Yeast extract production using spent yeast from beer manufacture: influence of industrially applicable disruption methods on selected substance groups with biotechnological relevance

Spent brewer's yeast is an excellent source of a variety of bioactive substances. In this study, for the first time, the focus was solely on investigating the influence of three industrially applicable cell disruption methods (cell mill, sonotrode, and autolysis) on selected substance groups relevant for physiology and process technology. A consistent spent yeast (Saccharomyces cerevisiae TUM 68) produced in a standardized industrial pilot top-fermenting process was used as a raw material. Using mechanical methods, i.e., cell mill and sonotrode, the protein content (as not hydrolyzed in free amino acids), the trehalose and the total fat content in the yeast extract were increased compared with those produced in the autolytic method. The analyzed B vitamin levels were also higher, the biologically active 5-CH3-H(4)folate in particular had the greatest proportion in the folate vitamer distribution of the mechanically produced yeast extracts. An increased level of non-fragmented genomic and mitochondrial DNA could also be found in the yeast extract produced via the mechanical methods. The antioxidative and reduction potential was decreased by the degradation of polyphenols and glutathione in the yeast extract following autolysis. The mineral, RNA, glycogen, glucose, fructose and ash contents did not differ significantly. Therefore, the cell mill and sonotrode offered a good alternative method to conventional autolytic procedures, especially to transfer physiologically relevant substance groups in higher concentrations to the yeast extract.