Fate of carbon in synthetic media fermentations containing Metschnikowia pulcherrima or Meyerozyma guilliermondii in the presence and absence of Saccharomyces cerevisiae.

While sequentially inoculating non-Saccharomyces yeasts with Saccharomyces cerevisiae can lower the alcohol contents of wine, the abilities of these yeasts to utilize/produce ethanol or generate other byproducts remained unclear. Metschnikowia pulcherrima or Meyerozyma guilliermondii were inoculated into media with or without S. cerevisiae to assess byproduct formation. Both species metabolized ethanol in a yeast-nitrogen-base medium but produced the alcohol in a synthetic grape juice medium. In fact, Mt. pulcherrima and My. guilliermondii generated less ethanol per gram of metabolized sugar (0.372 and 0.301 g/g, respectively) compared to S. cerevisiae (0.422 g/g). Sequentially inoculating each non-Saccharomyces species with S. cerevisiae into grape juice media achieved up to 3.0% v/v alcohol reduction compared to S. cerevisiae alone while producing variable glycerol, succinic acid, and acetic acid concentrations. However, neither non-Saccharomyces yeasts released appreciable CO2 under fermentative conditions regardless of incubation temperature. Despite equivalent peak populations, S. cerevisiae produced more biomass (2.98 g/L) than the non-Saccharomyces yeasts while sequential inoculations yielded higher biomass with Mt. pulcherrima (3.97 g/L) but not My. guilliermondii (3.03 g/L). To reduce ethanol concentrations, these non-Saccharomyces species may metabolize ethanol and/or produce less from metabolized sugars compared to S. cerevisiae but also divert carbon towards glycerol, succinic acid, and/or biomass.

Sensory properties of 6- and 18-month-stored wines made with pectinase-producing non-Saccharomyces yeasts.

Recently, the use and commercial availability of non-Saccharomyces yeasts (NSY) in winemaking to reduce alcohol content have increased. However, research exploring the influence on sensory quality of the wine, particularly during storage, is limited. Therefore, the objective of this study was to characterize the sensory profiles of Merlot and Chardonnay wines made with pectinase-producing NSY, with added substrate, that is, pectin. Apple pectin (0 or 0.5 g/L) was added to Merlot and Chardonnay grape musts after inoculation with (a) only Saccharomyces cerevisiae or (b) a three species mixture of NSY; after 3 days, S. cerevisiae was added. Addition of NSY with added pectin resulted in higher concentrations of d-galacturonic acid and glycerol concentration in the wines after 6 months of aging. However, mouthfeel (viscosity or weight) of wines with or without added pectin as determined by a sensory evaluation panel was not altered by the presence of these yeasts. Significant interactions among the yeast utilized, pectin addition, and 6-month aging affected some flavors (solvent) of Merlot, while addition of NSY increased other attributes (cherry) during aging. No sensory differences were perceived among Chardonnay samples due to NSY; however, aging from 6 to 18 months increased the intensity of 40 sensory attributes. Though mouthfeel was not specifically affected, the utilization of NSY may be a useful tool to alter wine quality in Merlot by increasing specific aromas during storage. PRACTICAL APPLICATION: We found that must fermented with pectinase-producing non-Saccharomyces yeasts (NSY) modified the chemical composition of the final young wine. After one additional year of aging, an increase in cherry flavor was observed in Merlot wines made with NSY, which may increase perceived quality. Thus, the use of these pectinase-producing NSY may be a useful tool for winemakers.

Impacts of non-Saccharomyces species and aeration on sequential inoculation with Saccharomyces cerevisiae to produce lower alcohol Merlot wines from Washington state.

BACKGROUND: Species of non-Saccharomyces yeasts isolated from Washington vineyards were evaluated for their abilities to reduce alcohol contents of wines. As many of these yeasts benefit from some oxygen, the effect of limited aeration was also studied. RESULTS: Although fermentations of a high sugar Merlot grape must (310 g L-1 ) did not reach dryness, inoculation of Metschnikowia chrysoperlae, Mt. pulcherrima, Meyerozyma guillermondii, Pichia kluyveri, or P. membranifaciens yielded in wines with lower amounts of ethanol without excessive levels of acetic acid. Aeration frequently resulted in wines with less ethanol but with more acetic acid compared to non-aerated fermentations. Inoculation of Mt. pulcherrima or My. guilliermondii into another Merlot grape must that contained a lower initial amount of fermentable sugar (266 g L-1 ) resulted in dry wines that contained less alcohol. CONCLUSIONS: Inoculation of My. guilliermondii or Mt. pulcherrima before primary alcoholic fermentation resulted in wines with reduced alcohol contents without excessive acetic acid production. © 2020 Society of Chemical Industry.

Carbohydrate Accumulation and Differential Transcript Expression in Winter Wheat Lines with Different Levels of Snow Mold and Freezing Tolerance after Cold Treatment.

Winter wheat (Triticum aestivum L.) undergoes a period of cold acclimation in order to survive the ensuing winter, which can bring freezing temperatures and snow mold infection. Tolerance of these stresses is conferred in part by accumulation of carbohydrates in the crown region. This study investigates the contributions of carbohydrate accumulation during a cold treatment among wheat lines that differ in their snow mold tolerance (SMT) or susceptibility (SMS) and freezing tolerance (FrT) or susceptibility (FrS). Two parent varieties and eight recombinant inbred lines (RILs) were analyzed. The selected RILs represent four combinations of tolerance: SMT/FrT, SMT/FrS, SMS/FrT, and SMS/FrS. It is hypothesized that carbohydrate accumulation and transcript expression will differ between sets of RILs. Liquid chromatography with a refractive index detector was used to quantify carbohydrate content at eight time points over the cold treatment period. Polysaccharide and sucrose content differed between SMT and SMS RILs at various time points, although there were no significant differences in glucose or fructose content. Glucose and fructose content differed between FrT and FrS RILs in this study, but no significant differences in polysaccharide or sucrose content. RNAseq was used to investigate differential transcript expression, followed by modular enrichment analysis, to reveal potential candidates for other mechanisms of tolerance, which included expected pathways such as oxidative stress, chitinase activity, and unexpected transcriptional pathways. These differences in carbohydrate accumulation and differential transcript expression begin to give insight into the differences of wheat lines when exposed to cold temperatures.

Growth and metabolism of non-Saccharomyces yeasts isolated from Washington state vineyards in media and high sugar grape musts.

Utilization of carbohydrates and amino acids/ammonium by selected non-Saccharomyces yeasts and impacts on alcoholic fermentation was evaluated using media and high sugar grape musts (>270 g/L). Consumption patterns of single cultures were ascertained in synthetic media and a Chardonnay grape must. While the non-Saccharomyces species maintained >106 cfu/mL after >40 days, concentrations of residual sugars ranged from 103 g/L (Wickerhamomyces anomalus) to 155 g/L (Candida californica), amino acids and ammonium were generally depleted (>85%), and excessive amounts of volatile acidity (>0.8 g/L) were sometimes produced (e.g., C. oleophila). To minimize problems associated with nutrient depletion before alcoholic fermentation, non-Saccharomyces yeasts were inoculated six days ahead of S. cerevisiae into Syrah grape musts. Syrah ferments inoculated with C. californica or Metschnikowia pulcherrima contained lower concentrations of residual sugar and ethanol compared to those with only S. cerevisiae. Furthermore, the presence of non-Saccharomyces yeasts influenced concentrations of glycerol and volatile aroma compounds. These results suggested potential use of some non-Saccharomyces yeasts towards reducing alcohol concentrations without risking slower alcoholic fermentations.

Trained and consumer panel evaluation of sparkling wines sweetened to brut or demi sec residual sugar levels with three different sugars.

The dosage liquid, added at the final stage of sparkling wine production, imparts residual sweetness to the wine. No study has yet analyzed the influence of dosage composition on the final wine's sensory profile or consumer acceptance. In this study, dosage composition was altered through the addition of different sugar types (ST; fructose, glucose, or sucrose) to produce seven sparkling wines of varying residual sugar levels (RSL), including no sugar added, brut (5.3-8.4gST/L) or demi sec (34.9-37.8gST/L). As evaluated by a trained panel (n=9), the interaction between ST and RSL influenced the perception of caramelized/vanilla/honey (CVH) flavor, sweet taste, and sour taste attributes (p<0.05). Demi sec wines displayed lower intensities of green flavor, yeasty flavor, and sour taste compared to the no sugar added wine (p<0.05). Consumers (n=126) also evaluated the sparkling wines and ST, RSL, and their interaction influenced consumer acceptance of different attributes, as well as the perception of the "refreshing" aspect of the wine (p<0.05). Overall consumer acceptance of sparkling wines was highly correlated (r2≤0.88) to CVH, floral, and fruity flavors, as well as sweet taste and creamy mouthfeel. External preference mapping revealed two clusters of consumers. Both consumer clusters liked wines sweetened with fructose, but Cluster 1 liked the demi sec sparkling wine sweetened with fructose (32.8g/L fructose) while Cluster 2 preferred the brut wine sweetened with fructose (8.4g/L fructose). These results suggest that consumer preference for sparkling wine was segmented based on sweetness preference. The results of this study offer winemakers knowledge about the influence of dosage composition on the sensory profile of sparkling wine.

Fabrication of biomimetically patterned surfaces and their application to probing plant-bacteria interactions.

We have developed a two-step replica molding method for rapid fabrication of biomimetically patterned plant surfaces (BPS) using polydimethylsiloxane (PDMS-BPS) and agarose (AGAR-BPS). Beyond providing multiple identical specimens that faithfully reproduce leaf surface microstructure, this approach also offers unique chemical, physical, and biological features. PDMS-BPS provide good structural durability for SEM examination, have surface wettability comparable to plant surfaces for coating development, and allow for real-time monitoring of biosynthesis through incorporation into microfluidic devices. AGAR-BPS are compatible with bacterial growth, recovery, and quantification, and enable investigation of the effects of surface topography on spatially varying survival and inactivation of Escherichia coli cells during biocide treatment. Further development and application of these biomimetically patterned surfaces to study (and possibly modify) other aspects of plant-bacteria interactions can provide insight into controlling pathogen contamination in a wide range of applications.