Nutritional Potential of Spent Brewer's Yeast, A Residual By-Product of Beer Production in Breweries for Future Applications

The recovery of by-products from food processing chains represents an area of interest in the current world. Waste from beer production, such as beer lees or spent brewer's yeast, constitutes between 1.5 and 3 kg/100 L of beer, representing a source of pollution but a by-product available in quantity. This study aims to characterize the beer lees from breweries and propose possible ways of recovery. The scientific methods have been applied to highlight the nutritional potential of this by-product. Spent brewer's yeast is a high-biological value protein source (46.77%) with a well-balanced amino acid profile. Amino acids (glutamic acid and aspartic acid) and the essential amino acids leucine, lysine and valine are the most abundant, while sulfur amino acids, such as methionine and cysteine, are the least abundant. With a high mineral content (7.3%), the spent brewer's yeast contains significant amounts of manganese 5.54x10-2 mg/k, sodium 3.92x10-2 mg/k, and potassium 3.59x10-2 mg /k. The B complex vitamins are present in large quantities, followed by vitamins C, A and D. Less than 3% of the composition of the spent brewer's yeast is made up of lipids. The most abundant of fatty acids determined for the saturated category is palmitic acid, while oleic acid represents monounsaturated fatty acids, and polyunsaturated fatty acids are represented by linoleic acid and linolenic acid. Carbohydrates (32.77 %) are also important constituents of the dry matter of this by-product. This study showed that spent beer yeast is a source of polyphenol. Spent brewer's yeast has advantages for being incorporated into animal nutrition to meet nutritional needs. Further studies could lead to the production of activated carbon and hydrogen as excellent sources of alternative energy.