Characterization of yeast with probiotic potential and its use in fermented non-dairy beverage

Abstract

The study of probiotic characteristics of different microorganisms and novel foods containing them has become of great importance. Specifically, it has been shown that yeasts have valuable probiotic characteristics. This work aimed to select potentially probiotic yeasts isolated from Brazilian fermented foods such as kefir, cocoaand indigenous beverages and to develop a non-dairy fermented beverage. In vitro characterization of probiotic traits was performed on 116 yeasts. Thirty-six yeasts were tolerant to gastrointestinal conditions evaluated by tolerance to pH 2.0, bile salts (0.3% m/v) and temperature of 37 °C. Out of the 36 yeasts, 15 isolates had the percentage of hydrophobicity, autoaggregation and coaggregation with Escherichia coli similar or higher (P <0,05) than the commercial probiotic strain Saccharomyces boulardii. All these strains had high percentage of adhesion to Caco-2 cells (> 63%) and antioxidant activity (ranging from 18 to 62%). The ability of yeasts to inhibit adhesion and infection of the food pathogens E. coli, Salmonella Enteritidis and Listeria monocytogenes in Caco-2 cells was also evaluated. The strains S. cereviseae CCMA 0731, S. cereviseae CCMA 0732 and Pichia kluyveri CCMA 0615 showed co-aggregation and considerable reduction of infection by pathogens in Caco-2 cells, being equal or greater than the commercial strain Saccharomyces boulardii. For the development of a corn-based beverage, the commercial probiotic strain Lactobacillus paracasei LBC-81 was tested in combination with the potentially probiotic yeasts S. cereviseae CCMA 0731, S. cereviseae CCMA 0732 and Pichia kluyveri CCMA 0615. All tested strains showed viability higher than 6 log CFU/mL, except P. kluyveri. Lactic and acetic acids were the main organic acids produced during fermentation. Ethanol was detected in the S. cerevisiae assays, but at concentrations lower than 0.5 g/L, characterizing a non-alcoholic beverage. Seventy volatile compounds have been detected, including acids, alcohols, aldehydes, esters, ketones and other compounds. Sensory analysis showed that consumers neither liked nor disliked it, which is an interesting result since no flavoring and/or sweetening agents were added. Three potentially probiotic yeasts were selected through a screening and characterized in this work. These yeasts were used in the production of corn-based fermented beverage, characterizing a nondairy probiotic food, which is an alternative to the increasingly demanding consumer market.