Comparison of various industrially applicable disruption methods to produce yeast extract using spent yeast from top-fermenting beer production: influence on amino acid and protein content

Abstract

The proteinogenic composition of yeast extract products varies from experience for manufacturing reasons, though also due to the yeast starting product. Therefore, this study is the first to focus solely on the influence of three industrially applicable cell disruption methods (cell mill, ultrasonic sonotrode and autolysis) on the amino acid and protein composition of a yeast extract. A consistent spent yeast (Saccharomyces cerevisiae TUM 68) produced in a standardized industrial pilot top-fermenting process was used as a raw material for the first time. The disruption effectiveness of autolysis (98%) was higher than that of the mechanical methods (80%), as well as the cleavage of amino acids from the cell protein (307, 155 and 115 mg per g yeast extract for autolysis, sonotrode and cell mill). The proteinogenic amino acid release profiles were dependent upon the disruption methods. The greater the released quantity of an amino acid during autolysis, the more the mean value fluctuated in the prepared yeast extract. Protein size fractionation of the extract using electrophoresis showed differences ranging between 1.5 and 95 kDa. All yeast extracts evidenced good nutritional potential according to FAO/WHO standards. The calculated data showed that the manufacturing method has a big impact on the proteinogenic composition of a yeast extract and the spent yeast TUM 68 used in this study can yield a protein-rich yeast extract.