The effects of Mn2+ on ethanol production by Kluyveromyces marxianus IMB3 during growth on lactose-containing media at 45�C

Abstract

It has previously been demonstrated that the thermotolerant yeast strain, K. marxianus IMB3 is capable of growth and ethanol production on lactose containing media at 45°C. Although the organism is capable of producing a β-galactosidase, that enzyme has been shown to be extremely thermolabile at 45°C and this has been reflected in reduced efficiencies with respect to conversion of lactose to ethanol. In this paper we demonstrate that addition of Mn2+ ions to enzyme preparations contributes significantly to enzyme stability at 45°C. We also demonstrate that addition of Mn2+ to fermentations results in increased efficiency of conversion of lactose to ethanol at this temperature.