γ-Glutamyl peptides can enhance basic taste sensations such as saltiness, sweetness, and umaminess, while the molecular mechanism and the difference in taste enhancement remain elusive. Thus, two complex conformations: taste type 1 receptor 1 (T1R1)-MSG and taste type 1 receptor 2 (T1R2)-sucrose were constructed to form binding receptors. These peptides showed affinity for the two receptors, but a higher affinity scores and more binding amino acid residues for the T1R1-MSG receptor, implying that they may exhibit a higher umami-enhancing effect. Thereinto, γ-glutamyl alanine (γ-EA) displayed the highest affinity for the two receptors through mobilizing multiple amino acid residues to form hydrophobic and hydrogen bonds, indicating it had the highest enhancement for umaminess and sweetness among these peptides. Sensory evaluation demonstrated the enhancement of γ-EA on umaminess was superior to that of sweetness. Generally, γ-glutamyl peptides could enhance basic taste sensation via activating taste receptor, and exhibited a highest umami-enhancing effect.

The high-glucose tolerance of yeast is the main factor determining the efficiency of high-density alcohol fermentation. Zygosaccharomyces mellis LGL-1 isolated from honey could survive under 700 g/L high-glucose stress and its tolerant characteristics were identified in our previous study. This study was performed to explore and clarify the high-glucose tolerance mechanism of Z. mellis LGL-1. Comparative transcriptomic analysis was used to analyze the genes with differential expression in Z. mellis under high-glucose conditions of 300, 500 and 700 g/L. With 300 g/L samples as reference, there were 937 and 2380 differentially expressed genes (DEGs) in the 500 and 700 g/L samples, respectively. Meanwhile, there was 825 significant DEGs in the 700 g/L samples compared with that of the 500 g/L samples. The result revealed that transcriptional changes in multiple metabolic pathways occur in response to high-glucose stress. q-RT PCR analysis further confirmed that several stress response pathways, such as the high osmolarity glycerol mitogen-activated protein kinase (HOG-MAPK) signal transduction pathway, trehalose synthesis pathway and oxidative stress response are closely related to high-glucose tolerance in Z. mellis. This study clarifies mechanisms of Z. mellis in response to high-glucose osmotic stress, providing theoretical basis for the process control of high-density alcohol fermentation.