This study aimed to gain insight into the interaction and metabolic mechanism between Aspergillus flavus U-16 and Saccharomyces cerevisiae HJ during co-fermentation. Despite the suppressed transcriptional activity of SU-16, its metabolites exerted a pivotal regulatory influence. The metabolites produced by SU-16 significantly increased the ethanol content to 17.0%. They also significantly increased the contents of crucial flavor substances, including amino acids (at least 5 times) and esters (up to 1100 mg/L). SU-16 produced 130 metabolites that may affect flavor compounds, while HJ mainly controlled the synthesis of 161 compounds. Metabolites of SU-16 with different molecular weights were observed to exert differential regulatory effects on the fermentation process and the metabolic pathway of HJ. The small molecule metabolites of SU-16 promoted the growth of HJ significantly. In contrast, its macromolecular metabolites were found to mainly affect the expression of genes related to carbohydrate and amino acid metabolism in the HJ genome.

To obtain protease- and lipase-producing halotolerant/halophilic strains suitable for shrimp paste (SP) fermentation, the microbial community structure and enzyme-producing microbial species were analyzed and predicted using metagenomics in 3 high-salt samples. Based on the linear salt gradient method, 128 strains were screened. Eight halotolerant/halophilic strains highly producing 2 types of enzymes were identified and inoculated into low-salt SP to assess the heterogeneity of SP. Physicochemical properties of SP indicated that Bacillus subtilis XJ-11, Virgibacillus halodenitrificans XJ-229, Piscibacillus halophilus XY-193, and Bacillus vallismortis HT-73 were more suitable for rapid fermentation of SP. Nutritional analysis showed that SP inoculated with V. halodenitrificans XJ-229 had the highest free amino acid content and SP inoculated with P. halophilus XY-193 had the highest unsaturated fatty acid content. The former had prominent umami, sweetness, and meaty aroma, weak bitterness and fishy flavor, and the closest flavor to the control (CP) based on sensory evaluation and E-nose analysis. A total of 61 volatile compounds were detected in all samples by SPME-GC-MS, of which 32, 23, 40, 24, and 28 were detected in the CP and SP inoculated with B. subtilis XJ-11, V. halodenitrificans XJ-229, P. halophilus XY-193, and B. vallismortis HT-73, respectively, with 12, 11, 12, 9, and 9 key flavor compounds. Among several samples, the highest levels of pyrazines, aldehydes, alcohols, and ketones were found in SP inoculated with B. subtilis XJ-11, V. halodenitrificans XJ-229, P. halophilus XY-193, and B. vallismortis HT-73, respectively. These results suggested that inoculation of different enzyme-producing halotolerant/halophilic strains resulted in differences in SP quality and main flavors. This study provides some references for process control and interpretation of heterogeneous mechanisms in low-salt SP fermented by inoculated strains.

Environment serves as the pivotal medium to produce fermented food, with fluctuations in environmental factors exerting a profound impact on the modulation of fermentation microbial communities. Such shifts are crucial for the distinctiveness of fermented food flavor and the variability in quality. Chinese liquor (Baijiu) is one of the typical representatives of spontaneous fermented food. In this review, the multifaceted relationship between regional environmental attributes and the fermentation dynamics of Baijiu was examined, with a spotlight on the strong-flavor, sauce-flavor, and light-flavor varieties. It reveals the influence of regional environmental factors and brewing environmental factors on microbial function and metabolism, which results in the formation of unique flavor characteristics of Baijiu. The 9 main factors affecting the microecology of Baijiu fermentation were further explored, including environmental sensitivity, microbial interactions, biogeographic patterns, and key abiotic factors such as temperature and humidity. Environmental factor management is crucial for controlling microbial community in fermentation. Intelligent detection of the fermentation system is combined with artificial intelligence to realize the digitalization of Baijiu fermentation, with a view to further studying the environmental mechanism or quantitative control relationship of natural fermentation, improving the environmental stability of natural fermentation, and promoting the mechanization and intelligence of fermentation production.

Huangjiu, as a traditional fermented beverage in China, is rich in volatile organic compounds (VOCs) and non-volatile compounds (NVCs). VOCs include alcohols, esters, aldehydes, and ketones, which contribute to the unique flavor of Huangjiu. NVCs include carbohydrates, peptides, organic acids and phenols, which are the basis for the health benefits of Huangjiu. The chemical composition of Huangjiu is quite complex, which significantly contribute to the flavor, stability and health benefits of Huangjiu. Metabolomic analysis provides an effective method for high-throughput identification of complex metabolites in Huangjiu, which helps to reveal the diversity and difference of NVCs in Huangjiu, as well as their changes during the brewing process. Moreover, the combination of metabolomics with big data, artificial intelligence, network pharmacology and other interdisciplinary technologies has helped to excavate and improve a large amount of information on bioactive components of Huangjiu, which has become a powerful tool for studying the functional components of Huangjiu. This article provides an overview of the development of metabolomics and its application in analyzing NVCs of Huangjiu, discusses the integration and development potential of multiple technologies such as artificial intelligence and big data into metabolomics, and highlights the importance of metabolomic technology in analyzing Huangjiu NVCs and evaluating their potential health effects. Furthermore, the article summarizes the composition characteristics, formation pathways, detection methods and biological activity of major NVCs in Huangjiu, and provides an outlook on future research directions. It is expected to provide a theoretical basis for improving the quality of Huangjiu, developing its functional components, inheriting and innovating Huangjiu culture.

In this investigation, headspace solid-phase microextraction (HS-SPME) coupled with comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC × GC-TOFMS) was used to analyze the volatile compounds of traditional semi-dry Huangjiu (Chinese yellow rice wine) of different ages. Furthermore, chemometrics was used to identify the aging markers. The results showed that a total of 351 compounds were identified in Huangjiu of six ages, of which 40 compounds were found in Huangjiu for the first time. The total number of volatile compounds showed an increasing trend with aging time. One-way analysis of variance (ANOVA) and correlation analysis found a strong correlation between the contents of 107 compounds that significantly changed and aging time, among which 55 compounds such as 2-acetylthiophene were found to be significantly correlated with aging time for the first time. Principal component analysis (PCA) and cluster analysis revealed that the aging process of traditional semi-dry Huangjiu could be divided into three stages: short-term aging (1–3 years), medium-term aging (6–12 years) and long-term aging (more than 15 years). By partial least squares-discriminant analysis (PLS-DA), 37 aging markers were selected, the contents of 12 compounds of which decreased significantly while the other 25 increased significantly during the aging process. Ten most representative key aging markers were finally identified based on Pearson correlation coefficients, among which 5 compounds including isoamyl butanoate, butanoic acid, 2-furanmethanol, 2-acetyl-5-methylfuran and o-cresol were defined as key aging markers of Huangjiu for the first time. This study provides a scientific basis for understanding the aging process, evaluating the quality and identifying the age of Huangjiu.

Excessive biogenic amines (BAs) not only impact the quality of fermented foods but also harm health. Although enzymatic methods are effective in controlling the BAs content, research remains limited. Saccharopolyspora hirsuta T14 was identified for its superior ability to degrade BAs. A novel approach to predict the functional information of all proteins in the genome using homology modeling has screened several genes involved in BAs metabolism. Transcriptional analysis revealed that three critical amine oxidase genes, PAO4, AO6, and MAO7, play dominant roles in this degradation. The primary amine oxidase PAO4, along with amine oxidase AO6 and monoamine oxidase MAO7 with molecular weights of 71.0 kDa, 46.7 kDa, and 47.0 kDa, respectively, were cloned, expressed and purified. Enzymatic and kinetic studies demonstrated that these three enzymes cooperatively degrade major BAs with varying catalytic efficiencies and tolerances to substrate inhibition. Structural analysis suggests that increased hydrogen bonding and hydrophobic interactions contribute to substrate specificity and tolerance. When applied individually to huangjiu (18%vol), the enzymes achieved BAs degradation rates of 36.51% ± 3.68%, 18.93% ± 2.47%, and 22.09% ± 3.65%, respectively, as measured by high-performance liquid chromatography (HPLC). These findings provide practical methods and a theoretical foundation for specific and synergistic degradation of various BAs.

Higher alcohols are key factors affecting sensory quality and post-drinking comfort of alcoholic beverages. A strategy combining solid-phase extraction and gas chromatography-mass spectrometry (SPE-GC-MS) was established to analyze the metabolism pattern of higher alcohols in rat plasma after gavage of 4 common alcoholic beverages including huangjiu, baijiu, wine and brandy.7 mL of dichloromethane was determined as the optimal extraction condition, and 8 higher alcohols were precisely quantified with detection limits of 1.82−11.65 μg/L, recoveries of 89.07%−110.89% and fine repeatability. The fastest absorption and elimination rates of plasma total higher alcohols were observed in baijiu and huangjiu group, respectively, and the highest peak concentration was found in brandy group. Additionally, the metabolic rate of plasma isoamyl alcohol in huangjiu group was faster than that in wine group at the same intragastric administration dosage. This study may provide potential insight for evaluation of alcoholic beverage quality.