ISOLATION OF WILD YEAST FOR POTENTIAL USE IN BEER PRODUCTION

Abstract

There is a limited amount of yeast strains that are currently used in industrial beer brewing. Wild yeasts could provide an alternative to common domesticated brewer’s yeasts by offering a new range of sensory characteristics and improved performance in harsh brewing conditions such as high gravity and high ethanol concentration in wort. High gravity brewing is practical and profitable as it increases production capacity, therefore reducing investment and energy costs. Exploiting the existing natural diversity could lead to finding superior industrial yeasts as well as a better understanding of biodiversity. The aim of the present study was to determine if wild yeast strains isolated from the ecosystem at a regional level (Northeast Mexico) showed favorable characteristics in the brewing process. Sixty-three yeast isolates were obtained from diverse samples including flowers and fruits. Five isolates were selected after three rounds of beer fermentation based on their sensory characteristics. Tests to assess growth over time, flocculation potential, ethanol yield, osmotolerance and ethanol tolerance were applied to two reference yeasts (commercial beer brewing strains) and to the selected isolates of interest which were identified as Saccharomyces cerevisiae by MEX67 amplification and ITS sequencing. The results indicated that the selected wild isolates exhibit characteristics comparable to commercial reference strains in terms of growth and stress tolerance.