13,700
edits
Changes
no edit summary
''Brettanomyces'' strains may possess both alpha and beta glucosidases. These enzymes allow ''Brettanomyces'' strains to break down a broad range of sugars, including longer chain carbohydrate molecules (polysaccharides, dextrins, and cellulose/cellobiose), and to liberate glycosidically bound sugars which are unfermentable to ''Saccharomyces'' yeasts. <ref name="Steensels"></ref><ref>[http://www.scribd.com/doc/277758178/Insight-into-the-Dekkera-anomala-YV396-genome Insight into the Dekkera anomala YV396 genome. Samuel Aeschlimann. Self published on Eureka Brewing Blog. Spet 2015.]</ref>.
Extracellular and intracellular alpha-glucosidase activity has been shown to break down sugars up to 9 carbons in one strain of ''B. lambicus'', which is partly responsible for the over-attenuation of wort that some strains of ''Brettanomyces'' an achieve <ref name="yakobson_introduction"></ref>. Alpha -glucosidases are the enzymes that allow them to break down maltose, turanose, melezitose, and trehalose, as well as dextrins such as maltotetraose and maltopentaose. These dextrins are left over after a normal ''Saccharomyces'' fermentation <ref name="Steensels"></ref>. Some polysaccharides can be fermented by ''Brettanomyces'', including starch, laminarin, and pectin <ref name="Crauwels1"></ref>.
Beta-glycosidases can break down the beta-glycosidic bond in disaccharides (cellulose, cellobiose, and gentiobiose) <ref name="ucdavis_chemwiki">[http://chemwiki.ucdavis.edu/Core/Organic_Chemistry/Carbohydrates/Disaccharides "Disaccharides." UC Davis Chemwiki. Retrieved 05/15/2016.]</ref>, as well as glycosides. Glycosides are sugar molecules connected to other organic compounds such as acids, alcohols, and aldehydes which are flavor and aroma inactive due to the sugar molecule attached. By cleaving off the sugar molecule through beta-glucosidase activity, ''Brettanomyces'' species can liberate these compounds (called aglycones) into their aroma-active and flavor-active states, or states that may become flavor and aroma active through further modification <ref>Daenen et al., 2008. Evaluation of the glycoside hydrolase activity of a Brettanomyces strain on glycosides from sour cherry (Prunus cerasus L.) used in the production of special fruit beers. FEMS Yeast Res. 8, 1103-1114.</ref>. Therefore ''Brettanomyces'' strains are able to produce novel flavors and aromas from hops, fruits, and fruit pits that ''Saccharomyces'' yeasts cannot produce. In addition, the liberated aroma and flavor active compounds may be further processed by ''Brettanomyces'' through ester production or destruction pathways. See [[Brettanomyces#Glycosides_and_Beta-Glucosidase_Activity|Beta-Glucosidase Activity]] for more information.