| The effect of four ratios of arginine:proline concentrations (1:1, 1:8, 1:20, and 1:0.25) in YAN normalized Chardonnay juice on the subsequent residual amino acid concentrations after primary fermentation was explored using two yeast strains: EC1118 and L2226. Fermentations achieved dryness uniformly and no variance in replication or strain was observed. Using MANOVA, hierarchical clustering techniques, and PCA, 1:0.25 juices resulted in the significant release of amino acids after primary fermentation. The release of 14 of 22 measured amino acids was significantly impacted by treatment alteration. The varying arginine:proline ratio may affect several biochemical pathways including permease regulation, epiarginase control, and proline accumulation. Permease expression is tightly regulated by the concentration of both extracellular and intercellular amino acid concentrations. When intercellular levels of both ornithine and arginine are high, as in 1:0.25, epiarginase control may shunt the metabolism of the aforementioned to proline and urea, respectively. Moreover, though proline is not metabolized under anaerobic conditions, proline may act as a membrane stabilizing component decreasing the release of amino acids when ethanol levels are high. From this study, the ratio of amino acids in juice may not only alter yeast biochemistry, but also the resulting amino acid concentrations released after primary fermentation. |
