Fermented Grains Research Articles

Targeted microbial collaboration to enhance key flavor metabolites by inoculating Clostridium tyrobutyricum and Saccharomyces cerevisiae in the strong-flavor Baijiu simulated fermentation system

Ethyl hexanoate and ethyl butyrate are indispensable flavor metabolites in strong-flavor Baijiu (SFB), but batch production instability in fermenting grains can reduce the quality of distilled Baijiu. Biofortification of the fermentation process by designing a targeted microbial collaboration pattern is an effective method to stabilize the quality of Baijiu. In this study, we explored the metabolism under co-culture liquid fermentation with Clostridium tyrobutyricum DB041 and Saccharomyces cerevisiae YS219 and investigated the effects of inoculation with two functional microorganisms on physicochemical factors, flavor metabolites, and microbial communities in solid-state simulated fermentation of SFB for the first time. The headspace solid-phase microextraction-gas chromatography-mass spectrometry results showed that ethyl butyrate and ethyl hexanoate significantly increased in fermented grain. High-throughput sequencing analysis showed that Pediococcus, Lactobacillus, Weissella, Clostridium_sensu_stricto_12, and Saccharomyces emerged as the dominant microorganisms at the end of fermentation. Co-occurrence analysis showed that ethyl hexanoate and ethyl butyrate were significantly correlated (|r| > 0.5, P < 0.05) with a cluster of interactions dominated by lactic acid bacteria (Pediococcus, Lactobacillus, Weissella, and Lactococcus), which was driven by the functional C. tyrobutyricum and S. cerevisiae. Mantel test showed that moisture and reducing sugars were the main physicochemical factor affecting microbial collaboration (|r| > 0.7, P < 0.05). Taken together, the collaborative microbial pattern of inoculation with C. tyrobutyricum and S. cerevisiae showed positive results in enhancing typical flavor metabolites and the synergistic effects of microorganisms in SFB.

Optimizing Baijiu fermentation with high-yield ethyl caproate-producing Candida parapsilosis strain

Ethyl caproate is an important flavor substance of Baijiu. It is effective to increase the content of ethyl caproate to improve the quality of strong-flavor Baijiu. In this study, the high-yielding ethyl caproate Candida parapsilosis strain F-5 was isolated from pit mud. Under optimized fermentation conditions, F-5 achieved an ethyl caproate yield of 53.69 mg/L. A novel strategy was employed by adding caproic acid and F-5 directly to the fermented grain. The application of F-5 in the fermentation of Xiaoqu and strong-flavor Baijiu significantly increased the ethyl caproate content by 24.86% and 17.45%, respectively. Transcriptomic analysis showed that Lip2 and esterase genes in the lipase synthesis pathway, and Fas1, Fas2, Eht1, and Faa4 genes in the acyltransferase pathway were significantly upregulated. These findings suggest that strain F-5 has the potential to contribute to the development of artificial pit mud and improve the flavor quality of strong-flavor Baijiu.

Research on temperature detection method of liquor distilling pot feeding operation based on a compressed algorithm

In the process of feeding the distilling bucket after vapor detection, the existing methods can only realize the lag detection after the steam overflow, and can not accurately detect the location of the steam, etc. At the same time, in order to effectively reduce the occupancy of the computational resources and improve the deployment performance, this study established infrared image dataset of fermented grains surface, and fused the YOLO v5n and the knowledge distillation and the model pruning algorithms, and an lightweight method YOLO v5ns-DP was proposed as as a model for detecting temperature changes in the surface layer of fermented grains during the process of feeding the distilling. The experimental results indicated that the improvement makes YOLOv5n improve its performance in all aspects. The number of parameters, GLOPs and model size of YOLO v5ns-DP have been reduced by 28.6%, 16.5%, and 26.4%, respectively, and the mAP has been improved by 0.6. Therefore, the algorithm is able to predict in advance and accurately detect the location of the liquor vapor, which effectively improves the precision and speed of the detection of the temperature of the surface fermented grains , and well completes the real-time detecting task.

Selective Elucidation of Living Microbial Communities in Fermented Grains of Chinese Baijiu: Development of a Technique Integrating Propidium Monoazide Probe Pretreatment and Amplicon Sequencing.

The fermentation process of Chinese Baijiu's fermented grains involves the intricate succession and metabolism of microbial communities, collectively shaping the Baijiu's quality. Understanding the composition and succession of these living microbial communities within fermented grains is crucial for comprehending fermentation and flavor formation mechanisms. However, conducting high-throughput analysis of living microbial communities within the complex microbial system of fermented grains poses significant challenges. Thus, this study addressed this challenge by devising a high-throughput analysis framework using light-flavor Baijiu as a model. This framework combined propidium monoazide (PMA) pretreatment technology with amplicon sequencing techniques. Optimal PMA treatment parameters, including a concentration of 50 μM and incubation in darkness for 5 min followed by an exposure incubation period of 5 min, were identified. Utilizing this protocol, viable microorganism biomass ranging from 8.71 × 106 to 1.47 × 108 copies/μL was successfully detected in fermented grain samples. Subsequent amplicon sequencing analysis revealed distinct microbial community structures between untreated and PMA-treated groups, with notable differences in relative abundance compositions, particularly in dominant species such as Lactobacillus, Bacillus, Pediococcus, Saccharomycopsis, Issatchenkia and Pichia, as identified by LEfSe analysis. The results of this study confirmed the efficacy of PMA-amplicon sequencing technology for analyzing living microbial communities in fermented grains and furnished a methodological framework for investigating living microbial communities in diverse traditional fermented foods. This technical framework holds considerable significance for advancing our understanding of the fermentation mechanisms intrinsic to traditional fermented foods.

Analysis of microbial community succession and its metabolic characteristics in the first and second rounds of cave-brewed sauce-flavor Baijiu

The natural cave located on the bank of the Chishui River in Guizhou is currently the only base in the country for brewing sauce-flavor Baijiu in the cave. Utilizing the natural cave for brewing not only enriches the microbial source of sauce-flavor Baijiu, but also helps in conserving land resources. This article studied the microbial communities and flavor compounds of fermented grains and the environmental microorganisms during the first and second rounds of heap fermentation in cave-brewed sauce-flavor Baijiu (CBSB). The results indicated that Thermomyces, Torulaspora, and Thermoascus were the dominant fungal genera during heap fermentation, while Virgibacillus, Kroppenstedtia, and Bacillus were the dominant bacteria. Daqu contributed 92.28% of the bacterial community and 73.89% of the fungal community to the fermented grains, while the cave air contributed 11.77% of the fungal community. During the heap fermentation process, a total of 79 volatile metabolites were identified, dominated by esters and alcohols. At the same time, 134 non-volatile metabolites were detected and most amino acids content increased gradually with heap fermentation time, while flavonoids showed the opposite trend. Correlations revealed that Saccharomyces was positively correlated with a number of esters and alcohols, and that Oceanobacillus promoted the synthesis of most flavonoids and organic oxides. The study provides data parameters for the environmental microbiology of the cave and also supports the exploration of the fermentation mechanism of CBSB.

Improving Muscat Hamburg Wine Quality with Innovative Fermentation Strategies Using Schizosaccharomyces pombe Derived from Fermented Grains of Sauce-Flavor Baijiu.

This study investigates innovative approaches to improve the quality and aroma characteristics of Muscat Hamburg wine production by substituting the conventional Saccharomyces cerevisiae yeast with an efficient fermentation strain of Schizosaccharomyces pombe. The typical use of S. cerevisiae in Muscat Hamburg wine often leads to uniformity and prolonged processing times, requiring subsequent malolactic fermentation to degrade excessive malic acid. The study advocates for the replacement of S. cerevisiae with a specific S. pombe strain, Sp-410, isolated from the fermented grains of sauce-flavor Baijiu, a Chinese spirit. Muscat Hamburg wine fermented with the S. pombe strain demonstrates decreased malic acid levels, offering a potential alternative to malolactic fermentation. However, exclusive S. pombe fermentation may result in an overproduction of acetic acid metabolites, leading to a monotonous taste. In response, the study proposes a mixed fermentation approach, combining the S. pombe strain with a Saccharomyces uvarum strain and a non-Saccharomyces yeast, Torulaspora delbrueckii. The optimized mixed fermentation strategies (M:SP+TD and M60SP+TD) involve specific proportions and intervals of inoculation, aiming to enhance the quality and aroma complexity of Muscat Hamburg wine. In conclusion, this research contributes to advancing the production of high-quality Muscat Hamburg wines, utilizing S. pombe as the primary yeast strain and implementing mixed fermentation methodologies.

Identification and Free Radical Scavenging Activity of Oligopeptides from Mixed-Distillate Fermented Baijiu Grains and Soy Sauce Residue.

This study aimed to explore the potential antioxidant activity and mechanism of oligopeptides from sauce-aroma Baijiu. The oligopeptides of Val-Leu-Pro-Phe (VLPF), Pro-Leu-Phe (PLF), Val-Gly-Phe-Cys (VGFC), Leu-Tyr-Pro (LYP), Leu-Pro-Phe (LPF), and Phe-Thr-Phe (FTF) were identified by liquid chromatography-mass spectrometry (LC-MS) from the mixed-distillate of Baijiu fermented grains and soy sauce residue (MDFS). The antioxidant mechanism of these oligopeptides on scavenging DPPH•, ABTS•+, and hydroxide radicals was investigated, respectively. Among them, VGFC had the strongest potential antioxidant activity, which was responsible for its hydrogen bonds with these radicals with high affinity. The binding energies between VGFC and these radicals were -1.26 kcal/mol, -1.33 kcal/mol, and -1.93 kcal/mol, respectively. Additionally, free radicals prefer to bind the oligopeptide composed of hydrophobic amino acid residues such as Leu, Val, Phe, and Pro, thus being scavenged for exerting antioxidant activity. It provided a new idea for the development and utilization of bioactive oligopeptides in sauce-aroma Baijiu.

Characterizing the Contribution of Functional Microbiota Cultures in Pit Mud to the Metabolite Profiles of Fermented Grains.

Elevating the flavor profile of strong flavors Baijiu has always been a focal point in the industry, and pit mud (PM) serves as a crucial flavor contributor in the fermentation process of the fermented grains (FG). This study investigated the influence of wheat flour and bran (MC and FC) as PM culture enrichment media on the microbiota and metabolites of FG, aiming to inform strategies for improving strong-flavor Baijiu flavor. Results showed that adding PM cultures to FG significantly altered its properties: FC enhanced starch degradation to 51.46% and elevated reducing sugar content to 1.60%, while MC increased acidity to 2.11 mmol/10 g. PM cultures also elevated FG's ester content, with increases of 0.36 times for MC-FG60d and 1.48 times for FC-FG60d compared to controls, and ethyl hexanoate rising by 0.91 times and 1.39 times, respectively. Microbial analysis revealed that Lactobacillus constituted over 95% of the Abundant bacteria community, with Kroppenstedtia or Bacillus being predominant among Rare bacteria. Abundant fungi included Rasamsonia, Pichia, and Thermomyces, while Rare fungi consisted of Rhizopus and Malassezia. Metagenomic analysis revealed bacterial dominance, primarily consisting of Lactobacillus and Acetilactobacillus (98.80-99.40%), with metabolic function predictions highlighting genes related to metabolism, especially in MC-FG60d. Predictions from PICRUSt2 suggested control over starch, cellulose degradation, and the TCA cycle by fungal subgroups, while Abundant fungi and bacteria regulated ethanol and lactic acid production. This study highlights the importance of PM cultures in the fermentation process of FG, which is significant for brewing high-quality, strong-flavor Baijiu.

Streptomyces beigongshangae sp. nov., isolated from baijiu fermented grains, could transform ginsenosides of Panax notoginseng.

A Gram-stain-positive actinomycete, designated REN17T, was isolated from fermented grains of Baijiu collected from Sichuan, PR China. It exhibited branched substrate mycelia and a sparse aerial mycelium. The optimal growth conditions for REN17T were determined to be 28 °C and pH 7, with a NaCl concentration of 0 % (w/v). ll-Diaminopimelic acid was the diagnostic amino acid of the cell-wall peptidoglycan and the polar lipids were composed of phosphatidylethanolamine, phosphatidylinositol, an unidentified phospholipid, two unidentified lipids and four unidentified glycolipids. The predominant menaquinone was MK-9 (H2), MK-9 (H4), MK-9 (H6) and MK-9 (H8). The major fatty acids were iso-C16 : 0. The 16S rRNA sequence of REN17T was most closely related to those of Streptomyces apricus SUN 51T (99.8 %), Streptomyces liliiviolaceus BH-SS-21T (99.6 %) and Streptomyces umbirnus JCM 4521T (98.9 %). The digital DNA-DNA hybridization, average nucleotide identity and average amino acid identify values between REN17T and its closest replated strain, of S. apricus SUN 51T, were 35.9, 88.9 and 87.3 %, respectively. Therefore, REN17T represents a novel species within the genus Streptomyces, for which the name Streptomyces beigongshangae sp. nov. is proposed. The type strain is REN17T (=GDMCC 4.193T=JCM 34712T). While exploring the function of the strain, REN17T was found to possess the ability to transform major ginsenosides of Panax notoginseng (Burk.) F.H. Chen (Araliaceae) into minor ginsenoside through HPLC separation, which was due to the presence of β-glucosidase. The recombinant β-glucosidase was constructed and purified, which could produce minor ginsenosides of Rg3 and C-K. Finally, the enzymatic properties were characterized.

Rapid determination of starch and alcohol contents in fermented grains by hyperspectral imaging combined with data fusion techniques.

Starch and alcohol serve as pivotal indicators in assessing the quality of lees fermentation. In this paper, two hyperspectral imaging (HSI) techniques (visible-near-infrared (Vis-NIR) and NIR) were utilized to acquire separate HSI data, which were then fused and analyzed toforecast the starch and alcohol contents during the fermentation of lees. Five preprocessing methods were first used to preprocess the Vis-NIR, NIR, and the fused Vis-NIR and NIR data, after which partial least squares regression models were established to determine the best preprocessing method. Following, competitive adaptive reweighted sampling, successive projection algorithm, and principal component analysis algorithms were used to extract the characteristic wavelengths to accurately predict the starch and alcohol levels. Finally, support vector machine (SVM)-AdaBoost and XGBoost models were built based on the low-level fusion (LLF) and intermediate-level fusion (ILF) of single Vis-NIR and NIR as well as the fused data. The results showed that the SVM-AdaBoost model built using the LLF data afterpreprocessing by standard normalized variable was most accurate for predicting the starch content, with an of 0.9976 and a root mean square error of prediction (RMSEP) of 0.0992. The XGBoost model built using ILF data was most accurate for predicting the alcohol content, with an of 0.9969 and an RMSEP of 0.0605. In conclusion, the analysis of fused data from distinct HSI technologies facilitates rapid and precise determination of the starch and alcohol contents in fermented grains.

PSVI-3 Effects of dried distillers grains on performance of suckling beef calves in a creep-feeding system

Abstract Dried distiller’s grains (DDG) have been successfully used in beef cattle diets due to their high protein content and increasing availability around the world. However, the chemical composition of DDG varies according to the type of fermented grain and processing methods, and its increased sulfur content can compromise animal performance. There are few studies evaluating DDG in supplements for beef calves in creep-feeding systems. Hence, our objective was to assess the effects of DDG on performance of suckling beef calves in a creep-feeding system. Nellore×Red Angus male calves (n = 37), weighing 162 ± 4.06 kg at 120 d of age, along with their respective dams (n =37 Nellore cows) were used. The cow-calf pairs were randomly assigned into eight paddocks formed by Urochloa decumbens pastures. Animals were subjected to a 14-dadaptation period and an additional 108-d period for performance evaluation. All animals had access to water and mineral mixture ad libitum. Four treatments were evaluated, as follows: control (mixture mineral only), supplement without DDG, or supplements including 375 and 750 g/kg DDG [dry matter (DM) basis]. The supplements were composed of ground corn, soybean meal, urea, and DDG, planned to contain 300 g CP/kg DM, and provided daily at 7.0 g/kg body weight (BW; as fed). Treatments were assigned to experimental units (i.e., calf) in a completely randomized design. Calves were weighed at the beginning and end of the experiment, as well as every 15 d, to adjust the amount of supplement to be provided. Comparisons between treatments were performed by decomposing its sum of squares into orthogonal effects as follows: 1) control (mineral mixture only) versus supplemented calves; 2) evaluation of the linear and quadratic effects of the inclusion of DDG in the supplements. Data were analyzed using the MIXED procedure of SAS 9.4 (α = 0.05). Supplementation enhanced (P &amp;lt; 0.05) average daily gain (ADG) and final body weight (FBW) when compared with control. On average, ADG was increased from 0.94 kg/d to 1.08 kg/d for control and supplemented calves, respectively. On the other hand, ADG and FBW decreased linearly as the DDG inclusion in the supplement increased (P &amp;lt; 0.05). The differential ADG of calves that received supplements with 375 and 750 g/kg DDG compared with calves that did not receive DDG was -0.046 and -0.096 kg, respectively. It is worth emphasizing that calves fed supplements with 375 g/kg and 750 g/kg DDG had a 14% and 46% less supplement intake, respectively, than animals that were not fed DDG. Supplementing beef calves in a creep-feeding system enhances animal performance. However, the inclusion of high DDG levels in supplements decreases the performance of suckling beef calves.

Comprehensive analysis of spatial heterogeneity reveals the important role of the upper-layer fermented grains in the fermentation and flavor formation of Qingxiangxing baijiu

Different spatial positions lead to inconsistent fermentation effects and flavors, however, the spatial heterogeneity of Qingxiangxing (QXX) Baijiu remains unknown. We investigated the microbes, flavors, and physicochemical properties of different layers in fermented grains of QXX Baijiu using Illumina HiSeq sequencing, two-dimensional gas chromatography–mass spectrometry (GC × GC–MS) and ultra-high performance liquid chromatography-mass (UHPLC-MS). A total of 79 volatiles, 1596 metabolites, 50 bacterial genera, and 52 fungal genera were identified. The contents distribution followed the order: upper layer > bottom layer > middle layer. Organic acids and derivatives were the main differential metabolites across the three layers. Starch, pH, and reducing sugar levels increased from the upper to bottom layer. Saccharomyces and Lactobacillus were dominant microbes. Pediococcus, the biomarker of upper layer, showed positive correlations with formic acid, ethyl lactate, acetic acid, ethyl linoleate, and ethyl oleate. These findings deepen our understanding of the fermentation and flavor formation mechanisms of QXX Baijiu.

Analysis of ester-producing performance in high-yield ethyl hexanoate yeast and the effect on metabolites in bio- enhanced Daqu, the starter for Baijiu and other traditional fermented foods.

Ethyl hexanoate, one of the key flavor compounds in strong-flavor Baijiu. To improve the content of ethyl hexanoate in strong-flavor Baijiu, a functional strain with high yield of ethyl hexanoate was screened and its ester-producing performance was studied. Upon identification, the strain was classified as Candida sp. and designated as ZY002. Under optimal fermentation conditions, the content of ethyl hexanoate synthesized by ZY002 can be as high as 170.56mg L-1. A fermentation test was carried out using the ZY002 strain bioaugmented Daqu to verify the role of the strain applied to Baijiu brewing. It was found that strain ZY002 could not only improve the moisture and alcohol contents of fermented grains but also diminish the presence of reducing sugar and crude starch. Furthermore, it notably amplified the abundance of flavor compounds. In this study, Candida sp. ZY002 with a high yield of ethyl hexanoate provided high-quality strain resources for the actual industrial production of Baijiu.

Isoflavone profile and soybean quality: Effects of genotype, cultivation environment and storage

The interaction between soybean genotypes and environmental conditions alters the chemical and phytochemical composition of soybeans. These changes influence the quality of soybeans during storage. Therefore, the study analyzed the influence of soybean genotypes (BMX ALVO RR, DM 57I52RSF IPRO, BRS 5601 RR, and 95r51), cultivation environment (Bagé, Cachoeira do Sul, Vacaria, and São Luiz Gonzaga), and storage time (0, 6, 12 months) on quality parameters and the isoflavone profile of soybeans. The analyses performed included titratable acidity, soluble protein, germination, electrical conductivity, soybean defects, colorimetric profile, and isoflavone profile. The Vacaria environment showed the lowest values for acidity (0.86–0.91%), lipase activity (6.14–14.2%), electrical conductivity (194.5–335.0 μS/cm), and fermented grains (0.45–1.4%) at the end of storage, regardless of the analyzed genotype, demonstrating to be a suitable environment for the cultivation of these genotypes. Additionally, the highest concentrations of isoflavones were also detected in the genotypes cultivated in Vacaria at the beginning of storage (2205.0–2983.8 μmol/g). Analyzing all the results, the 57i52RSF genotype cultivated in Vacaria showed the best quality during storage. On the other hand, the 95r51 genotype exhibited low quality during storage, especially when cultivated in São Luiz Gonzaga.

Dry Baking Yeast Use in the Fermented Grain Drinks Production

Fermented drinks production is a promising sector of the food industry. Therefore, the new technological solutions development aimed at product quality improvement and production optimization is always relevant. To optimize the fermentation stage and production in general, a man has to identify new resources – new yeast strains. The research aimed at studying the possibility of dry baking yeast “Saf-instant”, “Saf-levur”, “Nevada” and “Angel” use in the fermented grain drinks technology. The developed technology feature was wheat and oat malt use along with traditional barley and rye fermented malt. The authors introduced two formulations of drinks for production with the following composition: the first sample consists of barley malt 45 %, wheat malt 25 %, rye fermented malt 30 %; the second one – barley malt 45 %, oat malt 25 %, rye fermented malt 30 %. The authors optimized the grain wort preparation mode for each formulation with grinding stage adjustment according to temperature and pauses duration. Experimentally, a man established the recommended yeast administration rate at the fermentation stage – 20 million cells/cm3 of wort, optimal temperature (28–30 °C) and stage duration (17–18 hours). As a result, the yeast “Nevada” and “Angel” had the greatest fermentation activity. During fermentation, in drinks, in addition to ethyl alcohol and carbon dioxide, there were higher alcohols (isobutyl, propyl, isoamyl), esters (methyl acetate, isoamyl acetate), and organic acids (succinic, malic, citric, lactic, oxalic, formic, acetic). The organic acids presence enables to improve the beverages quality by its nutritional value increase. The resulting fermented grain drinks meet the standardized requirements for similar beverages fully in terms of quality. The developed technology using new yeast strains can be recommended for introduction into production.

Effects of Saccharomyces cerevisiae on microbial community and flavor metabolites in solid-state fermentation of strong-flavor Baijiu

Targeted biofortification is an effective way to regulate the microbial community succession and the production of flavor metabolites in the Baijiu fermentation. However, the high organic acid present in the Baijiu brewing process causes the gradual succession of exogenous functional microorganisms to be less dominant, ultimately resulting in defective flavor substances. In this study, a strain of Saccharomyces cerevisiae YS219 with high production of ethyl hexanoate and excellent organic acid tolerance was excavated, and the effects of this strain on the microbial composition and flavor metabolites during the fermentation of strong-flavor Baijiu were investigated. The microbial community was analyzed using the Illumina Miseq Pe300 Sequencing Platform, and at the genus level, Saccharomyces, Lactobacillus, and Pediococcus became the dominant genera after biofortification. A total of 77 flavor substances were detected in the biofortified fermented grains, and the contents of total esters and alcohols increased significantly. Among them, ethanol and ethyl hexanoate were significantly increased. Mantel test showed significant positive correlation between lactic acid and Pediococcus. Moreover, lactic acid, acetic acid, and ethanol were negatively correlated with most of the fermenting microorganisms. Following inoculation with S. cerevisiae YS219, Saccharomyces and Pediococcus exhibited a positively significant link with ethyl hexanoate, according to Spearman's correlation analysis. Taken together, the results demonstrate that the addition of S. cerevisiae with excellent organic acid tolerance and high ethyl hexanoate production helps to promote the change of microbial community and the elevation of ethanol and ethyl hexanoate.

Evolution of fermented grain yeast communities in strong-flavored baijiu and functional validation of yeasts that produce superior-flavored substances.

Baijiu is a well-known alcoholic beverage in China and the quality is determined by various microorganisms during the fermentation process. Yeast is one of the most important microorganisms in the fermentation of baijiu. It has a strong esterification capacity and also affects the aroma. High-throughput sequencing results showed that the fermented grains (jiupei) during baijiu production were mainly composed of eight highly abundant yeast species. The species and abundance of yeasts changed significantly with the fermentation process. The flavor of 30 yeast strains in the jiupei was determined by a sniffing test and gas chromatography-mass spectrometry (GC-MS). The strain with the highest flavor substance content (2.34 mg L-1), named YX3205, was identified as Clavispora lusitaniae. Tolerance results showed that C. lusitaniae YX3205 can tolerate up to 15% (v v-1) ethanol. In a solid-state simulated fermentation experiment, the content of 24 flavor substances was significantly increased in the fortified group, and the total ester content reached 4240.73 μg kg-1, which was 2.8 times higher than that of the control group. The present study demonstrated the potential of C. lusitaniae YX3205 to enhance the flavor of baijiu, thereby serving as a valuable strain for the improvement of the flavor quality of baijiu. © 2024 Society of Chemical Industry.

Study on the Fermented Grain Characteristics and Volatile Flavor Substances during the Tuqu Fermentation of Hunan Light-Flavor Baijiu.

The present study employed Hunan local Tuqu for fermentation and investigated the physicochemical properties, microbial community composition, and volatile flavor compounds of the fermented grains, as well as the correlation between the physicochemical indicators and the microbial community. The findings reveal that the activities of α-amylase and glucoamylase were highest during the initial stages of the fermentation process. The acid protease activity increased to 30.6 U/g on the second day and then decreased. Cellulose and lipase activities both showed an increasing trend. The moisture content increased sharply to 73.41% and then remained relatively stable. The acidity was highest on the eighth day. Fifty genera of bacteria and twenty-two genera of fungi were detected. Lactobacillus was dominant among bacteria, and Saccharomyces was dominant among fungi. A correlation analysis showed that there were positive correlations between moisture, acidity, cellulose, lipase activities and Lactobacillus, and there were positive correlations between moisture content, acidity, cellulase activity, acidic protease activity and Saccharomyces. A total of 46 volatile flavor compounds were detected, of which 6 alcohols and 14 esters constituted the major portion, and 9 key flavor compounds with an ROAV > 1 were identified throughout the fermentation process. Isoamyl acetate had the highest ROAV and made the greatest contribution to the flavor.

Microbial community dynamics and spatial distribution of flavor compound metabolism during solid-state fermentation of Baijiu enhanced by Wickerhamomyces anomalus

Biofortification of Baijiu fermentation process using exogenous functional strains can change the microbial community structure in the fermentation system, which in turn affects the flavor of Baijiu. In this study, we used a simulated solid-state fermentation of Baijiu to investigate the effects of the addition of Wickerhamomyces anomalus strain YM001 on the improvement of Baijiu flavor compounds and its mechanism. The results of microbial diversity analysis showed that Wickerhamomyces and Lactiplantibacillus were the dominant genera in the biofortified fermentation system. In addition, W. anomalus YM001 drove the change of bacteria with moisture and alcohol content, which will synthesise esters using ethanol and moisturet as substrates. The addition of W. anomalus YM001 increased the content of total esters in fermentation samples, especially ethyl acetate, and other compounds such as acetic acid and phenylethyl ester to some extent. W. anomalus YM001 altered the correlation between microorganisms and flavor compounds, with Latilactobacillus and Pediococcus showing a significant positive correlation with ethyl acetate and Weissella showing a significant negative correlation with ethyl caproate and ethanol. In addition, the metabolic properties of ethyl acetate, ethyl decanoate and phenethyl acetate were also altered. In summary, biofortification with W. anomalus YM001 altered the microbial community composition and the physicochemical properties of the fermented grains in the Baijiu brewing system, while elevating the contents of ethyl acetate, ethyl decanoate and phenyl acetate. These findings suggest that biofortification during Baijiu brewing improves Baijiu flavor and contributes to the overall quality of Baijiu.

The High-Throughput Screening of Microorganisms to Eliminate Ethyl Carbamate in Chinese Liquor.

Ethyl carbamate (EC) is a 2A classified carcinogen in Chinese liquor that has raised many problems regarding food safety. Applying microorganisms to control the content of EC precursors in fermented grains has been proven as an effective method to reduce EC in alcoholic beverages. However, the utilization of microorganisms to decrease the precursors of EC (urea and cyanide) is still incomplete in regard to Chinese liquor. Thus, it is necessary to isolate strains with the degradative activities of urea and cyanide. Herein, Bacillus sonorensis F3 and Bacillus licheniformis YA2 strains were isolated from the fermented grains through multiple rounds of high-throughput screening, and the degradative abilities in urea and cyanide reached 95.72% and 75.48%, respectively. In addition, the urease from the B. sonorensis F3 strain and the carbon nitrogen hydrolase from the B. licheniformis YA2 strain were identified by the heterogeneous expression in Escherichia coli. Then, both F3 and YA2 strains were combined at a ratio of 5:1 and applied to eliminate the EC in the simulated fermentation of Chinese liquor; as a result, 51.10% of EC was reduced without affecting the main composition of flavor substances. The obtained strains have great potential in terms of the improvement of quality and safety of Chinese liquor.