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Summary: The combined use of non‐Saccharomyces yeasts and Saccharomyces cerevisiae in mixed fermentation is considering as a potential way to improve the flavour characteristics of Mijiu (a traditional rice wine in China). In this study, we investigated the effects of mixed fermentation, including simultaneous and sequential inoculation fermentation, of typical non‐Saccharomyces yeast strains (Saccharomycopsis fibuligera; Candida glabrata) and an S. cerevisiae strain on the fermentation process and volatile compounds of Mijiu. The results showed that the fermentation rate of Mijiu was improved by the simultaneous inoculation fermentation of different non‐Saccharomyces yeasts and S. cerevisiae. However, the increase of volatile compounds in the simultaneous inoculation fermentation depended on non‐Saccharomyces yeast species, although the positive contribution of non‐Saccharomyces yeasts to volatile compounds of Mijiu was confirmed in their pure fermentation. The sequential inoculation fermentation significantly enhanced the content or complexity of volatile compounds of Mijiu but with low‐fermentation rate. This could be attributed to the change of the number of non‐Saccharomyces yeast cells during the mixed fermentation possibly caused by the inhibition of S. cerevisiae with high concentration on non‐Saccharomyces yeasts. Our work provided useful information on the mixed inoculation fermentation strategy combining suitable non‐Saccharomyces yeasts and S. cerevisiae for improving the fermentation rate and the aroma quality of Mijiu. [ABSTRACT FROM AUTHOR]

Ethanol tolerance is crucial for the oenological yeasts. Rosa roxburghii Tratt, a Rosaceae plant native to China, is rich in nutritional and medicinal ingredients. In this study, ethanol-tolerant non-Saccharomyces yeasts were screened, and their oenological properties were further evaluated. Three ethanol-tolerant yeast strains (designated as C6, F112, and F15), which could tolerate 12% (v/v) ethanol treatment, were isolated from R. roxburghii, and identified as Candida tropicalis, Pichia guilliermondii, and Wickerhamomyces anomalus, respectively. The winemaking condition tolerances of these ethanol-tolerant yeast strains were similar to those of Saccharomyces cerevisiae X16. However, their growth, sugar metabolic performance and sulphureted hydrogen activities, were different. The β-glucosidase production ability of strain W. anomalus F15 was lower than that of S. cerevisiae X16, and strains of C. tropicalis C6 and P. guilliermondii F112 were similar to S. cerevisiae X16. Electronic sensory properties of the R. roxburghii wines fermented using ethanol-tolerant yeasts together with S. cerevisiae showed no significant differences. However, the mixed inoculation of the ethanol-tolerant yeast strains with S. cerevisiae could regulate the volatile aroma characteristics of the fermented R. roxburghii wine, enriching and enhancing the aroma flavor. Therefore, the selected ethanol-tolerant yeasts have the potential for application in the production of unique R. roxburghii wine. [ABSTRACT FROM AUTHOR]

Background: Chinese strong-flavor baijiu (CSFB), one of the three major baijiu types, is the most popular baijiu type among consumers in China. A variety of microbes are involved in metabolizing raw materials to produce ethanol and flavor substances during fermentation, which fundamentally determined the quality of baijiu. It is of great importance to study microbial community of fermented grains (zaopei) during baijiu brewing process for improving its quality. In this study, we firstly used propidium monoazide (PMA) to treat zaopei samples from 5-year pit and 20-year pit for removing the interference of non-viable fungi, and analyzed the diversity of total fungi and viable fungi by quantitative PCR (qPCR) and high-throughput sequencing (HTS) based on ITS2 gene. Results: The results showed that total fungi and viable fungi displayed no significant differences at OTU, phylum, or genus levels during fermentation within two kinds of pits. A total of 6 phyla, 19 classes, and 118 genera in fungi were found based on OTUs annotation in zaopei samples from 5-year pit and 20-year pit. Besides, non-viable fungi had little effect on the fungal community diversity during the fermentation cycle. It was found that the most dominant viable fungi belonged to Saccharomyces, Kazachstania, Naumovozyma, and Trichosporon, and Naumovozyma was firstly detected in zaopei samples of CSFB. Moreover, based on the variation of flavor substances in zaopei samples, the quality of CSFB produced from older pit was better than that produced from younger pit. Conclusion: The non-viable fungi had little effect on the fungal diversity, structure, and relative abundance in zaopei samples of CSFB, and Naumovozyma was firstly detected in zaopei samples of CSFB. Our findings can be applied as guidance for improving the quality and stability of CSFB. [ABSTRACT FROM AUTHOR]

Xiaoqu , one of three traditional jiuqu in China, is a saccharifying and fermenting agent used in Xiaoqu jiu brewing, with different ingredient compositions and preparation techniques used in various regions. The yield and quality of Xiaoqu jiu are significantly affected by the metabolites and microbiota of Xiaoqu ; however, the associated relationship remains poorly understood. This study aimed to analyze this relationship in three typical traditional Xiaoqu from the Guizhou province in China. The non-volatile metabolites of Xiaoqu were detected using gas chromatography time-of-flight mass spectrometry, whereas the classification and metabolic potential of the microbiota were investigated using metagenomic sequencing. Results show that Firmicutes, Proteobacteria, and Actinobacteria represent the dominant bacterial phyla, with Lactobacillus, Bacillus, Acinetobacter, Leuconostoc , and Weissella found to be the dominant bacterial genera. Meanwhile, Ascomycota, Mucoromycota, and Basidiomycota are the dominant fungal phyla with Aspergillus, Saccharomyces, Pichia, Rhizopus , and Phycomyces being the predominant fungal genera. Functional annotation of the microbiota revealed a major association with metabolism of carbohydrates, cofactors, and vitamins, as well as amino acids. A total of 39 significantly different metabolites (SDMs) were identified that are involved in 47 metabolic pathways, primarily that of starch and sucrose; glycine, serine, and threonine; glyoxylate and dicarboxylate; pyruvate; as well as biosynthesis of pantothenate and CoA. Further, based on Spearman's correlation analysis, Aspergillus, Saccharomyces, Lactobacillus, Acetobacter, Weissella, Pantoea, Desmospora , and Bacillus are closely correlated with production of physicochemical indexes and SDMs. Moreover, the metabolic network generated for the breakdown of substrates and formation of SDMs in Xiaoqu was found to primarily center on the metabolism of carbohydrates and the tricarboxylic acid cycle. These results provide insights into the functional microorganisms and metabolic patterns present in traditional Guizhou Xiaoqu and might guide researchers in the production of stable and efficient Xiaoqu in the future. [ABSTRACT FROM AUTHOR]

• It is the first study on microbial diversity during persimmon wine fermentation. • Functional core microbiota was identified during the fermentation of persimmon wine. • Spontaneous fermentation increased the proportion of esters in persimmon wine. • Hanseniaspora and Rhodotorula play important roles in volatile compounds formation. In this study, we determined the composition of microorganisms in the spontaneous/inoculated fermentation process of persimmon (Diospyros kaki L., China) wine for the first time and compared the similarities and differences of microbial succession, change in volatile compounds, and variations in amino acids. We found that spontaneous persimmon wine fermentation (SPF) resulted in lower bacterial community diversity and higher fungi community diversity than inoculated persimmon wine fermentation (IPF). SPF increased the proportion of esters in overall volatile compounds (29.9 % vs 18.9 %) at the end of fermentation. According to partial least squares (PLS, VIP > 1.0) analysis and Spearman's correlation analysis, 18 (11 bacterial and 7 fungus) were identified as the functional core microbiotas in SPF. Among them, indigenous Saccharomyces , Hanseniaspora , Rhodotorula , Leuconostoc , and Lactobacillus play an important role in the formation of volatile compounds and are worthy of further study, while Escherichia-Shigella , Ralstonia and Zoogloea should be inhibited during the fermentation process. However, a key problem in SPF was the fermentation time, which was too long (about 27 days) and did not meet the needs of industrial production. Overall, the results showed the possibility of considering select indigenous aroma-producing microorganisms as persimmon wine fermentation starters to improve the unique characteristics of persimmon wine. [ABSTRACT FROM AUTHOR]

In this study, attention has been focused on the ecology of yeasts during the spontaneous and inoculated fermentation processes of Vidal blanc icewine in northeast China, which is very important for screening autochthonous yeast strains, understanding the roles of these strains, and managing fermentation. The strategies were to conduct spontaneous and inoculated laboratory-scale fermentation processes simultaneously and to analyze the samples taken at different fermentation stages by culture-dependent and -independent methods. Three hundred and thirty-eight yeast strains were isolated and twelve genera were identified by sequencing. During the spontaneous fermentation process, non- Saccharomyces yeasts were predominant in the initial and middle stages, whereas Saccharomyces dominated in the later stages; Candida was preponderant in the whole process, and its abundance in the final stages was only lower than Saccharomyces. The inoculated fermentation was characterized by a predominance of Saccharomyces throughout the fermentation process; non- Saccharomyces yeasts were observed in the early stage. The internal transcribed spacer (ITS) 2 region gene was firstly used to analyze the yeast diversity in the samples during the icewine fermentation processes by high-throughput sequencing (HTS), and a more complex mycobiota was revealed. Moreover, the dynamics of other major fungi (mainly Davidiella and Alternaria) during icewine fermentation processes were also revealed, which have never been reported in icewine before. [ABSTRACT FROM AUTHOR]

The aim of this work was to rapidly screen indigenous yeasts with high levels of β-glucosidase activity and assess the potential of glycosidase extracts for aroma enhancement in winemaking. A semiquantitative colorimetric assay was applied using 96-well plates to screen yeasts from 3 different regions of China. Isolates with high β-glucosidase activity were confirmed by the commonly used pNP assay. Among 493 non-Saccharomyces isolates belonging to 8 generas, 3 isolates were selected for their high levels of β-glucosidase activity and were identified as Hanseniaspora uvarum, Pichia membranifaciens, and Rhodotorula mucilaginosa by sequence analysis of the 26S rDNA D1/D2 domain. β-Glucosidase in the glycosidase extract fromH. uvarum strain showed the highest activity in winemaking conditions among the selected isolates. For aroma enhancement in winemaking, the glycosidase extract from H. uvarum strain exhibited catalytic specificity for aromatic glycosides of C13-norisoprenoids and some terpenes, enhancing fresh floral, sweet, berry, and nutty aroma characteristics in wine. [ABSTRACT FROM AUTHOR]

Abstract   Maotai-flavor liquor, a famous traditional Chinese drink, is distilled from fermented sorghum in the southern province of China. Moreover, it is of interest as one of the few examples of liquor distilled from the product of a fermentation using a wild microflora starter. Daqu is the starter of this fermentation process. Daqu is a mixture of two components: milled wheat and a complex microbial community. The composition and the effects of this microbial group are largely unknown. In this study, we have analysed the constituents of the microbial community and the development of microorganisms in the industrial Daqu preparation and ripening process. More than 200 colonies were isolated and characterized. The isolates were discriminated by phenotypic and conventional biochemical taxonomic methods. The results revealed the presence of bacteria, moulds and yeasts. Bacteria consist of Bacillus, Acetobacter, Lactobacillus, and Clostridium, among which Bacillus strains were found to be predominant. Moulds consisted of Aspergillus, Mucor, Rhizopus, Monascus and Trichoderma, and Aspergillus strains were found to be predominant in the six different biotypes. Yeasts comprised Saccharomyces, Hansenula, Candida, Pichia, and Torulaspora. The most frequently isolated yeasts belonged to the genus Saccharomyces. The microbial diversity shift showed that the microbial genera changed with increasing ripening time. Knowledge of the microbial diversity in Daqu provides a basis for microflora management and understanding of the role of microbes in the Daqu production process, and the contribution of Daqu performed as a starter culture to Maotai-flavor liquor. [ABSTRACT FROM AUTHOR]

The yeast Saccharomyces cerevisiae has been widely applied in fermentation industries, chemical industries and biological research and it is widespread in different environments, especially in sugar-rich environments. However, little is known about the occurrence, distribution and roles of S. cerevisiae in marine environments. In this study, only 10 strains among all the yeasts isolated from different marine environments belonged to S. cerevisiae. It was found that most of the strains of S. cerevisiae in marine environments occurred in guts, the surface of marine fish and mangrove trees. In contrast, they were not found in seawater and sediments. All the strains of S. cerevisiae isolated from the marine environments had a lower ability to produce ethanol than the highly alcohol-producing yeast Saccharomyces sp. W0 isolated from fermented rice, but the strains 2E00400, 2E00558, 2E00498, 2E00723, 2E00724 could produce higher concentrations of ethanol than any other marine-derived strains of S. cerevisiae obtained in this study. However, some of them had higher ethanol tolerance and higher trehalose content than Saccharomyces sp. W0. In particular, ethanol tolerance of the yeast strain 2E00498 was higher than that of Saccharomyces sp. W0. This may be related to the harsh marine environments from which they were isolated. Such yeast strains with higher alcohol tolerance could be used to further improve the alcohol tolerance of Saccharomyces sp. W0. [ABSTRACT FROM AUTHOR]

Vitis davidii Föex is widely planted in South China as a potential wine making grape. In this study, yeast communities during the spontaneous fermentations of two varieties of Vitis davidii Föex in Guizhou, China were investigated. Hanseniaspora uvarum , Pichia terricola , Saccharomyces cerevisiae / S. mikatae , and Schizosaccharomyces japonicus were the four main yeast species detected by culture-dependent and high-throughput sequencing approaches. However, the composition of minor yeast species was quite different as revealed by the two approaches. Ten yeast species including Debaryomyces hansenii , Rhodotorula mucilaginosa , Sporidiobolus paraoseus , Starmerella bacillaris , Zygoascus meyerae , etc. were detected by culture-dependent approaches, whereas the other five species were found by high-throughput sequencing analysis. S. japonicus was widely found during spontaneous fermentations and its concentrations were mostly higher than that of S. cerevisiae. The difference in grape varieties and fermentation conditions contributed to yeast diversity. The results of this study provide basic information on indigenous yeast diversity from Vitis davidii Föex in Guizhou, which would help to exploit the potential of non- Saccharomyces yeast species with good oenological attributes. Unlabelled Image • Vitis davidii Föex showed distinctive yeast diversity in spontaneous fermentations. • Schizosaccharomyces japonicus were predominant yeast species. • Saccharomyces cerevisiae / S. mikatae seemed not be able to compete with S. japonicus. • ITS-amplicon high-throughput sequencing could not detect all yeast species found. [ABSTRACT FROM AUTHOR]