Characterization of a Potential Bioactive Food Ingredient from Inner Cellular Content of Brewer's Spent Yeast

Yeast harvesting and re-pitching is a common practice in most breweries. The reuse of four to six generations before yeast disposal is frequent. Nevertheless, Brewer's spent yeast (BSY) is the second major brewing by-product, mostly used for animal feed. Despite its underutilization it can be a valuable source of bioactive compounds. In this work, a bioactive food ingredient was obtained from the inner cell content of BSY by mechanical disruption of yeast cell wall. Proximate composition, biological activities [proteolytic, antioxidant and angiotensin converting enzyme-inhibitory (ACE-I) activity] and amino acid profile of freeze-dried BSY extracts with different number of brewing reuses were assessed. Additionally, the stability of the biological properties during 6 months of extract storage at -25 degrees C was also evaluated. Proteins were the major components of BSY extracts and yeast re-pitching increased their content. The antioxidant activities of the BSY extracts were not influenced by the serial reuse of yeast biomass in brewing, neither by extracts storage. However, BSY extracts prepared from yeast with lower number of brewing reuses presented the highest proteolytic activity and maximum ACE-I activity. BSY extracts are promising as a protein rich bioactive ingredient for food industry, presenting an amino acid profile well balanced for human consumption.