Enzyme microgels in packed-bed bioreactors with downstream amperometric detection using microfabricated interdigitated microsensor electrode arrays

In this article, we describe the use of pH-responsive hydrogels as matrices for the immobilization of two enzymes, glucose oxidase (GOx) and glutamate oxidase (GlutOx). Spherical hydrogel beads were prepared by inverse suspen sion polymerization and the enzymes were immobilized by either physical ent rapment or covalent immobilization within or on the hydrogel surface. Packe d-bed bioreactors were prepared containing the bioactive hydrogels and thes e incorporated into flow injection (Fl) systems for the quantitation of glu cose and monosodium glutamate (MSG) respectively. The Fl amperometric detec tor comprised a microfabricated Interdigitated array within a thin-layer fl ow cell. For the Fl manifold incorporating immobilized GOx, glucose respons e curves were found to be linear over the concentration range 1.8-280 my dL (-1) (0.1-15.5 mM) with a detection limit of 1.4 mg dL(-1) (0.08 mM). Up to 20 samples can be manually analyzed per hour, with the hydrogel-GOx biorea ctor exhibiting good within-day (0-19%) precision. The optimized Fl manifol d for MSG quantitation yielded a linear response range of up to 135 mg dL(- 1) (8 mM) with a detection limit of 3.38 mg dL(-1) (0.2 mM) and a throughpu t of 30 samples h(-1). Analysis of commercially produced soup samples gave a within-day precision of 3.6%. Bioreactors containing these two physically entrapped enzymes retained > 60% of their initial activities after a stora ge period of up to 1 year. (C) 2001 John Wiley & Sons, Inc.