Study: species of probiotic bacteria in water kefir

A study on the microbial diversity in water kefir has been undertaken by Gulitz et al (2011)[1. International Journal of Food Microbiology, Volume 151, Issue 3, 15 December 2011, Pages 284–288, The microbial diversity of water kefir, Anna Gulitz, Jasmin Stadie, Mareike Wenning, Matthias A. Ehrmann, Rudi F. Vogel]

Ingredients in water kefir

• Kefir grains
• 8 per cent sucrose
• Dried fruits
• Slices of lemon

The mixture is left to ferment for one or two days at room temperature, resulting in a cloudy, carbonated straw-coloured drink. It is acidic, low in sugar and has a slight alcohol content.

Key findings

Over 450 bacterial isolates was obtained using different types of media.

The predominant bacteria present was Lactobacillus (82 per cent in water kefir I and 72 per cent in water kefir II). The most abundant species in water kefir I and II was Lactobacillus hordei and Lb. nagelii, with much fewer numbers of Lb. casei.

Other lactic acid bacteria (LAB) present were identified as Leuconostoc mesenteroides and Lc. citreum in all three water kefirs (I, II and III). In water kefir III, the most abundant species was Lc. mesenteroides (28 per cent) and Lc. citreum (24 per cent).

Non LABs found were Acetobacter fabarum and Ac. orientalis.

Saccharomyces cerevisiae, Lachancea fermentati, Hanseniaospora valbyensis and Zygotorulaspora florentina were isolated and identified.

The water kefir

The water kefir was long-term traditional household preparations, and was prepared under standard conditions, twice, to eliminate different cultivation methods. The water kefir was made from a mixture of water, dried figs, a slice of lemon, and sucrose, at 21 °C for three days. After fermentation, the grains were strained, washed with tap water and strained again.