Isolation and identification of Zalaria sp. Him3 as a novel fructooligosaccharides-producing yeast.

Abstract

This study aimed at obtaining a novel fructooligosaccharides (FOS)-producing yeast, which was different from conventional FOS producers, Aureobasidium spp. Strain Him3 was newly isolated from a Japanese dried sweet potato as a FOS producer. The strain exhibited yeast-like cells and melanization on the potato dextrose agar medium, and formed very weak pseudomycelia on the yeast extract polypeptone dextrose agar medium. Based on the internal transcribed spacer (ITS) region of ribosomal DNA and a partial β-tubulin gene sequences, the strain Him3 was identified as Zalaria sp. The β-fructofuranosidase (FFase) produced by strain Him3 was localized on the cell surface (CS-FFase) as well as in the culture broth (EC-FFase). The FOS production yields by CS-FFase and EC-FFase from 50% sucrose were 63.8% and 64.6%, respectively, to consumed sucrose after the reaction for 72h. We successfully isolated a novel black yeast, Zalaria sp. Him3, with effective capacity for FOS production. Phylogenetic analysis revealed that strain Him3 was distantly related with the conventional FOS producers, Aureobasidium spp. Since FFase of strain Him3 demonstrated high production yields of FOS, it could be applied to novel industrial production of FOS, which is different from conventional methods.