In general, the sugar solution beer is brewed from (wort) contains approximately 11-12% dissolved solids, largely consisting of sugars of various sizes (Casey, G.P., et al.). The most abundant sugars present in brewer’s wort are maltose (50 – 60%), maltotriose (15 – 20%), and glucose (10 – 15%) (Zastrow, C.R., et al.), being composed of two glucose subunits, three glucose subunits, and simple soluble glucose, respectively. This study sought to characterize the sugar metabolism profile of four non-traditional brewing yeasts of the genus Brettanomyces, namely B. bruxellensis, B. bruxellensis trois, B. claussenii, and B. lambicus, in a standard brewer’s wort. Fermentation samples were analyzed by HPLC, refractive index, specific gravity, and ethanol concentration in order to evaluate the rate, selectivity, and ethanol by-product formation of Brettanomyces yeast fermentation. Distinct sugar metabolism profiles for each individual strain are expected, allowing a better understanding about the reputed use of Brettanomyces in primary-, secondary-, and barrel-fermentation applications. It is of particular interest to examine the metabolism of maltotriose and other, higher-order glucose polymers, as these sugars are difficult or impossible for traditional brewing yeasts to metabolize, yet have significant impact on flavor, body and storage stability. There have been preliminary studies on the fermentative abilities of various Brettanomyces yeasts toward oligosaccharides larger than three subunits; however, findings have been inconclusive. An understanding of the impact these yeasts can have on a long-term fermentation has practical applications for predicting fermentation products under barrel-aging conditions.

Determination of sugar metabolism profiles for non-traditional brewing yeasts of the genus Brettanomyces

251st National Meeting (2016)

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