[Effects of tHMGR from three different plant sources on mevalonate (MVA) pathway flux in Saccharomyces cerevisiae].

In this study, we used bioinformatic tools to analyze the 3-hydroxy-3-methylglutaryl-CoA reductase(HMGR) genes from Glycyrrhiza uralensis, Artemisia annua, and Arabidopsis thaliana. The results indicated that GuHMGR and AaHMGR contained two transmembrane regions while AtHMGR had three transmembrane regions. GuHMGR, AaHMGR, and AtHMGR all had the active center for catalysis. Three truncated HMGR genes(tHMGRs) of G. uralensi, A. annua, and A. thaliana were respectively ligated to pYES3 vector to construct the recombinant plasmids pYES3-tGuHMGR,pYES3-tAaHMGR,and pYES3-tAtHMGR. Afterwards, the control plasmid pYES3 and the three plasmids and were respectively introduced into Saccharomyces cerevisiae Cen.pk2-1 D, which yielded strains Y0, Y1, Y2, and Y3, respectively. The content of squalene, lanosterol, and ergosterol in these strains was measured by GC-MS. The relative expression of tGuHMGR, tAaHMGR, and tAtHMGR in strains Y1, Y2, and Y3 was determined by quantitative real-time PCR. The results showed that the strain overexpressing tAaHMGR had the highest yield of squalene and the highest total yield of squalene, ergosterol, and lanosterol. The quantitative real-time PCR showed higher relative expression of tAaHMGR than tGuHMGR, consistent with the strain fermentation result. We selected a superior tHMGR by comparing the effects of different tHMGRs on the mevalonate(MVA) pathway flux in S. cerevisiae. The findings can provide a reference for the construction of S. cerevisiae strains with high yields of squalene and terpenoid precursors.

Dibasic Ammonium Phosphate Application Enhances Aromatic Compound Concentration in Bog Bilberry Syrup Wine.

A nitrogen deficiency always causes bog bilberry syrup wine to have a poor sensory feature. This study investigated the effect of nitrogen source addition on volatile compounds during bog bilberry syrup wine fermentation. The syrup was supplemented with 60, 90, 120 or 150 mg/L dibasic ammonium phosphate (DAP) before fermentation. Results showed that an increase of DAP amounts accelerated fermentation rate, increased alcohol content, and decreased sugar level. Total phenol and total flavonoid content were also enhanced with the increase of DAP amounts. A total of 91 volatile compounds were detected in the wine and their concentrations were significantly enhanced with the increase of DAP. Ethyl acetate, isoamyl acetate, phenethyl acetate, ethyl butanoate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, isobutanol, isoamyl alcohol, levo-2,3-butanediol, 2-phenylethanol, meso-2,3-butanediol, isobutyric acid, hexanoic acid, and octanoic acid exhibited a significant increase of their odor activity value (OAV) with the increase of DAP amounts. Bog bilberry syrup wine possessed fruity, fatty, and caramel flavors as its major aroma, whereas a balsamic note was the least present. The increase of DAP amounts significantly improved the global aroma attributes, thereby indicating that DAP supplementation could promote wine fermentation performance and enhance the sensory quality of bog bilberry syrup wine.