Search Results (290)

Biochar and zeolite are promising additives for improving composting; however, their effects during the co-composting of agricultural waste have not yet been sufficiently studied. This study evaluated their influence on the composting of green onion residues and chicken manure under psychrophilic conditions on a pilot scale using 200 kg piles. Three treatments were evaluated: a control, 5% biochar, and 2% zeolite. Both amendments increased the maximum composting temperature by approximately 3 °C and improved the germination index, with increases of around 10% for biochar and 26% for zeolite compared to the control. Biochar increased the relative abundance of the amoA gene, associated with ammonia oxidation and nitrification, suggesting greater biochemical potential for nitrification. During maturation, zeolite reduced pH and electrical conductivity, indicating greater compost stability. In fast-growing crops, compost from zeolite treatment did not significantly affect plant growth when applied alone, but improvements were observed when combined with synthetic fertilizer. Overall, both additives improved composting performance and compost quality, with zeolite showing the most consistent effects. Full article

This study assessed the performance of three microfiltration (MF) membrane modules: M1 (spiral, polyvinylidene fluoride), M2 (capillary, polypropylene), and M3 (capillary, α-Alumina) in treating backwash water from utility-scale surface water (SW) and infiltration water (IW) plants, each with a capacity of approximately 100,000 m³/day. Considering 168 h (one-week) filtration cycles, the membranes were evaluated for permeate flux, turbidity removal, dissolved organic carbon (DOC) removal, and reduction in total number of microorganisms (TNM). In contrast to most previous studies that have primarily examined surface water sources under laboratory conditions, this research contributes to the literature by evaluating membrane performance using actual backwash water from both SW and IW treatment plants. The comparative assessment of three structurally and materially distinct membrane modules under identical flow-through conditions yields new insights into the trade-offs among hydraulic performance, contaminant removal, and treatment cost. Logarithmic models fitted to permeate flux data yielded determination coefficients (R²) ranging from 0.60 to 0.99, supporting the prediction of early-stage performance. No consistent trend in flux decline was observed, mainly due to fluctuations in the water bacterial load. With a median TNM removal efficiency of 97%, M1 outperformed M2 and M3 (84% and 70%, respectively) in terms of microorganism removal. The effectiveness of DOC removal generally depended on the type of backwash water; the highest efficiency was observed for M2 in the case of backwash from IW treatment and for M1 in the case of backwash from SW treatment. M2 provided the highest permeate flux rates, regardless of water type or operational limitations. The ceramic membrane (M3) exhibited the greatest variability in hydraulic performance and removal efficiency, depending on the type of backwash water. A simplified cost analysis over two filtration cycles found that treatment costs were generally higher for SW backwash, with differences reaching up to 90% between membrane-water type combinations. Although treatment costs are higher than those for raw water treatment, the increasing water scarcity makes it a potential additional source of safe water. Full article

Antarctica’s extreme cryospheric conditions impose severe thermodynamic constraints on the natural attenuation of hydrocarbon pollutants. Despite the Antarctic Treaty System’s protections, the footprint of human logistics has left persistent reservoirs of petroleum hydrocarbons that threaten endemic biodiversity. This review critically synthesizes the state-of-the-art in Antarctic bioremediation, moving beyond traditional culture-dependent studies to integrate recent multi-omics breakthroughs (2020–2025). We analyze the molecular mechanisms limiting bioavailability in frozen soils and highlight the adaptive strategies of psychrophilic consortia, including the modification of membrane fluidity and the expression of cold-active enzymes (e.g., RHDs, AlkB). Notably, we discuss emerging findings on novel long-chain alkane degradation genes (almA, ladA) identified in 2025, which challenge previous assumptions about recalcitrance. Furthermore, the review evaluates the engineering bottlenecks of in situ versus ex situ strategies, emphasizing the synergistic potential of bacterial–fungal co-cultures and the ecological necessity of “climate-smart” remediation to mitigate methane emissions from thawing permafrost. By bridging the gap between fundamental microbial genetics and applied field engineering, we propose a roadmap for the next generation of biotechnological solutions in the warming polar environment. Full article

Psychrophilic organisms are able to grow at temperatures down to −15 °C, while hyperthermophiles can multiply at temperatures up to 122 °C. What structural changes in extremophile proteins are needed to maintain stable and biochemically active structures under such conditions? Understanding how such extremophiles accomplish this is relevant for human health, biotechnology, and our search for life elsewhere in the universe. The purpose of the current study is to report and compare the structures of four rubredoxins (Rds), the first ever two experimental psychrophile bacteria structures (from Gram-positive Clostridium psychrophilum and Gram-negative Polaromonas glacialis) and two hyperthermophiles from the Gram-negative Thermotoga maritima bacterium and the archaeon Pyrococcus yayanosii, also a piezophile, as part of a program to understand structural variations that support both stability and function under extreme conditions. These structures were obtained using synchrotron radiation X-ray diffraction at 100 K. All four structures had the expected overall rubredoxin fold. Rubredoxin from the only aerobic psychrophilic bacterium Polaromonas glacialis had larger variations in sequence and structure, whereas the other psychrophilic bacterium showed properties closely related to hyperthermophile rubredoxins. Multi-subunit structures showed similar RMSD variability independent from their thermal adaptation status. We propose including functional information in the analysis since temperature optimization may not be the only determinant for a specific protein adaptation. Full article

Decentralized biomethane is vital for the energy transition; however, small-scale plants face significant energy penalties. This study evaluates the mass and energy balance of a TRL 6 pilot biorefinery treating pig manure, integrating anaerobic digestion with a microalgae-based photobioreactor coupled to an absorption column for biogas upgrading (>93 vol% CH₄, dry basis). A Life Cycle Inventory (LCI) was used to compared a theoretical mesophilic design (Scenario I, 35 °C) against an experimental psychrophilic baseline (Scenario II, avg. 12 °C). The results indicate that while winter mesophilic heating consumes 58% of gross energy production, the passive psychrophilic strategy eliminates this demand, ensuring a positive Net Energy Balance year-round. Both scenarios achieved competitive Specific Energy Consumption (SEC) (1.20 vs. 4.17 kWh·m⁻³ CH₄), while upgrading reached peak efficiency at a 10 min Hydraulic Residence Time. Furthermore, solar-synchronized load-shifting allowed for 100% electrical self-sufficiency. We conclude that although passive operation offers a superior Energy Return on Investment during cold periods (average EROI of 2.35 vs. 1.44 under winter mesophilic conditions), active mesophilic heating yields a 3-fold revenue increase, making it the superior economic choice despite the thermal penalty. Full article

The emergence of drug-resistant Candida species has intensified efforts to discover novel bioactive compounds. Antarctic environments harbor psychrophilic microorganisms that produce unique secondary metabolites adapted to extreme conditions, making them valuable natural resources for drug discovery. During the 2020 Antarctic Scientific Expedition, we collected 19 sediment samples from the South Shetland Islands and isolated 14 fungal strains belonging to Cladosporium, Oidiodendron, Penicillium, Pseudeurotium, and Pseudogymnoascus genera. Total organic extracts obtained from 21-day cultures were evaluated for antimicrobial activity against pathogenic yeasts and bacteria. Oidiodendron sp. (ECA57-20) and Pseudogymnoascus sp. (ECA57-61) demonstrated strong anti-Candida activity with minimum inhibitory concentrations ranging from 7.81 to 62.5 µg/mL against C. albicans, Pichia kudriavzevii (C. krusei), C. tropicalis, Nakaseomyces glabratus (C. glabrata), and Clavispora lusitaniae (C. lusitaniae). GC-MS (gas chromatography mass spectrometry) metabolomic profiling suggests a broad diversity of secondary metabolites across active strains, which may contribute to the observed biological activities. These findings support the potential of Antarctic fungi as sources of alternative antifungal agents. Full article

The influence of passive and active modified-atmosphere packaging (MAP), antioxidants (citric acid and ascorbic acid) and their combinations with a mild thermal process on the shelf life of cut eggplants was evaluated. Eggplant slices were subjected to different treatments (a—MAP: packaged in air with 35 μm polypropylene; b—MAP1: packaged with 3% O₂ + 15% CO₂; c—MAP2: packaged with 5% O₂ + 15% CO₂; d—citric acid 1% + MAP; e—ascorbic acid (A2) 1% + MAP; f—A2 + MAP1; g—TT (50 °C for 1 min) + A2 + MAP; h—TT + A2 + MAP1; and i—control: no treatment) and stored for 12 days at 5 °C. The evolution of sensory characteristics such as color and the browning index, ascorbic acid (AA), total phenols (TP), antioxidant capacity (AC), microorganism count (mesophilic and psychrophilic aerobes, enterobacteria, molds and yeasts) and polyphenol oxidase PPO activity were periodically evaluated. Treatment h was the most effective in prolonging shelf life, maintaining eggplant’s optimal sensory characteristics for up to 10 days, with greater retention of AA and AC and without significantly varying the initial level of TP. Full article

Milk jam (dulce de leche) is a dairy product obtained by boiling milk with sugar, characterized by high sugar concentration and low water activity. Consumption of this product, which has unique color, taste, and consistency, has been increasing in Türkiye in recent years. However, scientific studies examining the microbiological and chemical quality of milk jam are quite limited. This study aimed to determine quality parameters of milk jams on the Turkish market, evaluate results against relevant standards and provide comprehensive information about current product quality. Twenty packaged milk jam samples from different brands were analyzed. Chemical analyses included pH value, acidity in terms of lactic acid, dry matter content, fat content, reducing sugar, total sugar, and sucrose. Microbiological analyses included counts of Total Mesophilic Aerobic Bacteria (TMAB), psychrophilic bacteria, yeast-mold, lactic acid bacteria, Enterobacteriaceae, coliform bacteria, and proteolytic bacteria. Relationships between obtained data were evaluated by Pearson correlation analysis. Chemical results showed pH 7.54 ± 0.63 (6.70–8.99), acidity 0.49 ± 0.19%, dry matter 62.42 ± 8.85%, and fat 1.51 ± 1.50%. Sugar analyses revealed reducing sugar 17.25 ± 6.16 g/100 mL, total sugar 37.88 ± 8.67 g/100 mL, and sucrose 19.59 ± 8.74 g/100 mL. Microbiological analyses detected TMAB in 50% of samples (4.51 ± 1.91 log CFU/g), yeast-mold in 45% (3.92 ± 1.26 log CFU/g), Enterobacteriaceae in 30% (3.15 ± 1.26 log CFU/g), coliforms in 25% (3.63 ± 1.06 log CFU/g), and proteolytic bacteria in 55% (4.21 ± 1.57 log CFU/g). Positive correlation was found between pH and sucrose (r = 0.466, p ≤ 0.05), and strong negative correlation between dry matter and proteolytic bacteria (r = −0.732, p ≤ 0.05). Significant standardization deficiencies and microbiological quality problems were identified in milk jam samples. High pH values and the presence of hygiene indicator microorganisms indicate the need for HACCP system implementation and increased hygiene controls in production. Full article

Temperature fluctuations strongly affect microbial viability, often inducing adaptive responses. In this study, we employed the psychrophilic bacterium Bacillus mycoides 41-22 and its associated phage VMY22, originally isolated from the Mingyong Glacier, to investigate phage adaptability under varied temperature conditions. Through selective enrichment at 4 °C, 15 °C, 28 °C, and 32 °C, we observed clear differences in phage infectivity, as assessed by plaque assays, along with genomic mutations and protein structural changes. Notably, mutations predominantly occurred in functional genes (ATPase, endolysin), while the examined structural loci remained conserved. Homology modeling revealed distinct adaptations in protein tertiary structures corresponding to environmental temperatures, suggesting that phage evolution mainly affects post-adsorption processes. Our findings elucidate a novel mechanism of temperature-driven functional protein evolution among cold-adapted bacteriophages (phage) and providing insights into their potential applications in microbial ecology and biotechnology. Full article

The objective of this study was to evaluate the individual and synergistic antimicrobial efficacy of Juniperus excelsa berry essential oil (JEO) and the cell-free supernatant (CFS) from Streptococcus thermophilus against Escherichia coli (ATCC 43888), Staphylococcus aureus (ATCC 25923), and multidrug-resistant Salmonella enterica serovar Infantis S2 isolated from chicken meat. In vitro antimicrobial effects were assessed using the agar well diffusion and microdilution methods (MIC and MBC assays). The in vivo antimicrobial effect of these natural bioactive substances in controlling microbial growth in chicken meat stored at 4 °C for 48 h was also evaluated. Bioactive components of JEO were determined via GC–MS, identifying alpha-pinene (84.56%) as the primary compound. In vitro assays revealed that JEO showed high antimicrobial activity against Gram-positive S. aureus with a zone diameter of 35.50 mm (p < 0.05). JEOCFS treatment, which is the combination of CFS and JEO, demonstrated a significant synergistic interaction against S. aureus, resulting in an MIC value of 25 mg/mL. CFS alone exerted a measurable inhibitory effect on S. aureus, with an MIC of 50 mg/mL, indicating its potential antimicrobial capability. Further evaluation of the in vivo antimicrobial efficacy using chicken meat stored at 4 °C revealed that the JEOCFS treatment significantly inhibited microbial growth (p < 0.05). After 48 h of storage under refrigerated conditions, the number of psychrophilic bacteria in the control group reached 8.40 log cfu/g, while it remained significantly lower at 6.44, 5.37, and 6.74 log cfu/g in the JEO, JEOCFS, and CFS treatments, respectively. These results indicate that the synergistic application of JEO and CFS effectively suppresses foodborne pathogens, particularly S. aureus, and extends the microbiological shelf life of refrigerated chicken meat. Full article

Microbiological contamination in public buildings is closely linked to human presence, such as airborne bacteria, fungi, and particulate matter, which strongly influence indoor air quality (IAQ). This study examined the distribution of microorganisms in a museum building in relation to time of day, air-handling unit (AHU) type, and ventilation operating mode. Exhibition rooms without natural light relied entirely on a central heating, ventilation and air conditioning (HVAC) system. Microbiological contamination was assessed using Koch’s passive sedimentation method over a 24 h cycle for two AHUs (I and III) and selected rooms, while CO₂ levels were monitored as indicators of occupancy and ventilation demand in line with EN 16798-1:2019 and ASHRAE 62.1-2022. Although the demand-controlled ventilation system increased the outdoor air fraction from 40% to 70–100% during peak visitor density, localized increases in microbial contamination occurred. AHU I showed higher loads of Staphylococcus sp. and fungi, while AHU III exhibited pronounced fungal peaks influenced by elevated humidity from an open water reservoir. Psychrophilic bacteria reached 140–230 CFU·m⁻³, mesophilic bacteria 230–320 CFU·m⁻³, and fungi up to 740 CFU·m⁻³. Most CFU values remained below commonly referenced upper limits (<1000 CFU·m⁻³), but several peaks exceeded lower recommended thresholds, indicating a need for improvements. Enhanced filtration, humidity control, increased airflow during high occupancy, and reducing moisture sources in AHUs may mitigate microbial growth and improve IAQ in public buildings. Full article

Freeze-thaw (F-T) cycles in seasonally frozen regions induce progressive volumetric strains leading to degradation of soils’ mechanical properties and performance of earthen infrastructure. Conventional chemical stabilization techniques often are not adaptive to cyclic thermal stresses and do not address the fundamental phase changes of porous media, underscoring the need for sustainable alternatives. This study explores the potential of extracellular polymeric substances (EPS) produced by the psychrophilic bacterium Polaromonas hydrogenivorans as a bio-mediated soil treatment to enhance freeze-thaw durability. Two EPS formulations were examined—EPS 1 (high ice-binding activity) and EPS 2 (low ice-binding activity)—to evaluate their effectiveness in improving volumetric stability and thawing strength of silty soil subjected to ten F-T cycles. Tests were conducted at four moisture contents (12%, 18%, 24%, and 30%) and three EPS concentrations (3, 10, and 20 g/L). Volumetric strain measurements quantified freezing expansion and thawing contraction, while unconfined compressive strength assessed post-thaw mechanical integrity. The untreated soils exhibited maximum net volumetric strains (γ_Net) of 5.62% and only marginal strength recovery after ten F-T cycles. In contrast, EPS 1 at 20 g/L mitigated volumetric changes across all moisture contents and increased compressive strength to 191.2 kPa. EPS 2 yielded moderate improvements, reducing γ_Net to 0.98% and enhancing strength to 183.9 kPa at 30% moisture. Lower EPS concentrations (3 and 10 g/L) partially mitigated volumetric strain, with performance strongly dependent on moisture content. These results demonstrate that psychrophilic EPS, particularly EPS 1, effectively suppresses ice formation within soil pores and preserves mechanical structure, offering a sustainable, high-performance solution for stabilizing frost-susceptible soils in cold-regions. Full article

This study evaluated the effects of different UV-C radiation doses combined with modified atmosphere packaging (MAP) on the conservation of minimally processed grated anco squash. The squash, obtained from producers in Santiago del Estero (Argentina), was washed, sanitized, cut, peeled, grated, and centrifuged. It was then subjected to UV-C treatments of 5 kJ/m² (T5), 15 kJ/m² (T15), 30 kJ/m² (T30), and 50 kJ/m² (T50). An immersion treatment with NaClO (100 ppm, 3 min) (TH) and an untreated control (TC) were also included. All samples were packaged in PVC trays and sealed with 35 μm polypropylene film, forming a passive MAP. Treatments T5 and T15 preserved acceptable sensory quality for up to 8 days, and no significant differences in color parameters were observed among treatments during storage. Overall, PC decreased by 12–20% and C by 15–37%, while AC increased by 15–40% after 8 days. Treatments T15, T30, and T50 effectively reduced psychrophilic microorganisms for up to 4 days, achieving reductions of 1–2 log compared to TH and TC (6 log CFU/g). By day 8, all treatments reached the microbial limit. In conclusion, the T15 treatment was the most suitable for preserving grated anco squash for up to 4 days at 5 °C, offering a potential alternative to sodium hypochlorite–based sanitization. Full article

White-nose syndrome (WNS) is an infectious disease of bats caused by the psychrophilic fungus Pseudogymnoascus destructans. Phenazine-1-carboxylic acid (PCA) is a microbial secondary metabolite with broad-spectrum antifungal activity. Previous studies show that PCA suppresses the growth of P. destructans at low concentrations, yet its mechanism remains unclear. Here, we evaluated the in vitro antifungal activity of PCA. We then investigated its potential mechanism using physiological and biochemical assays, as well as integrated transcriptomic and metabolomic analyses. PCA showed effective antifungal activity against P. destructans (EC₅₀ = 32.9 μg/mL). Physiological and biochemical assays indicated that PCA perturbed cell wall organization and increased membrane permeability, leading to leakage of intracellular contents. It also induced oxidative stress, DNA damage, and apoptosis. Multi-omics integration revealed that PCA markedly perturbed cell wall and membrane metabolism, virulence factor expression, and energy metabolism. It provoked oxidative stress while downregulating genes involved in the cell cycle, DNA replication, and repair. Together, these findings delineate the inhibitory effects of PCA on P. destructans in vitro, provide initial mechanistic insights into its antifungal action, and suggest that PCA merits further evaluation as a possible component of environmentally compatible strategies for WNS management. Full article

The biomass and lipid production responses of the psychrophilic marine thraustochytrid Thraustochytrium sp. RT2316-16 were assessed in chemically defined media comprising glucose, up to 17 amino acids and up to 9 B-vitamins and mineral salts. Compared to the control medium with all amino acids and B-vitamins (biomass concentration: 7.1 ± 0.1 g L⁻¹; total lipid content: 30.4 ± 0.5% of the DW), the growth of RT2316-16 was reduced by more than 50% in the medium that lacked cyanocobalamin or pyridoxamine. The total lipid content of the biomass grown in the absence of vitamins was 63% lower than in the biomass produced in the control medium. The composition of the B-vitamin mixture modulated the fatty acid composition, an effect that may have been related to the availability of dissolved oxygen. In bioreactor culture with the dissolved oxygen level controlled to ≥10% of air saturation, the microorganism consumed all 17 amino acids; 8 of the amino acids were fully consumed within a 0–33 h period, in which the specific growth rate was 0.065 h⁻¹. Under these culture conditions, the sum of eicosapentaenoic acid and docosahexaenoic acid in the total fatty acid content rose from 15% (at time 0) to 54% (after 95 h). A medium that contained the 9 amino acids that were not preferentially consumed favored the accumulation of total lipids, but reduced biomass growth. Full article