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OBJECTIVES: A chaperonin, PsyGroELS, from the Antarctic psychrophilic bacterium Psychrobacter sp. PAMC21119, was examined for its role in cold adaptation when expressed in a mesophilic Escherichia coli strain. RESULTS: Growth of E. coli harboring PsyGroELS at 10 °C was increased compared to the control strain. A co-expression system using PsyGroELS was developed to increase productivity of the psychrophilic enzyme PsyEst9. PsyEst9 was cloned and expressed using three E. coli variants that co-expressed GroELS from PAMC21119, E. coli, or Oleispira antarctica RB8ᵀ. Co-expression with PsyGroELS was more effective for the production of PsyEst9 compared tothe other chaperonins. CONCLUSION: PsyGroELS confers cold tolerance to E. coli, and shows potential as an effective co-expression system for the stable production of psychrophilic proteins.

Cultureable bacterial diversity of previously unexplored Siachen glacier, Pakistan, was studied. Out of 50 isolates 33 (66%) were Gram negative and 17 (34%) Gram positive. About half of the isolates were pigment producers and were able to grow at 4-37°C. 16S rRNA gene sequences revealed Gram negative bacteria dominated by Proteobacteria (especially γ-proteobacteria and β-proteobacteria) and Flavobacteria. The genus Pseudomonas (51.51%, 17) was dominant among γ- proteobacteria. β-proteobacteria constituted 4 (12.12%) Alcaligenes and 4 (12.12%) Janthinobacterium strains. Among Gram positive bacteria, phylum Actinobacteria, Rhodococcus (23.52%, 4) and Arthrobacter (23.52%, 4) were the dominating genra. Other bacteria belonged to Phylum Firmicutes with representative genus Carnobacterium (11.76%, 2) and 4 isolates represented 4 genera Bacillus, Lysinibacillus, Staphylococcus and Planomicrobium. Most of the Gram negative bacteria were moderate halophiles, while most of the Gram positives were extreme halophiles and were able to grow up to 6.12 M of NaCl. More than 2/3 of the isolates showed antimicrobial activity against multidrug resistant S. aureus, E. coli, Klebsiella pneumonia, Enterococcus faecium, Candida albicans, Aspergillus flavus and Aspergillus fumigatus and ATCC strains. Gram positive bacteria (94.11%) were more resistant to heavy metals as compared to Gram negative (78.79%) and showed maximum tolerance against iron and least tolerance against mercury.

Spirulina platensis has a wide range of activities, notably antibacterial property against food pathogens. This study investigates the antibacterial activity of S. platensis extract on Total Mesophilic and Psychrophilic Aerobic Bacteria. The results were compared using statistical analysis and the predicted model values using artificial intelligence-based models such as artificial neural network (ANN) and adaptive neuro fuzzy inference system (ANFIS) Models. The extraction of spirulina was done by using the freeze–thaw method with a concentration of 0.5, 1 and 5% w/v. Before the application of the extract, initial microbial load of fillets was analyzed the and the results were used as control. After application analysis was performed at 1, 24 and 48 h of storage at 4 °C. Based on the statistical analysis result the S. platensis extracts’ antimicrobial activity over TMAB of fresh tilapia fish fillets at 1, 24 and 48 h was using EA from 2.5 log10 CFU/g during the control stage to 1.8, 1.1 and 0.7 log10 CFU/g respectively whereas EB and EC was from 2.1 and 2.2 log10 CFU/g at control to 1.5, 0.8, 0.5 log10 CFU/g and 1.23, 0.6 and 0.32 log10 CFU/g respectively at the specified hour interval. Similarly, the three extracts over TPAB were from 2.8 log10 CFU/g at control time to 2.1, 1.5 and 0.9 in EA, while using EB reduces from 2.8 log10 CFU/g to 1.9, 1.3 and 0.8 log10 CFU/g at 1, 24 and 48 h respectively. Although EC presented the reduction from 1.9 log10 CFU/g to 1.4, 1 and 0.5 log10 CFU/g. This was supported by ANN and ANFIS models prediction.

Protein diffusion, critical for cellular metabolism, occurs in the highly crowded cytoplasm. Understanding how this dynamics changes when organisms are adapted to different thermal niches is a fundamental challenge in microbiology and biophysics. In Escherichia coli , protein diffusion undergoes a pronounced slowdown at temperatures near cellular death, coinciding with the early stages of unfolding. To determine whether this phenomenon is universal, we investigated psychrophilic and hyperthermophilic bacteria. In both species, a marked diffusion slowdown takes place at the onset of proteome melting. However, while the dynamic arrest is associated with the thermal death point for the hyperthermophilic proteome, the psychrophilic proteome maintains substantial mobility well beyond the cellular inactivation. The decoupling between metabolic viability and proteome dynamics and stability suggests that the functional processes of psychrophilic bacteria are temperature sensitive. This finding echoes the behavior of psychrophilic enzymes, manifesting a large temperature gap between optimal activity and unfolding. Protein diffusion is optimized to maintain functional fluidity at the organism’s working conditions, but its temperature dependence is controlled by the proteome folded state. Our findings redefine the relationship between cytoplasmic dynamics, proteome stability, and bacterial survival in cold environments. Authors combine neutron scattering and MD simulations to study psychrophilic bacteria, linking proteome dynamics to the state of the proteome folding in the context of differential thermal adaptation.

Pomegranate arils pose a significant challenge when it comes to preserving their nutritional value and preventing microbial contamination. This study aimed to explore the impact of thymol fumigation and active modified atmosphere packaging (MAP) on enzymatic activity and microbial contamination prevention in pomegranate arils. The results indicated that arils stored in a high O₂ atmosphere (HO₂A) with thymol had notably different catalase (CAT) and peroxidase (POD) activity levels compared to other treatments. These arils exhibited the highest CAT activity and the lowest POD activity. The highest phenylalanine ammonia-lyase (PAL) activity was observed in arils stored in HO₂A with thymol, although it was not significantly different from those stored in a high CO₂ atmosphere (HCO₂A) with thymol (P<0.05). Arils stored in a low oxygen atmosphere (LO₂A) and HCO₂A with thymol showed the highest polyphenol oxidase (PPO) activity levels, while arils in HO₂A with thymol had the lowest. The HO₂A with thymol treatment resulted in the lowest presence of psychrophilic bacteria, although it was not significantly different from arils stored in LO₂A with thymol (P<0.01). Based on cluster analysis results, HO₂A with thymol, LO₂A with thymol, and HCO₂A with thymol could be considered the most effective treatments for extending the storage life of packaged pomegranate arils.

Microbiological, chemical and sensory changes of sea bass slices wrapped with fish protein isolate (FPI)/fish skin gelatin (FSG) films incorporated with 3 % ZnO nanoparticles (ZnONP) (w/w, based on protein content) and 100 % basil leaf essential oil (BEO) (w/w, based on protein content) during storage of 12 days at 4 °C were investigated. Sea bass slices wrapped with FPI/FSG-ZnONP-BEO film had the lowest growth of psychrophilic bacteria, lactic acid bacteria and spoilage microorganisms including Pseudomonas , H₂S-producing bacteria and Enterobacteriaceae throughout storage of 12 days in comparison with those wrapped with FPI/FSG-BEO, FPI/FSG-ZnONP, FPI/FSG film, polypropylene film (PP film) and the control (without wrapping), respectively (P < 0.05). Lowered increases in pH, total volatile base, peroxide value and TBARS value were found in FPI/FSG-ZnO-BEO film wrapped samples, compared with others (P < 0.05). Sensory evaluation revealed that shelf-life of sea bass slices was longest for samples wrapped with FPI/FSG-ZnONP-BEO film (12 days), as compared to the control (6 days) (P < 0.05).

A new device that can generate cold plasma using air or helium at atmospheric pressure was designed. The whole sea bass was treated with atmospheric pressure air-plasma or atmospheric pressure helium-plasma (He-plasma) for 0.5, 1, 3, 5, 7, and 10 min. Immediate and potential residual effects of plasma treatments on sensory acceptability and quality were evaluated. The immediate effects were studied to reveal the effect of treatment on the freshness properties. The residual effects of cold plasma after 5 days of cold storage were examined to determine the changes during marketing. Sensory scores were above 7 (good) immediately after 0.5–7 min of air- or He-plasma treatments and did not change consumer purchase intention. The samples treated for 10 min scored lower and were found less preferable to purchase than the others. Sensory tests showed that the samples treated for 10 min were harder and dryer. The air-plasma treatment, especially for 7 and 10 min, significantly reduced mesophilic aerobic bacterial counts immediately after treatment. On the other hand, the increase in psychrophilic bacteria growth was better suppressed in He-plasma-treated samples after 5 days of storage, indicating He-plasma may be beneficial for delaying psychrophilic aerobic bacteria growth during cold storage. Generally, higher total color changes (ΔE) were detected when He-plasma was applied or treatment times increased. The thiobarbituric acid reactive substance (TBARS) values did not exceed the acceptable limits. The findings show the promising potential of cold plasma in the fresh fish industry.

Isolation, study and identification of bacteria producing the violet pigment violacein, which has a wide range of biological activities, is of interest for the biotechnological processes development. A violet-pigmented, Gram-stain-negative, rod-shaped, aerobic, nonmotile strain, designated S-LB17, was isolated from the water of Lake Baikal. Phylogenetic analysis of the 16S rRNA gene sequence showed that strain S-LB17 belonged to the genus Iodobacter, showing 98.7% similarity to the sequence of Iodobacter arcticus strain M4-16ᵀ. Comparison of the phenotypic properties of strain S-LB17 revealed multiple differences with type strains of I. arcticus and I. fluviatilis.

This study is aimed to determine the effects of different marination conditions (1, 2, 3, 4% acetic and 6, 8, 10% NaCl) on the anchovy fillets inoculated with Morganella psychrotolerans during refrigerated storage (4±1°C) for three months. According to the results of study, marination has great inhibitory effects on the growth of M . psychrotolerans . Total psychrophilic bacteria, total lactic acid bacteria, total yeast and mold, Total Enterobacteriaceae and M . psychrotolerans growth were not observed in the groups treated with 3 and 4% acetic acid. Control groups and fillets marinated with 1% acetic acid showed lower sensory scores. Those groups were rejected on 30th, 45th and 60th days of the storage, respectively, while the groups marinated with 2%, 3%, and 4% acetic acid had higher sensory scores and they were still acceptable until at the end of the study. According to peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) assessment, lipid oxidation was delayed in the fillets marinated with high acetic acid concentrations (3 and 4%) comparing with the control and other inoculated fillets. From this research it can be revealed that high acetic acid and salt concentrations suppress the bacteria growth in the anchovy fillets. Thus, marination process can be recommended to be used as a preservation method to inhibit bacterial growth in anchovy fillets for a safe consumption.

This study investigated the antioxidant and antimicrobial properties, as well as the volatile compounds, of Lactobacillus bulgaricus ( L. bulgaricus ) postbiotics (at concentration of 150 and 300 mg/L) and their combination with chitosan coatings (0.5% and 1%) on sausage quality (with 100 ppm nitrite) during 40 days of cold storage. The results were compared to a control group, as well as to sausages containing commercial formulation (120 ppm) and reduced (100 ppm) levels of nitrite. To further assess the antimicrobial effects, it also inoculated E. coli and Staphylococcus aureus ( S. aureus ) into the sausages in order to examine how the postbiotics and chitosan coatings impacted the growth of these foodborne pathogens during the 40-day cold storage period. The reults indicated that those containing 300 mg/L postbiotic and 1% chitosan generally met the desired condition for pH, moisture, fat, and total volatile base-nitrogen. These samples also showed the strongest inhibition of mesophilic and psychrophilic bacteria, mold and yeast. Notably, no E. coli or S. aureus were detected in any of the samples, indicating that the postbiotic and chitosan combination effectively inhibited the growth of these pathogens in sausages. The findings suggest that using chitosan coatings and L. bulgaricus postbiotic can enhance the quality of sausages, ultimately lowering the risk of contamination by harmful bacteria and improving overall food safety.