Investigation of the instability and low water kefir grain growth during an industrial water kefir fermentation process

Abstract

A poorly performing industrial water kefir production process consisting of a first fermentation process, a rest period at low temperature, and a second fermentation process was characterized to elucidate the causes of its low water kefir grain growth and instability. The frozen-stored water kefir grain inoculum was thawed and reactivated during three consecutive prefermentations before the water kefir production process was started. Freezing and thawing damaged the water kefir grains irreversibly, as their structure did not restore during the prefermentations nor the production process. The viable counts of the lactic acid bacteria and yeasts on the water kefir grains and in the liquors were as expected, whereas those of the acetic acid bacteria were high, due to the aerobic fermentation conditions. Nevertheless, the fermentations progressed slowly, which was caused by excessive substrate concentrations resulting in a high osmotic stress. Lactobacillus nagelii, Lactobacillus paracasei, Lactobacillus hilgardii, Leuconostoc mesenteroides, Bifidobacterium aquikefiri, Gluconobacter roseus/oxydans, Gluconobacter cerinus, Saccharomyces cerevisiae, and Zygotorulaspora florentina were the most prevalent microorganisms. Lb. hilgardii, the microorganism thought to be responsible for water kefir grain growth, was not found culture-dependently, which could explain the low water kefir grain growth of this industrial process.

Physiology of Acetic Acid Bacteria and Their Role in Vinegar and Fermented Beverages

“…Currently the main market for this beverage is in the United States, Japan, France, and Brazil, where it is consumed for its reported functional properties (Fiorda et al., ). The water kefir grain inoculum, and the nature of the substrate (such as the type of fruit used) determines the grain growth, the microbial species diversity, the metabolites formed, and their concentrations (Laureys, Aerts, Vandamme, & De Vuyst, ; Laureys & De Vuyst, ; Laureys, Van Jean, Dumont, & De Vuyst, ). In general, the microbiota of water kefir is known to be a stable consortium of different LAB (such as Lactobacillus, Leuconostoc ), AAB ( Acetobacter, Gluconacetobacter , and Gluconobacter ), and yeasts ( Kluyveromyces, Brettanomyces, Pichia , and Saccharomyces ).…”

“…Ethanol produced by yeasts may be metabolized to acetic acid by any viable AAB present (Magalhaes, Pereira, Dias, & Schwan, ). Growth of AAB particularly takes place under aerobic conditions, leading to increased acetic acid content, which may be unwanted (Gulitz, Stadie, Ehrmann, Ludwig, & Vogel, ; Laureys et al., ; Marsh, O'Sullivan, Hill, Ross, & Cotter, ). Under anaerobic conditions they remain in a viable but nonculturable (VBNC) state, being metabolically dormant, but can start to grow when oxygen becomes accessible (Laureys et al., ).…”

“…Growth of AAB particularly takes place under aerobic conditions, leading to increased acetic acid content, which may be unwanted (Gulitz, Stadie, Ehrmann, Ludwig, & Vogel, ; Laureys et al., ; Marsh, O'Sullivan, Hill, Ross, & Cotter, ). Under anaerobic conditions they remain in a viable but nonculturable (VBNC) state, being metabolically dormant, but can start to grow when oxygen becomes accessible (Laureys et al., ). While several species from the genera Acetobacter, Gluconacetobacter , and Gluconobacter have been recovered from water kefir fermentation processes, Acetobacter species seem to be best adapted to this ecosystem (Laureys & De Vuyst, ; Laureys et al., ; Magalhaes et al., ; Marsh et al., ).…”

“…Under anaerobic conditions they remain in a viable but nonculturable (VBNC) state, being metabolically dormant, but can start to grow when oxygen becomes accessible (Laureys et al., ). While several species from the genera Acetobacter, Gluconacetobacter , and Gluconobacter have been recovered from water kefir fermentation processes, Acetobacter species seem to be best adapted to this ecosystem (Laureys & De Vuyst, ; Laureys et al., ; Magalhaes et al., ; Marsh et al., ).…”

Pollution Abatement of Heavy Metals in Different Conditions by Water Kefir Grains as a Protective Tool against Toxicity

“…ese Water Kefir grains contain an insoluble polysaccharide and bacteria and yeasts responsible for the fermentation [1][2][3]. e insoluble Water Kefir grains act as inoculum when added to a mixture of water and sugar (sucrose), possibly with extra ingredients such as lemon, dried figs, and many others.…”