2.8. Immobilization of microorganisms in gel based on PVA
modified by N-vinylpyrrolidone
To prepare PVA modified by N-vinylpyrrolidone, an aqueous solution of cerium ammonium nitrate (NH4)2Ce(NO3)6 and
N-vinylpyrrolidone were added to an aqueous solution of PVA
(molecular mass, 1.0·105–1.1·105 amu) at constant mixing at 40 ◦C
for 3 h [10].
To produce the immobilized biocatalyst, 36 mg of microbial cells
mixed at a ratio of 1:1 (1:1:1 for the association consisting of 3
microorganisms) was added to 200 l of PVA gel modified by Nvinylpyrrolidone. A uniform distribution of cells in gel was achieved
by shaking on a CM70 M centrifuge (ELMI, Latvia) for 5 min. The
suspension produced was transferred onto a slide and dried for
24 h at room temperature. The thickness of the film produced was
15 m; the specific density of immobilized cells, 5.8 mg/cm2. The
immobilized biocatalyst was stored at 4 ◦C. To form the biosensor,
a fragment of produced gel 4 mm in diameter was fixed by a nylon
mesh on the surface of an oxygen electrode.