The research team, led by Huabin Tu, Guanyu Zhou, Yanfeng Liu, and Jian Chen, combined isothermal microcalorimetry, time-resolved transcriptomics, and untargeted metabolomics to systematically decipher the metabolic basis of interspecies cooperation under heat stress. Their work fills a critical mechanistic void: previous studies had established that a synergistic mutualism between Bacillus and Pediococcus is a key driver of heat generation in Daqu, with co-cultures producing significantly more metabolic heat than either monoculture, but the molecular underpinnings of that synergy remained entirely unresolved.

High-temperature Daqu is far more than a simple starter. It serves as a sophisticated carrier for microbial, enzymatic, and substrate systems that fundamentally determine the sensory characteristics, consistent quality, and economic value of the finished Baijiu. The signature high temperature drives a complex array of enzymatic and non-enzymatic reactions, most notably Maillard chemistry, which yields pyrazines, phenols, and furans that form the backbone of the sauce-like aroma profile. Precise regulation of the temperature trajectory during the critical early fermentation stage, before the first Daqu turning on day 9, is therefore paramount, as deviations disrupt microbial succession, enzyme kinetics, and flavor precursor formation.

The attainment of Daqu’s high-temperature environment emerges from the dynamic interplay between microbial metabolic heat generation and the thermal insulation properties of the solid-state substrate. Recent evidence indicates that thermogenesis is governed not by individual thermophilic taxa but by cooperative interactions within the microbial community. The point at which fermentation temperature rises to 45 degrees Celsius has been identified as the critical node at which temperature trajectories diverge: well-fermented batches attain the normal 60 to 65 degree range, whereas insufficiently fermented batches fail to reach it. A synergistic mutualism between Bacillus and Pediococcus, with an appropriate balance between the genera, is strongly associated with optimal thermal performance.

To probe this cooperation, the researchers worked with Bacillus velezensis YF83 and Pediococcus acidilactici YF45, both isolated from high-temperature Daqu at the first turning stage, where they were identified as the dominant Bacillus and Pediococcus species respectively. Using isothermal microcalorimetry on a solid wheat-flour substrate that simulates the Daqu environment, they measured heat production across different inoculation ratios at 25 and 45 degrees Celsius. At 25 degrees, heat capacity increased with the proportion of Bacillus, and the introduction of a small proportion of Pediococcus further enhanced heat generation during the mid-to-late cultivation stage. Under 45 degree conditions, all co-culture systems exhibited substantially higher cumulative heat output than their corresponding monocultures, regardless of inoculation ratio.

Population composition analysis revealed a dynamic coexistence pattern rather than a simple balance in abundance. At 45 degrees, Bacillus rapidly became dominant; in the 50:50 co-culture group, the relative abundance of Pediococcus and Bacillus at 6 hours was approximately 5.8:94.2, corresponding to a coexistence strength of 0.055. Yet by 12 hours, the ratio recovered to roughly 32.2:67.8, and coexistence strength rose to 0.218. Pediococcus was not eliminated under thermal stress but retained its ecological participation and interaction potential during the later thermogenic stage. Heat production in the mixed cultures at 12 hours was substantially higher than in the corresponding monocultures, indicating that this coexistence state positively contributed to thermogenesis.

Transcriptomic analysis of the 50:50 co-culture, comparing transcript abundances against biomass-weighted theoretical values calculated from the monocultures, revealed that co-culture-induced functional responses were strongly dependent on both time and temperature. Under 45 degree conditions, a large number of pathways exhibited positive transcriptional responses as early as 6 hours and remained highly active at 12 hours. These pathways were predominantly associated with nitrogen and amino acid metabolism and energy and redox metabolism. The most strongly enhanced functions included the tricarboxylic acid cycle, 2-oxocarboxylic acid metabolism, flagellar assembly, lipoic acid metabolism, and amino acid biosynthesis and degradation pathways, whereas only marginal changes were observed in glycolysis and gluconeogenesis. This pattern suggests that enhanced metabolic activity under thermal stress was not primarily driven by increased glycolytic flux but by intensified cellular turnover and biomass recycling.

Pediococcus predominantly contributed to aromatic amino acid biosynthesis and ubiquinone and other terpenoid-quinone biosynthesis pathways, both of which increased in parallel with the absolute biomass of Bacillus during co-cultivation. These pathways may provide nitrogen-containing metabolic intermediates or essential respiratory cofactors such as menaquinone. Although lactic acid bacteria generally do not rely on respiratory quinones for energy conservation, genomic analyses have demonstrated that Pediococcus and related lactic acid bacteria possess the genetic capacity for quinone precursor biosynthesis, and these compounds can function as shared metabolites supporting the growth and respiration of neighboring microorganisms.

Metabolomic analysis confirmed that the co-culture established a distinct metabolic state rather than a simple additive combination of the two monocultures. Several stress-protective compounds were elevated, including fraxetin, a potent antioxidant capable of scavenging heat-induced reactive oxygen species, and indolelactic acid, a characteristic tryptophan-derived metabolite produced by Pediococcus with potent antioxidant activity. Meanwhile, metabolites involved in amino acid biosynthesis, nitrogen metabolism, the tricarboxylic acid cycle, pyruvate metabolism, and fatty acid metabolism exhibited lower abundances in the co-culture than the weighted expectation, indicating that these intermediates were actively consumed and channeled into downstream reactions rather than accumulating, pointing to an elevated metabolic turnover rate.

Among the metabolites displaying striking temporal dynamics, chorismate stood out. Within the phenylalanine, tyrosine, and tryptophan biosynthesis pathway, quinic acid, shikimic acid, and anthranilic acid continuously decreased from 6 to 12 hours, while the corresponding pathway transcripts remained consistently upregulated. Chorismate accumulated 4.7-fold over the biomass-weighted expectation at 6 hours and then dropped to 0.5-fold at 12 hours, while L-tyrosine showed a reciprocal trend. This transition from accumulation to rapid depletion suggests that chorismate behaves as a key metabolic branch point underlying sustained heat production during the later stage of co-culture fermentation.

From a metabolic network perspective, chorismate occupies a central branching point between menaquinone biosynthesis and aromatic amino acid biosynthesis. Menaquinone functions as the principal lipid-soluble electron carrier in the respiratory chains of Gram-positive Firmicutes such as Bacillus, so the flux of chorismate toward menaquinone biosynthesis directly affects respiratory electron transport efficiency. On the other hand, chorismate is also a key precursor for tyrosine biosynthesis, whose conversion involves NAD(P)+-dependent oxidation reactions capable of generating reducing equivalents. Tyrosine catabolism produces fumarate and acetoacetate, with fumarate replenishing the tricarboxylic acid cycle and acetoacetate being further converted into acetyl-CoA for entry into central carbon metabolism.

The researchers integrated these findings into a mechanism model described as a cell turnover, nitrogen sharing, chorismate metabolic redirection framework. At 45 degrees, significant enrichment of the two-component system pathway indicated enhanced cellular capacity for sensing temperature, nutrient availability, and community status, reflecting elevated rates of cell damage and turnover. Cellular lysis continuously releases proteins, peptides, free amino acids, and other nitrogen-containing compounds, generating a renewable nitrogen reservoir for the microbial community. Concurrent upregulation of flagellar assembly and biofilm formation indicated extensive structural reorganization, imposing substantial energetic demands associated with respiration.

As carbohydrate-derived energy generation declined, the co-culture increasingly relied on the accumulated pool of free nitrogen compounds, with enhanced transcription of nitrogen metabolism and multiple amino acid metabolic pathways. The most strongly enriched pathways included lysine degradation, histidine metabolism, phenylalanine metabolism, and valine, leucine, and isoleucine degradation. Preferential utilization of branched-chain and aromatic amino acids is a common adaptive strategy in thermally stressed microorganisms, and their degradation products, including acetyl-CoA, succinyl-CoA, and pyruvate, can replenish central carbon metabolism through anaplerotic reactions, compensating for tricarboxylic acid cycle substrate depletion caused by heat-induced inactivation of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase.

The custom chorismate biosynthesis pathway, defined as 28 aro-family genes catalysing the seven committed steps from DAHP synthase to chorismate synthase, was upregulated over the weighted expectation at both 6 hours (6.1-fold) and 12 hours (9.2-fold). Among the four major downstream routes of chorismate metabolism, three were upregulated at 12 hours, while biosynthesis of siderophore group nonribosomal peptides was significantly suppressed. This indicates that the co-culture preferentially allocated metabolic resources toward energy production, antioxidant defense, and cellular restructuring while temporarily restricting the energetically expensive and temperature-sensitive siderophore biosynthetic pathway.

Remarkably, the chorismate consumed through aromatic amino acid biosynthesis was not preferentially directed toward the energetically demanding tryptophan branch. Instead, metabolic flux was selectively redirected toward tyrosine biosynthesis. This redirection confers three interconnected physiological advantages. First, de novo tryptophan biosynthesis is among the most ATP-intensive amino acid biosynthetic processes, whereas the chorismate-to-tyrosine route is thermodynamically more economical and includes dehydrogenase-catalyzed reactions capable of generating NADH. Second, accumulated tyrosine possesses strong radical-scavenging activity owing to its phenolic hydroxyl group, enabling direct neutralization of heat-induced reactive oxygen species within the extracellular microenvironment. Third, tyrosine accumulation appears tightly coupled with maintenance of respiratory metabolism, as tyrosine degradation products replenish the tricarboxylic acid cycle, and tyrosine residues participate directly in quinone binding and electron transfer processes. All seven core Men genes were detected, and the re-grouped menaquinone biosynthesis pathway was strongly induced in the co-culture at 45 degrees, by 1.8-fold at 6 hours and 5.3-fold at 12 hours.

To evaluate the robustness of this mechanism under production-like conditions, the researchers employed a simulated high-temperature Daqu system in which wheat and rice straw from a Moutai-flavor Baijiu producer in Maotai Town, Guizhou Province, were used to reproduce the porosity and oxygen gradients of industrial Daqu. The co-inoculated system consistently exhibited the highest thermogenic performance. At the key temperature differentiation stage on day 4, neither single-species-inoculated group maintained dominance: in the Bacillus-inoculated group, Bacillus was substantially displaced by the background microbiota, whereas in the Pediococcus-inoculated group Pediococcus accounted for only about half of the community. In contrast, the co-inoculated group maintained both inoculated strains at appreciable proportions, supporting the robustness of the two-strain interaction.

At the transcriptomic level, the 50:50 co-inoculated group significantly enriched multiple key pathways, including the two-component system, nitrogen metabolism, aromatic amino acid biosynthesis, lipoic acid metabolism, and the tricarboxylic acid cycle, highly consistent with the microcalorimetric co-culture experiments. Furthermore, to verify that chorismate metabolic reprogramming promotes fermentative heat production, 3 micromolar D-tyrosine was introduced into the co-culture to inhibit the metabolic flux from chorismate to L-tyrosine. D-tyrosine binds to the allosteric regulatory site of prephenate dehydrogenase, mimicking L-tyrosine to trigger feedback inhibition, while remaining recalcitrant to degradation via the L-tyrosine catabolic pathway. The addition of D-tyrosine suppressed the thermogenic capacity of the co-culture fermentation, with inhibition primarily observed after the 6-hour time point of the previously identified chorismate redirection phase.

The researchers acknowledge that the model proposed is an inference from transcriptomic, metabolomic, and phenotypic signatures rather than a set of directly measured rates. Precisely quantifying the metabolic flux between Bacillus and Pediococcus will require isotope-resolved tracing combined with species-resolved labelling analysis, genetic validation through knockout, auxotrophic, or secretion mutants, and targeted quantification of chorismate, tyrosine, and menaquinone-7 against authentic standards. With flux partitioning finely quantified, the regulatory structure of the interaction can be resolved, the wider microbiome can be modulated in increasingly complex communities, and the framework can ultimately support the rational evaluation and refined design of microbial communities in industrial Daqu production.

These findings deepen understanding of microbial community thermogenesis and heat adaptation mechanisms in open solid-state fermentation systems. They also identify practical and actionable microbial targets for regulation, providing support for improving the stability and controllability of high-temperature Daqu production. By revealing how a thermally induced dynamic coexistence pattern, dominated by Bacillus with Pediococcus acting as a functional facilitator, establishes the ecological foundation for stable thermogenesis, and how chorismate partitioning acts as a central metabolic branch point channeling carbon preferentially toward tyrosine biosynthesis and menaquinone formation, the study offers a compelling molecular narrative for one of the most remarkable microbial heat-generating systems in traditional food fermentation.

Subject of Research: Interaction-driven chorismate metabolic reprogramming underlies Bacillus – Pediococcus synergistic thermogenesis in high-temperature Daqu

Article Title: Interaction-driven chorismate metabolic reprogramming underlies Bacillus – Pediococcus synergistic thermogenesis in high-temperature Daqu

Article References: Tu, H., Zhou, G., Tan, F., Yang, F., Chen, L., Lu, J., Li, J., Liu, Y., & Chen, J. (2026). Interaction-driven chorismate metabolic reprogramming underlies Bacillus–Pediococcus synergistic thermogenesis in high-temperature Daqu. Food Chemistry: X, Article 104599. https://doi.org/10.1016/j.fochx.2026.104599

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104599

Keywords: Bacillus, Pediococcus, Daqu, Baijiu, chorismate, thermogenesis, solid-state fermentation, microbial interactions, Interaction-driven, metabolic, reprogramming, underlies

For decades, sub-therapeutic doses of antibiotics were routinely folded into animal feed to suppress intestinal pathogens, reduce sub-clinical infections, lower immune activation, and improve nutrient utilization. That convenience came at a steep price. The practice is now recognized as a major driver of antimicrobial resistance determinants circulating among pathogenic bacteria and commensal microbiota of animal origin, alongside dysbiosis and persistent antibiotic residues in meat, milk, and other animal products. The search for replacements has increasingly focused on probiotics, live microorganisms that promote growth performance by stabilizing gut microbial homeostasis, reinforcing intestinal barrier integrity, regulating tight junction expression, and stimulating mucosal immunity during critical developmental windows.

What sets the two strains at the heart of this study apart is their capacity to produce bacteriocins, ribosomally synthesized antimicrobial peptides that selectively inhibit competing and pathogenic microorganisms. Unlike conventional antibiotics, which can broadly bulldoze the gut ecosystem, bacteriocin production enables targeted suppression of undesirable taxa while preserving the resident microbial community. Both strains were previously isolated from cattle feces at the University of Ibadan Teaching and Research Farm and extensively characterized for probiotic properties, including tolerance to acidic pH and bile, absence of hemolytic activity, and organic acid production.

Before any calf received a single dose, the researchers turned to whole-genome sequencing to establish a rigorous safety profile. L. pentosus AA86 yielded a genome of 3,665,302 base pairs assembled into 112 contigs, while P. pentosaceus AA94 produced a smaller genome of 1,843,469 base pairs across 71 contigs. Critically, neither genome contained antimicrobial resistance genes, virulence factors, or plasmid-related elements, apart from a single Rep28 plasmid replicon carried by L. pentosus. More intriguingly, genomic screening with the BAGEL4 tool revealed pediocin-encoding genes in both isolates. Pediocin is a well-characterized class II bacteriocin with documented inhibitory activity against a broad range of bacterial taxa, including several Gram-positive pathogens and, under certain conditions, Gram-negative organisms. This genomic blueprint positioned the strains as candidates with built-in antimicrobial functionality before they ever entered an animal trial.

The feeding trial itself was elegantly simple. Eight calves, each weighing approximately 50 kilograms, were ear-tagged, penned individually to prevent cross-contamination, and randomly assigned to two groups. Six calves received a daily 10-milliliter oral gavage of a mixed suspension containing both bacterial strains at roughly 8.3 × 10^10 colony-forming units per milliliter, resuspended fresh each day in 10 percent reconstituted skimmed milk. Two control calves received sterile skimmed milk alone. No antibiotics or antibiotic feed additives were administered to any animal throughout the experiment. Fecal samples were collected directly from the rectum at three time points: before the intervention, at day 15, and at day 30, capturing the microbiota before, during, and after the probiotic course.

The sequencing pipeline was equally meticulous. The V3–V4 region of the 16S rRNA gene was amplified and sequenced on the Illumina MiSeq platform with paired-end chemistry, then processed through QIIME2 with Deblur denoising and Greengenes-based taxonomic classification. Alpha diversity metrics including Shannon index, observed features, Faith’s phylogenetic diversity, and Pielou’s evenness were computed alongside beta diversity measures such as weighted and unweighted UniFrac, Bray-Curtis, and Jaccard distances. Taxonomic read counts were then modeled with generalized linear mixed-effects models using a negative binomial distribution, with treatment, sampling time, and their interaction as fixed effects and calf identity as a random intercept to account for repeated measurements from the same animals. P-values were adjusted with the Benjamini-Hochberg false discovery rate correction.

The headline result was one of selective modulation rather than wholesale restructuring. Shannon diversity did not differ significantly between treatment groups or across sampling stages, and principal coordinate analysis of beta diversity showed no significant separation between intervention and control calves. This absence of a global diversity effect is consistent with a growing body of evidence that lactic acid bacteria-based probiotics often do not markedly alter overall microbial diversity, and with systematic reviews and meta-analyses of randomized trials reporting minimal probiotic effects on alpha diversity. The calf gut microbiota is, after all, in a state of gradual ecological assembly during early life, shaped by diet, host development, and microbial succession rather than abrupt compositional overhauls.

At the phylum level, however, the story sharpened considerably. Firmicutes showed a significant treatment-by-time interaction between the initial and final sampling points, with significantly lower abundance in probiotic-treated calves than in controls at day 30. Crucially, the two groups did not differ at baseline, and control calves showed no significant change over the same period, indicating that the divergence reflected a treatment-associated shift in microbial trajectories rather than a pre-existing difference. Bacteroidetes followed a complementary pattern: their abundance increased significantly from initial to final sampling within probiotic-treated calves, and estimated marginal means showed significantly higher Bacteroidetes levels in treated animals at the midpoint of the intervention. This compositional trend is widely interpreted as a gut ecosystem increasingly optimized for carbohydrate fermentation and metabolic efficiency, since Bacteroidetes in developing ruminants play a central role in degrading starch, fiber, and dietary protein while supporting short-chain fatty acid production during the transition toward functional ruminancy.

The direction of the Firmicutes-to-Bacteroidetes shift carries real health implications. Disproportionate expansion of Firmicutes relative to Bacteroidetes has been associated with dysbiosis across species; in calves, elevated Firmicutes coupled with reduced Bacteroidetes has been linked to diarrheal disease and impaired gut health, while similar shifts in humans have been connected to obesity, altered glucose metabolism, and gastrointestinal disorders. Genus-level patterns added further texture. In control calves, the abundance of Bacteroides, Parabacteroides, Mycoplasma, Shigella, and Staphylococcus decreased significantly between the middle and final sampling points, whereas Helicobacter rose significantly over the same interval. None of these temporal fluctuations appeared in the probiotic-treated calves, suggesting that supplementation may have attenuated some of the compositional volatility observed in the untreated microbiota. Lactobacillus abundance declined significantly in controls from initial to final and from middle to final sampling, while treated calves showed a decline only from initial to midpoint, hinting at a relative maintenance of resident Lactobacillus populations in the latter phase, though the absence of a significant treatment-by-time interaction means this observation remains explorative.

The authors are candid about the study’s constraints. The 30-day intervention was relatively short, limiting the ability to capture longer-term microbial adaptation or functional maturation, and the small cohort of eight calves, constrained by herd size at the research facility, may have reduced statistical power to detect subtle effects, particularly at the genus level. Relative abundance profiling also does not directly quantify absolute microbial loads or metabolic activity, and in vivo bacteriocin production was not measured. Still, the core message is compelling: early-life supplementation with genomically safe, pediocin-producing lactic acid bacteria appears to steer selected components of calf gut microbiota development, favoring a Bacteroidetes-enriched, fermentation-optimized ecosystem, without substantially altering global microbial diversity or community structure. Whether these taxonomic changes translate into measurable functional benefits, improved feed efficiency, and greater resilience to enteric disturbances will demand larger cohorts, extended follow-up, strain-resolved sequencing, functional metagenomics, metabolomic profiling, and host health outcomes. For now, the study offers a plausible microbiological basis for bacteriocin-producing probiotics as precision tools in the post-antibiotic era of livestock production.

Subject of Research: Modulation of Early‐Life Calf Gut Microbiota by Bacteriocin‐Producing Lactiplantibacillus pentosus AA86 and Pediococcus pentosaceus AA94

Article Title: Modulation of Early‐Life Calf Gut Microbiota by Bacteriocin‐Producing Lactiplantibacillus pentosus AA86 and Pediococcus pentosaceus AA94

Article References: Adetoye, A. A., Afolayan, A. O., Olatoye, I. O., Faneye, A. O., & Ayeni, F. A. (2026). Modulation of Early‐Life Calf Gut Microbiota by Bacteriocin‐Producing Lactiplantibacillus pentosus AA86 and Pediococcus pentosaceus AA94. MicrobiologyOpen, 15(5), Article e70438. https://doi.org/10.1002/mbo3.70438

Image Credits: AI Generated

DOI: 10.1002/mbo3.70438

Keywords: Modulation, Early, Life, Calf, Microbiota, Bacteriocin, Producing, Lactiplantibacillus, pentosus, AA86, Pediococcus, pentosaceus

The research team, led by Mengru Han and colleagues including senior author Baili Feng, selected two cultivars, Liuleng (black) and Ganqing10 (yellow), grown side by side in the same experimental plot of the Agricultural Science Research Institute of Gannan Tibetan Autonomous Prefecture. In previous work, the group had shown that black and yellow highland barley represent the extremes of compositional variation among colored cultivars, with black grains carrying roughly twice the flavonoids, phenolics, and anthocyanins of their yellow counterparts. The central question of the new study was whether those initial chemical differences would steer fermentation along fundamentally different trajectories, or whether the microbial communities driving the process would converge on a shared path regardless of raw material.

To find out, the researchers followed the traditional Tibetan brewing procedure. Barley grains were soaked, boiled, cooled, and inoculated with a starter combining indigenous Tibetan jiuqu—a traditional fermentation culture prepared from barley flour, plateau herbs, and aged starter—with high-activity dry yeast. The prepared grains then fermented in sealed earthenware jars at 29 degrees Celsius for 72 hours, with samples harvested at 0, 24, 48, and 72 hours. For each time point the team tracked antioxidant compound contents and radical-scavenging activities, sequenced bacterial 16S rRNA genes and fungal internal transcribed spacer regions to profile the microbiome, and used ultra-performance liquid chromatography coupled to tandem mass spectrometry to map the non-volatile metabolome at the final stage of fermentation.

The antioxidant measurements told a nuanced story. In both cultivars, fermentation pushed total phenolic content upward and anthocyanins peaked at 48 hours before easing slightly, while total flavonoid content declined progressively—suggesting that flavonoids were being transformed, deglycosylated, or converted into other phenolic derivatives rather than simply accumulating. Yellow barley showed the more dramatic relative gains, ultimately surpassing black barley in total phenolic content by the end of fermentation and posting a larger rise in total antioxidant capacity. Yet black barley never surrendered its lead in radical scavenging: it maintained consistently higher DPPH, ABTS, hydroxyl radical, and superoxide radical scavenging activities throughout all 72 hours, an advantage the authors attribute to its richer initial reserves of flavonoids, anthocyanins, and pigment-associated metabolites.

Microbial sequencing revealed a fermentation world that was simultaneously shared and distinct. In both jars, bacterial diversity fell steadily, and the fungal community collapsed toward near-total dominance by a single genus, Saccharomycopsis, whose competitive grip on carbohydrate utilization drove fungal diversity essentially to zero by the middle of fermentation. Among bacteria, Lactococcus flourished early, peaking at 24 hours, while Pediococcus rose steadily to dominate the late stage in both cultivars—an ecological succession that mirrors patterns seen in other cereal fermentations, where substrate consumption, acid accumulation, and falling pH progressively eliminate competitors and favor acid-tolerant lactic acid bacteria.

Beneath these broad similarities, however, the two cultivars hosted measurably different microbial worlds. Bacterial richness rose and then fell in black barley but followed the opposite pattern in yellow barley, and differences in alpha diversity were detectable even before fermentation began, hinting that the grains carried distinct resident microbiota shaped by their contrasting chemistry. LEfSe biomarker analysis identified cultivar- and stage-specific taxa: Gordonia and Frigoribacterium marked the 24-hour stage in black barley, Enterococcus marked 48 hours, and Levilactobacillus emerged at 72 hours, whereas yellow barley at 24 hours was characterized by Lactococcus and Flavobacterium. Principal coordinate analysis showed the overall bacterial community structures broadly overlapped, but the fungal communities differed significantly between cultivars, if modestly in magnitude.

Perhaps the most striking cultivar differences emerged from co-occurrence network analysis, which maps the statistical associations among microbial taxa. The yellow barley network was denser, more highly connected, and richer in positive correlations, suggesting a more cooperative, tightly interlinked community—the kind of structure that previous research has linked to efficient joint substrate utilization and metabolite exchange. The black barley network, by contrast, was more modular and compartmentalized, with taxa organized into relatively independent functional subgroups that may allow separate responses to acid stress, substrate availability, or phenolic inhibition. The putative keystone taxa also diverged sharply: Bacillus and Zoogloea anchored the black barley network, while Lactococcus, Enterococcus, and Aquabacterium held central positions in yellow barley. Predicted functional profiles from PICRUSt2 were broadly similar between cultivars—dominated by carbohydrate, amino acid, and energy metabolism—indicating a shared functional foundation, with differences concentrated in low-abundance pathways.

The metabolomics data sharpened the picture considerably. Principal component analysis and hierarchical clustering cleanly separated the fully fermented black and yellow samples, and while most detected metabolites were shared, black barley contained more cultivar-specific compounds. The metabolites enriched in black barley were overwhelmingly flavonoids and phenolic acids—derivatives of isoscoparin, tricin, chrysoeriol, caffeoyl compounds, and 1-acetyl-beta-carboline—and KEGG enrichment pointed squarely at flavonoid and anthocyanin biosynthesis pathways, including chrysoeriol aglycone, apigenin C-glycoside, and flavone and flavonol biosynthesis. Yellow barley, by contrast, accumulated more amino acids, small peptides, and their derivatives, suggesting its fermentation leaned more heavily toward primary nutrient transformation and the formation of taste-related compounds.

Correlation analyses then wove the three data layers together. Antioxidant indices were strongly and positively associated with specific flavonoid glycosides and phenolic derivatives: total flavonoid content tracked compounds such as chrysoeriol-7-O-rutinoside-5-O-glucoside and quercetin-5,4′-di-O-glucoside with correlation coefficients above 0.94, while anthocyanin content aligned with gallic acid and 1-acetyl-beta-carboline. Notably, the lactic acid bacterial genera Lactiplantibacillus and Levilactobacillus were the taxa most closely and positively correlated with antioxidant-related flavonoid and phenolic metabolites—a finding consistent with known β-glucosidase, esterase, and phenolic acid decarboxylase activities in some lactic acid bacteria that can liberate bound phenolics from grain matrices. Meanwhile, genera such as Aquabacterium, Bradyrhizobium, Lactococcus, and Microbacterium associated instead with peptide- and amino acid-derived metabolites, and Flavobacterium and Saccharomycopsis showed correlation patterns opposite to the antioxidant-linked lactic acid bacteria. The authors are careful to stress that these are statistical associations, not proof of causation, and that the functional predictions were inferred from taxonomy rather than measured directly by metagenomics or enzyme assays.

The study has clear limitations—pH, organic acids, and the free-versus-bound phenolic fractions were not fully characterized, and no cultivation or inoculation experiments were performed to test the candidate microorganisms directly. But the practical implications are compelling. For producers of highland barley wine and emerging functional foods, the work suggests that cultivar selection is a powerful lever: black barley delivers a fermented product with inherently stronger radical scavenging capacity, while yellow barley responds more dynamically to fermentation with larger relative gains in phenolics. Future experiments using sterile fermentations, defined co-cultures, and enzyme knockout studies could confirm whether Lactiplantibacillus and Levilactobacillus can be deployed as starter organisms to deliberately boost the phenolic content and antioxidant value of fermented cereal products. In an era when consumers increasingly seek foods with documented functional benefits, this plateau grain—and the microbes that transform it—may offer a scientifically grounded path from traditional brewing to evidence-based functional food design.

Subject of Research: Comparative multi-omics analysis of microbial succession, metabolite profiles, and antioxidant properties during fermentation of black and yellow highland barley.

Article Title: Comparative multi-omics analysis of microbial succession, metabolite profiles, and antioxidant properties in fermented black and yellow highland barley

Article References: Han, M., Hou, H., Wang, H., Zhang, M., Tang, X., Zhou, X., Liu, M., Ma, C., Yang, Q., & Feng, B. (2026). Comparative multi-omics analysis of microbial succession, metabolite profiles, and antioxidant properties in fermented black and yellow highland barley. Food Chemistry: X, 39, Article 104424. https://doi.org/10.1016/j.fochx.2026.104424

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104424

Keywords: highland barley, fermentation, antioxidant activity, flavonoids, anthocyanins, microbial succession, lactic acid bacteria, metabolomics, Pediococcus, Saccharomycopsis, Tibetan barley wine, functional foods