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Saccharomyces cerevisiae and grape juice are ‘natural companions’ and make a happy wine marriage. However, this relationship can be enriched by allowing ‘wild’ non‐Saccharomyces yeast to participate in a sequential manner in the early phases of grape must fermentation. However, such a triangular relationship is complex and can only be taken to ‘the next level’ if there are no spoilage yeast present and if the ‘wine yeast’ – S. cerevisiae – is able to exert its dominance in time to successfully complete the alcoholic fermentation. Winemakers apply various ‘matchmaking’ strategies (e.g. cellar hygiene, pH, SO₂, temperature and nutrient management) to keep ‘spoilers’ (e.g. Dekkera bruxellensis) at bay, and allow ‘compatible’ wild yeast (e.g. Torulaspora delbrueckii, Pichia kluyveri, Lachancea thermotolerans and Candida/Metschnikowia pulcherrima) to harmonize with potent S. cerevisiae wine yeast and bring the best out in wine. Mismatching can lead to a ‘two is company, three is a crowd’ scenario. More than 40 of the 1500 known yeast species have been isolated from grape must. In this article, we review the specific flavour‐active characteristics of those non‐Saccharomyces species that might play a positive role in both spontaneous and inoculated wine ferments. We seek to present ‘single‐species’ and ‘multi‐species’ ferments in a new light and a new context, and we raise important questions about the direction of mixed‐fermentation research to address market trends regarding so‐called ‘natural’ wines. This review also highlights that, despite the fact that most frontier research and technological developments are often focussed primarily on S. cerevisiae, non‐Saccharomyces research can benefit from the techniques and knowledge developed by research on the former.

Sulfur dioxide is the most used additive today for preventing browning in grape musts and wines. However, since wine consumers are increasingly interested in healthier wines, the wine industry is keen to reduce its use. Some promising alternatives to sulfur dioxide have been proposed in recent years, including glutathione, both pure and in the form of inactivated yeasts, and Metschnikowia pulcherrima used as a bioprotective agent. Some information exists about the protective effect against oxidation of glutathione but there is very few about the use of bioprotection for that purpose. Supplementation with glutathione, regardless of the commercial form, reduced oxygen consumption and browning intensity when laccase was not present in the grape juice. Metschnikowia pulcherrima also reduced browning intensity in the absence of laccase but increased the total oxygen consumption. However, in the presence of laccase, glutathione and Metschnikowia pulcherrima were not effective enough to adequately prevent the grape juice from browning. Glutathione, both pure and in the form of inactivated yeasts, and Metschnikowia pulcherrima are interesting tools for protecting grape must against browning, and thus reducing the use of sulfur dioxide.

Alcoholic fermentation is a crucial step of winemaking, during which yeasts convert sugars to alcohol and also produce or biotransform numerous flavour compounds. In this context, nutrients are essential compounds to support yeast growth and ultimately ensure complete fermentation, as well as optimized production of flavour compounds over that of off-flavour compounds. In particular, the vitamin thiamine not only plays an essential cofactor role for several enzymes involved in various metabolic pathways, including those leading to the production of wine-relevant flavour compounds, but also aids yeast survival via thiamine-dependent stress protection functions. Most yeast species are able to both assimilate exogenous thiamine into the cell and synthesize thiamine de novo. However, the mechanism and level of thiamine accumulation depend on several factors. This review provides an in-depth overview of thiamine utilization and metabolism in the model yeast species Saccharomyces cerevisiae, as well as the current knowledge on (1) the intracellular functions of thiamine, (2) the balance between and regulation of uptake and synthesis of thiamine and (3) the multitude of factors influencing thiamine availability and utilization. For the latter, a particular emphasis is placed on conditions occurring during wine fermentation. The adequacy of thiamine concentration in grape must to ensure successful fermentation is discussed together with the effect of thiamine concentration on fermentation kinetics and on wine sensory properties. This knowledge may serve as a resource to optimise thiamine concentrations for optimal industrial application of yeasts.Key points• Thiamine uptake is preferred over biosynthesis and is transcriptionally repressed.• Multiple factors affect thiamine synthesis, availability and uptake for wine yeast.• Thiamine availability impacts fermentation kinetics and wine’s sensory properties.

Metschnikowia pulcherrima (Mp) is a ubiquitous yeast that frequently appears in spontaneous fermentations. The current interest in Mp is supported by the expression of many extracellular activities, some of which enhance the release of varietal aromatic compounds. The low fermentative power of Mp makes necessary the sequential or mixed use with Saccharomyces cerevisiae (Sc) to completely ferment grape musts. Mp has a respiratory metabolism that can help to lower ethanol content when used under aerobic conditions. Also, Mp shows good compatibility with Sc in producing a low-to-moderate global volatile acidity and, with suitable strains, a reduced level of H2S. The excretion of pulcherrimin gives Mp some competitive advantages over other non-Saccharomyces yeasts as well as providing some antifungal properties.

Drinking wine is a processed beverage that offers high nutritional and health benefits. It is produced from grape must, which undergoes fermentation by yeasts (and sometimes lactic acid bacteria) to create a product that is highly appreciated by consumers worldwide. However, if only one type of yeast, specifically Saccharomyces cerevisiae, was used in the fermentation process, the resulting wine would lack aroma and flavor and may be rejected by consumers. To produce wine with a desirable taste and aroma, non-Saccharomyces yeasts are necessary. These yeasts contribute volatile aromatic compounds that significantly impact the wine’s final taste. They promote the release of primary aromatic compounds through a sequential hydrolysis mechanism involving several glycosidases unique to these yeasts. This review will discuss the unique characteristics of these yeasts (Schizosaccharomyces pombe, Pichia kluyveri, Torulaspora delbrueckii, Wickerhamomyces anomalus, Metschnikowia pulcherrima, Hanseniaspora vineae, Lachancea thermotolerans, Candida stellata, and others) and their impact on wine fermentations and co-fermentations. Their existence and the metabolites they produce enhance the complexity of wine flavor, resulting in a more enjoyable drinking experience.

Immobilized yeast cells are used industrially in winemaking processes such as sparkling wine and Sherry wine production. Here, a novel approach has been explored for the infusion and immobilization of yeast cells into filamentous fungal pellets, which serve as a porous natural material. This was accomplished through vacuum application to force the yeast cells towards the core of the fungal pellets followed by culture in YPD medium to promote their growth from the interior. This method represents an improved variation of a previous approach for the assembly of “yeast biocapsules,” which entailed the co-culture of both fungal and yeast cells in the same medium. A comparison was made between both techniques in terms of biocapsule productivity, cell retention capacity, and cell biological activity through an alcoholic fermentation of a grape must. The results indicated a substantial increase in biocapsule productivity (37.40-fold), higher cell retention within the biocapsules (threefold), and reduction in cell leakage during fermentation (twofold). Although the majority of the chemical and sensory variables measured in the produced wine did not exhibit notable differences from those produced utilizing suspended yeast cells (conventional method), some differences (such as herbaceous and toasted smells, acidity, bitterness, and persistence) were perceived and wines positively evaluated by the sensory panel. As the immobilized cells remain functional and the encapsulation technique can be expanded to other microorganisms, it creates potential for additional industrial uses like biofuel, health applications, microbe encapsulation and delivery, bioremediation, and pharmacy.Key points• New approach improves biocapsule productivity and cell retention.• Immobilized yeast remains functional in fermentation.• Wine made with immobilized yeast had positive sensory differences.

In this paper, the development of trench etching process and photolithography process for 6-inch 4H-SiC trench-type power MOSFET devices is mainly studied. Among them, the etching process successfully solved the anisotropy of dry etching of SiC, the different etching rates of different crystal planes, the difficulty of controlling the angle of the trench sidewall, and the easy formation of micro-trenches at the corners, etc. Successfully realized trenches with etch depth greater than 1.2um and sidewall angle greater than 90° in SiC. Subsequently, the trench was filled with SiO 2 to achieve no holes in the trench after filling, and then the photolithography process was studied. Photolithography process is resolved at the trench coating, exposing and developing the non-uniformity problem, achieve a full and uniform coating, self-aligned trench overlay and the overlay accuracy of less than 0.1um, and there is no residue of photoresist in the groove after development. This article uses scanning electron microscope (SEM) to measure the morphology of the trench after etching and photolithography to characterize the experimental results, and the results meet the process requirements. The successful development of this process will facilitate the research and development of deeper trench-type power MOSFET devices.

Background and Aims This study evaluated the impact that the non‐Saccharomyces yeasts, Torulaspora delbrueckii (TD), Lachancea thermotolerans (LT), Pichia kluyveri (PK), Metschnikowia pulcherrima (MP), Candida zemplinina (CZ) and Kazachstania aerobia (KA), in sequential inoculation with Saccharomyces cerevisiae (SC), had on the volatile chemical profile of Shiraz wine. Methods and Results Shiraz grape must was inoculated with monocultures of the non‐Saccharomyces yeasts, which were allowed to ferment until 2% v/v ethanol concentration was reached at which point, SC was added to complete the alcoholic fermentation. The control was SC in monoculture. The final wines were subjected to solid phase microextraction‐GC × GC‐time of flight‐MS to evaluate the untargeted volatile metabolite profile of each treatment. Each fermentation produced a unique chemical profile. The LT–SC sequential fermentation was the most significantly different from the control primarily in the ester, alcohol and terpene profile. The KA–SC sequential fermentation had the highest amount of volatile acidity, and the PK–SC sequential fermentation had a relatively high amount of acetaldehyde and a few esters. The MP–SC sequential fermentation also revealed a higher concentration of several esters. The TD–SC sequential fermentation was notable for its lack of a distinct pattern in comparison with that of the other fermentations. Conclusions Given these characteristics, the LT–SC sequential fermentation showed the most potential for increased chemical complexity of the Shiraz volatile profile. Significance of the Study The results demonstrate that there is no clear, singular trend for how different, non‐Saccharomyces species of yeast – once thought to be wholly unfavourable in wine fermentations – will impact wine chemistry, flavour or quality. Each species presents unique metabolic characteristics, many of which could be beneficial, and their potential application in the wine industry should be considered.

Agriculture surplus were used as substrates to synthesize γ-aminobutyric acid (GABA) by Lactobacillus plantarum DSM19463 for the manufacture of a functional beverage or as a novel application for dermatological purposes. Dilution of the grape must to 1 or 4% (w/v) of total carbohydrates favored higher cell yield and synthesis of GABA with respect to whey milk. Optimal conditions for synthesizing GABA in grape must were: initial pH 6.0, initial cell density of Log 7.0 cfu/mL, and addition of 18.4 mM l-glutamate. L. plantarum DSM19463 synthesized 4.83 mM of GABA during fermentation at 30°C for 72 h. The fermented grape must also contain various levels of niacin, free minerals, and polyphenols, and Log 10.0 cfu/g of viable cells of L. plantarum DSM19463. Freeze dried preparation of grape must was applied to the SkinEthic® Reconstructed Human Epidermis or multi-layer human skin model (FT-skin tissue). The effect on transcriptional regulation of human beta-defensin-2 (HBD-2), hyaluronan synthase (HAS1), filaggrin (FGR), and involucrin genes was assayed through RT-PCR. Compared to GABA used as pure chemical compound, the up-regulation HBD-2 was similar while the effect on the expression of HAS1 and FGR genes was higher.