam irradiation. The long-term performance of the sensors was evaluated and good performance in the glucose monitoring of a culture of Saccharomyces cerevisiae over 13 days was shown.