Utilization of post-fermentation yeasts for yeast extract production by autolysis: the effect of yeast strain and saponin from Quillaja saponaria

Spent yeasts, a co-product from fermentation processes, are a source for unconvential autolysis processes. In this study, five post-fermentation yeast strains that are often used in fermentation processes were used: Saccharomyces cerevisiae Ethanol Red (Lessafre), Kluyveromyces marxianus LOCK 0026, K. marxianus NCYC 179, Scheffersomyces stipitis NCYC 1541 and Pichia angusta NCYC 495. Autolysis was conducted at 50 degrees C for 48 hours in the presence of saponins from Quillaja saponaria. The concentrations of proteins and free amino acids in the yeast autolysates were evaluated using IR spectroscopy and chromatography. The lysates were found to be good sources of essential amino acids, which constituted between 29.3% (S. cerevisiae) and 40.7% (K. marxianus LOCK 0026) of the amino acid pools. The largest pools of free amino acids were found in autolysates of S. cerevisiae Ethanol Red (44.9 g/L) and P. angusta NCYC 495 (40.53 g/L). Saponin can be used as an auxiliary or alternative to conventional methods of cell lysis, especially since Q. saponaria extracts are approved for use in foods and could have significant health benefits. The usability of five post-fermentation yeast strains as a source of valuable nitrogen compounds in unconventional salt-free lysates was demonstrated for the first time in the present study. Copyright (C) 2017 The Institute of Brewing & Distilling