Cryostructured and Crosslinked Viable Cells Forming Monoliths Suitable for Bioreactor Applications

Applications of immobilized biocatalysts in both research and industry require highly active catalysts, preferably at a low cost. In this study, cryogels with high catalyst density were produced through cryostructuration of whole Escherichia coli (E.coli) cells. Prepared cryogels are macroporous materials composed of metabolically active cells crosslinked to each other via polymeric structures. Different macromolecular reagents: oxidized dextran (OxDex), polyvinyl alcohol (PVA) and polyethyleneimine (PEI), the two latter activated with glutaraldehyde (GTA) have been synthesized. Prepared polymers were tested as effective and mild crosslinkers for cells during the cryostructuration procedure. Combination of the two synthetic polymers: PEI+GTA and PVA+GTA was found most suitable for formation of macroporous and stable structures from cells without any toxic effect on them. About 90 % of beta-glucosidase activity in cells was retained after cross-linking with a combination of synthetic polymers, whereas E. coli crosslinked using GTA showed complete loss of activity. Preserved viability of cells in cryogel offers possibility to induce protein expression in cells after crosslinking. For beta-glucosidase induction post immobilization yielded 50 % activity of that from cells induced in free form before cryo-structurization. The results of the post immobilization studies indicate an interesting potential for handling very sensitive enzymes.