Development of a Bio-Selecting Agent Based on Immobilized Bacterial Cells with Amidase Activity for Bio-Detection of Acrylamide

Actinobacteria cells Rhodococcus erythropolis 4-1 and Rhodococcus erythropolis 11-2 and Proteobacteria Alcaligenes faecalis 2, which have amidase activity, were immobilized by entrapping barium alginate and agarose into the gel structure, as well as by obtaining biofilms on thermally expanded graphite (TEG). The operational stability of such immobilized biocatalysts after storage in frozen and dehydrated form was determined, and a prototype of a conductometric acrylamide biosensor based on such a bioselective agent was developed. The most preferred method for storing immobilized cells was freezing at temperatures from –20 to –80°C; long-term storage is also possible wet at 4–25°C. It was shown that these cells were most preferable for the biodetection of acrylamide A. faecalis 2, immobilized in an agarose gel structure. An agarose gel with bacterial cells immobilized in its structure had greater mechanical strength and stability during successive cycles of conversion of acrylamide into acrylic acid compared to barium alginate gel. The mechanical strength of barium alginate gel can be enhanced by the addition of carbon nanomaterials during cell immobilization. Growing biofilms on carbon materials used for manufacturing electrodes is also promising. Biofilms of R. erythropolis 11-2 on TEG are capable of converting acrylamide into acrylic acid in more than 20 reaction cycles while maintaining at least 50% amidase activity.