Torulaspora delbrueckii is a promising non-Saccharomyces yeast for beverage diversification, although its diversity and application in cider production remain poorly explored. This study characterized Patagonian T. delbrueckii isolates from wine- and cider-associated environments and evaluated their fermentative potential in apple must. Mitochondrial DNA-RFLP analysis showed that mitochondrial profiles varied according to the isolation source, while physiological characterization revealed differences in temperature, sulfite, and ethanol responses among isolates from different sources. Compared with wine isolates, cider isolates generally exhibited greater tolerance to high temperatures, lower sulfite tolerance, and shorter lag phases under ethanol stress. Eleven representative strains completed apple must microfermentations. Compared with a commercial Saccharomyces cerevisiae strain, T. delbrueckii produced higher glycerol and erythritol concentrations while achieving comparable or higher ethanol levels. Two contrasting strains were further evaluated in sequential mixed fermentations with S. cerevisiae. NPCC1340 enhanced glycerol and erythritol production, whereas NPCC1608 increased malic and succinic acids while maintaining low acetic acid levels. In mixed fermentations, ciders retained the characteristic metabolic profiles of each T. delbrueckii strain, whereas S. cerevisiae improved fermentation performance, producing intermediate fermentation kinetics. These findings reveal phenotypic diversity among Patagonian T. delbrueckii strains and suggest differences associated with their isolation sources, highlighting their potential as starter cultures for producing ciders with distinct chemical characteristics.
Chlorpyrifos (CPF) is the most commonly used organophosphorus insecticide in agriculture globally. This has raised concerns due to its persistence, bioaccumulation, neurotoxicity, and environmental and human health effects. Until 2020, CPF was the most commonly used pesticide in European Union (EU) food production. CPF is also used in other parts of the world, though it has been discontinued in the EU, as national pesticide surveillance programs indicate it is found in soil, water, and food. This type of persistence is potentially harmful to farmers, consumers, and animals because CPF is toxic. Markedly, CPF has the potential to change the microbiota composition of soils, i.e., fungal, bacterial, and actinomycete communities, and inhibit the mineralization of nitrogen. The key CPF activity is associated with the inhibition of acetylcholinesterase (AChE), leading to reproductive, neurotoxic, and genotoxic effects. Microbial degradation, especially when applied by means of bacteria, has become one of the promising alternatives to the traditional physicochemical means since it is inexpensive, does not harm the environment and may possibly be fully detoxified. This review summarizes the latest developments in the study of CPF-degrading bacteria, enzyme pathways, microbial diversity, and the evaluation of the environmental impact of microbial remediation. Recent research findings, genomic research developments, and potential applications of CPF-degrading bacteria are addressed. In addition, this study reveals the current knowledge gaps, presents biotechnological challenges, and suggests future directions in the application of field-scale studies, focusing on the application of microbial solutions in sustainable agriculture.
Excessive protein degradation reduces protein-use efficiency in ruminants. This in vitro study evaluated brown-sorghum-bran extract (SBE; 20 or 40 g/kg DM), BioProtect (15 or 30 mL/kg DM), and tannic acid (30 g/kg DM; positive control) in soybean and canola meals. Gas production and ammonia-N were assessed over 24 h; protein digestion and amino acid concentrations were also determined. Gas production and ammonia-N were generally lower in treated meals, with responses dependent on substrate, additive and incubation time (p ≤ 0.003). Substrate × additive interactions affected RDP, RUP and IVIDP (p < 0.001). The higher inclusion rates, 40 g/kg DM SBE and 30 mL/kg DM BioProtect, did not differ from tannic acid in RDP, RUP or IVIDP within either substrate. After in vitro intestinal digestion, total EAA showed a substrate × additive interaction (p = 0.033); 30 mL/kg DM BioProtect and 40 g/kg DM SBE produced among the highest total EAA concentrations in both substrates. Among the individual acid-hydrolysable EAA recovered from the liquid fraction after in vitro intestinal digestion, only methionine concentration was affected by additive treatment (p < 0.001). Overall, 30 mL/kg DM BioProtect and 40 g/kg DM SBE produced the most consistent responses for RDP, RUP and IVIDP; however, total digested CP decreased slightly (p < 0.001), and amino-acid responses were variable. In vivo studies are required to determine effects on amino-acid supply and animal responses.
Pulque is a traditional Mexican beverage produced by the spontaneous fermentation of “aguamiel”, the sap of several Agave species. Fermentation is driven by adding a previously fermented inoculum, locally known as “semilla”, whose microbial community contributes to the sensory and physicochemical properties of the beverage. The objective of this study was to provide a preliminary characterization of the microbial taxonomic composition and functional potential of pulque inoculant prepared from Agave mapisaga and Agave salmiana using shotgun metagenomic sequencing. Six inoculum samples were sequenced on the DNBSEQ using 150 bp paired-end reads. Metagenomic DNA was extracted using a CTAB-based protocol and analyzed in the Galaxy platform. The workflow included quality filtering, host-sequence removal, taxonomic classification with Kraken2, assembly with MEGAHIT, and functional annotation with eggNOG Mapper. Bacterial communities in inoculum from A. mapisaga and A. salmiana sap were dominated by Acetobacter (68.1% and 58.3%) and Leuconostoc (19.5% and 21.9%). Komagataeibacter was more abundant in A. mapisaga inoculum (3.8%), whereas Zymomonas was more abundant in A. salmiana inoculum (11.7%). The greatest species-level difference was observed for Zymomonas mobilis, whose mean relative abundance was 6.4-fold higher in A. salmiana. Fungal communities were dominated by Saccharomyces (91.4% and 72.7%) and Kluyveromyces (6.6% and 25.5%) in A. mapisaga and A. salmiana, respectively. Across all replicates, the most abundant species were Acetobacter sp. AC2005 (23.9%), Saccharomyces paradoxus (17.0%), and Zymomonas mobilis (12.9%), together accounting for approximately 54% of the total relative abundance. Kluyveromyces marxianus was 3.9-fold more abundant in A. salmiana inoculum, whereas Saccharomyces paradoxus was 1.26-fold more abundant in A. mapisaga inoculum. Alpha-diversity analysis indicated higher bacterial diversity in A. mapisaga inoculum, with a Shannon index of 2.74 and 35 exclusive species, whereas A. salmiana inoculum showed greater fungal diversity, with a Shannon index of 0.68. These differences were not statistically significant (p > 0.05). However, beta-diversity analysis suggested substantial separation between the microbial communities associated with the two Agave species (R2 ≈ 0.92). Functional annotation identified genes potentially associated with carbohydrate metabolism, sucrose degradation, and secondary metabolite biosynthesis. These findings suggest that the agave species used as the sap source may influence the taxonomic composition and functional potential of microbial communities involved in pulque fermentation.
2-Pyrone-4,6-dicarboxylic acid (PDC) is a promising pseudo-aromatic bio-based monomer for the production of biodegradable polyesters. Here, we combined metabolic engineering with fermentation process optimization to establish efficient de novo PDC biosynthesis in Corynebacterium glutamicum. To enhance the availability of protocatechuic acid (PCA), the direct precursor of PDC, endogenous PCA degradation was blocked, and precursor supply through the shikimate pathway was strengthened. Subsequently, the ligABC cluster from Sphingomonas paucimobilis SYK-6 was heterologously introduced to enable PDC formation from glucose. Medium screening identified a corn steep liquor-containing formulation that increased the PDC titer by 1.4-fold in shake-flask cultures. Further optimization of corn steep liquor concentration, dissolved oxygen, and glucose feeding rate in a 5-L bioreactor increased the PDC titer to 71.1 g/L at 90 h, with an average productivity of 0.8 g/L/h, the highest productivity for C. glutamicum-based PDC production reported to date.
Organic waste causes severe pollution, while agriculture lacks quality fertilizers. Solid-state fermentation solves both issues. Nevertheless, traditional methods are slow and lead to nitrogen loss. They also emit greenhouse gases and yield uneven products. This fails to reach modern low-carbon standards. We urgently need efficient solid-state fermentation systems. Therefore, this review summarizes recent advances in parameter optimization and cutting-edge innovations. Firstly, key solid-state fermentation operational parameters, such as carbon-to-nitrogen ratio, aeration frequency, temperature, humidity and pH, are analyzed. The optimization of these parameters facilitates nitrogen retention and mitigates pollutant emissions. Secondly, emerging enhancement strategies are discussed. Elaboration on the electron-shuttle effect of modified biochar and advances in synthetic microbial consortia is provided. For process coupling, the mechanisms of hydrothermal carbonization (HTC) combined with solid-state fermentation are explored. Bioelectrochemically assisted solid-state fermentation (MCFT/BFC) based on Direct Inter-Species Electron Transfer (DIET) is also examined. Furthermore, feasible mitigation approaches for pollutants including greenhouse gases and antibiotic resistance genes (ARGs) are summarized. Subsequently, the applications of mathematical models, the Internet of Things (IoT), and artificial intelligence in solid-state fermentation are introduced. Finally, current challenges in large-scale application and risk management are analyzed. Future prospects involving multi-omics, life cycle assessment (LCA), and functional customization are discussed. Low-carbon solutions for high-value waste utilization are provided in this review.
Hanseniaspora uvarum is consistently observed as the dominant non-Saccharomyces species in grape juice leading to spontaneous fermentations and is often considered a detrimental factor due to the increased volatile acidity associated with its abundance. This study investigated how fermentation temperature affects the competitive interaction between H. uvarum and Saccharomyces cerevisiae, and how these shifts influence microbial community structure during spontaneous grape juice fermentations. Defined single- and co-inoculated fermentations were conducted across a range of temperatures (17, 23, and 25 °C), and cell abundance was quantified by flow cytometry. In parallel, spontaneous fermentations were monitored using ITS metabarcoding to assess temperature-driven changes in fungal community composition. At 17 °C, H. uvarum dominated early fermentation due to its faster growth rate, resulting in slower sugar consumption and prolonged fermentations. Increasing fermentation temperature enhanced the early growth of S. cerevisiae. Consistent patterns were observed in spontaneous fermentations, where higher temperatures increased the relative abundance of S. cerevisiae and shortened fermentation time. These results demonstrate that fermentation temperature is a major driver of yeast competition and suggest that moderate increases in fermentation temperature may help limit excessive H. uvarum proliferation during spontaneous fermentations.
Rapid population growth, urbanization, and industrialization are continuously increasing global energy demand while intensifying climate change associated with fossil fuel consumption. In this context, renewable energy production from organic waste has gained increasing attention as a sustainable and environmentally friendly strategy. Anaerobic digestion (AD) offers significant potential for simultaneous waste stabilization and biomethane generation. However, many previous studies investigating lignocellulosic or nutrient-rich substrates have relied on physical, chemical, or thermal pretreatment methods to enhance biodegradability, despite their additional operational costs, energy consumption, and environmental impacts. Therefore, developing low-cost and pretreatment-free co-digestion strategies remains an important research need. This study investigated the biomethane production potentials of untreated chicken manure (CM) and duckweed (Lemna minor-LM) collected from the final sedimentation tanks of wastewater treatment plants under mono-digestion and co-digestion conditions. The study hypothesized that rapidly growing and widely available LM biomass could enhance methane production without requiring pretreatment. Among all reactors, CM0.75 (75% of the total TS derived from CM and 25% from LM and inoculum) achieved the highest performance with a cumulative biogas production of 5350 mL (74.2% of CH4) and a methane yield of 327 mL CH4/g VS, while mono-digestion of CM resulted in the lowest methane yield of 104 mL CH4/g VS. The results demonstrated that LM biomass naturally proliferating in wastewater treatment plants can be directly utilized as an effective co-substrate to improve biomethane production from poultry wastes. The proposed approach provides a cost-efficient, eco-friendly, and circular-economy-oriented alternative by eliminating the need for pretreatment while simultaneously valorizing problematic biomass generated in wastewater treatment facilities.
In dairy production, the fermentation process is a complex biochemical system that plays a significant role in determining the quality criteria of the final product. Traditional methods for controlling fermentation rely on limited and non-standard process parameters. In recent years, omics technologies have come to the forefront, enabling the monitoring of fermentation dynamics at the molecular level with their current, efficient, and reliable approaches. Thanks to omics approaches such as metabolomics, metagenomics, proteomics, and lipidomics, starter culture behavior, metabolite formation, aroma–texture formation, and microbial interactions in the fermentation process can be characterized more comprehensively. On the other hand, evaluating or calculating high-dimensional omics data using traditional statistical methods presents a challenge. Artificial intelligence applications are overcoming this challenge, offering significant opportunities for the accurate and reliable evaluation of data. Artificial intelligence-powered models hold promise in areas such as predicting fermentation kinetics, process control, optimizing quality criteria, and revealing the therapeutic potential of products through metabolites. This compilation aims to comprehensively address current approaches to modeling the fermentation process and quality parameters of dairy products using multi-omics technologies and artificial intelligence applications. In this respect, it will provide current and important perspectives for industrial applications and future studies.
Bioenergy biorefineries generate lignocellulosic by-products rich in fermentable sugars that can serve as renewable feedstocks for the production of high-value bioproducts, including microbial pigments with promising bioactive properties (antioxidant, antimicrobial, and anticancer). Therefore, this study aimed to identify a suitable inoculum preparation strategy, to optimize the culture medium, and to evaluate biopigment production using xylose-based media derived from sugarcane bagasse hemicellulosic hydrolysate (SBHH). Different inoculation strategies were evaluated (cell suspension, whole mycelial discs, and fractionated mycelial discs) and supplementation with Tween 80 (TW80). The medium composition was optimized using a Box–Behnken design, with xylose, yeast extract, and TW80 as variables, and fermentations were then conducted under selected inoculum conditions in semi-defined media and SBHH. The mycelial disc inoculation strategy was selected due to its high biopigment production and lower operational complexity, yielding 8.99, 8.48, and 11.78 AU of yellow, orange, and red biopigments, respectively. The optimized culture composition consisted of 55.65 g/L of xylose, 4.18 g/L of yeast extract, and 15.38 g/L of Tween 80. The cultivation of M. ruber in SBHH resulted in 12.73, 10.75, and 14.56 AU of yellow, orange, and red biopigments, respectively. Thus, the strategy of inoculum preparation associated with non-ionic surfactant proved promising for application in bioenergy biorefineries.
Oxygen management during alcoholic fermentation can redirect phenolic reactions and yeast-derived aroma formation, but the use of mild hyperbaric conditions as a micro-oxygenation strategy remains poorly characterized. This study evaluated the effects of hyperbaric micro-oxygenation at 1.40 ATA in a stainless-steel chamber on the fermentation of Vitis vinifera L. cv. Monastrell must, comparing treated and non-micro-oxygenated samples at the initial, mid-fermentation, and final stages. Physicochemical parameters, CIELAB color coordinates, total phenolic content, volatile organic compounds, and descriptive sensory attributes were analyzed. Hyperbaric micro-oxygenation did not impair fermentation completion, as both treatments reached final residual sugar values of 2.2 g/L and alcohol contents of 15.2–15.4% v/v. The treatment promoted a darker final chromatic profile, with lower L*, the highest overall color difference, and a marked increase in total phenolic content, reaching 1900.9 mg gallic acid equivalents/L compared with 1593.2 mg gallic acid equivalents/L in control. Volatile changes were compound, and stage-dependent, indicating modulation rather than generalized enhancement of aroma formation. Ethyl esters, particularly ethyl octanoate and ethyl decanoate, increased markedly under micro-oxygenation, while acetate esters such as ethyl acetate and hexyl acetate decreased relative to the initial must, reflecting a shift in the balance of aroma-active compounds rather than a uniform increase across all volatile families. These findings support mild hyperbaric micro-oxygenation as a promising non-thermal strategy to modulate Monastrell fermentation quality.
The growing demand for clean-label and low-sulphite wines has increased interest in alternative preservation strategies capable of reducing sulphur dioxide (SO2) usage while maintaining wine quality and stability. In this study, the effectiveness of Vitis vinifera leaf extract as a natural alternative to sulphur dioxide was evaluated in High Hydrostatic Pressure (HHP)-treated Fiano wines. Three experimental wines were produced: CW (control wine), SW (sulphited wine), and LW (leaf-extract wine). Following alcoholic fermentation, all wines were subjected to HHP treatment (600 MPa for 5 min) and stored at 4 °C for 60 days. Physicochemical parameters, volatile organic compounds (VOCs), and sensory characteristics were evaluated immediately after alcoholic fermentation and after HHP treatment followed by refrigerated storage. Compared with the control wine, LW exhibited approximately 20% higher total polyphenol concentrations, whereas SW showed the greatest preservation of fermentation-derived esters. HHP treatment induced only moderate changes in the volatile fraction, confirming the suitability of this non-thermal technology for wine stabilization. LW wines were characterized by higher abundances of terpene-related compounds, C6 alcohols, medium-chain fatty acids, and phenolic-associated volatiles, resulting in more pronounced floral, balsamic, herbaceous, and vegetal sensory attributes. Principal Component Analysis (PCA) explained 79.0% of the total VOC variability and clearly differentiated LW wines from CW and SW according to their volatile profiles, while sensory analysis confirmed the development of a distinctive aromatic identity associated with grapevine leaf extract. Overall, the results indicate that the combined application of V. vinifera leaf extract and HHP represents a promising strategy for the partial replacement of sulphur dioxide in white winemaking. This integrated approach contributes to wine stabilization while promoting the valorization of grapevine leaves as a sustainable winery by-product within a circular economy framework.
Bioactive peptides (BPs) are increasingly recognized for modulating the gut microbiome, metabolome, and brain function via the gut–brain axis. Kapi-pla, a traditional Thai fermented freshwater fish paste rich in proteins and peptides, is widely consumed in Southern Thailand. This study profiled the peptides of Phatthalung Kapi-pla (PK) and Songkhla Kapi-pla (SK) and investigated their impacts on gut microbiota and metabolome using a simulated colonic fermentation model with fecal samples from patients with Alzheimer’s disease (AD). Microbial composition and metabolites were assessed by 16S rRNA sequencing and LC–MS/MS, respectively. After 24 h fermentation, PK modestly increased Shannon diversity relative to the unsupplemented control, with richness indices unchanged, reduced Proteobacteria abundance and opportunistic pathogens such as Escherichia–Shigella and Klebsiella, and selectively increased short- and branched-chain fatty acids, including acetate, propionate, butyrate, and iso-valerate. PK further enhanced neuroactive metabolites relevant to AD pathology, underscoring its potential as a functional food ingredient to ameliorate AD-associated dysbiosis and support gut–brain axis health.
The integration of coupled dark fermentation (DF) and photofermentation (PF) systems represents a promising approach for concurrent H2 production and organic load reduction in carbohydrate–rich wastewater. However, their behavior under non–optimized, continuous industrial operation remains inadequately characterized, hindering practical implementation. This case study evaluated an integrated DF–PF system treating a synthetic sugar mixture mimicking acidic fruit and dairy processing wastewater. The system presented herein (5-L reactors) serves as an initial prototype to facilitate scaling to both pilot (40-L reactors) and, ultimately, industrial (600-L) scales using real effluents within the framework of a research project. The bioreactors were operated continuously with a 10 h hydraulic retention time and an organic loading rate of 2.5 g COD L−1 d−1. The pH and temperature were monitored but intentionally left uncontrolled. The DF stage facilitated by hydrogen–producing bacteria achieved H2 concentrations of up to 57% (v/v) and a maximum production rate of 177 mL H2 L−1 d−1; however, it demonstrated notable process instability due to the absence of controls. In contrast, the PF stage exhibited negligible H2 production (1.8% v/v) attributable to the displacement of Rhodopseudomonas species by microbial competition, thereby functioning predominantly as a polishing step. Overall, the coupled system achieved an average COD removal of 34%, highlighting the functional differentiation between stages and identifying microbial competition as the primary constraint under suboptimal conditions.
This study evaluated molasses-based liquid feeds containing conventional urea or a commercial fat-coated urea product marketed as slow-release urea (SRU). The effects on in vitro gas-production kinetics, rumen fermentation, and substrate degradability were examined. Treatments followed a 5 × 3 factorial design. The five formulations were 0% urea, 5% urea, 10% urea, 5% SRU, and 10% SRU. Each formulation was supplied at 0.9%, 1.8%, or 2.7% of the 0.5 g basal substrate dry matter (DM). Four independent incubation runs were conducted. A formulation × inclusion-level interaction was detected for gas-production lag time (p = 0.0046). The shortest lag time occurred with 10% SRU supplied at 2.7%. At 48 h, the 0.9% inclusion level resulted in greater dry matter and organic matter degradability than the 1.8% and 2.7% levels. The 5% SRU formulation had the lowest 24 h degradability, whereas 10% SRU had the greatest 48 h dry matter degradability. Ammonia nitrogen (NH3-N) was analyzed separately at each sampling time. The 10% conventional urea formulation had the greatest NH3-N concentration at 1 and 2 h. The 10% SRU formulation had the greatest concentration at 4, 6, and 12 h. These within-time differences do not demonstrate different ammonia-release patterns over time. At 12 h, the 10% SRU formulation had the greatest total volatile fatty acid concentration and propionate molar proportion. Protozoal counts were unaffected. The results reflect differences among the complete liquid-feed formulations. They do not provide direct evidence of controlled ammonia release or improved nitrogen–carbohydrate synchronization. Further in vivo studies using compositionally balanced formulations are required.
A 2 × 2 × 2 factorial experiment was conducted to study the individual and combined effects of barley variety (Tarım 92 and Bravo), homofermentative inoculant (HMF; Lactobacillus plantarum and Enterococcus faecium), and heterofermentative inoculant (HTF; Lactobacillus buchneri) on the fermentation characteristics, chemical composition, nutritive value indices, and in vitro digestibility of whole-crop barley silages which were harvested at the early dough stage. Forty-eight laboratory silos (six replicates per treatment) were ensiled for 120 days. Tarım 92 silage exhibited superior fermentation stability across all treatments, with pH ranging from 4.11 to 4.30, Flieg points of 102.94–115.47, and lower NH3-N concentrations (142.01–173.72 mg/kg TN (total nitrogen)), reflecting better protein preservation than Bravo silage. In contrast, the poorest fermentation outcome (pH 5.24; Flieg 47.06; NH3-N 307.48 mg/kg TN) was exhibited by the Bravo silage inoculated with only homofermentative inoculants. Significant three-way interaction effects were detected among barley variety, homofermentative inoculant, and heterofermentative inoculant (p < 0.05). The dual-inoculated Tarım 92 silage showed the optimum in vitro digestibility and nutritional value (TDN 77.14%; NEL 1.81 Mcal kg−1 DM; RFV 176.25; ADF 18.75%; IVOMD 65.72%; predicted DMI 3.06% BW), while higher amounts of butyric acid and NH3-N suggested that better nutritional value was not always accompanied by better protein preservation. The combined inoculation also yielded the best outcomes within Bravo treatments (RFV 144.00), whereas HTF inoculation alone reduced IVDMD and IVOMD below uninoculated controls. Overall, these results show that the response to microbial inoculation is genotype-dependent and a combination of homofermentative and heterofermentative inoculation for high-dry-matter barley varieties can enhance nutritive value and digestibility. However, fermentation quality indicators, particularly butyric acid and NH3-N, require consideration in the selection of technique.
The aim of this study was to investigate the effects of thermo-maceration and apple pomace addition on phenolic compound extraction during cider fermentation and on the volatile profile of the final product. Jonagold apples were milled, and the juice was divided into four groups: (1) Control: no apple pomace or thermo-maceration; (2) Control TM: thermo-maceration only; (3) CiderAP: apple pomace addition only; and (4) CiderAPTM: apple pomace addition combined with thermo-maceration. Apple pomace was added at 50% of the average pomace weight created during milling, and thermo-maceration consisted of heating the juice to 60 °C for 1 h prior to fermentation. Ciders were fermented at 20 ± 1 °C for 14 days. CiderAP and CiderAPTM showed higher total phenolic content (TPC) and antioxidant activity than the control treatments. The volatile profile was also modified, with CiderAPTM showing the highest phenylethyl alcohol concentration and esters exhibiting compound-specific responses. Statistical analysis showed that only apple pomace addition significantly increased TPC and antioxidant activity, while both apple pomace addition and thermo-maceration affected the volatile profile. Under the conditions evaluated, thermo-maceration did not increase TPC or antioxidant activity beyond the effect of apple pomace addition but did modify the volatile profile of the ciders. Further research should evaluate different thermo-maceration temperatures and durations to determine its potential application in cider production. The findings of this study provide valuable insights for cider makers on the valorization of apple pomace and potential use of thermo-maceration in cider production.
The management of organic waste in high-altitude mining poses a distinctive circularity challenge: waste is generated at sites decoupled from agricultural systems, while the same operations are legally required to revegetate the land they disturb. This study provides, to the best of our knowledge, the first primary-data environmental characterization of a real system that valorizes dining-facility organic waste from a high-altitude mining unit in northern Peru into a solid biofertilizer and a liquid biol, both applied in situ for land reclamation. Unlike methanogenic digesters, the system operates under a lactic (acidogenic) fermentation regime inoculated with effective microorganisms and does not recover biogas. A cradle-to-gate life cycle assessment (ISO 14040/14044) with Monte Carlo uncertainty propagation was combined with a well-established family of five circular economy indicators, adapted to the non-energy-recovery case by redefining the Energy Self-Sufficiency Ratio (ESSR) and the Decarbonization Circularity Indicator (DCI). The principal contribution is methodological: the framework is extended to a circularity archetype that previous, biogas-centered formulations could not represent, showing that a system can close its material and nutrient loops robustly (WVI = 0.97) while the energy loop is absent by design (ESSR = 0). The climate result is conditional and is a first-order greenhouse-gas (GHG) screening balance, not a physical carbon-sequestration claim: under the upper-bound assumption of full fertilizer substitution, the avoided fertilizer credit outweighs non-methane process emissions only below a narrow fugitive-methane threshold (≈0.32 kg CH4 per ton), a margin that narrows further once agronomic equivalence is discounted. The measured product acidity suggests that this condition is plausible, but, because methane was not measured directly, the low-emission interpretation is presented as a hypothesis requiring confirmation rather than as a demonstrated result. The environmental burden is driven by material and electricity inputs—chiefly the polypropylene containers and grid electricity—rather than by the biological process, which broadens the set of improvement priorities beyond methane management to include capital-good reuse and electricity decarbonization, without implying that methane can be neglected.
Spent green tea residues are an abundant lignocellulosic by-product that poses environmental disposal concerns, while its use in ruminant nutrition is constrained by low ruminal degradability associated with high fiber and phenolic contents. This study investigated the effects of gamma irradiation and solid-state fermentation using Saccharomyces cerevisiae, and their combination, on chemical composition and ruminal fermentation. Gamma irradiation reduced neutral detergent fiber (379 to 336 mg g−1 dry matter), acid detergent fiber (277 to 244 mg g−1 dry matter), and total phenolics (89 to 75 mg gallic acid equivalents g−1 dry matter) while increasing non-fiber carbohydrates (234 to 269 mg g−1 dry matter) and ash (32 to 44 mg g−1 dry matter). These modifications enhanced the gas production rate (3.26 to 3.37% h−1), neutral detergent fiber degradability (38.9 to 46.1%), and the acetate-to-propionate ratio (2.25 to 2.43) while reducing ammonia nitrogen (108 to 96 mg L−1), crude protein degradability (55.1 to 48.8%), and increasing rumen exoglycanase activity by 11% and xylanase activity by 15%. However, the methane proportion in total gas increased from 12.4 to 13.3% and methane yield per unit of degraded dry matter increased from 36.5 to 39.2 mL g−1 degraded dry matter. Solid-state fermentation using Saccharomyces cerevisiae alone did not change the chemical composition or ruminal fermentation of non-irradiated biomass. However, when applied to irradiated biomass, it increased the crude protein from 320 to 383 mg g−1 dry matter and ether extract from 31 to 49 mg g−1 dry matter, improved dry matter degradability (53.3 to 63.1%), organic matter degradability (55.3 to 64.3%), crude protein degradability (48.8 to 54.6%), total volatile fatty acids (49 to 57 mmol L−1), and net energy for lactation (2.43 to 3.02 MJ kg−1 dry matter), and maintained ammonia nitrogen at levels similar to the irradiated biomass. Although the combined treatment increased the methane yield per unit of incubated dry matter (19.2 to 23.4 mL g−1 dry matter), the methane yield per unit of degraded dry matter was lower than that of the irradiated biomass alone (37.0 vs. 39.2 mL g−1 dry matter degraded) and comparable to the untreated control (36.5 mL g−1 dry matter degraded). Overall, the integration of gamma irradiation as a pretreatment followed by solid-state fermentation with Saccharomyces cerevisiae enhances the nutritional value of spent green tea residues, supporting its valorization as a sustainable alternative ruminant feed resource.
In this study, Stevia fractions (root, leaf, stem and their mixture) were used for inulin extraction using aqueous extraction, enzyme-assisted extraction and enzyme-assisted decanter extraction. The extracts were used as carbon sources in submerged (SmF) fermentation, whereas the remaining solid residues were used as substrates in solid-state (SSF) fermentation for inulinase and FOS production by Aspergillus niger. The highest inulin concentration was obtained from the root extract produced by aqueous extraction at a 1:5 (w/v) ratio (197.55 g/L). The highest fructooligosaccharides (FOS) concentration (12.64 g/L) was achieved by root enzyme-assisted extraction. In SmF, the highest total FOS concentration (13.99 g/L) was obtained from leaf enzyme-assisted extracts (LEE), whereas in SSF, the maximum total FOS concentration (20.80 g/L) was achieved using leaf enzyme-assisted decanter extracts. Inulinase from the aqueous root extracts was 609.72 U/mL during SmF and the leaf enzyme-assisted decanter extracts was 450.86 U/mL during SSF. Inulin extraction from fractions of Stevia, high inulinase production in Smf, and enhanced FOS production from residual biomass in SSF enable the generation of multiple value-added products and support circular economy and biorefinery principles.
