The water kefir grain inoculum determines the characteristics of the resulting water kefir fermentation process

Aims To investigate the influence of the water kefir grain inoculum on the characteristics of the water kefir fermentation process. Methods and results Three water kefir fermentation processes were started with different water kefir grain inocula and followed as a function of time regarding microbial species diversity, community dynamics, substrate consumption profile, and metabolite production course. The inoculum determined the water kefir grain growth, the viable counts on the grains, the time until total carbohydrate exhaustion, the final metabolite concentrations, and the microbial species diversity. There were always 2-10 lactic acid bacterial cells for every yeast cell and the majority of these microorganisms was always present on the grains. Lactobacillus paracasei, Lactobacillus hilgardii, Lactobacillus nagelii, and Saccharomyces cerevisiae were always present and may be the key microorganisms during water kefir fermentation. Low water kefir grain growth was associated with small grains with high viable counts of microorganisms, fast fermentation, and low pH values, and was not caused by the absence of exopolysaccharide-producing lactic acid bacteria. Conclusions The water kefir grain inoculum influences the microbial species diversity and characteristics of the fermentation process. A select group of key microorganisms was always present during fermentation. Significance and Impact of the Study This study allows a rational selection of a water kefir grain inoculum. This article is protected by copyright. All rights reserved.