Mesophilic Research Articles

Phenotypic, genotypic, and resistome of mesophilic spore-forming bacteria isolated from pasteurized liquid whole egg

The production of whole-liquid eggs is of significant economic and nutritional importance. This study aimed to assess the phenotypic and genotypic diversity of mesophilic aerobic spore-forming bacteria (n = 200) isolated from pasteurized whole liquid egg and liquid egg yolk. The majority of the isolates were identified as belonging to the genera Bacillus (86 %), followed by Brevibacillus (10 %) and Lysinibacillus (4 %). For the phenotypic characterization, isolates were subjected to various heat shocks, with the most significant reductions observed at 80 °C/30 min and 90 °C/10 min for isolates recovered from raw materials. On the other hand, the decrease was similar for isolates recovered from raw material and final product at 100 °C/5 min and 110 °C/5 min. Genotypic genes related to heat resistance (cdnL, spoVAD, dacB, clpC, dnaK, and yitF/Tn1546) were examined for genotypic characterization. The dnaK gene showed a positive correlation with the highest thermal condition tested (110 °C/5 min), while 100 °C/5 min had the highest number of positively correlated genes (clpC, cdnL, yitF/Tn1546, and spoVAD). Whole Genome Sequencing of four strains revealed genes related to sporulation, structure formation, initiation and regulation, stress response, and DNA repair in vegetative cells. The findings of this study indicate that these mesophilic aerobic spore-forming bacteria may adopt several strategies to persist through the process and reach the final product. As the inactivation of these microorganisms during egg processing is challenging, preventing raw materials contamination and their establishment in processing premises must be reinforced.

Production of fresh cheese analogues; the impact of soy protein isolate and oat germ powder

AbstractPlant-based proteins are being rapidly explored in the food industry to produce healthy and nutritious foods. Herein, the effects of soy protein isolate (SPI) ratio to oat germ powder (OGP) (0:0, 3.7: 6.3, 5:5, 0:10, 10:0, and 6.3:3.7%) were studied on the physicochemical, colour, rheological, microbial, antioxidant, and sensory properties of wheyless cheese. The results showed that by increasing SPI and OGP levels, ash, white index value, elastic modulus, and complex viscosity decreased, while pH, fat in dry matter, Chroma, and total colour (ΔE) increased. Also, syneresis was only observed in the control sample and was not observed in other samples. Control sample together with sample containing 10% of OGP showed the highest microbial count (i.e., mesophilic bacteria and yeasts-moulds), while samples containing 10% of SPI showed the lowest microbial count. Furthermore, the growth of both coliform and psychrophilic bacteria in all samples was negligible. Based on the results of sensory evaluation, with increasing SPI and OGP, the sensory evaluation score of samples decreased but they were within the acceptable range. According to the results obtained in this study, the combinations of 5% SPI and 5% OGP or 3.7% SPI and 6.3% OGP are recommended to be used in wheyless cheese production.

Antibiotic residues and microbial contamination in pasteurized whole milk intended for human consumption.

Milk contamination for human consumption is one of the biggest concerns worldwide. To prevent milk contamination, it is important to implement sustainable production practices that ensure animal health and guarantee veterinary drugs have been used properly. This study aimed to detect antibiotic residues and microbial contamination in commercially available pasteurized whole milk intended for human consumption. We conducted a cross-sectional study on all brands of pasteurized milk (n = 17) for human consumption in Medellín, Colombia, from February 30 to April 30, 2022. Six milk samples of each brand were collected every 15 days, resulting in 102 samples. IDEXX SNAPduo™ ST Plus test (IDEXX Laboratories Inc, Maine, USA) was used to detect cephalosporins residues to detect beta-lactam and tetracyclines. We detected mesophilic aerobic bacteria and coliforms using Chromocult Coliform Agar® (Merck KGaA, Darmstadt, Germany) and Plate-Count Agar® (Merck KGaA), respectively. Beta-lactam residues were found in 24.4% of the brands. No tetracyclines or cephalosporins were detected. Mesophilic aerobic bacteria and coliform contamination were detected in 42.6% and 12.8% of the brands, respectively. No fecal coliform contamination was detected. This study demonstrated the presence of antibiotic residues and microbial contamination in commercially available pasteurized whole milk intended for human consumption in the study area, highlighting its potential public health implications.

Improving chicken meat shelf-life: Coating with whey protein isolate, nanochitosan, bacterial nanocellulose, and cinnamon essential oil

This research investigated the impact of a food coating including whey protein isolate (WPI), nanochitosan (NCH), bacterial nanocellulose (BN), and cinnamon essential oil (CEO) on the microbiological, chemical, and sensory characteristics of chicken fillets throughout 12 days of refrigerated storage. The following treatments were applied to the fillets after they were randomly separated into five groups: 1. Control, 2. WPI, NCH, and BN (WPI-NC), 3. WPI, NCH, and BN+ 0.5% CEO (WPI-NC+ 0.5% CEO), 4. WPI, NCH, and BN+ 1% CEO (WPI-NC+ 1% CEO), and 5. WPI, NCH, and BN+ 1.5% CEO (WPI-NC+ 1.5% CEO). The results revealed that incorporating CEO into the WPI-NC coating significantly improved its antibacterial activity, effectively retarding the proliferation of mesophilic bacteria, psychrotrophic bacteria, Pseudomonas spp., Enterobacteriaceae, Lactic acid bacteria, Staphylococcus aureus, and Mold and Yeast. Moreover, the coating delayed the increase of total volatile bases-nitrogen (TVB-N), peroxide value (PV), and thiobarbituric acid (TBA) levels, indicating reduced spoilage. Comparing coated fillets to the control group, sensory evaluations demonstrated that they maintained superior taste, color, and odor. Overall, the WPI-NC+ 1.5% CEO coating prolonged the shelf life of chicken breast fillets by more than 5 days compared to the uncoated (control) group.

Surface defects due to bacterial residue on shrimp shell

The changes in the surface chemistry and morphological structure of chitin forms obtained from shrimp shells (ShpS) with and without microorganisms were evaluated. Total mesophilic aerobic bacteria (TMAB), estimated Pseudomonas spp. and Enterococcus spp. were counted in Shp-S by classical cultural counting on agar medium, where the counts were 6.56 ± 0.09, 6.30 ± 0.12, and 3.15 ± 0.03 CFU/g, respectively. Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy (SEM)/Energy dispersed X-ray (EDX) were used to assess the surface chemistry/functional groups and morphological structure for ChTfree (non-microorganism), and ChTmo (with microorganisms). ChTfree FTIR spectra presented a detailed chitin structure by OH, NH, and CO stretching vibrations, whereas specific peaks of chitin could not be detected in ChTmo. Major differences were also found in SEM analysis for ChTfree and ChTmo. ChTfree had a flat, prominent micropore, partially homogeneous structure, while ChTmo had a layered, heterogeneous, complex dense fibrous, and lost pores form. The degree of deacetylation was calculated for ChTfree and ChTmo according to FTIR and EDX data. The results suggest that the degree of deacetylation decreases in the presence of microorganisms, affecting the production of beneficial components negatively. The findings were also supported by the molecular docking model.

Effect of the High Hydrostatic Pressure Process on the Microbial and Physicochemical Quality of Shalgam.

The processing of shalgam requires the use of an appropriate processing technique due to yeast overgrowth. With advancements in processing technology, high hydrostatic pressure (HHP) as nonthermal and nonchemical preservation has gained attention for its potential. Response surface methodology with the Box-Behnken experimental design was used to make sense of the effects of HHP parameters, namely, pressure (100-500 MPa), temperature (20-40 °C), and time (5-15 min), on microbial and physicochemical factors (pH, total soluble solids, titratable acidity, bioactive compounds, color values). The reduction in the counts of total mesophilic aerobic bacteria, lactic acid bacteria, and yeast-mold increased proportionally with the increase of all pressure levels, application temperatures, and pressurization times (p < 0.05). Stability was maintained in pH, total solubility, and some color parameters such as L*, a*, ΔE, yellow color tone, and red color tone. All findings of the bioactive components (phenolic content, flavonoid content, antioxidant activity, and monomeric anthocyanin content) in the RSM design showed a significant change only in proportion to the square of time (p < 0.05). The optimum pressurization parameter combination of shalgam was determined as a pressure of 367 MPa, temperature of 31.9 °C, and process time of 10.5 min. Under these conditions, values of yeast and mold (Y&M) reduction, total flavonoid content (TFC), total monomeric anthocyanin contents (TMACs), titratable acidity (TA), and reducing sugar content (RSC) were obtained as 4.30 log cfu/mL, 192.89 mg QE/100 mL, 11.88 mg/100 mL, 2.41 glacticacid/L, and 6.78 mg/100 mL, respectively. In particular, the findings in the basic color parameters proved that there was no significant change in the saturated red color of the shalgam. Gallic acid, caffeic acid, chlorogenic acid, catechin, cyanidin-3-O-glucoside, malvidin-3-O-glucoside, and peonidin-3-O-glucoside derivatives are dominant phenolic and anthocyanin compounds, which are frequently found in turnip plants. No important losses in bioactive components were observed, despite changes in pressure and temperature parameters. The HHP method can be suggested to have great potential in the processing of shalgam (fermented turnip beverage) in terms of its ability to maintain the flavors, colors, and nutrients, in addition to ensuring microbiological safety when compared to other preservation methods.

Calcium impregnation during isochoric cold storage to improve postharvest preservation of fresh blueberries

Isochoric cold storage can be used to extend the shelf-life of fresh produce by delaying senescence through storage at subfreezing temperatures as well as hinder microbial growth with pressure. The effect of isochoric impregnation with CaCl2 on qualitative parameters of blueberries during isochoric cold storage at −2.5 °C and refrigerated storage at 5 °C for four weeks was investigated in this study. The results showed the synergistic effect of calcium impregnation and isochoric cold storage on the quality of blueberries. Isochoric impregnated blueberries better retained their weight, had better mechanical properties and had higher nutrient contents (anthocyanins, total phenolics and antioxidant capacity) than non-impregnated blueberries refrigerated at 5 °C. The benefits of isochoric impregnation with CaCl2 were greater for samples stored under isochoric conditions than under refrigerated conditions. However, the impregnated refrigerated samples still had better quality properties than non-impregnated refrigerated samples. Furthermore, panelists found no significant differences in preference for any of the sensory attributes between fresh blueberries and impregnated blueberries. Also, isochoric cold storage inhibited the growth of mesophilic aerobic bacteria, yeasts and molds under isochoric and refrigerated storage conditions. In conclusion, this study showed the possibility of using isochoric cold storage with calcium impregnation to develop ready-to-eat fresh blueberries with higher nutrient content and extended shelf-life.

A Study of Resistome in Mexican Chili Powder as a Public Health Risk Factor.

Chili powder is an important condiment around the world. However, according to various reports, the presence of pathogenic microorganisms could present a public health risk factor during its consumption. Therefore, microbiological quality assessment is required to understand key microbial functional traits, such as antibiotic resistance genes (ARGs). In this study, metagenomic next-generation sequencing (mNGS) and bioinformatics analysis were used to characterize the comprehensive profiles of the bacterial community and antibiotic resistance genes (ARGs) in 15 chili powder samples from different regions of Mexico. The initial bacterial load showed aerobic mesophilic bacteria (AMB) ranging between 6 × 103 and 7 × 108 CFU/g, sporulated mesophilic bacteria (SMB) from 4.3 × 103 to 2 × 109 CFU/g, and enterobacteria (En) from <100 to 2.3 × 106 CFU/g. The most representative families in the samples were Bacillaceae and Enterobacteriaceae, in which 18 potential pathogen-associated species were detected. In total, the resistome profile in the chili powder contained 68 unique genes, which conferred antibiotic resistance distributed in 13 different classes. Among the main classes of antibiotic resistance genes with a high abundance in almost all the samples were those related to multidrug, tetracycline, beta-lactam, aminoglycoside, and phenicol resistance. Our findings reveal the utility of mNGS in elucidating microbiological quality in chili powder to reduce the public health risks and the spread of potential pathogens with antibiotic resistance mechanisms.

High-resolution structure and biochemical properties of the LH1–RC photocomplex from the model purple sulfur bacterium, Allochromatium vinosum

The mesophilic purple sulfur phototrophic bacterium Allochromatium (Alc.) vinosum (bacterial family Chromatiaceae) has been a favored model for studies of bacterial photosynthesis and sulfur metabolism, and its core light-harvesting (LH1) complex has been a focus of numerous studies of photosynthetic light reactions. However, despite intense efforts, no high-resolution structure and thorough biochemical analysis of the Alc. vinosum LH1 complex have been reported. Here we present cryo-EM structures of the Alc. vinosum LH1 complex associated with reaction center (RC) at 2.24 Å resolution. The overall structure of the Alc. vinosum LH1 resembles that of its moderately thermophilic relative Alc. tepidum in that it contains multiple pigment-binding α- and β-polypeptides. Unexpectedly, however, six Ca ions were identified in the Alc. vinosum LH1 bound to certain α1/β1- or α1/β3-polypeptides through a different Ca2+-binding motif from that seen in Alc. tepidum and other Chromatiaceae that contain Ca2+-bound LH1 complexes. Two water molecules were identified as additional Ca2+-coordinating ligands. Based on these results, we reexamined biochemical and spectroscopic properties of the Alc. vinosum LH1–RC. While modest but distinct effects of Ca2+ were detected in the absorption spectrum of the Alc. vinosum LH1 complex, a marked decrease in thermostability of its LH1–RC complex was observed upon removal of Ca2+. The presence of Ca2+ in the photocomplex of Alc. vinosum suggests that Ca2+-binding to LH1 complexes may be a common adaptation in species of Chromatiaceae for conferring spectral and thermal flexibility on this key component of their photosynthetic machinery.

Investigating the effect of cold atmospheric plasma treatment on the microbial load of raw potato slices.

Potatoes (Solanum tuberosum), as starchy plants, have been highly esteemed for their rich supply of nutrients. Numerous studies have investigated the potential health benefits of potatoes and explored potential solutions. Among these considerations, the discussion regarding microbial contaminants has remained an important topic. The present study used cold atmospheric plasma (CAP) to evaluate the microbial quality (including mesophilic and psychrotrophic bacteria and mold and yeasts) of raw potato slices during a 14-day storage period. To achieve this goal, the duration of CAP exposure was set at 5, 10, and 15 min, utilizing an electric voltage of 60 kV and a specific frequency of 20 kHz. The findings revealed the effectiveness of CAP pre-treatment in inhibiting microbial growth over the 14 days when compared to the control sample (untreated sample), with a statistically significant difference (P < 0.05). Moreover, with an extension of the CAP exposure duration to 15 min, there was a significant reduction in the logarithmic count of mesophilic, psychrotrophic microorganisms, molds, and yeasts (4.95, 2.85, and 2.22CFU/g, respectively) in comparison to the control groups (7.5, 5.62, and 5.5CFU/g) on days 0, 7, and 14 of the storage periods (P < 0.05). The results of this study highlight the potential of CAP pre-treatment on reducing the microbial load in raw potato slices prior to frying, which could potentially influence the overall quality of potato-based products.

Physical and chemical properties, hygienic quality and fatty acid profile in milk of lactating Lacaune dairy sheep

Abstract. In recent years, there has been globally increasing interest in dairy sheep breeding, including Lacaune sheep, which is supported by a high demand for sheep's milk on the market. This paper elaborates on the influence of a sheep's lactation stage on the physical and chemical properties, hygienic quality and content of fatty acids in milk produced by Lacaune sheep kept in intensive breeding. The research was conducted on 30 Lacaune sheep, which were tested in the early (60th day), middle (120th day) and late (180th day) stages of lactation. Density, freezing point and titration acidity were determined by applying the infrared spectrometry method, and indicators of the hygienic quality of milk, such as somatic cell count (SCC), were determined by the fluoro-opto-electronic method, and the total count of aerobic mesophilic bacteria (CFU) was determined by the flow cytometry method. The fatty acid profile of feed and milk was obtained by gas–liquid chromatography. Depending on the stage of lactation, results referring to the chemical composition of Lacaune sheep's milk showed a significant increase in the content of fat, protein, total dry matter and casein together with a significant decrease in the content of lactose in the late stage of lactation. There was also a significant increase confirmed for the concentration of urea and the freezing point in milk along with the lactation progress. Depending on the stage of lactation, milk yield in Lacaune sheep significantly decreased as lactation progressed. Analysis of the fatty acid composition in milk of Lacaune sheep proved a significant decrease in the concentrations of C4 : 0, C6 : 0, C11 : 0, C12 : 0, C13 : 0, C15 : 0, C17 : 1, C18 : 2n6 and C18 : 3n6 as well as the n6 concentrations and the n6 / n3 ratio. The opposite trend was observed for concentrations of C10 : 0, C14 : 1, C16 : 0, C16 : 1, C18 : 0, C20 : 2, C18 : 3n3, C20 : 3n6, C20 : 5n3 and C22 : 6n3 as well as for the n3 concentrations. When compared to the early lactation stage, the C18 : 3n6 and n6 concentrations were significantly lower in the late lactation stage, while the C20 : 2 and C20 : 5n3 concentrations were significantly lower in the middle lactation stage when compared to the late lactation stage. There were many significant positive and negative correlations determined between the researched properties of milk. The research results obtained with Lacaune sheep's milk can be compared to the results of other studies, except for the lower content of milk fat. This confirms the good adaptability of Lacaune sheep to different breeding conditions and the necessity to provide sheep with quality pastures for grazing.

Exploring Microbial Diversity in Green Honey from Pulau Banggi Sabah: A Preliminary Study

The microbiological composition of honey can include microorganisms that are beneficial or harmful to human health. Therefore, it is essential to investigate the microbiological quality of different honey types available in the market. However, there is limited information available on the analysis, isolation, and characterization of honey-associated microbes, especially for green honey from Banggi Island. Green honey is sourced from underground areas within the island's forest. This study aimed to assess the microbiological quality of raw (freshly collected) and processed green honey by examining the presence of bacteria, yeast, molds, and pathogens. The results revealed that raw green honey had a slightly higher total plate count (770 ± 0.03 cfu/g) compared to processed green honey (640 ± 0.02 cfu/g). Both raw and processed green honey contained Lactobacillus spp. with counts of 350 ± 0.02 cfu/g and 160 ± 0.02 cfu/g, respectively. Bacillus count was higher in raw green honey (110 ± 0.01 cfu/g) compared to processed green honey (5 ± 0.01 cfu/g). Molds were only detected in raw green honey, while osmophilic yeast counts were higher in raw green honey (16000 ± 0.03 cfu/g) compared to processed green honey (120 ± 0.02 cfu/g). Mesophilic bacteria, thermophilic bacteria, coliforms, E. coli, and Staphylococcus aureus were not detected in either raw or processed green honey. Furthermore, green honey was free from pathogenic bacteria such as Salmonella spp., Listeria spp., and Shigella spp. Bacteria isolated from green honey included Lysinibacillus macrolides, Lysinibacillus boronitolerans, Paenibacillus cineris, Paenibacillus favisporus, and Bacillus oleronius, none of which were pathogenic. This study identified important microorganisms present in green honey, which have the potential to provide beneficial effects without posing any harm to human health.

Sanitary quality and bacteriological antibiotic-resistance pattern of frozen raw chicken meat sold in retail market in Benin

To cover the meat needs of its population, Benin imports large quantities of raw frozen chicken meat from the European Union, United States and Brazil. Consumers can purchase this meat either in open markets (OM) or in frozen meat retail stores (FMRS). The present study aimed to assess the safety of imported raw chicken sold in Benin and the antibiotics susceptibility of Escherichia coli, Staphylococcus aureus and Pseudomonas spp. isolates retrieved from these foodstuffs. Seventy-two samples of imported raw chicken (36 from OM and 36 from FMRS) were randomly purchased from different retail outlets in May 2021 and May 2023 and analyzed using standard microbiological methods. Fifty-two, 36 and 58 isolates of E. coli, S. aureus and Pseudomonas spp., respectively, were tested for their susceptibility to antimicrobials. Aerobic mesophilic bacteria (AMB) and Pseudomonas spp. were the most frequent and dominant flora with density reaching 9.4 and 7.5 Log10 CFU/g, respectively. The highest microbial load recorded for E. coli, S. aureus, Bacillus cereus, Campylobacter spp. and Listeria monocytogenes were 7.0, 4.6, 3.7, 2.4 and 1.4 Log10 CFU/g, respectively, while 73.6, 55.5, 33.3, 2.8 and 1.4 % of the samples tested positive for these bacteria, respectively. None of the samples contained Salmonella spp. Samples collected in OM had concentrations of AMB, Pseudomonas spp., S. aureus and E. coli significantly higher (p < 0.05) than those from FMRS. Moreover, samples collected in OM in 2023 have significantly higher AMB and E. coli microbial loads (p < 0.05) than those collected in 2021, while there was no significant difference (p > 0.05) between samples collected in FMRS over the two sampling periods. The frequencies of multidrug resistant (MDR) E. coli, S. aureus and Pseudomonas spp. were 21.2, 36.1 and 32.8 %, respectively. This study highlights the fact that frozen chicken meat purchased by consumers from retailers in Benin is not always of good quality, with a health risk related to S. aureus and/or L. monocytogenes, emphasizing the need for improvements in hygienic and preservation practices. In addition, this study revealed that imported frozen chicken meat can be a potential source of MDR bacteria.

Effect of ultrasound technique to improve quality of Iranian industrial honey by controlling crystallization process.

This experiment aimed to assess the effects of ultrasound techniques on the quality of Iranian industrial honey. Honey samples were subjected to ultrasound waves at different frequencies and various parameters. The results showed that both ultrasound treatments (30 or 42 kHz) changed the physical, biochemical, antioxidant, and antibacterial characteristics of honey. Ultrasound treatments at 20 or 45°C for 1, 5, or 10 min reduced moisture, acidity, sugars, ABTS levels, 5-hydroxymethylfurfural content, clostridium, aerobic mesophilic bacteria count, and osmophile count while increasing diastase, phenol, and proline levels. Ultrasound treatment of honey samples at 30 and 42 kHz and different temperatures for varying durations led to a decrease in acidity after 90 and 180 days. Treating honey samples with 42 kHz ultrasound at 45°C for 10 min led to a significant reduction in the amount of reducing sugar. Ultrasonication at different frequencies and temperatures led to higher levels of phenol, ABTS, and proline production, along with a considerable decrease in the total count of aerobic mesophilic bacteria. Our study unveils the potential of ultrasonication to enhance honey quality through multifaceted improvements. Treatment significantly augmented phenolic content and antioxidant capacity, opening avenues for novel honey preservation and quality enhancement strategies. Additionally, ultrasonication effectively controlled honey crystallization while simultaneously improving biochemical, antioxidant, and antibacterial properties. This demonstrates its potential as a comprehensive strategy for honey quality improvement.

Thermophilic PHP Protein Tyrosine Phosphatases (Cap8C and Wzb) from Mesophilic Bacteria.

Protein tyrosine phosphatases (PTPs) of the polymerase and histidinol phosphatase (PHP) superfamily with characteristic phosphatase activity dependent on divalent metal ions are found in many Gram-positive bacteria. Although members of this family are co-purified with metal ions, they still require the exogenous supply of metal ions for full activation. However, the specific roles these metal ions play during catalysis are yet to be well understood. Here, we report the metal ion requirement for phosphatase activities of S. aureus Cap8C and L. rhamnosus Wzb. AlphaFold-predicted structures of the two PTPs suggest that they are members of the PHP family. Like other PHP phosphatases, the two enzymes have a catalytic preference for Mn2+, Co2+ and Ni2+ ions. Cap8C and Wzb show an unusual thermophilic property with optimum activities over 75 °C. Consistent with this model, the activity-temperature profiles of the two enzymes are dependent on the divalent metal ion activating the enzyme.

Molecular characterization of the PhiKo endolysin from Thermus thermophilus HB27 bacteriophage phiKo and its cryptic lytic peptide RAP-29.

In the era of increasing bacterial resistance to antibiotics, new bactericidal substances are sought, and lysins derived from extremophilic organisms have the undoubted advantage of being stable under harsh environmental conditions. The PhiKo endolysin is derived from the phiKo bacteriophage infecting Gram-negative extremophilic bacterium Thermus thermophilus HB27. This enzyme shows similarity to two previously investigated thermostable type-2 amidases, the Ts2631 and Ph2119 from Thermus scotoductus bacteriophages, that revealed high lytic activity not only against thermophiles but also against Gram-negative mesophilic bacteria. Therefore, antibacterial potential of the PhiKo endolysin was investigated in the study presented here. Enzyme activity was assessed using turbidity reduction assays (TRAs) and antibacterial tests. Differential scanning calorimetry was applied to evaluate protein stability. The Collection of Anti-Microbial Peptides (CAMP) and Antimicrobial Peptide Calculator and Predictor (APD3) were used to predict regions with antimicrobial potential in the PhiKo primary sequence. The minimum inhibitory concentration (MIC) of the RAP-29 synthetic peptide was determined against Gram-positive and Gram-negative selected strains, and mechanism of action was investigated with use of membrane potential sensitive fluorescent dye 3,3'-Dipropylthiacarbocyanine iodide (DiSC3(5)). The PhiKo endolysin is highly thermostable with melting temperature of 91.70°C. However, despite its lytic effect against such extremophiles as: T. thermophilus, Thermus flavus, Thermus parvatiensis, Thermus scotoductus, and Deinococcus radiodurans, PhiKo showed moderate antibacterial activity against mesophiles. Consequently, its protein sequence was searched for regions with potential antibacterial activity. A highly positively charged region was identified and synthetized (PhiKo105-133). The novel RAP-29 peptide lysed mesophilic strains of staphylococci and Gram-negative bacteria, reducing the number of cells by 3.7-7.1 log units and reaching the minimum inhibitory concentration values in the range of 2-31 μM. This peptide is unstructured in an aqueous solution but forms an α-helix in the presence of detergents. Moreover, it binds lipoteichoic acid and lipopolysaccharide, and causes depolarization of bacterial membranes. The RAP-29 peptide is a promising candidate for combating bacterial pathogens. The existence of this cryptic peptide testifies to a much wider panel of antimicrobial peptides than thought previously.

Multi-step semi-synthesis, structural characterization and growth factor interaction study of regiochemically sulfated diabolican polysaccharides

Diabolican is an exopolysaccharide (EPS) produced by Vibrio diabolicus HE800, a mesophilic bacterium firstly isolated from a deep-sea hydrothermal field. Its glycosaminoglycan (GAG)-like structure, consisting of a tetrasaccharide repeating unit composed of two aminosugars (N-acetyl-glucosamine and N-acetyl-galactosamine) and two glucuronic acid units, suggested to subject it to regioselective sulfation processes, in order to obtain some sulfated derivatives potentially acting as GAG mimics. To this aim, a multi-step semi-synthetic approach, relying upon tailored sequence of regioselective protection, sulfation and deprotection steps, was employed in this work. The chemical structure of the obtained sulfated diabolican derivatives was characterized by a multi-technique analytic approach, in order to define both degree of sulfation (DS) and sulfation pattern within the polysaccharide repeating unit, above all. Finally, binding affinity for some growth factors relevant for biomedical applications was measured for both starting diabolican and sulfated derivatives thereof. Collected data suggested that sulfation pattern could be a key structural element for the selective interaction with signaling proteins not only in the case of native GAGs, as already known, but also for GAG-like structures obtained by regioselective sulfation of naturally unsulfated polysaccharides.

Lignocellulolytic Potential of Microbial Consortia Isolated from a Local Biogas Plant: The Case of Thermostable Xylanases Secreted by Mesophilic Bacteria.

Lignocellulose biomasses (LCB), including spent mushroom substrate (SMS), pose environmental challenges if not properly managed. At the same time, these renewable resources hold immense potential for biofuel and chemicals production. With the mushroom market growth expected to amplify SMS quantities, repurposing or disposal strategies are critical. This study explores the use of SMS for cultivating microbial communities to produce carbohydrate-active enzymes (CAZymes). Addressing a research gap in using anaerobic digesters for enriching microbiomes feeding on SMS, this study investigates microbial diversity and secreted CAZymes under varied temperatures (37 °C, 50 °C, and 70 °C) and substrates (SMS as well as pure carboxymethylcellulose, and xylan). Enriched microbiomes demonstrated temperature-dependent preferences for cellulose, hemicellulose, and lignin degradation, supported by thermal and elemental analyses. Enzyme assays confirmed lignocellulolytic enzyme secretion correlating with substrate degradation trends. Notably, thermogravimetric analysis (TGA), coupled with differential scanning calorimetry (TGA-DSC), emerged as a rapid approach for saccharification potential determination of LCB. Microbiomes isolated at mesophilic temperature secreted thermophilic hemicellulases exhibiting robust stability and superior enzymatic activity compared to commercial enzymes, aligning with biorefinery conditions. PCR-DGGE and metagenomic analyses showcased dynamic shifts in microbiome composition and functional potential based on environmental conditions, impacting CAZyme abundance and diversity. The meta-functional analysis emphasised the role of CAZymes in biomass transformation, indicating microbial strategies for lignocellulose degradation. Temperature and substrate specificity influenced the degradative potential, highlighting the complexity of environmental-microbial interactions. This study demonstrates a temperature-driven microbial selection for lignocellulose degradation, unveiling thermophilic xylanases with industrial promise. Insights gained contribute to optimizing enzyme production and formulating efficient biomass conversion strategies. Understanding microbial consortia responses to temperature and substrate variations elucidates bioconversion dynamics, emphasizing tailored strategies for harnessing their biotechnological potential.

Improved postharvest quality attributes of sweet and sour cherry by using low pressure UVC versus light-emitting diodes (LEDs)

The aim of this study was to evaluate the effects of LPUVC253.7 nm and LEDs405.5 nm light on sweet and sour cherries, to assess the potential of post-harvest illumination for fruit shelf-life and quality extension. Fresh cherries were treated at several doses (up to 1.56 kJ m−2) in a lab design chamber. Microbiological parameters, total phenolic content, antioxidant activity, and quality properties such as weight loss, color, pH, and total soluble solids content, were assessed before and after illumination and during storage time up to 24 days at 4 and 25 °C. Studies on inactivation of natural fruit microbiota and artificially inoculated potential spoilage bacteria Pseudomonas syringae and Aureobasidium pullulans were performed. A maximum reduction of 1.89 and 1.66 log on total aerobic mesophilic bacteria and total mold and yeasts was obtained after light illumination at 253.7 nm on spiked cherry fruits. Regarding fruit quality properties, both light (LPUVC253.7 nm and LEDs405.5 nm) illumination caused no change (p > 0.05) in quality parameters compared with non-treated fruits.Industrial relevance: There is an increasing global demand from consumers for agricultural products high nutritional quality with no or minimal chemical preservatives. Postharvest physical ultraviolet-C (UVC) treatment before or during cold storage can inactivate microbial contaminants, alleviate low-temperature damage, reduce postharvest decay, and extend shelf life of fruits while improving chemical safety. The present study indicated that post-harvest LPUVC and LEDs illumination of cherries can be used as a clean and environmental forthcoming process to extend the shelf-life of fruits with highly preserved quality.

Use of encapsulated pomegranate seed oil in novel coarse and nanosized materials for improving the storage life of strawberry

Different-sized pomegranate seed oil-based emulsions (coarse (CsP) and nanoemulsions (NsP): 1246 and 325 nm) were successfully prepared. Strawberries treated with NsP and CsP showed a significant decrease (p < 0.05) in yeast-mold counts (TMY) by 1.80 log CFU g−1, and mesophilic aerobic bacteria counts (TMAB) decreased (p < 0.05) by 0.91 log CFU g−1, respectively. CsP- and NsP-treated strawberries had a TPC of 74.45 and 82.35 mg GAE kg−1, respectively, while control samples had a TPC of 44.24 mg GAE kg−1. The strawberries treated with NsP exhibited the highest antioxidant capacity with 179.44 mol TEAC g−1. After treatment with a coarse emulsion, severity levels of A. niger and B. cinerea were 60 and 73 % while the nanoemulsion treatment significantly reduced severity levels to 55.3 and 56 %. The coarse and nanoemulsions may have potential use within the food industry owing to their antioxidant and antifungal properties as well as their ability to enhance strawberry quality and function.