The aim of this paper was to evaluate the suitability of Siran, a highly porous mineral carrier, to immobilization of Kluyveromyces fragilis--directly lactose-fermenting yeast. The ethanol concentration in the post-fermentation mash was 4.7-5.8% v/v and was less advantageous than in previous experiments with calcium alginate (on average 6.04% v/v in 9 sequential fermentations). The introduction of another yeast strain to the experiment--S. cerevisiae--enhanced the efficiency of the lactose mash fermentation. The ethanol concentration in the mash in sequential series of the process increased on average to 6.14% v/v.