As consumers increasingly pursue foods with superior quality and enriched flavor, fermented products have attracted considerable attention due to their unique sensory properties and nutritional advantages. Aroma-producing yeasts, as pivotal microbial catalysts in fermentation processes, are widely utilized in the production of a broad range of fermented foods, including alcoholic beverages, fermented dough-based products, and fermented soybean products. This review synthesizes recent research progress on aroma-producing yeasts in fermented foods, beginning with a systematic overview of their taxonomic classification and key biological characteristics. The primary aroma-active metabolites synthesized by these yeasts are esters and alcohols, which play a decisive role in determining the flavor profiles of fermented food products. Next, the mechanisms underlying aroma biosynthesis in these yeasts are elaborated. By regulating metabolic pathways, these yeasts synthesize a diverse array of aromatic metabolites, which in turn impart unique sensory attributes to fermented foods. In-depth exploration of these mechanisms not only facilitates the clarification of the functional roles of aroma-producing yeasts during fermentation but also establishes a solid theoretical foundation for further optimizing the flavor quality of fermented products. Lastly, the current application status of aroma-producing yeasts in fermented food manufacturing is summarized. This review offers valuable insights and guidance for the innovative development of the fermented food industry, while concurrently promoting in-depth research and expanded industrial application of aroma-producing yeasts in the field of food science and technology.

Beer aroma is strongly influenced by terpenes, many of which exist in hops as non-volatile glycosides. β-Glucosidase (BGL) can release these bound terpenes, but its role in brewing remains underexplored. In this study, twelve non-Saccharomyces yeasts were screened, and Pichia kudriavzevii KD4 was identified as the best BGL producer. Co-fermentation with Saccharomyces cerevisiae US05 under optimized conditions enhanced floral and fruity aromas of beer, increasing esters and terpene alcohols, particularly linalool, nerol, and geraniol. The BGL from KD4 (PkBGL) was heterologously expressed in P. pastoris, exhibiting optimal activity at 50 °C and pH 5.5, and showing stability under low-temperature, acidic, ethanol-, and isoα-acid-rich conditions. Enzymatic assays confirmed efficient hydrolysis of hop glycosides, while molecular docking revealed stable binding of linalyl and nerol glycosides via hydrogen bonding and hydrophobic interactions. These results highlight PkBGL as a promising tool for aroma enhancement in beer through selective terpene release.

Intracellular metabolites markedly change in yeast during fermentation, especially under various stresses in beer post-fermentation. To address the current limitations in understanding the regulatory mechanisms in this complex environment, industrial brewing yeast was analyzed using integrated transcriptomics and proteomics across the post-fermentation phases, dynamically profiling the transcriptional levels and protein abundances of differentially expressed genes. As a result, 6110 differentially expressed genes (DEGs) and 3533 differentially expressed proteins (DEPs) were identified. Additionally, transcriptomics showed the induced expression of low-pH- and oxidative stress-related genes (HAL1, HAL4, YAP5), gluconeogenesis- and sugar transport-related genes (HXT, MAL, FBP), and mannan synthetic genes (FSK, MNN) during early post-fermentation. Moreover, heat-shock-related genes were upregulated throughout post-fermentation. Furthermore, proteomics revealed the sustained upregulation of glucosidase Scw, mannoprotein Pir, hexose transporter Hxt, and heat-shock proteins (Hsp). These findings indicate that yeast adapts to stress in the wort environment during post-fermentation by enhancing cell wall biosynthesis, activating heat-shock responses, and modulating metabolic pathways. These integrated omics analyses provide guidance for selecting robust, tolerant strains to industrial-scale stresses and improving beer flavor profiles, establishing a theoretical foundation for optimizing brewing and enhancing beer quality.

Cellular metabolic state and its heterogeneity are pivotal features that determine fermentation productivity, yet label-free monitoring has generally been difficult. Employing beer fermentation by Saccharomyces pastorianusas a model, we demonstrated that temporal sampling of ramanomes, the collection of spontaneous Single-Cell Raman Spectra (SCRS) from an isogenic population, provides rich insights into the profiles and inter-conversion of both intra- and extra-cellular metabolites. Among 43 extracellular metabolic phenotypes, ramanomes successfully modeled 19 of them, including the extracellular levels of four alcohols, four esters, four amino acids, two acids, and four mono- and di-saccharide substrates, plus the alcohol-to-ester ratio. Moreover, Intra-Ramanome Correlation Analysis (IRCA) revealed potential metabolic interactions in pairs of intracellular metabolites, extracellular metabolites, and medium substrates. Specifically, carbohydrates were the most active intracellular metabolites, while proteins significantly influenced alcohol and ester synthesis on Day 1 of fermentation. Additionally, both alcohols and esters showed negative correlations with extracellular amino acids and acids. The global-IRCN average degree, reflecting metabolic network complexity, increased over time and was positively correlated with extracellular levels of key products such as n-propanol and various esters, while negatively correlated with acetic acid and certain sugars. Therefore, by enabling non-destructive, label-free, and rapid modeling of both intra- and extracellular metabolite levels, ramanomics can find wide applications in process monitoring and control.

Off‐flavor compounds are commonly detected in various non‐distilled alcoholic beverages, including beer, wine, rice wine, and sake. These chemicals, such as aldehydes, ethers, biogenic amines, bitter peptides, and sulfur compounds, have significant influences on the quality and price of commercial products. Thus, understanding their precursors and formation is important to maintain their concentrations below acceptable thresholds by optimizing fermentation parameters. This review summarizes the sensory thresholds, sources, formation mechanisms, detection methods, and control strategies for major off‐flavor compounds in a range of non‐distilled alcoholic beverages. Practical examples are critically assessed to highlight the benefits and limitations of these strategies, laying a foundation for further improvements in taste and quality. © 2025 Society of Chemical Industry.

Objectives: Premature yeast flocculation (PYF) poses a significant threat to beer quality and economic efficiency in the brewing industry. While previous research has focused primarily on genomic and proteomic aspects, the metabolic mechanisms underlying PYF remain poorly understood. This study aimed to elucidate the metabolic differences associated with varying degrees of PYF through a metabolomics-based approach.Materials and Methods: Metabolomic profiling was conducted on unfermented wort (WORT) and samples obtained from the 3-d European Brewery Convention (EBC) fermentation test, which exhibited different PYF severities. Differential metabolites were identified and compared between groups. Correlation analysis was performed to assess the association between metabolite levels and fermentation duration. Additionally, reverse addition experiments were conducted to evaluate the role of specific metabolites in promoting PYF.Results: A total of 46 differential metabolites, including arginine, daidzein, and galangin, were identified in the EBC group, whereas 30 differential metabolites such as daidzein, galangin, and tenuazonic acid were found in the WORT group, with 13 metabolites shared between both groups. In the PYF36 group, correlation analysis revealed that galangin and daidzein levels were positively associated with fermentation duration. Reverse addition experiments demonstrated that galangin significantly promoted PYF, as indicated by increased wort clarity, identifying it as a positive regulatory factor.Conclusions: This study provides the first comprehensive insight into the metabolic alterations associated with PYF. The identification of galangin as a key promoter of PYF offers a novel target for controlling this phenomenon, potentially enhancing beer production efficiency and quality in the brewing industry.

Lacticaseibacillus paracasei is a typical food spoilage bacterium especially in beer. Due to the negative impact of L. paracasei on food preservation, a rapid detection method for L. paracasei based on polymerase spiral reaction (PSR) was established and its application was verified using different types of food samples in this study. Firstly, target digging was performed using bioinformatics techniques. A target gene pheS was selected and species-specific primers were designed. Secondly, the PSR assay was established with chromogenic reaction, which avoid false positive result due to open lid. The specificity of target and primers was tested, and the limit of detection (Kolodkin-Gal in Science 328:627–629, 2010) (5.2 × 104 fg/μL) was examined. Thirdly, the application of PSR assay in solid and liquid food samples were verified by artificial contamination model. The PSR assay was more efficiency in liquid food (LOD: 103 CFU/mL) than in solid food (LOD: 104 CFU/mL). Thus, L. paracasei screening in 3 types of beer (LOD: 103 CFU/mL) was further performed to verify to efficiency of PSR assay in screening of beer spoilage bacteria. In conclusion, pheS targeting PSR assay is useful as a rapid detection method for L. paracasei in solid and liquid food samples especially in beer.

Saccharomyces cerevisiae (baker's yeast, budding yeast) is one of the most important model organisms for biological research and is a crucial microorganism in industry. Currently, a huge number of Saccharomyces cerevisiae genome sequences are available at the public domain. However, these genomes are distributed at different websites and a large number of them are released without annotation information. To provide one complete annotated genome data resource, we collected 2,507 Saccharomyces cerevisiae genome assemblies and re-annotated 2,506 assemblies using a custom annotation pipeline, producing a total of 15,407,164 protein-coding gene models. With a custom pipeline, all these gene sequences were clustered into families. A total of 1,506 single-copy genes were selected as marker genes, which were then used to evaluate the genome completeness and base qualities of all assemblies. Pangenomic analyses were performed based on a selected subset of 847 medium-high-quality genomes. Statistical comparisons revealed a number of gene families showing copy number variations among different organism sources. To the authors' knowledge, this study represents the largest genome annotation project of S. cerevisiae so far, providing rich genomic resources for the future studies of the model organism S. cerevisiae and its relatives.IMPORTANCESaccharomyces cerevisiae (baker's yeast, budding yeast) is one of the most important model organisms for biological research and is a crucial microorganism in industry. Though a huge number of Saccharomyces cerevisiae genome sequences are available at the public domain, these genomes are distributed at different websites and most are released without annotation, hindering the efficient reuse of these genome resources. Here, we collected 2,507 genomes for Saccharomyces cerevisiae, performed genome annotation, and evaluated the genome qualities. All the obtained data have been deposited at public repositories and are freely accessible to the community. This study represents the largest genome annotation project of S. cerevisiae so far, providing one complete annotated genome data set for S. cerevisiae, an important workhorse for fundamental biology, biotechnology, and industry.

Fucoxanthin (FX), a natural compound derived from marine algae, and FX-based nanoparticles (FZ) were investigated for their potential in regulating glucose and lipid metabolism. Gavage interventions with FX, FZ, and zein hydrolysate (ZH) were administered to obese mice, resulting in significant outcomes. These interventions led to variations in growth rates, reduced blood glucose levels, improved lipid profiles, and ameliorated liver pathology. Our mRNA expression analysis revealed modulation of key genes involved in glucose metabolism. Gut analysis, including short-chain fatty acid detection and 16S rRNA gene sequencing, provided insights into gut microbiota modulation. Notably, differences observed in vivo between FX and FZ were attributed to their distinct release rates during in vitro digestion in the stomach and intestine. This comprehensive study validates our methods, modeling, and metabolic parameter determination, reinforcing the significance of our results. In conclusion, our findings highlight the promising potential of FX-encapsulated interventions in modulating metabolic pathways. Furthermore, they emphasize the crucial role of gut microbiota dynamics in the strategic mitigation of disorders associated with obesity.

Why was the work done: Yeast flocculation is an important parameter in brewery fermentation, as beer quality is affected by the onset and intensity of cell aggregation. Malt induced premature yeast flocculation (PYF) is described as a rapid decline of yeast cells in suspension during fermentation even in the presence of sufficient nutrients. Though occurring only sporadically, premature yeast flocculation can represent a significant risk to brewery operations. What are the main findings: This review considers the known and suspected mechanisms underlying both normal and abnormal flocculation. Particular effort is made to propose definitive methods for the detection of PYF and to summarise potential strategies to alleviate premature yeast flocculation, with emphasis on relevant approaches for industrial brewing. Why is the work important: Recent research has provided new insights to elucidate the mechanisms involved in premature yeast flocculation, though a complete understanding has yet be reached. Given the association of PYF with poor field conditions during barley growth, it may be expected that climate change will contribute to an increase in the frequency or severity of PYF. This review is intended to serve as a resource for further research on the topic as well as development of practical prevention or mitigation strategies.

Malt-induced premature yeast flocculation (PYF) is a sporadic problem within the brewing industry. The use of PYF malts is concomitant with a number of negative impacts on beer quality, including incomplete fermentation and/or flavor defects. Although malt-induced PYF is widely acknowledged, actions taken so far have proved insufficient to solve the PYF-related issues. To limit the detrimental effects of PYF malts on beer production, an adaptive laboratory evolution (ALE) process was applied in this study to an industrial lager brewing yeast strain (TT02), in an attempt to generate variant strains with improved fermentation performance in PYF wort. Through a batch fermentation-based adaptation process, evolved variants were isolated and screened for their phenotypic and metabolic traits. The investigation focused mainly on the tendency to remain in suspension, fermentation capacity and final acetaldehyde concentration. We successfully obtained a variant (TT02-30 T) with improved fermentation properties. The improvement was seen in worts prepared from different types of PYF malt as well as normal malt. Furthermore, ALE of lager brewing yeast in PYF wort yielded a wide array of mutations. Several changes in the genomes (copy number variation in flocculin encoding gene FLO1 and a missense SNP in a putative mitochondrial membrane protein coding gene FMP10) of the variant strains relative to the original strain were observed. These could potentially contribute to the improved yeast suspension during fermentation. Importantly, mutational enrichment in genes related to ion binding in PYF-evolved strains suggests the involvement of the yeast ion transportation process in dealing with the PYF stress. Our study demonstrates the possibility of attenuating yeast sensitivity to PYF malts over time through adaptive laboratory evolution via spontaneous mutation.

Fucoxanthin (FX) is a carotenoid with antioxidant, anti-obesity, anti-diabetic, anti-cancer and anti-bacterial activities. It is poorly water soluble and highly sensitive to light, heat and the surrounding environment. Therefore, how to effectively encapsulate it and stabilize it for entry into the human body has become a key research question at present. This study developed a single-carrier to encapsulate FX and showed excellent characterization results. The experimental results showed that the diameters of FX-ZH particles prepared by the four encapsulation processes ranged from 143.83 to 216.93 nm. Comparison of antioxidant activity and stability to temperature and pH of the four complexes showed significant differences, with the best performance of the nanoparticles prepared using water-soluble method and a slow-speed stirrer. The nanocomplexes were proved to be more stable and more bioavailable, with a significant 34.41% increase in FX content relative to free FX in the intestinal phase. Inhibition of human leukaemia cells HL-60 cells remained high, with 11.14% +/- 6.03% inhibition at FX concentrations of 1 mu g/mL. This study encapsulated FX based on colloidal nanoparticle systems for the first time using a single-carrier material, an innovation and breakthrough that could simplify the experimental steps and provide the necessary basis for industrial realization. (C) 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Mixed culture fermentation with lager yeast is relatively new in brewing. Maintaining the proportion of strains during fermentation is important to assure the quality of beer and accordingly needs to be monitored. The current discriminatory methods have limited application for lager strains. In the present study, a rapid method to monitor the strain proportion of strains in mixed samples of two different lager yeast strains was developed using microsatellite polymerase chain reaction (PCR) and GeXP Genetic Analysis System. Microsatellite markers in the lager yeast genome were searched using SSR Hunter software. Quantitative PCR using these microsatellite markers was performed and PCR products were analysed by capillary electrophoresis. One locus - mitochondrial carnitine acetyltransferase – was found to discriminate the two strains. A standard curve was generated based on the premixed samples of the two strains enabling the proportion of the stains to be determined. This method is a fast and reliable approach to monitor the strain proportion of mixed lager yeast fermentation. © 2020 The Institute of Brewing & Distilling

Lager酵母(Saccharomyces pastorianus)是由酿酒酵母(S.cerevisiae)与真贝氏酵母(S.eubayanus)通过自然杂交获得的异源多倍体菌株.Lager酵母保留了来自于两个亲本的染色体,同时也产生了新的重组片段,这就赋予Lager酵母适合低温发酵、麦芽三糖利用率高等重要特性.根据菌株的染色体含量,可以将Lager酵母分为两个类型:Group Ⅰ型(Saaz型)与GroupⅡ型(Frohberg型).近年来,多株Lager酵母菌株陆续完成了全基因组测序,为探索不同类型Lager酵母起源提供了基因组学基础.该文综述了Lager酵母的起源及基因组信息,并讨论了不同类型Lager酵母进化的模型.

为探究麦汁中氨基酸在啤酒酿造中的作用,研究了麦汁中4种关键氨基酸(谷氨酸、脯氨酸、缬氨酸和赖氨酸)对酵母发酵性能的影响.以工业Lager酵母(Saccharomyces pastorianus TT-1)为研究对象,通过关键氨基酸添加的发酵实验,在合成培养基中对关键氨基酸在酵母增殖及风味物质代谢中的作用进行了分析,并进一步在工业生产麦汁中对其作用进行了验证.结果表明,谷氨酸和脯氨酸抑制酵母增殖;赖氨酸会促进酵母的增殖;缬氨酸会促进高级醇的生成.

The objective of this study was to investigate the effect of adding selected amino acids (glutamate, proline, lysine and valine) to brewing wort on the generation of aroma active compounds along with the transcriptional profiling of genes involved in nitrogen regulation. The results showed that changes in the amino acid levels had no significant impact on the general course of fermentation except for the addition of lysine, which prolonged the period that lager yeast was in suspension. Flavour profile of lager were significantly affected by valine addition, which improved the degree of fermentation and alcohol concentration. Changes in the amount of isoamyl alcohol caused by varied amino acid conditions were particularly important as it fluctuated across the flavour threshold. Amino acid supplementation resulted in a reduction in yeast total amino acid utilisation except for valine. Furthermore, we found that nitrogen regulation genes were differentially expressed according to the amino acid added and stage of yeast growth, demonstrating that divergent mechanisms and pathways are involved in transcriptional regulation down-regulating activators or up-regulating repressors of nitrogen catabolite repression pathway at the mid-exponential stage. An enexpected expression of genes related to SPS sensing system and the TOR pathway was found during the late exponential stage. Overall, our results indicate that, during lager yeast fermentation, the production of aroma active compounds and nitrogen regulation can be significantly affected by changing wort amino acid composition. (C) 2018 The Institute of Brewing & Distilling

Aroma-active higher alcohols and esters are produced intracellularly in the cytosol by fermenting lager yeast cells, which are of major industrial interest because they determine aroma and taste characteristics of the fermented beer. Wort amino acid composition and their utilization by yeast during brewer's wort fermentation influence both the yeast fermentation performance and the flavour profile of the finished product. To better understand the relationship between the yeast cell and wort amino acid composition, Plackett-Burman screening design was applied to measure the changes in nitrogen composition associated with yeast amino acids uptake and flavour formation during fermentation. Here, using an industrial lager brewing strain of Saccharomyces pastorianus, we investigated the effect of amino acid composition on the accumulation of higher alcohols and volatile esters. The objective of this study was to identify the significant amino acids involved in the flavour production during beer fermentation. Our results showed that even though different flavour substances were produced with different amino acid composition in the fermentation experiments, the discrepancies were not related to the total amount of amino acids in the synthetic medium. The most significant effect on higher alcohol production was exercised by the content of glutamic acid, aromatic amino acids and branch chain amino acids. Leucine, valine, glutamic acid, phenylalanine, serine and lysine were identified as important determinants for the formation of esters. The future applications of this information could drastically improve the current regime of selecting malt and adjunct or their formula with desired amino acids in wort. Copyright (C) 2017 The Institute of Brewing & Distilling

Flash pasteurization (37 and 100 pasteurization units, PU) and conventional tunnel pasteurization (15 PU) processing of wheat beers were evaluated by examining their impacts on microorganisms, colour, colloidal haze and flavour stability during 84 days of storage at 20 degrees C. The results revealed that the microbiological stability of 37 and 100 PU flash-pasteurized beers was comparable with that of the 15 PU sample, and the development of both yeast and lactic acid bacteria was inhibited for 84 days of storage. The conventional tunnel-pasteurized wheat beer resulted in a higher thermal load relative to the flash-pasteurized samples based on the results of oxidative stability. These three pasteurized beers showed a similar decrease in haze intensity throughout the storage period. Meanwhile, flash-pasteurized beers had better colour and colloidal haze stability than the tunnel-pasteurized beer. It was also found by dynamic light scattering analysis that the temperature in the flash pasteurizer has the desired effect on the protein denaturation and particle size distribution. Therefore, flash pasteurization is a promising method to increase the shelf-life of wheat beers instead of conventional tunnel pasteurization. Copyright (c) 2017 The Institute of Brewing & Distilling