Bacterial Diversity and Lactic Acid Bacteria with High Alcohol Tolerance in the Fermented Grains of Soy Sauce Aroma Type Baijiu in North China

Phenolic metabolites changes during baijiu fermentation through non-targeted metabonomic

To investigate the changes of phenolic metabolite during different grains fermentation stages of Chinse Baijiu, the ultra-performance liquid chromatography-quadrupole time of-flight mass spectrometry (UHPLC-QTOF-MS) was applied to identify and analyze the different phenolic metabolites, combined with principal component analysis and partial least squares discriminant analysis. Results indicated that significant differences in phenolic metabolites during different fermentation stages were found. Among the 231 phenolic metabolites detected, 36, 31, 19, 23, 14, and 50 differential phenolic metabolites were screened between different groups using partial least squares discriminant analysis. Twelve metabolic pathways with high correlation of differential phenolic metabolites and 23 main participating differential metabolites were identified through KEGG metabolic pathway enrichment analysis. The present study preliminarily revealed the differences of phenolic metabolites at different fermentation stages, and providing a theoretical basis for the further improving of the taste and quality of Chinese Baijiu.

Exploiting the beneficial effects of Salvia officinalis L. extracts in human health and assessing their activity as potent functional regulators of food microbiota

Salvia officinalis L. has attracted scientific and industrial interest due to its pharmacological properties. However, its detailed phytochemical profile and its correlation with beneficial effects in the human microbiome and oxidative stress remained elusive. To unveil this, S. officinalis was collected from the region of Epirus and its molecular identity was verified with DNA barcoding. Phytochemical profile for both aqueous and ethanol-based extracts was determined by high-pressure liquid chromatography-tandem mass spectrometry and 103 phytochemicals were determined. The effect of S. officinalis extracts as functional regulators of food microbiota by stimulating the growth of Lacticaseibacillus rhamnosus strains and by suppressing evolution of pathogenic bacteria was verified. Furthermore, we recorded that both extracts exhibited a significant cellular protection against H2O2-induced DNA damage. Finally, both extracts exhibited strong inhibitory effect towards LDL oxidation. This study provides a comprehensive characterization of S. officinalis on its phytochemical components as also its potential impact in human microbiome and oxidative stress.

Unraveling the chemosensory characteristics dependence of sauce-flavor baijiu on regionality using descriptive sensory analysis and quantitative targeted flavoromics

Descriptive sensory analysis, headspace solid-phase microextraction-gas chromatography-mass spectrometry, gas chromatography-flame ionization detector and multivariate statistical analysis were used to elucidate the regional dependence of sauce-flavor baijiu (SFB). Although SFB samples from different regions couldn't be clearly classified by sensory profiles, they could be clearly divided into 5 groups in principal component analysis plot based on quantitative targeted flavoromics analysis. And then, the relationship between sensory attributes and volatile compounds were investigated by network analysis. Twenty regional aroma markers were identified by multivariate statistical analysis to distinguish SFB samples from different regions. Furthermore, the influence of manufacturing operation on SFB in Guizhou region was further analyzed. Thirty-eight potential compounds were significant different in Guizhou SFB samples with different manufacturing operations. This study not only provides a better understanding of regional dependence on SFB flavor, but also further clarifies the inheritance importance of manufacturing operation in traditional SFB production.

Temporal Profile of the Microbial Community and Volatile Compounds in the Third-Round Fermentation of Sauce-Flavor baijiu in the Beijing Region

Sauce-flavor baijiu produced in the Beijing and Guizhou regions has regional characteristic flavors, but the differences in flavor compounds and reasons for their formation remain unclear. The sauce-flavor baijiu brewing process involves several rounds of fermentation. In this study, we investigated the temporal distribution of microbial communities and flavor substances during the third round of sauce-flavor baijiu fermentation in the Beijing region, and we then compared and analyzed the differences of flavor substances and microorganisms in the fermented grains of sauce-flavor baijiu in the Beijing and Guizhou regions. It was found that 10 bacterial genera and 10 fungal genera were dominant in the fermented grains. The acidity of the fermented grains had a significant driving effect on the microbial community succession. A total of 81 volatile compounds were identified and quantified in the fermented grains, of which esters and alcohols were relatively abundant. The differences in 30 microbial community compositions and their resulting differences in terms of the fermentation parameters of fermented grains are responsible for the differences in the profiles of flavor compounds between sauce-flavor baijiu produced in the Beijing and Guizhou regions.

Characterization of Autochthonous Lactic Acid Bacteria Isolated from a Traditional Ethiopian Beverage, Tella

This study aimed to isolate lactic acid bacteria (LAB) from a traditional Ethiopian fermented product, Tella, and evaluate their functional properties. Of forty-three isolates, seven LAB were screened and identified as Pediococcus pentosaceus, Latilactobacillus curvatus, Leuconostoc mesenteroides, and Lactiplantibacillus plantarum species. The isolates were tested for their alcohol tolerance, acid and bile resistance, auto-aggregation, co-aggregation, hydrophobicity, antibacterial activity, and antibiotic susceptibility. LAB isolates, specifically P. pentosaceus TAA01, L. mesenteroides TDB22, and L. plantarum TDM41, showed a higher degree of alcohol tolerance in 8% and 10% (w/v) ethanol concentrations. Additionally, these three isolates displayed survival rates >85% in both acidic pH and bile environments. Among the isolates, L. plantarum TDM41 demonstrated the highest auto-aggregation, co-aggregation, and hydrophobicity with (44.9 ± 1.7)%, (41.4 ± 0.2)%, and (52.1 ± 0.1)% values, respectively. The cell-free supernatant of the isolates exhibited antibacterial activity against foodborne pathogens of Escherichia coli, Salmonella Enteritidis, and Staphylococcus aureus. Each isolate exhibited various levels of resistance and susceptibility to seven antibiotics and resistance was observed against four of the antibiotics tested. After performing a principal component analysis, Pediococcus pentosaceus TAA01, L. mesenteroides TDB22, and L. plantarum TDM41 were selected as the most promising ethanol-tolerant probiotic isolates.

Selecting autochthonous lactic acid bacteria for co-inoculation in Chinese bayberry wine production: Stress response, starter cultures application and volatilomic study

This study focused on isolating and characterising autochthonous lactic acid bacteria (LAB) from spontaneously fermented Chinese bayberry (CB) and their potential application in CB wine fermentation in co-inoculation with yeast starter cultures. Numerous LAB, including Lactiplantibacillus (Lp.) plantarum (9), Limosilactobacillus (Lb.) fermentum (6), Lactococcus (Lc.) lactis (3), Enterococcus (Ec.) hirae (1), Leuconostoc (Le.) mesenteroides (1), and Weissella (Ws.) cibaria (1), were isolated and identified. The isolated strains Lp. plantarum ZFM710 and ZFM715, together with Lb. fermentum ZFM720 and ZFM722, adapted well to unfavourable fermentation environment, including ethanol, osmolality, and acidity stresses, were selected for producing CB wine by co-inoculation with Saccharomyces cerevisiae. During fermentation, the presence of LAB promoted the development of S. cerevisiae, while the population dynamics of LAB in different groups at different stages showed strain-specific differences. Fermentation trials involving LAB yielded a lower ethanol concentration except for Lp. plantarum ZFM715. Compared to the pure S. cerevisiae fermented sample, the addition of LAB led to a clear modulation in organic acid composition. Lb. fermentum strains in co-fermentation led to significant decreases in each classified group of aroma compounds, while Lp. plantarum ZFM715 significantly increased the complexity and intensity of aroma compounds, as well as the intensities of fruity and floral notes. The study selects interesting strains for the design of starter cultures for use in CB wine production, underlining the interest in the selection of autochthonous LAB in fruit wines, with the aim of improving the adaptation of bacteria to specific environmental conditions and shaping the unique traits of the finished products.

Spatial heterogeneity of microbiota and flavor across different rounds of sauce-flavor baijiu in Northern China

Sauce-flavor baijiu (SFB) is a traditional Chinese distilled liquor crafted through a distinctive brewing process, involving seven rounds of stack fermentation (SF) and pit fermentation (PF). To date, there remains a knowledge gap regarding the microbial succession and flavor throughout all rounds of SFB with distinctive northern characteristics. Through LEfSe analysis, Saccharopolyspora, Virgibacillus, Thermoascus and Thermomyces, and Lactobacillus and Issatchenkia were found to be the most differentially representative genera in SF and PF, respectively. A total of 93 volatile flavor compounds were found in base baijius through the gas-chromatography mass spectrometry. Moreover, 29 volatile flavor substances with significant difference in base baijius of different rounds were revealed using the OPLS-DA model and VIP values and Spearman correlation analysis shows that bacteria have a greater impact on differential flavor compounds than fungi. This study provides a new perspective and insight into the brewing of northern SFB.

Comparison of fungal communities and flavour substances in surface and inner layers of fermented grains during stacking fermentation of sauce-flavour baijiu

The stacking fermentation process plays a vital role in the production of sauce-flavour baijiu. The aim of this paper is to elucidate the effects of environmental variables on the fungal communities of different layers of fermented grains (zaopei) during the sixth round of stacking and the changes in volatile flavour substances during this process. The composition of the fungal communities in different layers during the stacking fermentation process was analysed. Principal coordinate analysis (pCoA) showed that the dominant fungal communities in different layers differed significantly with the stacking fermentation process. The dominant fungal genera were Thermoascus, Thermomyces and Issatchenkia. The total content of flavouring substances in the surface layer of zaopei were higher, but the types of flavouring substances were less than in the inner layer. The relationship between temperature, moisture content, acidity, starch content and reducing sugar content and microbial community was analysed by Redundancy analysis. The results showed that the correlation between microbial communities and physicochemical indexes in different layers of zaopei varied. The core fungal genera in the surface layer were mainly influenced by acidity, and the microorganisms in the inner layer were more strongly correlated with temperature. Spearman correlation coefficient revealed the correlation between fungal community and volatile flavour substances, and the results showed that microorganisms in different layers of zaopei have different correlations with flavour substances. This study contributes to the understanding of the evolution of different layers fungal communities during the stacking of sauce-flavour baijiu and their relationship with volatile aroma substances.

Comparison of microbial communities and volatile profiles of wines made from mulberry and grape

In this study, three kinds of wines separately made from mulberry (MW), grape (GW), or mulberry/grape (MGW) were developed and their enological parameters, sensory scores, volatile components, and microbiota were investigated and compared. Contrary to the order of residual sugar and acidity of the three kinds of wines, the order of alcohol content from high to low is GW, MW, and MGW. A total of 60 volatile components (VCs), including esters (17), alcohols (12), acids (6), aldehydes (7), ketones (3), alkenes (3), amines (3), alkanes (4), pyrazines (2), benzene (1), sulfide (1), and thiazole (1), were identified by gas chromatography-ion mobility spectrometer (GC-IMS). The fingerprint of VCs and principal component analysis revealed that the volatile profiles of MGW and GW were more similar in comparison to that of MW and were significantly correlated with the mass ratio of mulberry to grape. Lactobacillus, Weissella, Pantoea, Leuconostoc, Lactococcus, Paenibacillus, Pediococcus, and Saccharomyces were identified as the main microflora at the genus level shared by the MW, MGW, and GW, suggesting that the heterolactic bacteria may contribute more to the high content of volatile acids in MW and MGW. The heatmap of core microbiota and main VCs of MW, MGW, and GW suggested the complicated and significant correlation between them. The above data implied that the volatile profiles were more closely related to the raw materials of winemaking and markedly affected by the fermentation microorganisms. This study provides references for evaluation and characterization of MGW and MW and improvement of MGW and MW winemaking process. KEY POINTS: • Fruit wine enological parameters, volatile profile, and microbiota were compared. • Sixty volatile compounds were identified by GC-IMS in three types of fruit wines. • Winemaking materials and microbiota affect volatile profiles of the fruit wines.

Non-gene-editing microbiome engineering of spontaneous food fermentation microbiota-Limitation control, design control, and integration

Non-gene-editing microbiome engineering (NgeME) is the rational design and control of natural microbial consortia to perform desired functions. Traditional NgeME approaches use selected environmental variables to force natural microbial consortia to perform the desired functions. Spontaneous food fermentation, the oldest kind of traditional NgeME, transforms foods into various fermented products using natural microbial networks. In traditional NgeME, spontaneous food fermentation microbiotas (SFFMs) are typically formed and controlled manually by the establishment of limiting factors in small batches with little mechanization. However, limitation control generally leads to trade-offs between efficiency and the quality of fermentation. Modern NgeME approaches based on synthetic microbial ecology have been developed using designed microbial communities to explore assembly mechanisms and target functional enhancement of SFFMs. This has greatly improved our understanding of microbiota control, but such approaches still have shortcomings compared to traditional NgeME. Here, we comprehensively describe research on mechanisms and control strategies for SFFMs based on traditional and modern NgeME. We discuss the ecological and engineering principles of the two approaches to enhance the understanding of how best to control SFFM. We also review recent applied and theoretical research on modern NgeME and propose an integrated in vitro synthetic microbiota model to bridge gaps between limitation control and design control for SFFM.

Analysis of the Effect of Mixed Fermentation on the Quality of Distilled Jujube Liquor by Gas Chromatography-Ion Mobility Spectrometry and Flavor Sensory Description

Distilled jujube liquor is an alcoholic beverage made from jujube, which has a unique flavor and a sweet taste. The purpose of this study was to explore the effect of mixed fermentation on the quality of distilled jujube liquor by comparing the performance of mixed fermentation between S. cerevisiae, Pichia pastoris and Lactobacillus. The results showed that there were significant differences in the quality of the jujube liquor between the combined strains. Moreover, Lactobacillus increased and P. pastoris reduced the total acid content. The results from an E-nose showed that the contents of methyl, alcohol, aldehyde, and ketone substances in the test bottle decreased significantly after decanting, while the contents of inorganic sulfide and organic sulfide increased. Fifty flavor compounds were detected, including nineteen esters, twelve alcohols, seven ketones, six aldehydes, three alkenes, one furan, one pyridine, and one acid. There were no significant differences in the type or content of flavor compounds. However, PLS-DA showed differences among the samples. Eighteen volatile organic compounds with variable importance in projection values > 1 were obtained. There were sensory differences among the four samples. Compared with the sample fermented with only S. cerevisiae, the samples co-fermented with Lactobacillus or with P. pastoris had an obvious bitter taste and mellow taste, respectively. The sample fermented by all three strains had a prominent fruity flavor. Except for the sample fermented with only S. cerevisiae, the jujube flavor was weakened to varying degrees in all samples. Co-fermentation could be a valuable method to improve the flavor quality of distilled jujube liquor. This study revealed the effects of different mixed fermentation modes on the sensory flavor of distilled jujube liquor and provided a theoretical basis for the establishment of special mixed fermentation agents for distilled jujube liquor in the future.

Correlational Analysis of the Physicochemical Indexes, Volatile Flavor Components, and Microbial Communities of High-Temperature Daqu in the Northern Region of China

Daqu is a microbial-rich baijiu fermentation starter. The high-temperature Daqu plays an essential role in the manufacturing of sauce-flavored baijiu. However, few studies have focused on three kinds of high-temperature Daqu (white, yellow, and black Daqu) in northern China. In this study, the physicochemical indexes, volatile flavor compounds, and microbial characteristics of the three different colors of high-temperature Daqu in northern China were comparatively analyzed to reveal their potential functions. White Daqu (WQ) exhibited the highest liquefying power and starch, and black Daqu (BQ) showed the highest saccharifying and esterifying powers. A total of 96 volatile components were identified in the three types of Daqu, and the contents of the volatile components of yellow Daqu (YQ) were the highest. The microbial community structure analysis showed that Bacillus and Byssochlamys were dominant in BQ, Kroppenstedtia and Thermoascus were dominant in WQ, and Virgibacillus and Thermomyces dominated the YQ. The RDA analysis revealed the correlation between the dominant microorganisms and different physicochemical indexes. The Spearman correlation analysis indicated that Oceanobacillus, Saccharopolyspora, Staphylococcus, Pseudogracilibacillus, Byssochlamys, and Thermomyces showed positive correlations with part of the majority of the key volatile flavor compounds. This work provides a scientific basis for the actual production of different colors of high-temperature Daqu in the northern region of China for sauce-flavored baijiu.

Comparative Genomics Analysis Provides New Insights into High Ethanol Tolerance of Lactiplantibacillus pentosus LTJ12, a Novel Strain Isolated from Chinese Baijiu

Lactic acid bacteria have received a significant amount of attention due to their probiotic characteristics. The species Lactiplantibacillus plantarum and Lactiplantibacillus pentosus are genotypically closely related, and their phenotypes are so similar that they are easily confused and mistaken. In the previous study, an ethanol-resistant strain, LTJ12, isolated from the fermented grains of soy sauce aroma type baijiu in North China, was originally identified as L. plantarum through a 16S rRNA sequence analysis. Here, the genome of strain LTJ12 was further sequenced using PacBio and Illumina sequencing technology to obtain a better understanding of the metabolic pathway underlying its resistance to ethanol stress. The results showed that the genome of strain LTJ12 was composed of one circular chromosome and three circular plasmids. The genome size is 3,512,307 bp with a GC content of 46.37%, and the number of predicted coding genes is 3248. Moreover, by comparing the coding genes with the GO (Gene Ontology), COG (Cluster of Orthologous Groups) and KEGG (Kyoto Encyclopedia of Genes and Genomes) databases, the functional annotation of the genome and an assessment of the metabolic pathways were performed, with the results showing that strain LTJ12 has multiple genes that may be related to alcohol metabolism and probiotic-related genes. Antibiotic resistance gene analysis showed that there were few potential safety hazards. Further, after conducting the comparative genomics analysis, it was found that strain LTJ12 is L. pentosus but not L. plantarum, but it has more functional genes than other L. pentosus strains that are mainly related to carbohydrate transport and metabolism, transcription, replication, recombination and repair, signal transduction mechanisms, defense mechanisms and cell wall/membrane/envelope biogenesis. These unique functional genes, such as gene 2754 (encodes alcohol dehydrogenase), gene 3093 (encodes gamma-D-glutamyl-meso-diaminopimelate peptidase) and some others may enhance the ethanol tolerance and alcohol metabolism of the strain. Taken together, L. pentosus LTJ12 might be a potentially safe probiotic with a high ethanol tolerance and alcohol metabolism. The findings of this study will also shed light on the accurate identification and rational application of the Lactiplantibacillus species.

Metagenomic Analysis of Liquor Starter Culture Revealed Beneficial Microbes' Presence

Wines are complex matrices famous for their pleasant aroma and exceptional flavor. Baijiu (white wine) is a traditional Chinese liquor with a soft mouthfeel, fragrant taste, and long-lasting aftertaste. Baijiu is distilled from sorghum and wheat via solid fermentation. As in wines, the microbial ecosystem of Baijiu is a key decisive factor influencing aroma and consumer preferences. Microbial diversity in Baijiu has been intensively investigated. It is important to note that probiotics are a mixture of bacteria and yeast primarily intended to improve health. Our study aimed to characterize the microbial ecosystem of Zaopei Baijiu Daqu (ZBD) starter cultures for specific microbes with probiotic properties. The DNA samples of ZBD starters were analyzed using a metagenomic 16S rRNA approach to characterize the bacterial and ITS for fungal diversity. Weissella cibaria was the most dominant species in the bacterial community, while Saccharomycopsis fibuligera was the most abundant fungal species. Furthermore, functional prediction analysis identified unique pathways associated with microbial diversity relevant to functional innovation. These associated pathways include fermentation, amino acid metabolism, carbohydrate metabolism, energy metabolism, and membrane transport. This study identified beneficial microbes in the starter culture, opening a path for further in-depth analysis of those microbes by isolating and evaluating them for a valuable role in in vitro and in vivo studies.

Effect of Environmental Microorganisms on Fermentation Microbial Community of Sauce-Flavor baijiu

The compositions of the microbial community in fermented grains of Sauce-flavor baijiu produced in different regions have diverse characteristics; however, the reasons for this remain unclear. The present study investigated the contributions of environmental microorganisms to the microbial community as well as the volatile compounds in the fermented grains of Sauce-flavor baijiu produced in the Beijing region using high-throughput sequencing combined with sourcetracker analysis, and compared the differences of environmental microorganism and their roles in the production process of Sauce-flavor baijiu from different regions.The results showed that the environmental microorganisms in the tools were the main contributors of the bacterial and fungal communities in fermented grains during heap fermentation and at the beginning of pit fermentation. At the end of pit fermentation, pit mud was the main environmental source of bacterial community in fermented grains, while tools and Daqu were the main environmental sources of fungal community in fermented grains.Environmental microorganisms thrived on the functional microorganisms in the fermented grains of Sauce-flavor baijiu produced in the Beijing region and thus shaped the profiles of volatile compounds. Environmental microorganisms of Sauce-flavor baijiu in the Guizhou province and the Beijing region differed significantly, which is partially responsible for the distinctive characteristics in the microbial community structure of Sauce-flavor baijiu-fermented grains from different regions.