Cell chromatography: Separation of different microbial cells using IMAC supermacroporous monolithic columns

Supermacroporous monolithic columns with CU2+-IDA ligands have been successfully used for chromatographic separation of different types of microbial cells. The bed of monolithic matrix is formed by a cryogel of poly(acrylamide) cross-linked with methylenebis(acrylamide) and has a network of large (10- 100 mu m) interconnected pores allowing unhindered passage of whole cells through the plain cryogel column containing no ligands. Two model systems have been studied: the mixtures of wild-type Escherichia coli (w.t. E. coli) and recombinant E. coli cells displaying poly-His peptides (His-tagged E. coli) and of w.t. E. coli and Bacillus halodurans cells. Wild-type E. coli and His-tagged E. coli were quantitatively captured from the feedstock containing equal amounts of both cell types and recovered by selective elution with imidazole and EDTA, with yields of 80% and 77%, respectively. The peak obtained after EDTA elution was 8-fold enriched with His-tagged E. coli cells as compared with the peak from imidazole elution, which contained mainly weakly bound w.t. E. coli cells. Haloalkalophilic B. halodurans cells had low affinity to the CU2+-IDA cryogel column and could be efficiently separated from a mixture with w.t. E. coli cells, which were retained and recovered in high yields from the column with imidazole gradient. All the cells maintained their viability after the chromatographic procedure. The results show that chromatography on affinity supermacroporous monolithic columns is a promising approach to efficient separations of individual cell types.