The effect of Mn2+ on ethanol production from lactose using Kluyveromyces marxianus IMB3 immobilized in magnetically responsive matrices

The thermotolerant, ethanol producing yeast strain, a marxianus IMB3 was immobilized in calcium alginate containing magnetically responsive Fe3O4 particles. In these studies the beta-galactosidase derived from K. marxianus IMB3 was immobilized onto the Fe3O4 particles prior to inclusion into the alginate matrix. Ethanol production by the immobilized microorganism in the presence of Fe3O4 reached a maximum of 16 g/L on 40 g/L lactose whereas prior immobilization of the enzyme to the particles and inclusion into the alginate matrix increased ethanol production to a maximum concentration of 18 g/L. When Mn2+ was incorporated into fermentations containing the immobilized enzyme in the alginate matrix, ethanol production increased further to a maximum concentration of 20 g/L. In addition, the behaviour of the magnetically responsive biocatalyst containing the co-immobilized enzyme was examined in a batch-fed system in the presence and absence of Mn2+.