Search Results (77)

This study evaluated the antimicrobial properties of Piper carpunya extracts, which are traditionally used by Ecuadorian indigenous communities, and validated the in vitro findings in a real food matrix. Three different extracts (ethanolic, hydroethanolic, and aqueous-lyophilized) were evaluated by the agar well diffusion method against a panel of 20 microbial strains comprising both foodborne pathogens and spoilage microorganisms. The extracts with the highest yield and antimicrobial activity were then tested in a precooked risotto formulated under commercial conditions, in challenge tests with Clostridium perfringens. All extracts inhibited C. perfringens at a minimum inhibitory concentration below 80 mg/mL, the ethanol extract being the most effective. In the risotto model, the ethanol–water extract (8%, w/w) reduced C. perfringens counts by approximately 2 log CFU/g relative to the inoculated control and also lowered aerobic mesophilic and psychrophilic counts, whereas the freeze-dried extract was less effective and bacterial counts declined only until day 4 of storage. Both extracts slightly reduced pH and water activity and, rather than protecting the lipid fraction, exhibited a prooxidant effect; nevertheless, malondialdehyde remained below 0.35 mg/kg throughout the 30-day storage period, well below the thresholds associated with perceptible rancidity. P. carpunya extracts show potential as natural ingredients for improving the microbiological safety of ready-to-eat foods, and their chemical and sensory characterization is required before practical application. Full article

A previous study demonstrated that quorum sensing (QS) genes from the psychrophilic bacterium Aliivibrio logei can be used in Escherichia coli to obtain bacterial cultures with controlled amounts of a target protein. However, the QS system may be induced non-uniformly across the cell population. In this study, we used an expression vector containing luxR/luxI regulatory genes from A. logei carrying sfGFP as a reporter gene. Reporter expression was regulated by the autoinducer 3OxoC6-HSL, activated at 22 °C, and terminated at 37 °C. Flow cytometry was used to assess the GFP fluorescence distribution at the single-cell level. The system provided dose-dependent unimodal expression lacking formation of distinct ON/OFF subpopulations, while the robust coefficient of variation decreased with increasing autoinducer concentration. The autoinducer synthase LuxI enabled autoinduction, but under the tested conditions, no substantial effect on expression homogeneity was detected. Raising the temperature to 37 °C effectively halted expression, allowing intermediate target protein values to be fixed at the single-cell level. Overall, the developed system represents a promising tool for biotechnological applications requiring precise and uniform control of expression. Full article

Edible coatings derived from fish by-products offer promising, sustainable approaches for seafood preservation. This study evaluated catfish skin gelatin as a carrier for antimicrobial agents to enhance microbiological stability, oxidative stability, and shelf life of fresh catfish fillets during refrigerated storage. Shelf life was defined as the storage period required for microbial and quality parameters to reach spoilage-associated limits. Treatments included control (C), lactic acid (LA), potassium sorbate (PS), gelatin (G), gelatin + LA (G+LA), and gelatin + PS (G+PS). Microbial quality (Aerobic Plate Count, psychrophiles, Pseudomonas spp., yeasts), physicochemical properties (pH, moisture, color), and lipid oxidation (TBARS) were assessed. Based on APC and psychrophiles, gelatin combined with antimicrobials was associated with extended shelf life relative to the control, with G+PS (15 days) and G+LA (12 days) compared to 9 days for untreated fillets, while LA and PS alone showed limited effects. All treatments maintained pH < 7.0, and color changes were minimal except for increased b* in LA treatments. TBARS increased during storage, particularly with LA, but remained below 5 mg MDA/kg. Overall, gelatin-based systems, particularly with PS or LA, offer a cost-effective, sustainable approach to potentially improve refrigerated fish quality while valorizing fish by-products. Further work is needed to optimize formulations and validate results under commercial conditions. Full article

This study aimed to develop shrimp gravlax (Penaeus japonicus) as a ready-to-eat seafood product and to determine its shelf life. The product was prepared using a curing method and stored at 4 °C for 30 days. Quality changes were monitored at five-day intervals through analyses of TVB-N, TBARs, peroxide value, pH, water activity, total mesophilic aerobic bacteria, and total psychrophilic bacteria. Gradual shifts in quality parameters were observed during storage, with notable increases in TVB-N, lipid oxidation markers, and microbial counts. Sensory scores declined over time, yet the product remained acceptable until approximately day 25. These findings suggest that shrimp gravlax has a shelf life of around 25 days under the studied conditions. To support freshness evaluation, machine learning models including Support Vector Machine (SVM), K-Nearest Neighbors (K-NN), and Decision Tree (DT) were applied. After data augmentation and parameter optimization, the models achieved high classification performance, reaching up to 100% under optimized conditions. The classification outcomes aligned well with experimental observations, highlighting the potential of machine learning to strengthen shelf-life assessment when multiple quality indicators are considered together. Nevertheless, the models were developed under a single storage condition and focused on classification rather than time-series prediction. Further research using independent datasets and varied storage environments will be necessary to enhance model generalizability. In conclusion, shrimp gravlax can be regarded as a promising ready-to-eat product. Combining traditional processing methods with machine learning provides a practical and innovative approach to shelf-life evaluation in seafood systems. Full article

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

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

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

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

The effect of active packaging on maintaining the quality of cherry tomatoes and kale during storage was investigated. The active packaging consisted of kraft paper sheets coated with thymol/eugenol (50:50) encapsulated in β-cyclodextrin. Cherry tomatoes were stored at 10, 15, and 22 °C for 15, 14, and 8 days, respectively, while kale was stored at 2, 8, 15, and 22 °C for 21, 16, 9, and 7 days. Physicochemical (pH, total soluble solids, titratable acidity, colour, and firmness), microbiological (mesophilic, psychrophilic, enterobacteria, moulds, and yeasts) and pigment/bioactive/nutritional (chlorophylls, carotenoids, total phenolic content, vitamin C, and total antioxidant capacity) characteristics were analysed. Active packaging significantly reduced microbial growth, particularly enterobacteria and moulds, in cherry tomatoes and psychrophiles and moulds in kale, without negatively affecting the physicochemical quality. The microbial kinetics were successfully described using the Baranyi–Ratkowsky predictive model, which quantified the effects of temperature and active packaging on microbial growth parameters. This modelling approach revealed that active packaging increased the minimum growth temperature and reduced the specific growth rate of key microbial groups, confirming its inhibitory action under different storage conditions. The use of active packaging slowed colour degradation in kale by reducing chlorophyll loss up to 50% at 22 °C and maintained tomato firmness and colour during storage. Furthermore, a strong correlation (R² = 0.87) between colour index and carotenoid content was found, enabling the non-destructive prediction of ripening in tomatoes. Overall, active packaging enhanced microbial stability, delayed visual deterioration, and sustainably extended the shelf life and post-harvest quality of perishable products, offering a promising alternative to conventional preservation methods. Full article

Plastic pollution, particularly from polyethylene terephthalate (PET), poses significant environmental concerns due to ecosystem persistence and extensive packaging use. Conventional recycling methods face inefficiencies, high costs, and limited scalability, necessitating sustainable alternatives. Biodegradation via PET hydrolases offers promising eco-friendly solutions, although most natural PET-degrading enzymes are thermophilic and require energy-intensive high temperatures. In contrast, psychrophilic enzymes function efficiently at extremely low temperatures but often lack stability under moderate conditions. Therefore, this study aimed to enhance the ability of the Mors1 enzyme from Moraxella TA144 to operate effectively under mesophilic conditions, which is closer to the optimal conditions for environmental application. Three strategic hydrophobic substitutions (K93I, E221I, and R235F) were introduced in loop regions, generating the mutant variant Mors1^MUT. Comparative characterization revealed that Mors1^MUT retained 98% of its activity at pH 9 and displayed greater resilience across both acidic and alkaline conditions than did the wild-type enzyme. Thermal stability assays revealed that Mors1^MUT preserved 61% of its activity at 40 °C and 14% at 50 °C, whereas the wild-type enzyme was fully inactivated at these temperatures. The enzymatic hydrolysis of PET films significantly improved with Mors1^MUT. Gravimetric analysis revealed weight losses of 0.83% for Mors1^WT and 3.46% for Mors1^MUT after a 12-day incubation period. This corresponds to a 4.16-fold increase in hydrolysis efficiency, confirming the enhanced catalytic performance of the mutant variant. The improvement was further validated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and attenuated total reflectance–Fourier transform infrared (ATR-FTIR) analysis. Optimization of the reaction parameters through response surface methodology (enzyme load, time, pH, temperature, and agitation) confirmed increased PET hydrolysis under mild mesophilic conditions. These findings establish Mors1^MUT as a robust mesophilic PETase with enhanced catalytic efficiency and thermal stability, representing a promising candidate for sustainable PET degradation under environmentally relevant conditions. Full article