Microbial communities and volatile metabolites in different traditional fermentation starters used for Hong Qu glutinous rice wine

Exogenous Mogroside V Drove Microbial Carbohydrate Metabolism and Consequently Enhanced Fruity Aroma in Greengage Wine

The microbial community is essential for the formation of aroma development in high-acidity greengage wine fermentation. Recent observations also highlight positive effects of mogroside V (MG V) on microorganisms in fermented foods, but the underlying chemical and biological mechanisms remain inadequate. The results indicated differences in the physicochemical properties among greengage wines, particularly a 50% increase in the ethanol conversion rate. Concurrently, GC-MS and sensory analyses demonstrated that MG V augmented carbohydrate conversion into ethyl esters (twice as much as in the control group), exhibiting tropical fruit and floral aroma profiles. The perceived intensity of these aromatic compounds increased by over 30%, thereby enriching the overall aromatic harmony of the wine. Integrated analysis of KEGG pathways and CAZymes annotations demonstrated that the enhancement of ethyl ester formation by MG V depends on improvement of the transport of carbohydrates and MG V, as well as accelerating the flux of pyruvate to acetyl-CoA in yeast. In conclusion, our study presents a targeted strategy for the high-acidity fruit wine industry of modulating this metabolic node in yeast, thereby achieving a focused enhancement of tropical fruit aroma characteristics in fruit wines.

Analysis of the Changes in Physicochemical Properties and Microbial Communities During Fermentation of Sweet Fermented Rice

As a traditional rice wine, sweet fermented rice (SFR) is widely loved because of its unique flavor and high nutritional value. However, the physicochemical properties, microbial community composition, and metabolic pathway changes during the fermentation process of sweet wine have not been evaluated, and these changes can lead to unstable SFR quality. In this study, we used high-throughput sequencing technology to analyze and elucidate the dynamic changes in the microbial community, metabolic pathways, and carbohydrate enzyme functions in traditional SFR fermentation broth. The results revealed that Rhizopus abundance = 160,943.659 and Wickerhamomyces abundance = 241,660.954 were the predominant fungal genera in the fermentation process from the beginning (A0) to the end (A43) of SFR fermentation. The results of the diversity analysis revealed that the structure and composition of the microbial communities first increased but then decreased. Metabolic pathway analysis showed that energy production and conversion, carbohydrate transport, and amino acid transport were the most active metabolic pathways in fermentation. Moreover, the three primary functions of glycosyltransferases (GTs), glycoside hydrolases (GHs), and carbohydrate-binding modules (CBMs) in carbohydrate enzyme analysis were involved in the whole fermentation process. This study only provides some insight into the dynamic changes in the microbial population of SFR single samples prepared under fixed conditions. It provides a reference for optimizing the physicochemical properties of SFR fermentation broth, controlling the microbial community structure, optimizing fermentation conditions, and improving product quality.

Dynamics of microbial communities and metabolites during the fermentation of Ningxia goji berry wine: An integrated metagenomics and metabolomics approach

Ningxia Goji Berry Wine (NGBW), a traditional Chinese fermented beverage, exhibits complex flavor quality changes during fermentation, the mechanisms of which remain insufficiently elucidated. This study aimed to elucidate the dynamic shifts in physicochemical properties, metabolites, and microbial communities throughout the controlled fermentation process of NGBW. Metabolomic analysis identified 8 key differential volatile metabolites (VOCs) and 406 differential non-volatile metabolites. The enrichment analysis of KEGG metabolic pathways revealed that, during the fermentation of NGBW, ten critical metabolic pathways-Purine metabolism, Glycine, Serine, and Threonine metabolism, Galactose metabolism, and the Citric Acid (TCA) Cycle-play essential roles. Amplicon sequencing indicated that 25 bacterial genera dominated the microbial ecosystem (relative abundance ≥ 0.1 %). Spearman correlation analysis revealed significant associations between 5 core microorganism and flavor compounds, and 25 core microbes with non-volatile metabolites, suggesting their pivotal roles in flavor formation. This study provides a theoretical basis for optimizing the fermentation process and enhancing the flavor quality of NGBW.

Assessment of wheat Qu fermented at medium and high temperatures: Effects of Bupleurum addition on fermentation characteristics, volatile profiles, and microbial communities

The quality of wheat Qu significantly influences rice wine production. However, quality control is often challenging due to variations in raw materials, preparation methods, and climatic conditions. Nevertheless, the impact of traditional northern Chinese craftsmanship techniques on the quality of wheat Qu remains largely unexplored, and addressing this gap is crucial for standardizing fermentation processes and optimizing rice wine production. In this study, we investigated the impact of traditional northern Chinese wheat Qu craftsmanship techniques on product quality by comparing the fermentation characteristics, volatile profiles, and microbiomes of three types of wheat Qu (medium-temperature wheat Qu without Bupleurum; medium-temperature wheat Qu with Bupleurum; and high-temperature wheat Qu with Bupleurum). We found that Bupleurum addition and thermal treatment can alter the microbial communities enriched in starters, enhancing fermentation performance and aroma characteristics. Additionally, we identified key aroma compounds and microbial biomarkers that could distinguish among different types of wheat Qu. Finally, statistical analyses and functional prediction assessments suggested that fungi likely drive microbial succession and metabolism in wheat Qu. These findings enable the development of strategies for optimizing wheat Qu production.

Acidity, sugar, and alcohol contents during the fermentation of Osmanthus-flavored sweet rice wine and microbial community dynamics

Sweet rice wine is a popular traditional Chinese rice wine widely loved by Chinese people for its high nutritional value. Osmanthus flower petals contain various nutrients and have good medicinal value. However, the dynamics of the sugar level, acidity, alcohol content, and microbial community during the fermentation of Osmanthus-flavored sweet rice wine have not been evaluated, which can lead to the unstable quality of Osmanthus flower sweet rice wine (OFSRW). In this study, the dynamic changes in sugar level, acidity, alcohol content, microbial community composition, and microbial metabolic pathways during traditional fermentation of OFSRW at four-time points-0 h (AG0), 24 h (AG24), 36 h (AG36), and 43 h (AG43)-were analyzed via direct titration, total acid assays, alcoholometry, and high-throughput macrogenomic techniques. First, we found that bacteria were the dominant microorganisms in the early stage of OFSRW fermentation (AG0), fungi were the dominant microorganisms in the middle and late stages of fermentation (AG24 and AG36), and Rhizopus was the main fungal genus throughout fermentation. Acidity and total sugars increased with fermentation time, and alcohol was not detected until the end of fermentation. Diversity analysis revealed that the dominant species at the beginning of natural fermentation was A. johnsonii, and R. delemar became the dominant species as natural fermentation progressed. Metabolic pathway analysis revealed that energy production and conversion, carbohydrate transport, amino acid transport, and metabolic pathways were the most active metabolic pathways in the fermenter. These results provide a reference basis for changes in the microbial community during the fermentation of cinnamon-flavored sweet rice wine.

Isolation and Evaluation of Rhizopus arrhizus Strains from Traditional Rice Wine Starters (Jiuqu): Enzyme Activities, Antioxidant Capacity, and Flavour Compounds

Seventy-eight autochthonous strains of Rhizopus arrhizus were isolated from rice wine starter samples across twenty-nine regions in China to evaluate their potential in traditional rice wine fermentation. Strains were assessed for enzyme activity, antioxidant properties, amino acid production, and volatile flavour compounds. Significant variation in enzyme activities was observed, with acidic protease activity ranging from 280 to 1023 U/g, amylase from 557 to 1681 U/g, and esterase from 370 to 2949 U/g. Strains W17 and W42 exhibited the highest enzyme activities and antioxidant capacities, with a total phenolic content of 828 mg/L, total flavonoids of 215 μg/L, and an ABTS scavenging rate of 96.3%. They also produced high levels of glutamic acid (up to 3083 mg/L), enhancing the flavour profile. Histamine levels were low, ranging from 8 to 205 μg/L, ensuring product safety. Analysis of volatile compounds identified 80 substances, including 16 key aroma-active compounds, contributing to a complex flavour profile. These results provide a basis for selecting R. arrhizus strains to optimise rice wine fermentation, addressing market demand for diverse and functional products.

The Impact of Fermentation Methods on the Quality and Bacterial Diversity of Dazhu Glutinous Rice Wine

Dazhu glutinous rice wine is a well-known traditional Chinese rice wine, and many local factories and handicraft workshops use different fermentation methods to produce it. Still, the influence of fermentation processes on glutinous rice wine is unclear. This study aimed to compare the difference between the two fermentation methods in the quality and bacterial composition of Dazhu glutinous rice wine. Results showed that the alcoholic content (P < 0.0001) and acidity (P < 0.01) in the rice wine fermented after packaging (PFRW) were higher than in the rice wine packaged after fermentation (FPRW), but the total sugar content was lower. Most amino, such as glutamic acid proline, and lactic acid were significantly higher in FPRW (P < 0.0001). In addition, the aroma, flavor and taste were better in FPRW than in PFRW. The Limosilactobacillus fermentum, Pediococcus pentosaceus, and Lactococcus lactis were dominant bacteria in FPRW, positively associated with amino acid and lactic acid. At the same time, Alcaligenaceae and Pedobacter nutriment were dominant bacteria in PFRW and negatively correlated with the quality. These implied that lactic acid bacteria significantly contributed to accumulating flavor ingredients and improving the quality of Dazhu glutinous rice wine. This study provides reference data for improving the quality of rice wine.

Research advances in technologies and mechanisms to regulate vinegar flavor

New vinegar needs a long maturing time to improve its poor flavor before sale, which greatly increases its production cost. Therefore, it is urgent to explore regulation technologies to accelerate vinegar flavor maturation. Based on literature and our research, this review introduces the latest advances in flavor regulation technologies of vinegar including microbial fortification/multi starters fermentation, key production processes optimization and novel physical processing technologies. Microbial fortification or multi starters fermentation accelerates vinegar flavor maturation via enhancing total acids, esters and aroma precursors content in vinegar. Adjusting raw materials composition, fermentation temperature, and oxygen flow reasonably increase alcohols, organic acids, polyphenols and esters levels via generating more corresponding precursors in vinegar, thereby improving its flavor. Furthermore, novel processing technologies greatly promote conversion of alcohols into acids and esters in vinegar, shortening flavor maturation time for over six months. Meanwhile, the corresponding mechanisms are discussed and future research directions are addressed.

The dynamic of physicochemical properties, volatile compounds and microbial community during the fermentation of Chinese rice wine with diverse cereals

This study investigates the impact of liquid state fermentation on the key flavor compounds and microbial community structure in Chinese rice wine brewed from five different raw materials: buckwheat, sorghum, japonica rice, glutinous rice, and black rice. Using HS-SPME-GC-MS and HPLC, the volatile compounds were analyzed across various grain liquefaction methods, detecting 82 volatiles, including esters, alcohols, aldehydes, and acids. The concentration of flavor compounds such as esters, amino acids, phenolic acids, and organic acids varied significantly depending on the raw material used. Based on odor activity values, 31 key compounds were identified, including 15 ethyl esters, like ethyl laurate, responsible for the unique and complex aroma of the rice wines. Bitter amino acids, making up over 50 % of the total amino acids, were predominant. Among the varieties, the buckwheat-fermented wine exhibited the highest ester content (27.39 mg/L), nearly double that of other samples, along with elevated amino acids (1.47 mg/mL) and phenolic acids (904.29 mg/L). Black rice ranked second in amino acid content (0.93 mg/mL), while glutinous rice had the highest organic acid content (239.76 mg/mL). Metagenomic sequencing on the fifth day of fermentation revealed significant differences in microbial community structure among the raw materials. Saccharomyces, Aspergillus, Thermomyces, Epicoccus, and Albertella were dominant fungi, while Weissella, Thermoactinomyces, Bacillus, and Saccharopolyspora were dominant bacteria. Sensory analysis showed that buckwheat-fermented rice wine was distinguished by its honey, floral, creamy, and umami attributes, while balancing alcohol, acidity, bitterness, and Qu aroma. The results demonstrate the significant influence of raw material selection and liquefaction method on both flavor profile and microbial diversity in Chinese rice wine.

Exploring microbial dynamics and metabolic pathways shaping flavor profiles in Huangjiu through metagenomic analysis

In the production of Huangjiu (Chinese rice wine), fermentation microbiota plays a crucial role in flavor formation. This study investigates the microbial dynamics and metabolic pathways that shape the flavor profiles of Huangjiu using different starters. Sensory evaluation and metabolite analysis of six starters revealed significant differences in ester, fruity, and sweet aromas. Saccharomyces, Aspergillus, and Rhizopus were identified as the dominant genera significantly impacting fermentation. Metagenomic species and functional gene annotations of Huangjiu starters elucidated the metabolic pathways for key flavor compounds synthesis pathways. Enzyme genes involved in these pathways were classified and annotated to microbial genera using the NR database, identifying 231 classes of relevant catalytic enzymes and 154 microbial genera. A metabolic relationship between flavor compound formation and different microbial genera was established using catalytic enzymes as a bridge. This study highlights the impact of starter composition on the final product and provides new insights for optimizing starters to enhance Huangjiu flavor quality.

Analysis of the association between microbiota and flavor formation during Zizhong Dongjian fermentation process

Zizhong Dongjian (ZZDJ) is one of the most famous and popular fermented vegetables in China. The aim of this study was to explore the microbial communities and volatile flavor compounds of ZZDJ during different fermentation periods, as well as to reveal the potential correlation between microbiota and flavor. A total of 84 volatile flavor compounds were detected in 0-year to 3-year ZZDJ samples. Hydrocarbons were the most abundant flavor compounds in 0-year and 1-year samples, while esters became the predominant flavor components in 2-year and 3-year samples. Furthermore, Loigolactobacillus, Pseudomonas, and Virgibacillus were most predominant bacteria during the fermentation process of ZZDJ. Interestingly, all the fungi identified were yeasts. Among them, Zygosaccharomyces and Symmetrospora dominated alternatively throughout the fermentation process of ZZDJ. Through analysis of relativity between flavor compounds and microorganism of ZZDJ, we found that Uncultured Pseudomonas sp., Virgibacillus sediminis, Zygosaccharomyces rouxii, and Symmetrospora marina might play important roles in flavor information of ZZDJ.

Metatranscriptomics reveals microbial community function succession and characteristic flavor formation mechanisms during black rice wine fermentation

Black rice wine (BRW) is a traditional Chinese rice wine with unique flavors; however, the formation pathways of flavor compounds driven by microbiota remain unclear. This study employed HPLC and GC-MS to reveal that during BRW fermentation, free amino acids increased sevenfold, volatile compounds doubled, and 28 key characteristic flavor compounds were identified. Metatranscriptomic analysis indicated that during fermentation, driven by physicochemical factors and microbial interactions, Saccharomyces gradually became the dominant active microorganism (relative abundance 87.01%-97.70%). Other dominant microorganisms (relative abundance >0.1%), including Saccharomycopsis, Pediococcus, Wickerhamomyces, and Weissella, significantly decreased. Meanwhile, the microflora's signature functions underwent succession: transcription early, carbohydrate metabolism mid-stage, and autophagy late. These microbial and functional successions facilitated the accumulation of flavor compounds. Metabolic network reconstruction revealed that Saccharomyces was pivotal in substrate degradation and flavor formation, while other dominant microorganisms actively promoted these processes. This study provides insights into regulating BRW's flavor through microorganisms.

Influence and metabolomic basis of an indigenous yeast CECA, from Ningxia wine region of China, on the aroma and flavor of Cabernet Sauvignon wines

In this study, three fermentation treatments of spontaneous fermentation (SF), direct inoculation of CECA (YF), and inoculation with CECA after addition of dimethyl dicarbonate (YDF) were carried out. Multivariate statistical analysis approved that CECA inoculation significantly influenced the composition of 141 metabolites (15 volatile organic compounds (VOCs) and 126 non-VOCs), mainly consisting of 36 acids and derivatives and 25 lipids and lipid-like molecules. YF and YDF wines exhibited similar correlations with aroma types, while there were differences in the kinds and number of VOCs. Moreover, CECA-inoculated fermentation was more favorable to the formation of aftertaste-A, umami, sourness, and richness. The KEGG metabolic pathway analysis indicated that the inoculation strategy significantly affected the amino acid metabolism. The antimicrobial treatment effectively enhanced bitterness, astringency, umami and saltiness while reducing acidity. Further studies are needed to assess the effects of antimicrobial treatment on lipid metabolism.

Investigation into the Production of Melanin from By-Products of Huangjiu Brewing

Melanin is a high value bioproduct generated through the fermentation of Aureobasidium pullulans, playing a crucial role in various fields, including food, medicine, environmental protection, and materials science. However, its high production costs and low synthetic yields significantly limit its applications. Therefore, it is essential to identify high-yield strains, reduce production costs, and optimize fermentation strategies. In this study, a high melanin-yielding Aureobasidium pullulans 53LC7 was screened and identified, and the fermentation process was optimized based on melanin yield, color value, and pullulan yield. The results indicated that the melanin yield peaked at an initial pH of 6.0, temperature of 27 °C, fermentation time of 6.5 d, and inoculation quantity of 2.5%, achieving a melanin yield of 16.33 g/L. Subsequently, huangjiu lees, a byproduct of huangjiu production, was incorporated into the fermentation medium, resulting in a melanin yield of 5.91 g/L. This suggests that the Aureobasidium pullulans was not effectively utilizing huangjiu lees. To address this, we employed an adaptive evolution strategy, which increased the melanin yield to 8.72 g/L. The enhanced production was correlated with the expression of key genes, including FKS, PKS, and Cmr1. Finally, cellulase was utilized to convert the crude fibers in huangjiu lees, which were difficult to utilize, into usable substrates, while pullulanase was employed to minimize byproduct formation in the fermentation system, resulting in a melanin yield of 19.07 g/L. This study not only provides promising strains for further research but also offers valuable insights for resource production technologies.

Application of fixed-frequency ultrasound in the cultivation of Saccharomyces cerevisiae for rice wine fermentation

BACKGROUND

Rice wine (RW) fermentation is limited by its long fermentation time, weak taste and unpleasant flavors such as oil and odor. In this study, a novel ultrasound technology of Saccharomyces cerevisiae was used with the aim of improving fermentation efficiency and volatile flavor quality of RW.

RESULTS

The results showed that fixed-frequency ultrasonic treatment (28 kHz, 45 W L-1, 20 min) of S. cerevisiae seed culture at its logarithmic metaphase significantly increased the biomass and alcohol yield by 31.58% and 26.45%, respectively, and reduced fermentation time by nearly 2 days. Flavor analysis indicated that the flavor compounds in RW, specifically the esters and alcohols, were also increased in quantity after the ultrasonic treatment of S. cerevisiae seed liquid. Isobutyl acetate, ethyl butyrate, ethyl hexanoate and phenethyl acetate contents were increased by 78.92%, 129.19%, 7.79% and 97.84%, respectively, as compared to the control.

CONCLUSION

Ultrasonic treatment of S. cerevisiae reduced fermentation time and enhanced the flavor profile of RW. This study could provide a theoretical and/or technological basis for the research and development of RW. © 2024 Society of Chemical Industry.

Transcriptome Analysis Reveals the Variations in Enzyme Production of Saccharopolyspora rosea A22 under Different Temperatures

Saccharopolyspora is a key microorganism in the fermentation of traditional fermented foods, capable of producing saccharifying and liquefying enzymes at elevated temperatures. However, the specific mechanisms and regulatory pathways governing Saccharopolyspora's response to ambient temperatures are not yet fully understood. In this study, the morphological differences in Saccharopolyspora rosea screened from traditional handmade wheat Qu at different temperatures were initially explored. At 37 °C, the mycelium exhibited abundant growth and radiated in a network-like pattern. As the temperature increased, the mycelium aggregated into clusters. At 50 °C, it formed highly aggregated ellipsoidal structures, with the mycelium distributed on the spherical surface. Subsequently, we assessed the biomass, saccharifying enzyme activity and liquefying enzyme activity of Saccharopolyspora rosea cultured at 37 °C, 42 °C and 50 °C. Furthermore, transcriptome analysis demonstrated that Saccharopolyspora rosea employs mechanisms related to the carbon metabolism, the TCA cycle, glycine, serine and threonine metabolisms, and microbial metabolism in diverse environments to coordinate its responses to changes in environmental temperature, as verified by the expression of typical genes. This study enhances our understanding of the differences in high-temperature enzyme production by Saccharopolyspora, and offers valuable guidance for the traditional fermented food industry to drive innovation.

A Comparative Study of Microbial Communities, Biogenic Amines, and Volatile Profiles in the Brewing Process of Rice Wines with Hongqu and Xiaoqu as Fermentation Starters

Rice wine is primarily crafted from grains through saccharification and liquification with the help of Qu. Qu plays an important role in the formation of the flavor quality of rice wine. Hongqu and Xiaoqu represent two prevalent varieties of Qu that are typically utilized in the brewing process of rice wine and play a crucial role in its production. In this study, GC, GC-MS, HPLC, and metagenomic sequencing techniques were used to contrast the microbial flora, biogenic amines, and aroma characteristics developed during the fermentation of rice wines, with Hongqu and Xiaoqu being used as initiating agents for the brewing process. The results show that the content of higher alcohols (including n-propanol, isobutanol, 3-methyl-1-butanol, and phenethyl alcohol) in rice wine brewed with Xiaoqu (XQW) was significantly higher than that in rice wine brewed with Hongqu (HQW). Contrarily, the concentration of biogenic amines in HQW surpassed that of XQW by a notable margin, but tyramine was significantly enriched in XQW and not detected in HQW. In addition, a multivariate statistical analysis revealed distinct disparities in the constitution of volatile components between HQW and XQW. Hexanoic acid, ethyl acetate, isoamyl acetate, ethyl caproate, ethyl decanoate, 2-methoxy-4-vinylphenol, etc., were identified as the characteristic aroma-active compounds in HQW and XQW. A microbiome analysis based on metagenomic sequencing showed that HQW and XQW had different dominant microorganisms in the brewing process. Burkholderia, Klebsiella, Leuconostoc, Monascus, and Aspergillus were identified as the primary microbial genera in the HQW fermentation period, while Pediococcus, Enterobacter, Rhizopus, Ascoidea, and Wickerhamomyces were the main microbial genera in the XQW brewing process. A bioinformatics analysis revealed that the concentrations of microbial genes involved in biogenic amines and esters biosynthesis were significantly higher in HQW than those in XQW, while the content of genes relevant to glycolysis, higher alcohol biosynthesis, and fatty acid metabolism was significantly higher in XQW than in HQW, which are the possible reasons for the difference in flavor quality between the two kinds of rice wine from the perspective of microbial functional genes.

Characterization of key aroma compounds in a novel Chinese rice wine Xijiao Huojiu during its biological-ageing-like process by untargeted metabolomics

Xijiao Huojiu (Xijiao), an ancient Chinese rice wine (ACRW), is produced using traditional methods, which involve biological-ageing-like process and result in distinctive sensory profiles. However, its aroma composition is still unclear. In this study, the aroma characteristics of three samples with varying ageing times were examined. Xijiao_SCT, with a short cellar time, exhibited a strong fruity and floral aroma and a less grain-like aroma. Conversely, Xijiao_LCT, which had a long cellar time, had a deep cocoa- and caramel-like aroma. A total of 27 key odorants that greatly influenced the aroma characteristics of Xijiao were identified. Comparative studies were used to identify 12 key odorants that distinguish Xijiao from modern Chinese rice wine (MCRW) and grape wines (GW). Additionally, 13 dominant latent ageing markers differentiated Xijiao_SCT from Xijiao_LCT. Our results suggested that ACRW and MCRW have overlapping but distinct volatile metabolomic profiles, highlighting the characteristics of ACRW during ageing process.

Comparative analysis of sensory features, microbial diversity, and their correlations in light-flavor Daqu from different regions

This study performed a comparative analysis of the sensory and microbial profiles of light-flavor Bijou (LFD) from Taiyuan (Shanxi Province) and Suizhou (Hubei Province) in China. The results of the electronic nose showed that the aromatic substances of the LFD from Taiyuan (TLFD) were significantly higher (p < .05), while alcohol and aldehyde substances were significantly lower (p < .05) compared with the LFD from Suizhou (SLFD). The average response values of sensors W1C (sensitive to aromatic hydrocarbons), W3C (sensitive to amine and aromatic components), W5C (sensitive to olefins, aromatics, and polar molecules), and W2S (sensitive to alcohol and aldehyde compounds) to TLFD were 0.26, 0.33, 0.34, and 7.72, whereas the response values to SLFD were 0.25, 0.32, 0.33, and 8.04, respectively. The electronic tongue results showed that the aftertaste A (bitter aftertaste) and aftertaste B (astringent aftertaste) of the TLFD were significantly higher (p < .05) and umami was significantly lower (p < .05) as compared to the SLFD. The relative intensities of the aftertaste A, aftertaste B, and umami indicators of TLFD were 0.10, -0.008, and -0.22, respectively, while those of SLFD were -0.23, -0.36, and 0.835, respectively. MiSeq high-throughput sequencing results showed that TLFD exhibited lower fungal richness and diversity compared to SLFD. The dominant bacterial genera were mainly Bacillus (58.12%), Kroppenstedtia (10.11%), and Weissella (6.26%), and the dominant fungal genera were Saccharomycopsis (67.53%), Rasamsonia (9.90%), and Thermoascus (7.10%). Streptomyces and Staphylococcus were identified as the key characteristic microorganisms in TLFD, while Kroppenstedtia, Rasamsonia, and Thermoascus were the key characteristic microorganisms in SLFD. Correlation analysis indicated a stronger correlation between microorganisms and sensory characteristics in SLFD samples. This study provides valuable insights into the sensory and microbiological characteristics of LFD from different regions and offers a new perspective for understanding the production of differently flavored light-flavor Baijiu.

Application of Strain Selection Technology in Alcoholic Beverages: A Review

The diversity of alcohol beverage microorganisms is of great significance for improving the brewing process and the quality of alcohol beverage products. During the process of making alcoholic beverages, a group of microorganisms, represented by yeast and lactic acid bacteria, conducts fermentation. These microorganisms have complex synergistic or competitive relationships, and the participation of different microorganisms has a major impact on the fermentation process and the flavor and aroma of the product. Strain selection is one of the key steps. Utilizing scientific breeding technology, the relationship between strains can be managed, the composition of the alcoholic beverage microbial community can be improved, and the quality and flavor of the alcoholic beverage products can be increased. Currently, research on the microbial diversity of alcohol beverages has received extensive attention. However, the selection technology for dominant bacteria in alcohol beverages has not yet been systematically summarized. To breed better-quality alcohol beverage strains and improve the quality and characteristics of wine, this paper introduces the microbial diversity characteristics of the world's three major brewing alcohols: beer, wine, and yellow wine, as well as the breeding technologies of related strains. The application of culture selection technology in the study of microbial diversity of brewed wine was reviewed and analyzed. The strain selection technology and alcohol beverage process should be combined to explore the potential application of a diverse array of alcohol beverage strains, thereby boosting the quality and flavor of the alcohol beverage and driving the sustainable development of the alcoholic beverage industry.

Comprehensive analysis of flavor formation mechanisms in the mechanized preparation Cantonese soy sauce koji using absolute quantitative metabolomics and microbiomics approaches

Based on the widespread application and under-research of mechanized preparation Cantonese soy sauce koji (MP), absolute quantitative approaches were utilized to systematically analyze the flavor formation mechanism in MP. The results indicated that the enzyme activities increased greatly during MP fermentation, and 4 organic acids, 15 amino acids, and 2 volatiles were identified as significantly different flavor actives. The flavor parameters of MP4 were basically identical to those of MP5. Furthermore, microorganisms were dominated by Staphylococcus, Weissella, and Aspergillus in MP, and their biomass demonstrated an increasing trend. A precise enumeration of microorganisms exposed the inaccuracy of relative quantitative data. Concurrently, Staphylococcus and Aspergillus were positively correlated with numerous enzymes and flavor compounds, and targeted strains for enhancing MP quality. The flavor formation network comprises pathways including carbohydrate metabolism, lipid metabolism and oxidation, and protein degradation and amino acid metabolism. In summary, the fermentation period of MP can be substantially shortened without compromising the product quality. These findings lay the groundwork for refining parameters in modern production processes.

Environmental factors drive microbial community succession in biofortified wheat Qu and its improvement on the quality of Chinese huangjiu

Wheat Qu plays the role of saccharification fermentation, providing microorganisms and flavor in the fermentation of huangjiu, and the use of functional microorganisms to fortify wheat Qu is becoming increasingly popular. Yet, the mechanisms promoting microbial successions of wheat Qu remain unclear. In this study, we first correlated microbial community succession with physicochemical factors (moisture, temperature, acidity, glucoamylase and amylase) in inoculated raw wheat Qu (IRWQ) with Saccharopolyspora rosea. The Mantel test was performed to investigate the significance and found that temperature (r = 0.759, P = 0.001), moisture (r = 0.732, P = 0.006), and acidity (r = 0.712, P = 0.017) correlated significantly with the bacterial community in phase 1 (0-40 h). Meanwhile, temperature correlated significantly with the fungal community in phases 1 and 2 (40-120 h). To confirm the effect of temperature on microbial communities, the artificial reduction of bio-heat (37°C) in IRWQ also reduced the relative abundance of heat-resistant microorganisms including Bacillus and Saccharopolyspora. A higher abundance of Saccharopolyspora (87%) in IRWQ was observed following biofortified inoculation of S. rosea, in which glucoamylase activity increased by 40% compared to non-inoculated raw wheat Qu (NIRWQ) (1086 U/g vs 776 U/g). Finally, the IRWQ was employed to mechanized huangjiu fermentation and it was found to reduce the bitter amino acid and higher alcohol content by 27% and 8%, respectively, improving the drinking comfort and quality of huangjiu.

Monaspin B, a Novel Cyclohexyl-furan from Cocultivation of Monascus purpureus and Aspergillus oryzae, Exhibits Potent Antileukemic Activity

Natural products are a rich resource for the discovery of innovative drugs. Microbial cocultivation enables discovery of novel natural products through tandem enzymatic catalysis between different fungi. In this study, Monascus purpureus, as a food fermentation strain capable of producing abundant natural products, was chosen as an example of a cocultivation pair strain. Cocultivation screening revealed that M. purpureus and Aspergillus oryzae led to the production of two novel cyclohexyl-furans, Monaspins A and B. Optimization of the cocultivation mode and media enhanced the production of Monaspins A and B to 1.2 and 0.8 mg/L, respectively. Monaspins A and B were structurally elucidated by HR-ESI-MS and NMR. Furthermore, Monaspin B displayed potent antiproliferative activity against the leukemic HL-60 cell line by inducing apoptosis, with a half-maximal inhibitory concentration (IC50) of 160 nM. Moreover, in a mouse leukemia model, Monaspin B exhibited a promising in vivo antileukemic effect by reducing white blood cell, lymphocyte, and neutrophil counts. Collectively, these results indicate that Monaspin B is a promising candidate agent for leukemia therapy.

Effects of different lactic acid bacteria on the characteristic flavor profiles of Chinese rice wine

BACKGROUND

It has been well accepted that lactic acid bacteria (LAB) are the main bacterial genera present during the brewing of Chinese rice wine (CRW). LAB plays a decisive role in the flavor quality of CRW; however, its application in CRW has previously been overlooked. Therefore, effects of different LAB as co-fermenter on the flavor characteristics of CRW were investigated.

RESULTS

Co-fermentation of LAB increased the utilization rate of reducing sugar, concentration of lactic acid, amino acid nitrogen and total acidity, as well as the content of volatile flavor compounds. Different LAB doses had little effect on the flavor profiles of CRW, but the species of LAB greatly affected the flavor characteristic. The flavor of CRW co-fermented with Lactococcus lactis was characterized by long-chain fatty acid ethyl esters, while co-fermentation with Weissella confusa highlighted the ethyl esters of low molecular weight and short carbon chains in the resultant CRW. Alcohol compounds were dominant in the CRW co-fermented using Pediococcus pentosaceus.

CONCLUSION

The co-fermentation of LAB increased the number of volatile flavor compounds, especially esters. LAB exhibited great potential in the application of CRW industry to enrich the flavor characteristics and enhance the flavor diversity of the final product. © 2023 Society of Chemical Industry.

Correlation between changes in flavor compounds and microbial community ecological succession in the liquid fermentation of rice wine

Microorganisms play an important role in regulating flavor compounds in rice wine, whereas we often don't understand how did they affect flavor compounds. Here, the relations between flavor compounds and microbial community ecological succession were investigated by monitoring flavor compounds and microbial community throughout the fermentation stage of rice wine. The composition of microbial community showed a dynamic change, but 13 dominant bacterial genera and 4 dominant fungal genera were detected throughout the fermentation stages. Saccharomyces presented a strong negative correlation with fungi genera but had positive associations with bacteria genera. Similarly, flavor compounds in rice wine were also showed the dynamic change, and 112 volatile compounds and 17 free amino acids were identified in the whole stages. The alcohol-ester ratio was decreased in the LTF stage, indicating that low temperature boosts ester formation. The potential correlation between flavor compounds and microbial community indicated that Delftia, Chryseobacterium, Rhizopus and Wickerhamomyces were the core functional microorganisms in rice wine. These findings clarified the correlation between changes in flavor compounds and in microbial community in the liquid fermentation of rice wine, and these results have some reference value for the quality improvement and technological optimization in liquid fermentation of rice wine.

Insights into microbial communities and metabolic profiles in the traditional production of the two representative Hongqu rice wines fermented with Gutian Qu and Wuyi Qu based on single-molecule real-time sequencing

Hongqu rice wine, a famous traditional fermented alcoholic beverage, is brewed with traditional Hongqu (mainly including Gutian Qu and Wuyi Qu). This study aimed to compare the microbial communities and metabolic profiles in the traditional brewing of Hongqu rice wines fermented with Gutian Qu and Wuyi Qu. Compared with Hongqu rice wine fermented with Wuyi Qu (WY), Hongqu rice wine fermented with Gutian Qu (GT) exhibited higher levels of biogenic amines. The composition of volatile flavor components of Hongqu rice wine brewed by different fermentation starters (Gutian Qu and Wuyi Qu) was obviously different. Among them, ethyl acetate, isobutanol, 3-methylbutan-1-ol, ethyl decanoate, ethyl palmitate, ethyl oleate, nonanoic acid, 4-ethylguaiacol, 5-pentyldihydro-2(3H)-furanone, ethyl acetate, n-decanoic acid etc. were identified as the characteristic aroma-active compounds between GT and WY. Microbiome analysis based on high-throughput sequencing of full-length 16S rDNA/ITS-5.8S rDNA amplicons revealed that Lactococcus, Leuconostoc, Pseudomonas, Serratia, Enterobacter, Weissella, Saccharomyces, Monascus and Candida were the predominant microbial genera during the traditional production of GT, while Lactococcus, Lactobacillus, Leuconostoc, Enterobacter, Kozakia, Weissella, Klebsiella, Cronobacter, Saccharomyces, Millerozyma, Monascus, Talaromyces and Meyerozyma were the predominant microbial genera in the traditional fermentation of WY. Correlation analysis revealed that Lactobacillus showed significant positive correlations with most of the characteristic volatile flavor components and biogenic amines. Furthermore, bioinformatical analysis based on PICRUSt revealed that microbial enzymes related to biogenic amines synthesis were more abundant in GT than those in WY, and the enzymes responsible for the degradation of biogenic amines were less abundant in GT than those in WY. Collectively, this study provides important scientific data for enhancing the flavor quality of Hongqu rice wine, and lays a solid foundation for the healthy and sustainable development of Hongqu rice wine industry.

Comparative analysis of microbial communities and volatile flavor components in the brewing of Hongqu rice wines fermented with different starters

As one of the quintessential representatives of Chinese rice wine, Hongqu rice wine is brewed with glutinous rice as the main raw material and Hongqu (Gutian Qu or Wuyi Qu) as the fermentation starter. The present study aimed to investigate the impact of Hongqu on the volatile compositions and the microbial communities in the traditional production of Gutian Hongqu rice wine (GT) and Wuyi Hongqu rice wine (WY). Through the OPLS-DA analysis, 3-methylbutan-1-ol, isobutanol, ethyl lactate, ethyl acetate, octanoic acid, diethyl succinate, phenylethyl alcohol, hexanoic acid and n-decanoic acid were identified as the characteristic volatile flavor components between GT and WY. Microbiome analysis revealed significant enrichments of Lactobacillus, Pediococcus, Aspergillus and Hyphopichia in WY brewing, whereas Monascus, Saccharomyces, Pantoea, and Burkholderia-Caballeronia-Paraburkholderia were significantly enriched in GT brewing. Additionally, correlation analysis showed that Saccharomyces, Lactobacillus, Weissella and Pediococcus were significantly positively correlated wih most characteristic volatile components. Conversely, Picha, Monascus, Franconibacter and Kosakonia showed significant negative correlations with most of the characteristic volatile components. Furthermore, bioinformatical analysis indicated that the gene abundances for enzymes including glucan 1,4-alpha-glucosidase, carboxylesterase, alcohol dehydrogenase, dihydroxy-acid dehydratase and branched-chain-amino-acid transaminase were significantly higher in WY compared to GT. This finding explains the higher content of higher alcohols and characteristic esters in WY relative to GT. Collectively, this study provides a theoretical basis for improving the flavor profile of Hongqu rice wine and establishing a solid scientific foundation for the sustainable development of Hongqu rice wine industry.

Diversifying the Flavor of Black Rice Wines through Three Different Regional Xiaoqus in China and Unraveling Their Core Functional Microorganisms

The flavor of black rice wine (BRW) can be diversified by the Xiaoqus, from different regions; however, the functional microbiota that contributes to its flavor remains unclear. Accordingly, this study selected three regional Xiaoqus from Sichuan Dazhu (Q1), Jiangxi Yingtan (Q2), and Hubei Fangxian (Q3) as starters to investigate flavor compounds and microbial communities during BRW brewing. Results indicated that altogether 61 flavor substances were identified, 16 of which were common characteristic flavor compounds (odor activity value > 0.1). Each BRW possessed unique characteristic flavor compounds. O2PLS and Spearman's correlation analysis determined that characteristic flavor compounds of BRW were mainly produced by Saccharomyces cerevisiae, non-Saccharomyces yeasts, and lactic acid bacteria, with the common core functional strains being Wickerhamomyces and Pediococcus, and with their unique core functional strain likely causing a unique characteristic flavor. This study could promote the high-quality development of the black rice wine industry.

Integrated meta-omics approaches reveal Saccharopolyspora as the core functional genus in huangjiu fermentations

Identification of the core functional microorganisms in food fermentations is necessary to understand the ecological and functional processes for making those foods. Wheat qu, which provides liquefaction and saccharifying power, and affects the flavor quality, is a key ingredient in ancient alcoholic huangjiu fermentation, while core microbiota of them still remains indistinct. In this study, metagenomics, metabolomics, microbial isolation and co-fermentation were used to investigate huangjiu. Although Aspergillus is usually regarded as core microorganism in wheat qu to initiate huangjiu fermentations, our metagenomic analysis showed that bacteria Saccharopolyspora are predominant in wheat qu and responsible for breakdown of starch and cellulose. Metabolic network and correlation analysis showed that Saccharopolyspora rectivirgula, Saccharopolyspora erythraea, and Saccharopolyspora hirsuta made the greatest contributions to huangjiu's metabolites, consisting of alcohols (phenylethanol, isoamylol and isobutanol), esters, amino acids (Pro, Arg, Glu and Ala) and organic acids (lactate, tartrate, acetate and citrate). S. hirsuta J2 isolated from wheat qu had the highest amylase, glucoamylase and protease activities. Co-fermentations of S. hirsuta J2 with S. cerevisiae HJ resulted in a higher fermentation rate and alcohol content, and huangjiu flavors were more similar to that of traditional huangjiu compared to co-fermentations of Aspergillus or Lactiplantibacillus with S. cerevisiae HJ. Genome of S. hirsuta J2 contained genes encoding biogenic amine degradation enzymes. By S. hirsuta J2 inoculation, biogenic amine content was reduced by 45%, 43% and 62% in huangjiu, sausage and soy sauce, respectively. These findings show the utility of Saccharopolyspora as a key functional organism in fermented food products.

Microbial Communities and Correlation between Microbiota and Volatile Compounds in Fermentation Starters of Chinese Sweet Rice Wine from Different Regions

Chinese sweet rice wines (CSRW) are traditional, regionally distinct alcoholic beverages that are generally brewed with glutinous rice and fermentation starters. This study aimed to characterize microbial communities and volatile compounds of CSRW starters and explore correlations between them. The major volatiles in starters include 1-heptanol, 1-octanol, 2-nonanol, phenylethyl alcohol, 2-nonanone, acetophenone, and benzaldehyde. Microbiological analysis based on high-throughput sequencing (HTS) technology demonstrated that starter bacterial communities are dominated by Weissella, Pediococcus, and Lactobacillus, while Saccharomycopsis and Rhizopus predominate in fungal communities. Carbohydrate and amino acid metabolism are the most active metabolic pathways in starters. Spearman correlation analysis revealed that 15 important volatile compounds including alcohols, acids, aldehydes and esters were significantly positively correlated with nine microbial genera (|r| > 0.7, p < 0.05), including five bacterial genera (i.e., Weissella, Pediococcus, Lactobacillus, Bacillus, and Nocardiopsis) and four fungal genera (i.e., Saccharomycopsis, Rhizopus, Wickerhamomyces, and Cyberlindnera), spanning 19 distinct relationships and these microorganisms were considered the core functional microorganisms in CSRW starters. The most important positive correlations detected between phenylethyl alcohol and Weissella or Saccharomycopsis and between 2-nonanol and Pediococcus. This study can serve as a reference to guide the development of defined starter cultures for improving the aromatic quality of CSRW.

The dynamics of physicochemical properties, microbial community, and flavor metabolites during the fermentation of semi-dry Hakka rice wine and traditional sweet rice wine

The dynamics of physicochemical properties, microbial community and flavor metabolites during fermentation of two typical Hakka rice wine were investigated. Results showed that total sugar content was 136.83 g/L in sweet rice wine, which almost 8 times higher than that in semi-dry rice wine. Its amino acid contents especially bitterness amino acids were also higher than those in semi-dry rice wine. Most organic acids in Hakka rice wine had the tendency of increase in initial stage of fermentation, following a decrease and finally being almost stable. A total of 131 volatiles including esters, alcohols, aldehydes, acids, ketones were detected. Pediococcus, Bacillus, Acinetobacter, Pantoea, Enterobacter and Lactobacillus were the dominant bacterial genera and Monascus, Saccharomyces, Rhizopus were the dominant fungal genera, which are strongly associated with the significant changes in flavor metabolites during Hakka rice wine fermentation. The obtained findings provided reference data for the optimization of Hakka rice wine fermentation.

The Production of Intensified Qu and Its Microbial Communities and Aroma Variation during the Fermentation of Huangjiu (Chinese Rice Wine)

In recent years, intensified Qu (IQ) has been gradually applied to brewing in order to improve the aroma of Huangjiu (Chinese rice wine). In this study, Saccharomyces cerevisiae and Wickerhamomyces anomalus solutions were added to Fengmi Qu (FMQ) from Fangxian, China to produce IQ, and brewing trial was conducted. High-throughput sequencing (HTS) was used to analyze the microbial community in fermentation broth of IQ (IQFB). Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and sensory evaluation were performed to analyze volatile aroma compounds (VACs) in sample without Qu and both fermentation broths. The results showed that Pediococcus, Cronobacter, Enterococcus, Weissella, and Acinetobacter and Saccharomycopsis, Wickerhamomyces, and Saccharomyces were dominant bacterial and fungal groups, respectively. A total of 115 VACs were detected, and the content of esters including ethyl acetate, isoamyl acetate, and so on was noticeably higher in IQFB. The finding of sensory evaluation reflected that adding pure yeast to Qu could enhance fruit and floral aromas. Correlation analysis yielded 858 correlations between significant microorganisms and different VACs. In addition, prediction of microbial community functions in IQFB revealed global and overview maps and carbohydrate metabolism to be the main one. This study is advantageous for further regulation of the fermentation process of Huangjiu by microbial means.

The differences in main components, enzyme activity, and microbial composition between substandard and normal jiuyao

BACKGROUND

Jiuyao is a critical fermenting agent in traditional huangjiu brewing and it affects the quality of huangjiu. To assess and monitor the quality of jiuyao effectively we determined the differences between two common types of substandard jiuyao and normal jiuyao, with emphasis on the comparison of the main components, enzymatic activity, volatile substances, and microbial community structure.

RESULTS

The water and starch content, acid protease activity, and esterification capability of type I substandard jiuyao were significantly lower than those of the normal jiuyao, and the protein contents, liquefaction capability, glycation capability, and neutral protease activity were substantially higher than those of the normal jiuyao. Type II substandard jiuyao had significantly lower indices than the normal group except for the starch and free amino acid content, which were significantly higher than those of the normal jiuyao. Significant differences were observed between substandard and normal jiuyao in the content of 21 volatile compounds. 2-Pentylfuran could be used as a marker of substandard jiuyao. Type I substandard jiuyao contained a higher abundance of aerobic Pediococcus and Marivita in comparison with the normal jiuyao. Type II substandard jiuyao consisted of a greater abundance of anaerobic Mucor and Staphylococcus.

CONCLUSION

The quality of jiuyao was significantly affected by the water content. Due to the different abundances of aerobic and anaerobic bacteria in jiuyao, oxygen may also be an important parameter affecting the quality of jiuyao. We believe that the present study offers a theoretical basis for the evaluation and control of the quality of jiuyao. © 2023 Society of Chemical Industry.

Enhancement in the physicochemical properties, antioxidant activity, volatile compounds, and non-volatile compounds of watermelon juices through Lactobacillus plantarum JHT78 fermentation

In this study, the influences of Lactobacillus plantarum JHT78 fermentation on the physiological properties, antioxidant activities, and volatile/non-volatile metabolites of watermelon juices were comprehensively investigated. The results indicated that total polyphenols flavonoids and anthocyanin in the watermelon juices remarkably increased through L. plantarum JHT78 fermentation. L. plantarum JHT78 fermentation enhanced the antioxidant activities, lipase inhibition, and α-glucosidase activities of watermelon juices. A total of 62 volatile compounds were detected using HS-SPME-GC-MS, mainly including 11 acids, 8 aldehydes, 7 ketones, and 7 alcohols. The abundance of 19 volatile compounds especially for acids remarkably increased for the fermentated watermelon juice. Furthermore, non-volatile compounds detected by UHPLC-QTOF-MS revealed that L. plantarum JHT78 significantly altered the non-volatile compounds of watermelon juices, especially increased indole-3-lactic acid. The results confirmed that L. plantarum JHT78 enhanced the functionality of watermelon juices thus providing a theoretical basis for the development of LAB on plant-based beverages.

Analysis of the formation mechanism of volatile and non-volatile flavor substances in corn wine fermentation based on high-throughput sequencing and metabolomics

The purpose of this study was to reveal the relationship between core microorganisms and flavor substances in the fermentation process of corn wine. Microbial diversity, volatile and non-volatile flavor substances were detected by high-throughput sequencing (HTS), headspace solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) and gas chromatography time of flight mass spectrometry (GC-TOF-MS). High performance liquid chromatography (HPLC) was used to detect organic acids in corn wine fermentation, and its physiochemical properties were tracked. The results showed that physiochemical factors changed obviously with fermentation time. Bacillus, Prevotella_9, Acinetobacter and Gluconobacter were the predominant bacterial. Rhizopus and Saccharomyces were the dominant fungi. Acetic acid and succinic acid were important organic acids in corn wine. According to variable importance of projection (VIP) > 1 and P < 0.05, 24 volatile flavor substances with significant difference were screened out from 52 volatile flavor substances. Similarly, 25 non-volatile flavor substances with significant differences were screened out from the 97 reliable metabolites identified by 223 chromatographic peaks. Eight key metabolic pathways were enriched from 25 non-volatile flavor substances according to path influence values > 0.1 and P < 0.05. Based on Two-way Orthogonal Partial Least Squares (O2PLS) model and Pearson correlation coefficient, Saccharomyces, Rhizopus, uncultured_bacterium, Aneurinibacillus, Wickerhamomyces and Gluconobacter may be the potential volatile flavor-contributing microorganism genus in corn wine. The Pearson correlation coefficient showed that Saccharomyces was significantly positively correlated with malic acid, oxalic acid, valine and isoleucine, and Rhizopus was positively correlated with glucose-1-phosphate and alanine. These findings enhanced our understanding of the formation mechanism of flavor substances in corn wine and provided the theoretical basis for stabilizing flavor quality of corn wine.

Fungal Biomarkers in Traditional Starter Determine the Chemical Characteristics of Turbid Rice Wine from the Rim of the Sichuan Basin, China

The fungal community in Qu plays a key role in the formation of turbid rice wine (TRW) style. The Sichuan Basin and its surrounding areas have become one of the main TRW production regions in China; however, the fungal community in Qu and how they affect the characteristics of TRW remain unknown. Therefore, this study provided insight into the fungal biomarkers in Qu from Guang'an (GQ), Dazhou (DQ), Aba (AQ), and Liangshan (LQ), as well as their relationships with compounds in TRW. The main biomarkers in GQ were Rhizopus arrhizus, Candida glabrata, Rhizomucor pusillus, Thermomyces lanuginosus and Wallemia sebi. However, they changed to Saccharomycopsis fibuligera and Mucor indicus in DQ, Lichtheimia ramose in AQ, and Rhizopus microsporus and Saccharomyces cerevisiae in LQ. As a response to fungal biomarkers, the reducing sugar, ethanol, organic acids, and volatile compounds were also changed markedly in TRWs. Among important volatile compounds (VIP > 1.00), phenethyl alcohol (14.1-29.4%) was dominant in TRWs. Meanwhile, 3-methyl-1-butanol (20.6-56.5%) was dominant in all TRWs except that fermented by GQ (GW). Acetic acid (29.4%) and ethyl palmitate (10.1%) were dominant in GW and LW, respectively. Moreover, GQ biomarkers were positively correlated with acetic acid and all unique important volatile compounds in GW. DQ biomarkers had positive correlations with unique compounds of acetoin and ethyl 5-chloro-1,3,4-thiadiazole-2-carboxylate in DW. Meanwhile, the AQ biomarkers were positively correlated with all AW unique, important, and volatile compounds. Although there were not any unique volatile compounds in LW, 16 important volatile compounds in LW were positively related to LQ biomarkers. Obviously, biomarkers in different geographic Qu played vital roles in the formation of important volatile compounds, which could contribute specific flavor to TRWs. This study provided a scientific understanding for future efforts to promote the excellent characteristics of TRW by regulating beneficial fungal communities.

Effects of fermented feed of Pennisetum giganteum on growth performance, oxidative stress, immunity and gastrointestinal microflora of Boer goats under thermal stress

Introduction

This study was conducted to evaluate the effects of fermented feed of Pennisetum giganteum (P. giganteum) on growth performance, oxidative stress, immunity and gastrointestinal microflora of Boer goats under thermal stress.

Methods

The study was conducted during 45 days using twenty 2 months Boer goats. The goats were randomly allocated into two groups: NPG (n = 10; normal P. giganteum) and FPG (n = 10; fermented feed of P. giganteum), and the ratio of concentrates to roughage was 3:2. Both groups of animals were kept in sheds and exposed to summer thermal stress from 10:00 h to 18:00 h (temperature and humidity index, THI > 78). At the end of the study, the animals were slaughtered and assessed for various characteristics.

Results

The findings from the study revealed that FPG-feeding significantly increased (p < 0.05) average daily gain (ADG, 48.18 g) and carcass weight (4.38 kg), while decreased (p < 0.01) average daily feed intake (ADFI, 0.74 kg/d; p < 0.01) and the feed:gain (F/G, 15.36) ratio. The CAT, GSH-Px activities and GSH in serum, liver and spleen, and the levels of IgA, IgG, IgM, IL-2, IL-4 and IL-1β in serum of FPG-fed goats were significantly higher (p < 0.05) than those of NPG-feeding goats. Further, we found that FPG feed is rich in nutrients with Lactobacillus (65.83%) and Weissella (17.80%). Results for gastrointestinal microbiota composition showed that FPG-feeding significantly enhanced the abundance of Lactobacillus and unidentified Clostridiales, and reduced Anaerovibrio and Methanobrevibacter. Meanwhile, Spearman's correlation analysis showed that these microbiotas were closely related to the improvement of oxidative stress and immune indexes of goats.

Discussion

These results demonstrated that FPG-feeding not only reduces oxidative stress and improves ROS clearance to enhance antioxidant defense system, but also improves gastrointestinal microbiota to enhance immune function by overcoming the adverse effects of heat stress, and further improve growth performance of goats.

Analysis of the Microbial Community Structure and Volatile Metabolites of JIUYAO in Fangxian, China

JIUYAO is an important saccharification starter in the production of huangjiu and is also an important source of flavor. In this study, the microbial community structure of JIUYAO from Fangxian was studied by high-throughput sequencing (HTS) technology for the first time. The volatile flavor compounds of the JIUYAO metabolites were also analyzed by headspace solid-phase microextraction combined with full two-dimensional gas chromatography-mass spectrometry (HS-SPME-GC×GC/MS) for the first time. The results showed that there were 15 dominant bacterial genera, including Weissella, Pediococcus, unclasssified_k_norank_d_Bacteria, Lactobacillus, Leuconostoc, etc. Thirteen species of dominant fungi included Wickerhamomyces, Saccharomycopsis, Rhizopus, etc. The different samples of JIUYAO were similar in their microbial species, but the number of species was significantly different. A total of 191 volatile flavor compounds (VFCs) were detected, among which esters, alcohols, acids, and alkenes were the main flavor compounds, and 21 terpenoids were also detected. In addition, the functional prediction of micro-organisms in JIUYAO revealed that global and overview maps, amino acid metabolism, and carbohydrate metabolism were the dominant categories. Through correlation analysis, 538 potential correlations between the dominant micro-organisms and the different flavor compounds were obtained. This study revealed the interactions between the micro-organisms and the volatile metabolites in JIUYAO, which provided reliable data for the analysis of the microbial community structure of Fangxian JIUYAO and provided theoretical support for the quality evaluation of JIUYAO.

The Existing Recovery Approaches of the Huangjiu Lees and the Future Prospects: A Mini Review

Huangjiu lees (HL) is a byproduct in Chinese Huangjiu production with various nutrient and biological functional components. Without efficient treatment, it could cause environmental issues and bioresource wasting. Existing dominant recovery approaches focus on large-scale disposal, but they ignore the application of high-value components. This study discusses the advantages and limitations of existing resourcing approaches, such as feed, food and biogas biological production, considering the efficiency and value of HL resourcing. The extraction of functional components as a suggestion for HL cascade utilization is pointed out. This study is expected to promote the application of HL resourcing.

Effect of Starters on Quality Characteristics of Hongsuantang, a Chinese Traditional Sour Soup

Hongsuantang (HST) is a traditional Chinese and famous sour soup. However, the quality of naturally fermented HST is not controllable. We investigated the effects of different lactic acid bacteria starters on HST acid production, color, antioxidant capacity, total phenols, total carotenoids, organic acids, volatile substances, and sensory properties to determine the most suitable strain for HST production. The results showed that among the seven lactic acid bacteria strains used to inoculate fermented HST, Lactiplantibacillus plantarum SQ-4 exhibited the most excellent fermentation characteristics. SQ-4 rapidly reduced the HST’s pH by 0.77. It significantly increased the HST’s color, organic acids, total phenols, carotenoids, lycopene, and free radical scavenging ability. Lactiplantibacillus plantarum SQ-4 was an excellent starter for preparing HST with good acid production capacity, moderate sourness and spiciness, and good sensory and other characteristics. Each starter produces its distinct flavor components. α-Pinene, myrcene, α-copaene, and guaiol were vital aroma compounds in HST fermentation by the starter. This study laid a foundation for selecting HST starters and potential industrial production.

Microbial succession and its correlation with the dynamics of volatile compounds involved in fermented minced peppers

Fermented minced peppers are a traditional fermented food that has a unique flavor due to various microbial communities involved in fermentation. Understanding the changes in microbial communities and volatile components of fermented minced peppers is particularly important to unveil the formation of unique flavor of fermented peppers. In this study, the microbial communities and volatile compounds in fermented minced pepper was analyzed by high-throughput sequencing and GC-MS, as well as their underlying correlations were also established. Results indicated that 17 genera were identified as dominant microorganisms in the fermentation of minced pepper, accompanied by the detection of 64 volatile compounds. Further hierarchical clustering analysis (HCA) displayed that dynamic change of volatile metabolites were involved in the fermentation process, where alkane volatile components were mainly generated in the early stage (3–5 days), and alcohols volatile components were in the middle stage (7–17 days), while ester volatile components were mainly produced in both the early stage (3–5 days) and last stage (17–20 days). Bidirectional orthogonal partial least squares (O2PLS) analysis revealed that 11 genera were core functional microorganisms of fermented minced pepper. Cladosporium and Hansenpora were significantly correlated with the formation of 9 and 6 volatiles, respectively. These findings provide new insights into aroma profile variation of fermented minced peppers and underlying mechanism of characteristic aroma formation during fermentation.

The dynamics of microbial community and flavor metabolites during the acetic acid fermentation of Hongqu aromatic vinegar

In this study, we investigated the dynamics of microbial community and flavor metabolites during the traditional fermentation of Hongqu aromatic vinegar (HAV) and subsequently explored the potential relationship between microbiota and flavor metabolites. The microbiome analysis based on high-throughput sequencing (HTS) of amplicons demonstrated that Lactobacillus, Acetobacter and Clostridium were the dominant bacterial genera, while Alternaria, Candida, Aspergillus and Issatchenkia were the dominant fungal genera during the acetic acid fermentation (AAF) of HAV. A total of 101 volatile flavor compounds were identified through gas chromatography-mass spectrometry (GC-MS) during HAV fermentation, including esters (35), alcohols (17), aldehydes (11), acids (11), ketones (7), phenols (10), and others (10). Redundancy analysis (RDA) was used to reveal the correlation between microbiota and volatile flavor compounds. Lactobacillus and Acetobacter were the two bacterial genera that have the great influence on the production of volatile flavor components in HAV. Among them, Lactobacillus was positively correlated with a variety of ethyl esters, while Acetobacter positively contributed to the formation of several organic acids. Furthermore, the non-volatile metabolites were detected by ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS). A total of 41 dipeptides were identified during HAV fermentation, and most of them may have sensory characteristics and biological activities. RDA showed that Aspergillus, Epicoccum, Issatchenkia, Candida and Malassezia were the most influential fungal genera on non-volatile metabolites. In particular, Epicoccum was first reported in Hongqu vinegar and showed a positive correlation with the production of various organic acids. In conclusion, this study provides a scientific basis for understanding the flavor generation mechanism of HAV, and may be valuable for developing effective techniques to select suitable strains to improve the flavor quality of HAV.

Complete genome sequence, metabolic model construction, and huangjiu application of Saccharopolyspora rosea A22, a thermophilic, high amylase and glucoamylase actinomycetes

Saccharopolyspora is an important microorganism in the fermentation process of wheat qu and huangjiu, yet the mechanisms by which it performs specific functions in huangjiu remain unclear. A strain with high amylase and glucoamylase activities was isolated from wheat qu and identified as Saccharopolyspora rosea (S. rosea) A22. We initially reported the whole genome sequence of S. rosea A22, which comprised a circular chromosome 6,562,638 bp in size with a GC content of 71.71%, and 6,118 protein-coding genes. A functional genomic analysis highlighted regulatory genes involved in adaptive mechanisms to harsh conditions, and in vitro experiments revealed that the growth of S. rosea A22 could be regulated in response to the stress condition. Based on whole-genome sequencing, the first genome-scale metabolic model of S. rosea A22 named iSR1310 was constructed to predict the growth ability on different media with 91% accuracy. Finally, S. rosea A22 was applied to huangjiu fermentation by inoculating raw wheat qu, and the results showed that the total higher alcohol content was reduced by 12.64% compared with the control group. This study has elucidated the tolerance mechanisms and enzyme-producing properties of S. rosea A22 at the genetic level, providing new insights into its application to huangjiu.

Study of Fungal Communities in Dry Red Wine Fermentation in Linfen Appellation, Shanxi

In this study, the fermentation mash of Cabernet Sauvignon, Cabernet Franc, and Matheran from Linfen, Shanxi Province, was sequenced using the Illumina MiSeq high-throughput sequencing platform to analyze the structural diversity of fungal communities in different samples. The results showed that a total of 10 phyla, 125 families, and 187 genera were detected in the nine samples of this study. The main fungal phyla were Ascomycota, Basidiomycota, and Mortierellomycota. The main fungal genera are Hanseniaspora, Mortierella, Sclerotinia, Aureobasidium, Saccharomyces, Aspergillus, Clavulina, Candida, etc. Hanseniaspora was the dominant genus in the pre-fermentation stage, accounting for more than 70%; Saccharomyces was the dominant genus in the middle and late fermentation stage, accounting for more than 75% in the middle fermentation stage and up to 90% in the late fermentation stage. This study provides a theoretical basis for monitoring and optimizing winemaking processes and introducing wine grape varieties in the Linfen region of Shanxi.

Effects of the microbial community on the formation of volatile compounds and biogenic amines during the traditional brewing of Hongqu rice wine

As a typical representative of Chinese rice wine (Huangjiu), Hongqu rice wine is famous for its red color, mellow taste and strong fragrance. However, due to the open brewing environment and traditional fermentation technology, there are some safety risks in traditional brewed Hongqu rice wine, such as a certain amount of biogenic amines. In this study, the dynamic changes and the differences of microbial communities and volatile flavor components between two types of Hongqu rice wine with high and low biogenic amine contents (LBAW and HBAW) during the traditional brewing were systematically investigated. The results showed that the total biogenic amine contents in LBAW and HBAW were 20.91 and 69.06 mg/L, respectively. The contents of putrescine, cadaverine, spermine and spermidine in HBAW were significantly higher than those in LBAW, and it was noteworthy that spermine content in HBAW was 17.62 mg/L, which was not detected in LBAW. In addition, the volatile flavor characteristics of the two kinds of Hongqu rice wine were obviously different. The contents of acetophenone, n-butyl butanoate and benzothiazole were obviously higher in HBAW, while the contents of isoamyl acetate, ethyl lactate, ethyl caprate and phenylethyl alcohol were significantly higher in LBAW. High-throughput sequencing of 16S/ITS amplicon revealed that Weissella, Kosakonia, Pantoea, Monascus, Saccharomyces and Millerozyma were the predominant microbial genera during the traditional brewing of HBAW, while Weissella, Kosakonia, Monascus, Saccharomyces and Issatchenkia were the predominant microbial genera during the traditional brewing of LBAW. Correlation analysis revealed that biogenic amines were significantly negatively correlated with unclassified_o_Saccharomycetales, Cyberlindnera, Zygoascus, Aspergillus and Acinetobacter, but positively correlated with Lactobacillus, Pediococcus, Millerozyma and Apiotrichum. In addition, we also found that Lactobacillus, Pediococcus and Saccharomyces were significantly positively correlated with most of the volatile flavor components, while Candida, Trichosporon and Monascus were significantly negatively correlated with most of the volatile flavor components. In addition, bioinformatical analysis based on PICRUSt demonstrated that the key enzymes for biogenic amine biosynthesis were more abundant in the microbial community of HBAW than LBAW. These findings demonstrate that the formations of volatile flavor and biogenic amines in Hongqu rice wine are influenced by microbial community during the fermentation. This work facilitates scientific understanding of the formation mechanism of biogenic amines, and may be useful to develop effective strategies to improve the quality of Hongqu rice wine.