Search Results (567)

Livestock manure management remains a significant environmental challenge due to nutrient losses that may contribute to soil and water contamination. This study investigated nitrogen and phosphorus transformations, as well as organic matter stabilisation, in poultry manure subjected to microbial inoculation under controlled laboratory conditions (EI) and long-term field storage (EII). In the laboratory experiment, chicken and turkey manure were treated with denitrifying bacteria, conditioning bacteria, or their combination. The results indicate treatment-dependent differences in ammonium accumulation and nitrate formation in leachates, with the combined microbial inoculum suggesting reduced nutrient mobility compared with the untreated controls. In the field experiment, temporal changes in nitrogen fractions revealed an initial phase of intensive mineralisation, followed by gradual stabilisation of nitrogen forms. Phosphorus concentrations (total phosphorus—P_tot and orthophosphate—PO₄³⁻) decreased over time, suggesting reduced potential for leaching, although the underlying mechanisms likely include immobilisation and redistribution within the manure matrix. Differences in nutrient dynamics between chicken and turkey manure were observed. A humification stabilisation index (HSI) was applied to describe changes in organic matter quality during manure storage, indicating progressive transformation towards more stable forms. However, due to the limited replication and the lack of continuous monitoring of key process parameters, the results should be interpreted as indicative rather than conclusive. Overall, the study suggests that microbial inoculation may influence nutrient transformations and support manure stabilisation processes, highlighting its potential as a complementary strategy in environmentally oriented manure management strategies. Full article

A livestock farm in southern Taiwan produces wastewater with high concentrations of nitrogen and organics, which inhibit anaerobic methanogens and limit the efficiency of its biogas system. To enhance energy recovery, this study developed a liter-scale microbial fuel cell (MFC) system aimed at harvesting electricity from livestock wastewater, serving as a supplementary energy recovery pathway alongside the biogas process. According to the five analyses, the chemical oxygen demand (COD) of raw wastewater ranged from 14 to 21 g L⁻¹, with acetate concentrations ranging between 40 and 112 mM. Propionate and butyrate were consistently below 32 mM and 18 mM, respectively. Ammonium ranged from 1.1 to 1.7 g-N L⁻¹, indicating the wastewater’s high organic load and elevated nitrogen content. Two liter-scale MFCs, ch5 and ch7, were operated for over 70 d. From days 7 to 28, both MFCs employed a fill-and-draw mode, achieving optimal COD removal exceeding 80%. After resolving leakage issues between days 30 and 40, the system was restarted on day 40, yielding 76% (ch5) and 82% (ch7) of COD removal. Continuous operation began on day 59, and both reactors maintained COD removal rates above 80% for most of the subsequent two-week period. The best power outputs for ch5 and ch7 reached 1.11 and 0.82 W m⁻³, respectively. Although both liter-scale reactors achieved COD removal and measurable power output, the most important finding was obtained from the inoculum comparison experiments. After 54 days of acclimating to raw wastewater solids, no significant current was observed. In contrast, digestate solids acclimated with carbon powder for 22 d produced a peak current of 42.5 A m⁻³ at 147 h, with COD removal rates of 67–73% and complete removal of organic acids. The key conclusion of this study is that anaerobic digestate exhibits electroactive microbial potential, whether operated in liter-scale reactors or acclimated with carbon powder. Further investigation into the microbial community structure is warranted to optimize system performance. Full article

Hydrogenotrophic denitrification (H₂Den) is a promising strategy for NO₃⁻ removal from a supply water with low or negligible organic carbon content. However, its performance may be affected by emerging contaminants (ECs), which pose increasing risks to the environment and human health. This study investigates the acute effect of two widely detected ECs, acetaminophen (ACN) and chloramphenicol (CHP), at a 200 mg/L concentration, on H₂Den using anaerobic granular sludge (AnGS) as inoculum. Acute exposure to ACN enhanced NO₃⁻ removal, likely due to the formation of oxidizable metabolites serving as electron donors through the heterotrophic pathway. On day 3, the residual NO₃⁻ concentration had already dropped below the regulatory limit of 50 mg/L, reaching 4.3 mg NO₃⁻/L. In contrast, CHP initially inhibited the denitrification process, resulting in limited NO₃⁻ removal, i.e., a residual concentration of 145.4 mg NO₃⁻/L on day 3. Nevertheless, short-term microbial adaptation likely enabled performance recovery under CHP exposure. On day 6, both EC exposure tests allowed a NO₃⁻ removal above 97%, although CHP resulted in residual NO₂⁻, i.e., 37 mg NO₂⁻/L. In the presence of ACN, the accumulation of gaseous denitrification intermediates was observed, with NO concentration in the headspace peaking at 9.5% (i.e., 16.2 × 10⁻² µg NO/min/g VS) on day 6. Thus, in terms of either the production of gaseous intermediates or the presence of residual nitrogen in the liquid phase, ACN and CHP significantly influenced the denitrification performance, highlighting the importance of considering their presence in the operation of the denitrification process. Full article

Microbial inoculation is widely used to improve composting performance, yet its effectiveness hinges on inoculum composition, substrate characteristics, and composting technology, which remain poorly understood. This study compared single versus mixed inoculants across different substrates and assessed their interactions with biochar amendment and nanomembrane covering, focusing on organic matter transformation, inorganic nutrient dynamics, and biological pollution control. Mixed inoculation significantly improved heating performance in cattle manure compost compared to single strains (p < 0.05) and sustained thermophilic conditions in sludge-sawdust compost, but showed limited impact in chicken manure-sludge compost. It reduced humic acid (HA) accumulation in chicken manure-sludge compost (14.29% to −39.28%) while increasing HA content in sludge-sawdust compost (3.55–5.41 g/kg, p < 0.05). Inorganic nitrogen retention was enhanced; specifically NO₃⁻-N concentrations rose by 175.1–222.6% in the chicken manure-sludge and by 6.7–17.9% in the sludge-sawdust compost. Microbial community analysis indicated enrichment of inoculant strains during the thermophilic phase, supporting nitrogen conservation and humification. However, inoculation increased potential pathogenic bacteria by over 51.2% across all composts and enriched predicted antibiotic resistance genes (ARGs) by 9.9–22.96% in chicken manure-sludge compost, while reducing the membrane covering’s inhibitory effect on predicted ARGs (rebound by 29.5%). Moreover, we found that the predicted ARG profiles, derived from 16S-based PICRUSt2 functional inference, covaried strongly with microbial community structure, with environmental factors such as organic carbon shaping predicted ARG dynamics mainly through indirect effects on microbial communities. These findings highlight that while mixed inoculation boosts composting efficiency, it also raises biosafety concerns. Thus, a comprehensive evaluation integrating organic, inorganic, and biological perspectives is essential before promoting thermophilic inoculants. Full article

Soil salinization is a significant environmental factor limiting agricultural production. Developing salt–alkali-tolerant microbial resources is important for the improvement of saline–alkali land. Plant growth-promoting rhizobacteria stimulate crop growth by producing the plant growth hormone indole-3-acetic acid (IAA), but their fermentation process under salt stress still needs optimization. Single-factor experiments and response surface methodology (RSM) were used to systematically optimize the fermentation conditions of the salt–alkali-tolerant Vreelandella titanicae J113. Key influencing factors were screened using the single-factor experiment design, and optimal process parameters were determined using the Box–Behnken design. IAA production and cell biomass were used as evaluation indicators to study the interactions of carbon sources, nitrogen sources, inorganic salts, temperature, cultivation time, and inoculum size. The optimal fermentation process was obtained: starch concentration 17.5 g/L, NaCl concentration 32.5 g/L, yeast extract 5 g/L, cultivation temperature 30 °C, inoculum size 3%, and cultivation time 144 h. After optimization, IAA production reached 23.02 μg/mL, an increase of 115% compared with before optimization. Salt stress experiments showed that the strain could still maintain high IAA production under 3% NaCl, demonstrating good salt tolerance. Maize seed germination experiments demonstrated that the optimized fermentation broth significantly promoted seed germination and seedling growth under salt stress conditions, with root length, fibrous root number, and fresh weight increasing by 61–86%, 137–200%, and 25–57%, respectively, compared to the control group. This study established an efficient IAA fermentation process for the salt–alkali-tolerant Vreelandella titanicae J113, providing technical support for developing microbial plant growth regulators suitable for saline–alkali land. The optimized strain exhibits excellent growth-promoting potential under salt stress conditions, offering favorable application prospects. Full article

Soybean molasses, a by-product of alcohol-based soy protein concentrate production, is rich in stachyose and other functional oligosaccharides, but its high sucrose content and other fermentable non-target sugars hinder the efficient purification of stachyose. In this study, the sugar-utilization patterns of four commonly used microbial chassis or production strains, Escherichia coli W, E. coli BL21, Saccharomyces pastorianus Weihenstephan 34/70, and Komagataella phaffii (formerly Pichia pastoris) GS115, were systematically compared to identify a suitable host for selective stachyose enrichment. Among them, E. coli W showed the best performance in rapidly consuming non-target sugars while retaining stachyose. Based on this strain, a CRISPR–Cas9 engineering strategy was applied by deleting the endogenous α-galactosidase gene melA and overexpressing the sucrose permease gene cscB. The resulting strain selectively and nearly completely removed sucrose and other non-target sugars from soybean molasses, increasing the proportion of stachyose from <30% to >90% of total soluble solids. Further optimization of nitrogen source level, inoculum size, and initial °Brix improved fermentation performance. These results demonstrate an effective biological pre-purification strategy for selective stachyose enrichment from soybean molasses. Full article

Corn dust is an abundant agro-industrial by-product with potential as an alternative energy source. Its use in animal feeding, however, is restricted by high fiber content and low digestibility. This study evaluated the effects of non-starch polysaccharide (NSP) enzymes and yeast (Candida tropicalis KKU20) on the chemical composition, fermentation characteristics, and microbial populations of fermented corn dust. The experiment was conducted using a completely randomized design with a 3 × 2 factorial arrangement plus an additional control treatment. Factor A consisted of three levels of enzyme supplementation (0.02%, 0.04%, and 0.06% of dry matter), and Factor B consisted of yeast supplementation (without yeast or with C. tropicalis KKU20, approximately 1 × 10¹³ cells/g of inoculum). The control treatment consisted of fermented corn dust without enzyme or yeast supplementation. Samples were fermented for 15 days prior to analysis. Yeast inoculation increased crude protein and non-fiber carbohydrate contents while reducing neutral detergent fiber, acid detergent fiber, and acid detergent lignin (p < 0.05). Significant enzyme × yeast interactions were observed for several components, particularly fiber fractions (p < 0.05). The reduction in fiber was more pronounced when enzymes were combined with yeast. Predicted energy values, including metabolizable and digestible energy, were increased following yeast supplementation (p < 0.05). Fermentation characteristics were mainly affected by yeast. Yeast-treated samples exhibited higher pH and ammonia–nitrogen concentrations, indicating increased nitrogen turnover during fermentation. In contrast, lactic and propionic acid concentrations were higher in treatments without yeast, while yeast inoculation was associated with lower acetic acid and slightly higher butyric acid levels. Microbial analysis indicated interactions between treatments for lactic acid bacteria populations, reflecting competition for available substrates. No coliform bacteria were detected, indicating acceptable hygienic quality. Overall, yeast inoculation modified the chemical composition of corn dust, particularly by increasing crude protein and reducing fiber fractions, while NSP enzymes contributed to fiber degradation, especially when combined with yeast. However, these changes reflect compositional modification rather than confirmed feeding value, and further evaluation under rumen or in vivo conditions is required. Full article

γ-Aminobutyric acid (GABA), a major inhibitory neurotransmitter, is known for its physiological functions in alleviating anxiety and improving sleep. Currently, high-yielding GABA food products are mainly obtained through screening wild-type high-producing strains (e.g., Saccharomyces cerevisiae isolated from Sichuan pickles yielding 0.67 g/L) or employing co-culture systems (e.g., Enterococcus faecium and Lactiplantibacillus plantarum reaching 6.35 g/L). While effective, these methods often rely on natural screening strains or multi-microbial interactions. This study employed CRISPR-Cas9 technology to knockout the UGA1 gene in Saccharomyces cerevisiae, a key gene responsible for GABA degradation. Starting from the low higher alcohol Saccharomyces cerevisiae SY-LH, we successfully constructed the recombinant strain SY-LHU. Remarkably, this study discovered a significant upregulation of GAD1 gene expression following UGA1 knockout, which further enhanced GABA synthesis capacity. Under optimal fermentation conditions (inoculum size 4 × 10⁷ cells/mL, wort concentration 10 °P, sugar addition 60 g/L, 30 °C for 10 days, and mixing the malt broth every 48 h), the validation fermentation was performed and the GABA content in the wort beverage reached 280.36 mg/L, representing a 385.4% increase compared to the pre-optimization level. Furthermore, sensory evaluation by a trained panel yielded a mean score of 88, with no significant off-flavors detected, demonstrating the product’s high consumer acceptance. This pioneering work provides a novel and feasible technical pathway for developing functional alcoholic beverages with sleep-aiding properties. Full article

Phytophthora cinnamomi Rands, an oomycete pathogen of global relevance, is a major driver of cork oak (Quercus suber L.) decline and mortality in Mediterranean forests. Its management remains challenging in multifunctional landscapes where forestry and agriculture intersect, such as Mediterranean oak dehesas. Conventional fungicides are used against P. cinnamomi, but their negative environmental impacts underscore the need for alternative management in agroforestry systems. This study evaluated whether a commercially available microbial biostimulant, VESTA, enhances physiological performance and mitigates pathogen pressure in Q. suber. Seedlings were inoculated with P. cinnamomi and treated with the bioinoculant via fertigation or watering to substrate saturation, under controlled greenhouse conditions. Plant physiological parameters and soil oomycete inoculum concentrations were measured to assess treatment efficacy. Both application methods significantly improved physiological performance in inoculated and mock-inoculated plants. Photosynthesis, stomatal regulation, and water balance were most affected. Quantitative PCR analyses revealed a strong pathogen reduction, with DNA concentrations approximately tenfold lower in treated substrates (~0.001 ng mL⁻¹) than untreated controls (~0.011 ng mL⁻¹). Overall, the product enhanced Q. suber resilience by improving plant physiological responses and reducing pathogen abundance, supporting its potential as a bio-based tool for nurseries and restoration in Mediterranean ecosystems. Field studies are needed to validate these findings under natural variability and optimize long-term application strategies. Full article

Solid-state fermentation (SSF) is a long-established biotechnological approach gaining renewed interest for its ability to enhance nutrient availability and improve the functional properties of agro-industrial by-products. This strategy is particularly relevant for early post-weaning piglets, which are highly susceptible to weaning stress due to an immature digestive system and a gut microbiota not yet adapted to solid feed. In this study, the fermentation parameters of flaxseed cake were optimized using a Plackett–Burman experimental design. Protease activity was selected as the response variable due to its relevance for improving protein degradation and potential digestibility in fermented feed ingredients. Accordingly, based on the statistical analysis, the conditions selected for the in vivo trial were 1% molasses, 0.5% yeast extract, 0.05% CaCl₂, 0.5% NaCl, 7.5% inoculum (4.12 × 10⁹ CFU/mL), 60% moisture, and 72 h fermentation. Fermentation time was identified as the main factor positively influencing protease production, while higher CaCl₂ concentrations and inoculum levels negatively affected enzyme activity. Optimization increased protease activity, microbial viability and free amino acid content. In addition, SSF reorganizes the carbohydrate profile by reducing structural fiber fractions, with neutral detergent fiber and acid detergent fiber decreasing by 27% and 29%, respectively, while simultaneously increasing soluble carbohydrates by 14.67%. Phytic acid content being also reduced by 23.81%. A pilot nutritional trial on post-weaned piglets (35 days old) showed that including 8% fermented flaxseed cakes (FFSC group) improved body weight, average daily gain, feed conversion ratio, and diarrhea score, without affecting average daily feed intake, compared with 8% unfermented flaxseed cakes (FSC group). These performance improvements were accompanied by changes in fermentation metabolites and gut microbial composition. Lower isovalerate concentrations suggested reduced proteolysis, while higher propionate levels may contribute to increased blood glucose availability in the FFSC group. These changes coincided with a shift in microbial composition, characterized by a reduced abundance of methanogenic archaea and increased abundances of taxa such as Lactobacillus, Enterococcus, and members of the Lachnospiraceae and Eubacteriaceae families. Full article

Black Soldier Fly larvae (BSFL) bioconvert a wide variety of organic waste into value compounds including the residual frass, a by-product exploitable as compost for plant growth. The use of a non-standardized waste diet that varies in terms of properties does not ensure the maintenance of a highly fertile and healthy BSF colony able to produce viable inoculum (5–7-day-old larvae) for waste bioconversion. The Gainesville diet (GD) is a balanced formulation to ensure full larval development in fertile adults, resulting in a stable rearing colony. On a large scale, the bioconversion supply chain can produce different types of frass. Frass derived from the Gainesville diet (GDf), from fruit and vegetable waste (FVWf), and from milled fruit and vegetable waste (MWf) was composted and then compared to evaluate its fertilizing effect on lettuce growth in two pot-growing experiments. Each compost was added at concentrations of 2.5, 5, and 10%. The growth of lettuce improved significantly with the addition of composted frass in a dose-dependent manner when compared to unfertilized soil. GDf 10% gave the significantly best performance in terms of plant height (20.8 cm versus 17.9 cm) and fresh weight (113.5 g versus 87.7 g) compared to FVWf. In the experiment, the combined use of composted frass at 10% of both GDf and FVWf with a double mineral fertilizer application showed no significant differences compared to triple application. However, GDf provided significantly greater chlorophyll content than FVWf. These results highlight how, under the conditions tested in the present work, the frass of the entire productive chain of BSF is a high value by-product. Full article

Lactiplantibacillus plantarum EL2, isolated from traditional fermented yak milk in the high-altitude Gannan Tibetan Autonomous Prefecture, produces the class IIb bacteriocin PlnJK. This study established three distinct cultivation models that critically influenced bacteriocin yield. Microbial co-culture was found to enhance the stress tolerance of EL2, significantly boosting PlnJK production. The optimal inducing strain, Enterococcus faecalis MH2, increased the bacteriocin inhibition zone diameter from 15.38 mm to 25.58 mm. Following optimization of key parameters—initial inoculum concentration (10⁷ CFU/mL), inoculation ratio (3:1, EL2:MH2), and initial pH (6.0)—the inhibition zone diameter reached 30.32 mm, representing a 1.97-fold increase over pure culture. Co-culture not only advanced the onset but also extended the duration of bacteriocin synthesis. Throughout the 24 h incubation, cell density, AI-2 autoinducer concentration, and the expression of key regulatory genes were significantly elevated in co-culture compared to monoculture, aligning with a cell-density-dependent, quorum-sensing (QS) regulatory paradigm. Bacteriocin production was co-regulated by two QS pathways: the AI-2/luxS system and the plnA-mediated autoinducing peptide (AIP). Gene expression analysis revealed differential temporal regulation: luxS expression was higher during the exponential phase (2.29 vs. 1.42 in stationary phase), while plnA exhibited the opposite pattern (1.42 in exponential vs. 2.21 in stationary phase). This indicates that the AI-2/luxS pathway drives strong induction during active growth, whereas plnA/AIP-mediated promotion becomes predominant later. The stationary-phase effect is likely triggered by the accumulation of specific MH2 metabolites, which impose an environmental stress on EL2, stimulating the pln-encoded regulatory system and further enhancing bacteriocin yield. This work provides an economically viable strategy and a novel theoretical framework for optimizing microbial cultivation, enhancing bacteriocin production, and elucidating the complex QS-mediated regulatory mechanisms involved. Full article

Sodium hypochlorite (NaClO) is frequently utilized in food processing. More than 90% of Salmonella spp. isolates from poultry supply chains exhibited tolerance to NaClO, with MIC values exceeding 256 mg/L. Exposure to NaClO disinfection may lead to the emergence of bacterial tolerance to chlorine, which is frequently associated with antibiotic cross-resistance. This work employed a resazurin-based assay for rapid evaluation of the NaClO chlorine tolerance of Salmonella. The results were compared to the broth microdilution method for assessing bacterial tolerance. At the initial inoculum of 10⁷ CFU/mL, NaClO tolerance was successfully identified via colorimetry within 2 h. Notably, the fluorescence-based evaluation yielded significant results even sooner, showing a marked increase in intensity within 1 h of resazurin incubation. Even with an inoculum of 10⁵ CFU/mL, the resazurin-based method determines NaClO tolerance in just 6 h. Conversely, traditional broth microdilution requires an overnight culture to manifest sufficient turbidity for optical density monitoring. Furthermore, the broth microdilution method revealed NaClO tolerance (MIC > 256 mg/L) in 1.6% (1/64) of the Salmonella isolates. The modified resazurin assay, by contrast, detected tolerance in 6.3% (4/64) of isolates. The reference that differentiates between resistant and sensitive strains was 3.2 × 10⁵ RFU. When the strains exhibited an MIC value of 256 mg/L, the fluorescence intensity varied from around 1.2 × 10⁵ to 4 × 10⁵ RFU, reflecting inactivation effects at practical chlorine concentrations. This methodology is recognized as a rapid, high-throughput, and quantitative screening approach for assessing bacterial chlorine resistance. Full article

Brassicaceae plants are generally considered non-mycorrhizal; however, recent studies have challenged this non-host status, suggesting occasional colonization during reproductive stages or by overlooked fungi such as Mucoromycotina Fine Root Endophytes (MFRE). To re-evaluate the non-host status of Brassicaceae, we cultivated five Brassicaceae species, including rapid life cycle Brassica rapa (Fast plants) using field soil containing both Glomeromycotina Arbuscular Mycorrhizal Fungi (G-AMF) and MFRE. To ensure inoculum potential, a co-planting system with lettuce (Lactuca sativa) as a nurse plant was employed. While lettuce roots were rapidly colonized by both G-AMF and MFRE, no mycorrhizal colonization was observed in any Brassicaceae roots throughout their entire life cycle, from vegetative growth to flowering and seed maturation in Fast plants. Furthermore, co-planting with Brassicaceae did not significantly affect the mycorrhizal colonization or shoot phosphorus concentrations of the neighboring lettuce. These results demonstrate that Brassicaceae plants maintain a robust non-host status against both G-AMF and MFRE. Moreover, they function as “neutral non-hosts” that do not disrupt the symbiotic networks of neighboring plants. This characteristic reinforces the value of Brassicaceae in sustainable crop rotation systems. Full article

Brazzein is a sweet-tasting protein with high stability across a wide range of pH and temperature conditions. This study aimed to develop a simplified peptone-based medium (PSM) for the recombinant expression of brazzein in Pichia pastoris X-33 and to evaluate the effect of two inoculum concentrations (5%, 10%, and 15%) on cell growth and protein production in flask fermentations. Subsequently, fermentation was scaled up to a 2 L bioreactor using PSM and a 10% inoculum, achieving a yield of 0.196 g·L⁻¹ after 216 h of induction. These results demonstrate that the PSM medium promotes robust biomass growth and efficient brazzein expression, representing a cost-effective alternative to conventional complex media. Additionally, the effect of pH (5.0, 5.5, and 6.0) and temperature (20, 25, and 28 °C) on brazzein production was evaluated, revealing that fermentation at pH 5.0 and 28 °C resulted in the highest protein concentration (0.422 g·L⁻¹, unpurified). Finally, kinetic models based on the Monod and Luedeking–Piret equations were developed to describe the relationship between biomass formation, substrate consumption, and recombinant protein production. Full article