AimsTo evaluate the impact of coculturing Bifidobacterium animalis subsp. lactis HN019 with yeasts on microbial viability and metabolite production. Methods and ResultsMonocultures and bacteria-yeast cocultures of B. lactis HN019 and 10 different yeast strains belonging to different species in skim milk media were fermented at 37 degrees C. The presence of yeasts enhanced the growth rate and metabolic activities of B. lactis HN019, which might be attributed to their antioxidative properties. The viability of yeasts, when cocultured with bifidobacteria, was either unaffected or suppressed, depending on the strain. When the B. lactis HN019 monoculture and cocultures with Saccharomyces cerevisiae EC-1118, Pichia kluyveri FrootZen and Kluyveromyces lactis KL71 were fermented to pH 47, there were no significant differences in their organic acid composition. On the other hand, cocultures produced significantly higher quantities of alcohols and/or esters than the monoculture. Coculturing B. lactis HN019 with yeasts did not improve the viability of the probiotic during storage at 10 degrees C for 8weeks, as the bifidobacteria itself demonstrated satisfactory survival in the fermented SMM. ConclusionsCoculturing B. lactis HN019 with yeasts accelerated the growth of the bifidobacteria and increased the production aroma-active volatile metabolites. Significance and Impact of the StudyThis study demonstrates the potential of utilizing specific yeast species as starter or adjunct cultures to simultaneously improve the growth of fastidious bifidobacteria and modulate the organoleptic properties of fermented food products.