Identification and characterisation of lactic acid bacteria and yeasts isolated from kefir grains in Taiwan

The microbial composition of kefir grains of household origin from Taiwan was studied using scanning electron microscopy, and lactic acid bacteria and yeasts were isolated from these kefir grains and characterised with respect to their growth, lactic acid and ethanol production in milk. The lactic acid bacteria were localised mainly in the surface layer and yeasts at the centre of the grains. The lactic acid bacteria isolated from kefir grains were identified as Lactobacillus helveticus and Leuconostoc mesenteroides, and the yeasts were identified as Kluyveromyces marxianus and Pichia fermentans. From the results of studying the growth characteristics of the above strains, Lb. helveticus possessed better growth characteristics, and K. marxianus exhibited better L-lactic acid and ethanol production. D-lactic acid was the major form produced by Ln. mesenteroides. P. fermentans was a lactose-non-fermenting yeast, therefore the active proteolytic enzymes were essential for its growth in milk.