Magnetic immobilisation is an extremely useful technique. Immobilising cells or enzyme in gel materials which contain colloidal ferrites or magnetite allows the use of magnets to retrieve the contents of the materials in the reactor. The University of Lund pioneered this type of research. My first example used Ferrofluid™ which formed part of a standard mix in calcium alginate gel to fix Saccharomyces cerevisiae but which did not affect the performance of the immobilised yeast, their growth or the operating stability of the immobilised cells (Larsson and Mosbach, 1979). This example illustrated the production of ethanol which is still of interest in the present day – over 30 years on. It’s particularly useful when handling viscous substrates or particulate-containing media because the catalysts can be separated from substrate and product without too much loss. There was also the issue of maintaining the flow of reactants and substrates in the packed beds in which the immobilised cells found themselves.

Methods for the preparation of micron-sized magnetic adsorbents derivatised with iminodiacetic acid (IDA) as a metal chelating agent have also been tried and tested for the recovery of various target proteins. One feature was their excellent stability (O’Brien et al., 1996).

The subject is widely discussed in various reviews on magnetic immobilisation and recovery –see Whitesides et al., (1983). Purification of proteins is covered by Safarik and Safarikova (2004).

References

Larsson, P.O., Mosbach, K. (1979) Alcohol production by magnetic immobilised yeast. Biotech. Letts. 1 (12) pp. 501-506 DOI 10.1007/BF01387977

O’Brien, S.M., Thomas, O.W.T., Dunnill, P. (1996)  Non-porous magnetic chelator supports for protein recovery by immobilised metal affinity adsorption. J. Biotechnol. 500(1) pp. 13-25

Safarik, I., Safarikova, M. (2004) BioMagnetic Research and Technology, 2:7  doi:10.1186/1477-044X-2-7

Whitesides, G.M., Kazlauskas, R.J., Josephson, L. (1983) Magnetic Separations In Biotechnology. Trends in Biotechnol. 1(5) pp 144-148