The metagenomic composition of water kefir microbiota

Abstract

Water kefir is a sourish, slightly alcoholic, and carbonated drink in which different dried fruits are added to the sucrose-containing solution and fermented using water kefir grains. Kefir grains in polysaccharide structure include Lactic Acid Bacteria (LAB), yeasts, and/or acetic acid bacteria that use sucrose as an energy source. Water kefir grains contain a varying number of microbiota with various microbiological compositions, depending on their origin. The present study metagenomically determined the microbial flora of water kefir grains obtained from five different commercial sources. According to the metagenomic composition results obtained with the selected specific primers, the dominant bacterial species in water kefir grains were determined to be Lactobacillus ruminis and Bacillus methanolicus, and the most common species were Lactococcus lactis and Enterococcus faecium. Achromobacterx ylosoxidans were detected in only one sample. Pichia kudriavzevii was the dominant yeast species, and Saccharomyces cerevisiae, Eremothecium cymbalariae, Candida glabrata, and Ogataea parapolymorph were seen as common yeast species in all kefir yeasts. Other yeast types showed differences. It was revealed that natural water kefir grains contained probiotic bacteria including Lactobacillus ruminis, so kefir produced using these types of grains can exert functional properties. Another important conclusion is that, albeit, at low levels, kefir grains contain strains that have probiotic potential, including Lactococcus lactis, Enterococcus faecium, and Lactobacillus reuteri.