An alpha-galactosidase from Thermus sp. T2, a hexameric protein, has been immobilized on cyanogen bromide agarose, retaining its activity almost intact, but without any significant improvement in enzyme stability. In fact, enzyme subunits could be desorbed from the immobilized preparation by boiling the solution in the presence of SDS (detected by SDS-PAGE) and a dependence of the enzyme stability on the enzyme concentration could be detected under certain conditions. The further cross-linking of this immobilized preparation with aldehyde-dextran permitted to improve the enzyme stability, avoiding the release of enzyme subunits to the reaction medium that could produce enzyme inactivation or food contamination. (c) 2007 Elsevier Ltd. All rights reserved.