Identification by PCR and evaluation of probiotic potential in yeast strains found in kefir samples in the city of Santa Maria, RS, Brazil

Daniela Cassanego,Marcio Mazutti,Neila Richards,Maurício Ramírez-Castrillon,Patricia Valente

doi:10.1590/1678-457x.13617

Daniela Cassanego, Marcio Mazutti + Show 3 more

Open Access

https://doi.org/10.1590/1678-457x.13617

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Abstract

Abstract Kefir is a product elaborated from the symbiotic fermentation of different microorganisms. The Kluyveromyces and Saccharomyces genera are the major representatives of the yeasts found in kefir microbiota. The only pobiotic yeast commercialized as an oral medication, is the Saccharomyces boulardii. The present work involved the microbiological quality examination of six kefir samples in the city of Santa Maria/RS, the yeasts isolation present in the samples and the identification of them by PCR (Polymerase chain reaction). Then, their probiotic potential was evaluated by in vitro technique. After that, microbiological analysis confirmed that kefir samples were suitable for consumption once the microbiological quality was established. Nineteen yeast strains were isolated from six different kefir samples; it was identified, by PCR analysis, but only three species were identified from these microorganisms in the present article: Saccharomyces cerevisiae, Hanseniospora uvarum and Kazachstania unispora. Nevertheless, by simulating the passage of isolated strains through the gastrointestinal environment, it was observed that they could not be considered probiotics. The results indicate that, in an isolated way, the yeast presents in kefir samples, in the city of Santa Maria, RS, can´t be considered probiotics according to the tests performed.

Highlights

Kefir is a viscous, acid and slightly alcoholic solution, produced through fermented milk by means of “grains” as starter culture (Food and Agriculture Organization, 2003)
The milk is cooled at temperature 20-25 °C and the inoculation occurs with kefir grains
In view of the current interest in the yeast research with probiotic potential, and the presence of microorganisms in kefir, the aim of this article is to isolate and identify, through PCR analysis, the yeast species found in different kefir samples from Santa Maria/RS, Brazil

Summary

Introduction

Acid and slightly alcoholic solution, produced through fermented milk by means of “grains” as starter culture (Food and Agriculture Organization, 2003). The grains are composed of an inert matrix made up of polysaccharides and proteins. The matrix is densely populated by lactic acid bacteria species, acetic acid bacteria, and yeasts (Leite et al, 2012, 2013). The traditional method of producing kefir is occurred by directly inoculation of grains in the milk. The milk may be whole, skimmed or semi skimmed and must have been gone through heat treatment equivalent to pasteurization or ultra-pasteurization. The milk is cooled at temperature 20-25 °C and the inoculation occurs with kefir grains. The period of fermentation is 18-24 hours at 20-25 °C, the grains are separated from the milk by filtering. The produced kefir is stored at 4 °C and it is ready for consumption (Otles & Cagindi, 2003)

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