Identification of Wild Yeast Strains and Analysis of Their β-Glucan and Glutathione Levels for Use in Makgeolli Brewing

Makgeolli, also known as Takju, is a non-filtered traditional Korean alcoholic beverage that contains various floating matter, including yeast cells, which contributes to its high physiological functionality. In the present study, we assessed the levels of β-glucan and glutathione in various yeast strains isolated from traditional Korean Nuruk and selected a β-glucan- and glutathione-rich yeast strain to add value to Makgeolli by enhancing its physiological functionality through increased levels of these compounds. Yeast β-glucan levels ranged from 6.26% to 32.69% (dry basis) and were strongly species-dependent. Dried Saccharomyces cerevisiae isolated from Nuruk contained 25.53 µg/mg glutathione, 0.70 µg/mg oxidized glutathione, and 11.69 µg/g and 47.85 µg/g spermidine and L-ornithine monohydrochloride, respectively. To produce functional Makgeolli, a β-glucan- and glutathione-rich yeast strain was selected in a screening analysis. Makgeolli fermented with the selected yeast strain contained higher β-glucan and glutathione levels than commercial Makgeolli. Using the selected yeast strain to produce Makgeolli with high β-glucan and glutathione content may enable the production of functional Makgeolli.