Temporal production of platelet-activating factor by brewer's yeast

The biochemical performance of brewer's yeast (Saccharomyces cerevisiae) during the fermentation process will significantly influence beer quality. Yeast produces a number of biochemical compounds, including platelet-activating factor (PAF; 1-o-alkyl-2-o-acetyl-sn-glycero-3-phosphocholine). PAF is a potent signaling phospholipid with pleiotropic physiologic-biochemical properties in addition to activating platelets. PAF appears to be of critical importance for many cellular events, including division and metabolism. Yeast cells produce PAF, and this unique biochemical controls the cell-cycle phase in budding yeast. The study objective was to determine temporal PAF production by ale and lager yeast strains at two different culture temperatures (14 and 20°C). At different culture times (1-100 hr), aliquots (100 μL) of media were removed for PAF analysis by a specific radioimmunoassay ( 125 I). There was a significant difference (P < 0.001) between ale (16.35 ± 1.28 pM/10 6 cells) and lager yeast (26.68 ±2.15 pM/10 6 cells) in PAF levels. Both culture temperature and time had significant (P < 0.001) effects on PAF production. There was a cyclic pattern to PAF production in both strains of yeast; however, this was most evident in the lager strain. The data confirms that brewer's yeast produces PAF and production levels are cyclic in nature and strain and temperature dependent. Additional studies are warranted to determine the impact of PAF in yeast fermentation and attendant beer quality.