Combined effects of trehalose and cations on the thermal resistance of b-galactosidase in freeze-dried systems

MAZZOBRE, MARÍA FLORENCIA; BUERA, MARÍA DEL PILAR

BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1999 vol. 1473 p. 337 - 344

0304-4165

The purpose of this study was to investigate the combined effects of trehalose and cations on the preservation of Lgalactosidasein freeze-dried systems and their relationship to physical properties. Differential scanning calorimetry wasemployed to measure the glass transition temperature (Tg) and the endothermal peak area, related to the amount ofcrystalline trehalose dihydrate present in the samples. In systems in which the trehalose matrix was humidified to conditionswhich allowed a high proportion of trehalose to crystallize, the enzyme was rapidly inactivated upon heating at 70³C. In theseconditions the addition of CsCl, NaCl and particularly KCl or MgCl2, improved the enzyme stability with respect to thatobserved in matrices containing only trehalose. For a given moisture content, addition of salts produced very little change onthe glass transition temperature; therefore the protective effect could not be attributed to a higher Tg value. Thecrystallization of trehalose dihydrate in the humidified samples was delayed in the trehalose/salt systems (principally in thepresence of Mg2?) and a parallel improvement of enzyme stability was observed.