Abstract

The efficiency of binding during enzymeimmobilisation does not only depend on the chemical properties of the enzyme and the matrix particle, but also on their surface potential. Zetapotential quantifies the electrostatic interactions between enzyme and matrix particles, and can therefore, be used as an indicator of the binding efficiency in the enzymeimmobilisation studies. In order to establish a correlation between the zetapotential and the binding efficiency, we used CALA (Candida antarcticaA-type lipase) as a model protein for immobilisation on non-porous magnetic microparticles with epoxy (M-PVA E02), carboxy (M-PVA C12) and amine (M-PVA N12) terminations.

We observed maximal binding of CALA onto the M-PVA N12 beads, due to the electrostatic attraction between negatively charged protein and carrier particles with slightly positive zetapotential. The binding of CALA was lower when M-PVA E02 beads were used, followed by M-PVA C12 beads. The decreasing binding efficiency was obviously the result of increasing electrostatic repulsion between the interaction partners. This could be correlated to the increasing negative zetapotential of the magnetic particles.

Moreover, the medium of suspension of the particles also makes a significant difference. We found highest specific activity of the lipase immobilised on M-PVA E02 beads in a medium concentrated buffer (0.3 M). The results demonstrate a clear correlation between zetapotential and binding efficiency but no correlation between the bead related specific activity and the zetapotential. These findings are advocating the possibility of using the zetapotential as adiagnostictool in enzymeimmobilisation.