Search Results (307)

Constipation is a widespread gastrointestinal condition with complex causes and limited therapeutic efficacy of current treatments. Probiotics and natural-function foods like dark tea (DT) have emerged as promising alternatives. We investigated the protective effects of dark tea (DT) and Lactiplantibacillus paracasei K34-fermented dark tea (FDT) against constipation induced by loperamide (LOP) in mice. FDT exhibited a superior effect over DT in alleviating constipation, as evidenced by increased fecal water content, reduced defecation time, and accelerated small intestinal transit. FDT also restored serum gastrointestinal neurotransmitters and repaired intestinal barrier damage more effectively. FDT intervention significantly increased the richness and altered the composition of gut microbiota, notably elevating Lactobacillus, Ligilactobacillus, and Actinobacteria, while reducing Prevotellaceae_UCG-001. Correlation analysis linked these microbial shifts with improved motility and anti-inflammatory responses. Untargeted metabolomics indicated that fermentation drastically enriched key bioactive compounds in FDT compared to DT, including cyclic dipeptide (cyclo-(Gly-Pro), 132.4-fold) and hydroxylated linoleic acid derivatives (N-(17-hydroxy-9,12-octadecadienoyl)-glutamine, 123.8-fold). KEGG pathway analysis suggested fermentation upregulated tryptophan metabolism and branched-chain amino acid biosynthesis, while downregulating flavone biosynthesis. Collectively, probiotic fermentation enhances the anti-constipation efficacy of DT, which is achieved via a synergistic mechanism involving neuroendocrine modulation, intestinal barrier repair, gut microbiota composition, and transformation of bioactive metabolites. Full article

Ofloxacin (OFL) exists widely in raw materials of organic fermentation, which can inhibit hydrogen production of dark fermentation. In this study, the inhibition of OFL on hydrogen production was studied from the aspects of hydrogen production performance, bacterial community and functional genes using glucose as a model substrate. The results showed that OFL exposure ≥ 10 mg/L significantly decreased the hydrogen production. With an OFL exposure concentration of 500 mg/L, the hydrogen yield reduced to 48.35 ± 2.13 mL/g glucose and the lag period prolonged to 26.48 ± 0.40 h, compared with those of control without ofloxacin exposure (169.99 ± 9.68 mL/g glucose and 8.98 ± 0.07 h), respectively. The efficient hydrogen-producing bacteria, Clostridium, were inhibited and the dominant microbial population was transformed, leading to change in metabolic pathway of fermentation from butyric acid type to ethanol type. Correspondingly, the proportion of butyrate in metabolites decreased from 66.46% to 0.00%, the proportion of acetate decreased from 26.12% to 3.69%, and the proportion of ethanol increased from 3.13% to 96.31%. OFL exposure showed significant downregulation of predicted functional genes involved in glycolysis and hydrogen production, such as K00845, K00532, and K03737, fundamentally resulting in significant inhibition of glycolysis and pyruvate metabolism for hydrogen production. Full article

The purpose of this study was to examine how hydraulic retention time (HRT) influences biohydrogen generation and the formation of end-products during the co-digestion of olive mill wastewater (OMW), cheese whey (CW), and sewage sludge (SS) mixed in a 40:40:20 (v/v/v) ratio. The relationship between the substrates, resulting metabolites, and microbial communities was also explored. Continuous fermentation trials were carried out under both mesophilic (37 °C) and thermophilic conditions using HRTs of 12, 24 and 48 h. Acetic, propionic, and butyric acids were identified as the main end-products. The highest hydrogen production rate (4.4 ± 0.5 L H₂/L_reactor/day) occurred under thermophilic conditions at an HRT of 24 h, whereas under mesophilic operation at the same HRT the hydrogen production reached 3.0 ± 0.3 L H₂/L_reactor/day. In contrast, the greatest accumulation of volatile fatty acids (VFAs) was observed under mesophilic conditions (10.02 g/L), while thermophilic operation at 24 h HRT resulted in 5.54 g/L of total VFAs. The improved performance under thermophilic fermentation is likely linked to the suppression of hydrogen-consuming bacteria at elevated temperatures, which favors rapid hydrogen producers. Microbial community analysis indicated dominance of Firmicutes and persistent Lactobacillus prevalence across conditions. Shorter HRT at 37 °C promoted community diversification with genera such as Olsenella, Dialister, and Prevotella increasing in relative contribution. Under thermophilic operation, consortia remained Lactobacillus-dominant but showed significant temporal restructuring. The predominance of acetic acid (~2.80 g/L) and butyric acid (~2.60 g/L) indicates that hydrogen generation mainly followed the acetic and butyric pathways. This study reveals how targeted control of HRT and temperature can steer microbial communities toward highly hydrogen-productive consortia in the continuous dark fermentation of mixed agro-industrial wastes. Full article

Wheat and rice are major sources of human nutrition worldwide. Solid-state fermentation (SSF) with lignocellulolytic mushrooms can enhance their nutritional value and increase their functional properties. However, this technology is not yet widely applied. In this work, whole wheat and brown rice hydrated to 60% were used as substrates for the edible mushroom Pleurotus ostreatus and the medicinal Ganoderma sessile, which were incubated for 14 days at 25 °C in the dark. The fermented substrate biomass was incorporated into standard sugar-snap cookie recipes, substituting 20% of the wheat flour. We evaluated the technological and nutritional properties of alternative fermented flours and cookies. Both the fermented flours and cookies exhibited increased soluble and total protein content, antioxidant power, and phenol content, indicating overall functional improvement. Fermented G. sessile flour also showed increased triterpenoid content. The physical quality of cookies remained within expected ranges, demonstrating the feasibility of the application. These results highlight the potential of SSF as a method for nutritional and functional enrichment of grains and extend the health benefits of mushrooms to populations relying on low-cost, grain-derived carbohydrates. Further studies on digestibility and in vivo activity of metabolites are needed to confirm the potential health benefits of fermented flours. Full article

Residues generated during fruit processing constitute an abundant and underutilized biomass rich in bioactive compounds, pigments, structural polysaccharides, lipids, and fermentable carbohydrates. Although their potential for biorefinery applications is widely recognized, existing studies are often fragmented, focusing on isolated products, which limits a comprehensive understanding of integrated valorization strategies. To address this gap, this study presents an integrative review supported by bibliometric analysis to identify global research trends, dominant technological pathways, and key challenges associated with the use of fruit residues in biorefineries. The review covers technologies for extracting phenolic compounds, essential oils, pigments, and structural fibers, as well as lipid recovery, enzyme production, and biochemical routes for bioethanol, biohydrogen, and biogas generation. The review reveals that emerging technologies, such as pressurized fluid extraction, microwave-assisted extraction, and ultrasound-assisted extraction, enable efficient recovery of antioxidant compounds, high-purity pectin, and fermentable sugars, particularly when applied in sequential and integrated processing schemes. Bioethanol production is the most extensively investigated route, with yields strongly dependent on biomass composition and pretreatment strategies, identifying banana, cashew, apple, mango, coconut, and palm residues as promising feedstocks. In addition, biohydrogen production via dark fermentation and anaerobic digestion for biogas generation shows high technical feasibility, especially when integrated with upstream extraction steps. Overall, integrated valorization of fruit residues emerges as a key strategy to enhance economic performance and environmental sustainability in agro-industrial systems. Full article

The mechanism of the quality formation of dark tea is not fully clear, particularly under variable fermentation temperatures. In this study, the tea fermented with Aspergillus niger (AN) at 25 (AN25) and 37 °C (AN37) exhibited the highest quality. Different fermentation temperatures primarily influenced the degradation of fatty acids and the hydrolysis of glycosides in the tea, with 37 °C being the most favorable for the release and accumulation of volatile compounds. Eighteen key volatiles were identified. Among these, benzaldehyde (a 120.9% increase compared to CK), α-ionone (957.8%), linalool (172.2%), and nonanal (22.8%) were present at high levels in AN37, and these compounds served as the main aroma contributors. Inoculation with AN and fermentation temperature primarily influences the levels of total polyphenols, organic acids and their derivatives, as well as amino acids and their metabolites in dark tea. Total polyphenols, flavonoids, and nucleotide and its metabolites were more rapidly consumed at 25–37 °C, contributing to the improved taste of the tea infusion. Additionally, EGC, GC, melezitose, and sucrose showed significant negative correlations with the taste quality of the tea infusion (p < 0.05). These results are conducive to further understanding of the quality formation of dark tea. Full article

Pile fermentation is a crucial process for developing the characteristic mellow taste and aged aroma of dark tea, yet the internal quality transformation mechanism of this process is still unclear. This study employed a high-sensitivity analytical platform based on gas chromatography–mass spectrometry (GC-MS) to systematically investigate the dynamic interplay between key chemical components, enzyme activities, and volatile compounds during the pile fermentation of primary dark tea. Our findings revealed a significant decrease in ester-type catechins, crude protein, and protopectin, alongside a notable accumulation of non-ester-type catechins, gallic acid, and soluble components. The multi-enzyme system—comprising PPO/POD, pectinase/cellulase, and protease—cooperatively drove the oxidation of phenols, cell wall degradation, and the release of aromatic precursors. This was complemented by GC-MS analysis, which identified and quantified 103 volatile compounds across nine chemical classes. The total content of volatile compounds increased significantly, with alcohols, esters, and aldehydes/ketones being the dominant groups. Floral and fruity compounds such as linalool and geraniol accumulated continuously, while esters exhibited an initial increase followed by a decrease. Notably, carotenoid degradation products, including β-ionone, were significantly enriched during the later stages. This study revealed a “oxidation–hydrolysis–reconstruction” metabolic mechanism co-driven by microbial activity and a multi-enzyme system, providing a theoretical foundation for the precise regulation of pile fermentation and targeted quality improvement of primary dark tea. Full article

Fu brick tea (FBT) develops its characteristic qualities through fermentation, yet how variation in the chemical composition of raw dark tea (RDT) is associated with microbial succession and final tea quality remains unclear. In this study, three grades of RDT (premium-grade (1M), first-grade (2M), and second-grade (3M)) were processed into FBT under identical conditions to examine the relationship between initial composition, microbial community structure, and sensory attributes. Results revealed that high-grade RDTs (1M) contained higher levels of water extracts (WE, 36.35 ± 0.14 (%), p < 0.05), total polyphenols (TP, 14.93 ± 0.19 (%), p < 0.05), and free amino acids (FAA, 2.90 ± 0.03 (%), p < 0.05), promoting Aspergillus (96.06% in C1M, compared with 66.43% in C2M and 55.01% in C3M) dominance and resulting in brighter liquor with enhanced body and smoothness. Correlation analyses demonstrated a coherent sequence from substrate composition to microbial assembly and then to quality-related chemistry. WE, TP, and FAA were positively correlated with Aspergillus abundance and body and smoothness (p < 0.05), whereas soluble sugars correlated with Rhodotorula and sweetness (p < 0.05). These findings support a substrate-mediated association framework in which the chemical composition of RDT is closely aligned with microbial community structure and sensory differentiation during FBT fermentation, providing a scientific basis for raw material grading and fermentation management in dark tea production. Full article

Hydrogen production technologies are undergoing rapid diversification, driven by the dual imperative of decarbonization and resource circularity. While conventional water electrolysis, particularly PEM and alkaline systems, represents a mature and scalable solution for centralized hydrogen generation, biologically mediated pathways such as microbial electrolysis cells (MECs), dark fermentation, and anaerobic digestion are gaining visibility as decentralized, low-energy alternatives. This review presents a bibliometric analysis of hydrogen research from 2021 to 2026, based on three multi-query strategies that retrieved 6017 works in MQ1, 7551 works in MQ2, and 1930 works in MQ3. The year 2026 is included in the dataset because Scopus indexes articles already accepted and released in early access, assigning them their forthcoming official publication year. Keyword co-occurrence mapping using VOSviewer highlights thematic clusters and disciplinary shifts. The results reveal a strong dominance of electrochemical research, with biohydrogen production emerging as a distinct but less mature frontier rooted in biotechnology and environmental science. MECs, in particular, occupy a transitional zone between electrochemical and biological paradigms, offering multifunctional platforms for simultaneous waste valorization and hydrogen generation. However, their low Technology Readiness Levels (TRLs) and unresolved engineering challenges limit their current scalability. The comparative analysis of bibliometric queries underscores the importance of integrating electrochemical and biotechnological approaches to build a resilient and context-adaptive hydrogen economy. This study provides a structured overview of the evolving knowledge landscape and identifies key directions for future interdisciplinary research and innovation. Full article

Second cheese whey (SCW), a major by-product of ricotta cheese production, poses significant environmental challenges due to its high organic load. Biohydrogen (bio-H₂) and poly-β-hydroxybutyrate (PHB) production offer a sustainable reuse of SCW, that provides ideal nutrients for microbial growth. This study aimed to convert SCW into Bio-H₂ and PHB using a 5-liter tubular bioreactor in a sequential lactic fermentation and photofermentation system. Two lighting conditions were tested: white LED (WL) and selected LED (SL). Optimal results were achieved with a co-inoculum of Lactococcus lactis MK L84 and Lacticaseibacillus paracasei MK L49 at pH 4.5–5.5, followed by photofermentation with Rhodopseudomonas palustris 42OL under SL condition. The process yielded an average of 0.47 L of H₂ per liter of substrate and 1.66% wPHB/wCDW. This approach successfully transformed dairy waste into high-value products, promoting circular economy principles. Full article

Broccoli waste (Brassica oleracea), comprising non-commercialized stems and leaves, represents a valuable substrate for bioenergy and commodity recovery within agro-industrial systems. This study evaluates the potential of dark fermentation (DF) to produce hydrogen (H₂) and carbon dioxide (CO₂) from unpretreated broccoli residues. Batch experiments (120 mL) yielded maximum gas production rates of up to 166 mL/L·d, with final compositions of 41.43 mol% and 58.56 mol% of H₂ and CO₂, respectively. Based on these results, two biorefinery models were simulated using COCO v3.10 and SuperPro Designer^® v12.0, incorporating absorption and cryogenic separation technologies in the purification stage. Two scenarios were considered: Option A (169.82 kmol/day; H₂: 0.5856 mol fraction, CO₂: 0.4143 mol fraction) and Option B (72.84 kmol/day; H₂: 0.6808 mol fraction, CO₂: 0.3092 mol fraction). In both configurations, the purities of the final streams were the same, being 99.8% and 99.8% for both H₂ and CO₂, respectively. However, energy consumption was 43.76% higher in the cryogenic H₂/CO₂ separation system than in the absorption system. Noteworthily, this difference does not depend on the stream’s composition. Furthermore, from a financial standpoint, the cryogenic system is more expensive than the absorption system. These findings confirm the feasibility of designing biorefineries for H₂ production with high CO₂ recovery from broccoli waste. However, the economic viability of the process depends on the valorization of the secondary effluent from the fermentation reactor, which may require subsequent anaerobic digestion stages to complete the degradation of residual organic matter and enhance overall resource recovery. Full article

Biohydrogen production can be derived from low-value lignocellulosic biomass; however, in many biohydrogen producing systems, xylose is utilized less efficiently than glucose, which limits overall substrate conversion. To address this issue, Fe/Mn-modified biochar was employed to enhance dark fermentation of glucose–xylose mixed sugars, and its performance was compared with other inoculum treatments. The biochar addition achieved a hydrogen yield of 2.57 ± 0.10 mol-H₂/mol-sugar, representing 14.6% enhancement over untreated controls, while enabling complete substrate utilization across varying xylose proportions. Biochar supplementation also reduced the lag phase by 24.4% and increased hydrogen productivity by 47.3% in mixed-sugar cultivation. Integrated analyses of the experimental data revealed the dual role of Fe/Mn-modified biochar in constructing conductive extracellular polymeric substance networks and directing metabolic flux toward high-yield butyrate pathways. This work establishes Fe/Mn-biochar as a multifunctional microbial engineering tool that alleviates carbon catabolite repression and promotes the enrichment of hydrogen-producing bacteria (HPB), thereby providing a practical and effective strategy for enhanced biohydrogen production from lignocellulosic biomass. Full article

Global dependence on fossil fuels generates severe environmental and socioeconomic impacts, driving the urgent search for sustainable energy alternatives. In response to this global challenge, this research conducts a bibliometric analysis of hydrogen production via biohybrid systems, using publications indexed in Scopus from 2005 to 2025 and analyzed with VOSviewer. The results revealed a significant increase in research output since 2015, driven primarily by interdisciplinary developments in biotechnology, nanotechnology, and bioelectrochemistry, as well as by international sustainability policies. Four main research approaches were identified: bio-assisted photocatalysis, bio-electrochemical systems, dark fermentation, and enhanced artificial photosynthesis with nanomaterials. Despite the progress achieved, significant limitations remain in energy efficiency, operational costs, and the oxygen sensitivity of key enzymes. The study emphasizes that interdisciplinary collaboration is crucial to overcoming these barriers, highlighting priority areas for future research to strengthen the potential of biohybrid hydrogen as a viable and sustainable solution in the global energy transition. Full article

Dark fermentative hydrogen production is constrained by challenges including low hydrogen yield and operational instability. Magnetic nanoparticles (MNPs) have emerged as promising additives for enhancing biohydrogen production due to their unique physicochemical characteristics, such as high specific surface area, excellent electrical conductivity, and inherent magnetic recyclability. This review systematically compares the enhancement mechanisms of MNPs in two distinct microbial systems: pure cultures and mixed cultures. In pure cultures, MNPs function primarily at the cellular and molecular levels through the following: (1) serving as sustained-release sources of essential metallic cofactors like Fe and Ni to promote hydrogenase synthesis and activation; (2) acting as efficient electron carriers that facilitate intracellular and extracellular electron transfer; and (3) redirecting central carbon metabolism toward high-hydrogen-yield acetate-type fermentation. In mixed cultures, which are more representative of practical applications, MNPs operate at the ecological level through the following: (1) modifying microenvironmental niches to exert selective pressure that enriches hydrogen-producing bacteria, such as Clostridium; (2) forming conductive networks that promote direct interspecies electron transfer and strengthen syntrophic metabolism; and (3) enhancing system robustness via toxin adsorption and pH buffering. Despite promising phenomenological improvements, critical knowledge gaps remain, including unclear structure–activity relationships of MNPs, insufficient quantification of electron transfer pathways, unknown genetic regulatory mechanisms, and overlooked magnetobiological effects. Future research should integrate electrochemical monitoring, multi-omics analyses, and advanced characterization techniques to deepen the mechanistic understanding of nanomaterial–microbe interactions. This review aims to provide theoretical insights and practical strategies for developing efficient and sustainable MNP–microorganism hybrid systems for scalable biohydrogen production. Full article

This study aimed to investigate the effects of different light treatments on the growth, antioxidant activity, and metabolite profiles of Samsoniella hepiali. Mycelial biomass, bioactive components, antioxidant capacity, and metabolomic profiles were analyzed under dark, continuous light, and 12 h light/12 h dark cycle conditions. The results showed that the 12 h light/dark cycle significantly reduced dry mycelial weight compared to the dark and continuous light groups (p < 0.001), while no significant difference in biomass was observed between the latter two. Polysaccharide (Pol) content did not differ significantly among the three groups. In terms of antioxidant activity, the continuous light group exhibited the highest protein (Prot) content, total phenolic (TP) content, DPPH radical scavenging activity, and ferric reducing antioxidant power (FRAP) as well as the lowest superoxide anion (·O₂⁻) content. The dark group showed the highest activities of superoxide dismutase (SOD) and catalase (CAT). Correlation analysis revealed that total phenolic (TP) content was significantly positively correlated with 2,2-Diphenyl-1-picrylhydrazy (DPPH) and FRAP (p < 0.01), and significantly negatively correlated with superoxide anion content (p < 0.05). Non-targeted metabolomics identified 3643 metabolites, primarily amino acids and derivatives, organic acids, and glycerophospholipids. KEGG enrichment analysis indicated significant accumulation of differential metabolites such as linoleic acid, tyrosine, and phosphatidylcholine across comparison groups. These findings provide insights into the regulatory role of light exposure on the antioxidant capacity of S. hepiali and support its further development in fermented mycelial products. Full article