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Valuation of brewers spent yeast polysaccharides: A structural characterization approach

Pinto, Mariana, Coelho, Elisabete, Nunes, Alexandra, Brandão, Tiago, Coimbra, Manuel A.
Carbohydrate polymers 2015 v.116 pp. 215-222
acid hydrolysis, alpha-amylase, brewing industry, byproducts, endo-1,4-beta-glucanase, glucose, polymers, polysaccharides, potassium hydroxide, solubilization, yeasts
Brewers spent yeast (BSY) is a by-product from beer industry that can be exploited as source of glucans and mannoproteins, with potential biological activities. In order to solubilize these carbohydrate-rich polymeric materials, a sequential extraction with hot water and alkaline solutions (0.1–8M KOH) was performed. Mannoproteins were mainly (85%) extracted with 4M KOH whereas glucans were extracted with 8M KOH and in an amount that accounted only for 34% of total glucose. Final residue still accounted for 34% of the initial glucans and contained 98% of glucose. Cellulase and α-amylase treatments showed the presence of both α- and β-(1→4)-Glc linkages. To promote total solubilization of these insoluble glucans, the final residue was submitted to a partial acid hydrolysis. This work is the first report showing that the most abundant polysaccharides in BSY are polymers that contain structural features similar to cellulose, thus justifying their resistance to alkaline extractions, acid hydrolysis, and insolubility in water.