Log Unit Reduction Research Articles

Dose-dependent inactivation of Plasmodium falciparum in red blood cell concentrates by treatment with short-wavelength ultraviolet light.

Plasmodium species are naturally transmitted by Anopheles mosquitos. The parasite infects red blood cells (RBCs) and can be transfused with blood products. In non-endemic areas, the main risk of infection arises from travellers coming back and people immigrating from malaria-endemic regions. Endemic countries face a permanent risk of infection from transfusion-transmitted malaria (TTM). TTM may cause life-threatening complications in patients dependent on blood donations. This study aimed to investigate the efficacy of Plasmodium falciparum inactivation in RBC units by treatment with short-wavelength ultraviolet C (UVC) light in the absence of photochemical additives. RBC units were spiked with P. falciparum to a parasite density of 0.1%-1% and irradiated with up to 4.5 J/cm2 UVC. The parasite density of UVC-treated dilution series and untreated controls were compared over 3 weeks after irradiation. The lowest dose of 1.5 J/cm2 UVC led to a 3.1 log reduction in parasite load compared with the untreated control. The inactivation capacity was dose-dependent. Strikingly, 4.5 J/cm2 led to ≥5.3 log unit reduction, which was equivalent to a complete inactivation in two out of three experiments. Pathogen reduction with UVC light was previously shown to be effective for different bacteria and viruses, but the inactivation of parasites in RBC concentrates was not addressed until now. The present study provides evidence for significant inactivation of P. falciparum-infected RBCs by UVC light.

Distribution and dynamics of antibiotic resistance genes in sludge under discharge plasma oxidation

Antibiotic resistance genes (ARGs), emerging environmental contaminants, have been largely accumulated in sludge during wastewater treatment. Discharge plasma oxidation, an advanced oxidation technology, has been demonstrated as an effective strategy in sludge pretreatment. However, the effect of plasma oxidation on the distribution and dynamics of ARGs in sludge is unknown. Herein, the variations of four typical ARGs (tetC, tetW, blaTEM-1, aac(3)-Ⅱ) and one integron (intI-1) in sludge during discharge plasma treatment were investigated. The results showed that under low discharge voltage or short treatment time, weak plasma oxidation enriched the contents of ARGs and intI-1 in sludge (with 1.14 log unit maximum increment) via proliferating biomass or promoting horizontal gene transfer. Further increasing discharge voltage or prolonging treatment time, strong plasma oxidation eliminated target genes due to the destroyed bacteria or inhibited horizontal transfer of ARGs. Especially, the homogeneous condition greatly promoted the reduction of ARGs in liquid phase (up to 1.52 log unit reduction). Furthermore, the correlation analysis between intI-1 and ARGs implied that tetC and tetW abundances might be significantly affected by intI-1 through horizontal transfer. At the same time, the microbial communities in sludge were investigated to help understand the effect of plasma oxidation on ARGs variation. Notably, the most predominant phylum Proteobacteria and genus Acinetobacter resisted the oxidative infringement from plasma to maintain high relative abundances (52.05 % in solid phase and 84.10 % in liquid phase for Proteobacteria, 13.82 % in solid phase and 78.00 % in liquid phase for Acinetobacter at 20 kV). Meanwhile, the co-occurrence analysis between genes and dominant genera further showed that Romboutsia sp. might be a potential host bacteria of ARGs and intI-1 in solid phase, and Acidovorax sp., Parachlamydia sp., and Armatimonadetes_gp5 sp. might be the potential hosts of tetW, tetC, and intI-1 in liquid phase.

What is the most effective percentage of Rose Bengal on polyamide fabrics for the visible-light photoinactivation of Gram-positive bacteria?

Heterogeneous photocatalysts based on fabric materials have achieved great relevance for water disinfection. However, studies have yet to be performed looking for the best percentage of a photosensitizer on fabric, considering the 1O2 generation efficiency as well as the charge distribution of the dye fabrics surface for bacterial inactivation. Therefore, polyamide fabrics (PAF) dyed at different Rose Bengal (RB) percentages (RB-PAF) as an anionic photosensitizer were prepared to determine the best value for photodynamic inactivation of Gram-positive bacteria (Enterococcus faecalis). Time-resolved and steady-state emission measurements, as well as laser flash photolysis experiments, were also performed. RB-PAF at a percentage of 1% (on-weigth-of-fiber, o.w.f.) showed 100% inactivation efficiency against E. faecalis (reduction of more than 6 log10 units in the viable count) in only 15 min. Contrarily, fabrics with RB values of 0.5 or 3% (o.w.f.) showed no bacterial inactivation or only a small activity (1 log10 unit reduction), respectively. Results revealed that the effects observed by RB-PAF are mediated by 3RF* and the subsequent generation of 1O2. The insignificant photooxygenation of 9,10-dimethyl anthracene observed for RB-PAF at 0.5% explains the lack of bacterial inactivation, while the low effect observed for RB-PAF at 3% is produced by electrostatic repulsions between the anionic RB and the bacteria surface. These results reveal that in order to design newly dyed fabrics for disinfection, it is important to optimize the percentage of dye to avoid aggregation of photosensitizers and to obtain an adequate net negative charge distribution in the antimicrobial fabrics.

Effect of injection water ionic strength on estimating hydraulic parameters in a 3D sand tank using silica encapsulated magnetic DNA particles

We investigated the applicability of Silica encapsulated, superparamagnetic DNA particles (SiDNAmag) in determining aquifer hydraulic parameters at different ionic strengths (1 mM, 5 mM, and 20 mM phosphate buffer) of injection suspension. Thereto, in a homogeneous, unconsolidated sand tank we pulse - injected two uniquely sequenced SiDNAmag at two injection points. At 0.5 m and 0.8 m downstream from the injection points, we measured the concentration of SiDNAmags at three vertically distributed and two horizontally distributed sampling locations. We estimated the hydraulic parameter distributions from the SiDNAmag breakthrough curves through a Monte – Carlo approach and compared the parameter distributions with salt tracer breakthrough curves. Our results indicated that at all the ionic strengths, the times of peak concentrations, and the shapes of the breakthrough curves were similar to the salt tracer. As compared to the salt, a 1 – 3 log units reduction in the maximum effluent concentration of SiDNAmag was due to kinetic attachment. The attachment rate reduced from 1 mM to 5 mM phosphate buffer possibly due to competitive adsorption of phosphate onto the favourable attachment sites. SiDNAmag attachment rate further increased in 20 mM buffer suspension, possibly due to the compression of electric double layer and reduction in energy barrier for attachment. The parameter distributions of hydraulic conductivity (k), effective porosity (ne), longitudinal dispersivity (αL), vertical transverse dispersivity (αTV /αL) and horizontal transverse dispersivity (αTH /αL) estimated from the SiDNAmag and the salt tracer breakthrough curves were statistically similar. Our work contributes to the applicability of colloidal SiDNAmags for determining hydraulic parameters at different ionic strength conditions.

In vitro evaluation of probiotic properties and selenium bioaccumulation of lactic acid bacteria isolated from poultry gastrointestinal, as an organic selenium source

The purpose of this study was to examine the probiotic characteristics and selenium (Se) bioaccumulation potential of five Lactobacillus strains in vitro. Lactobacillus acidophilus, L. delbrueckii subsp. lactis, L. reuteri, L. gallinarum, and L. animalis were among the strains employed. As significant aspects of probiotics, identification, and evaluation of their survival potential in the gastrointestinal system were undertaken. Although all experimental Lactobacillus strains bioaccumulated Se (IV) concentrations in media culture, three Lactobacillus strains (L. animalis, L. gallinarum, and L. acidophilus) bioaccumulated the highest Se concentrations (23.08, 8.62, and 8.51 mg/g, respectively) after culture in the presence of 1.5 mg/ml sodium selenite. By disc diffusion, all isolates were evaluated for antibiotic susceptibility against six antibiotics, including ciprofloxacin, ampicillin, methicillin, streptomycin, tetracycline, and trimethoprim-sulfamethoxazole. Many of the isolates tested positive for resistance to some of the antibiotics utilized. The L. reuteri and L. gallinarum were found to be resistant to about 50% of the antibiotics that were tested. In terms of acid tolerance, L. animalis showed significant resistance at acidic pH by 1.72 log unit reduction whereas L. delbrueckii and L. galliinarum showed significant sensitivity at acidic pH (P > 0.05). Bile tolerance was addressed as an important aspect of the safety assessment for probiotics. There were variances in acid and bile tolerance among species, although all of them tolerated stress conditions to an acceptable degree. Upon comparing the various species, it was observed that L. gallinarum exhibited a significant decline in growth, as evidenced by a decrease of 1.39 log units in cell viability. On the other hand, L. acidophilus and L. animalis demonstrated remarkable bile tolerance, with 0.09 and 0.23 log unit reduction respectively (P < 0.05). These results suggest that L. animalis, L. gallinarum, and L. acidophilus, can be good candidates to evaluate them in vivo in further investigations due to their tolerance to acid, and bile, antibiotic resistance, and strong ability to bioaccumulate Se in chickens.

Importance of Pre-Milking Udder Hygiene to Reduce Transfer of Clostridial Spores from Teat Skin to Raw Milk.

Butyric acid producing clostridia (BAPC) cause the so-called late-blowing defect, a serious quality problem in semi-hard and hard cheeses. Late-blown cheeses are characterized by undesired slits and cracks, irregular eyes, and off-flavors due to excessive amounts of gas and organic acids produced by clostridia. Clostridial transfer to raw milk can occur during milking through dirty teats. Therefore, teat cleaning before milking is a key factor in preventing clostridial contamination of the milk. However, different cleaning methods are used, and little information is available on the efficacy of routine teat cleaning in reducing clostridial endospores. The main objectives of this study were to assess the extent of udder contamination with BAPC spores and to investigate the efficacy of routine teat cleaning on BAPC spore counts in milk. In a longitudinal study, eight dairy farms were visited during five sampling events. Clostridial spore counts were quantified from teat skin before and after routine teat cleaning, in pooled quarter milk samples from individual cows, and in bulk tank milk samples using a most probable number method. In addition, farm management data were collected periodically through a survey, and average cow cleanliness was assessed by a veterinarian. On average, teat cleaning resulted in a 0.6 log unit reduction in BAPC spores on teat skin, and a strong positive correlation was found between BAPC spore concentrations on teat skin after cleaning and in pooled quarter milk samples. Seasonal variations and the potential influence of differences in farm management were also noted. Interestingly, average cow cleanliness correlated strongly with BAPC spore levels in milk, suggesting the potential for a quick and rough estimation method of clostridial contamination that could be implemented by farmers.

Color-variable dual-dyed photodynamic antimicrobial polyethylene terephthalate (PET)/cotton blended fabrics.

The urgent demand for scalable, potent, color variable, and comfortable antimicrobial textiles as personal protection equipment (PPE) to help reduce infection transmission in hospitals and healthcare facilities has significantly increased since the start of the COVID-19 pandemic. Here, we explored photodynamic antimicrobial polyethylene terephthalate/cotton (TC) blended fabrics comprised of photosensitizer-conjugated cotton fibers and polyethylene terephthalate (PET) fibers dyed with disperse dyes. A small library of TC blended fabrics was constructed wherein the PET fibers were embedded with traditional disperse dyes dominating the fabric color, thereby enabling variable color expression, while the cotton fibers were covalently coupled with the photosensitizer thionine acetate as the microbicidal agent. Physical (SEM, CLSM, TGA, XPS and mechanical strength) and colorimetric (K/S and CIELab values) characterization methods were employed to investigate the resultant fabrics, and photooxidation studies with DPBF demonstrated the ability of these materials to generate reactive oxygen species (i.e., singlet oxygen) upon visible light illumination. The best results demonstrated a photodynamic inactivation of 99.985% (~ 3.82 log unit reduction, P = 0.0021) against Gram-positive S. aureus, and detection limit inactivation (99.99%, 4 log unit reduction, P ≤ 0.0001) against Gram-negative E. coli upon illumination with visible light (60min; ~ 300mW/cm2; λ ≥ 420nm). Enveloped human coronavirus 229E showed a photodynamic susceptibility of ~ 99.99% inactivation after 60min illumination (400-700nm, 65 ± 5mW/cm2). The presence of the disperse dyes on the fabrics showed no significant effects on the aPDI results, and furthermore, appeared to provide the photosensitizer with some measure of protection from photobleaching, thus improving the photostability of the dual-dyed fabrics. Taken together, these results suggest the feasibility of low cost, scalable and color variable thionine-conjugated TC blended fabrics as potent self-disinfecting textiles.

Sustainable Water Treatment with Induced Bank Filtration

This study demonstrates that an induced bank filter (IBF) system can treat raw water polluted with Escherichia coli (E. coli) bacteria. Similar to riverbank filtration (RBF), induced or reversed bank filtration relies on natural processes to clean water, including filtration through layers of allochthone alluvial sediments and a bioactive layer that forms on top of the filter after a ripening period. At the study site, located in Southwestern India, villagers rely on a mountain spring for their water supply. Although of generally high quality, the spring water contains E. coli bacteria (up to ~2000 MPN/100 mL). Raw water diverted from this spring was gravity-fed into the IBF system, which consisted of a (1) flow regulator, (2) pre-filter and (3) the actual IBF filter. Designed and constructed based on pilot testing of prototype filters, a full-scale filter (5 m by 7 m by 2 m) was built and its performance and maintenance requirements were studied during both the monsoon season and the dry season. The data show that the IBF significantly improved the water quality. Turbidity and E. coli concentrations were reduced to or below the detection limit (approximately 2.5 log unit reduction). During the peak of the monsoon season (August), E. coli was present in the IBF effluent after a storm destroyed the cover of the IBF tank. The IBF construction and maintenance costs were documented. Extrapolated over a 10-year period, the cost of IBF water was 3 and 10 times lower than reverse osmosis or water supplied by truck, respectively. This study demonstrates that IBF can be part of an affordable water supply system for rural villages in mountainous terrain where conventional RBF systems cannot be installed or where other water treatment technologies are out of financial reach.

Characterization of Planktochlorella nurekis Extracts and Virucidal Activity against a Coronavirus Model, the Murine Coronavirus 3.

Certain members of the Coronaviridae family have emerged as zoonotic agents and have recently caused severe respiratory diseases in humans and animals, such as SARS, MERS, and, more recently, COVID-19. Antivirals (drugs and antiseptics) capable of controlling viruses at the site of infection are scarce. Microalgae from the Chlorellaceae family are sources of bioactive compounds with antioxidant, antiviral, and antitumor activity. In the present study, we aimed to evaluate various extracts from Planktochlorella nurekis in vitro against murine coronavirus-3 (MHV-3), which is an essential human coronavirus surrogate for laboratory assays. Methanol, hexane, and dichloromethane extracts of P. nurekis were tested in cells infected with MHV-3, and characterized by UV-vis spectrophotometry, nuclear magnetic resonance (NMR) spectroscopy, ultraperformance liquid chromatography-mass spectrometry (UPLC-MS), and the application of chemometrics through principal component analysis (PCA). All the extracts were highly efficient against MHV-3 (more than a 6 Log unit reduction), regardless of the solvent used or the concentration of the extract, but the dichloromethane extract was the most effective. Chemical characterization by spectrophotometry and NMR, with the aid of statistical analysis, showed that polyphenols, carbohydrates, and isoprene derivatives, such as terpenes and carotenoids have a more significant impact on the virucidal potential. Compounds identified by UPLC-MS were mainly lipids and only found in the dichloromethane extract. These results open new biotechnological possibilities to explore the biomass of P. nurekis; it is a natural extract and shows low cytotoxicity and an excellent antiviral effect, with low production costs, highlighting a promising potential for development and implementation of therapies against coronaviruses, such as SARS-CoV-2.

Performance assessment of a modified trickling filter and conventional activated sludge process along with tertiary treatment in removing emerging pollutants from urban sewage

The absence of effective wastewater treatment technology to eliminate emerging pollutants from municipal sewage has become a pressing issue. In this study, the efficacy of a novel modified trickling filter (MTF), conventional activated sludge process (ASP) and two tertiary systems (UV and ozonation) were compared in eliminating antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs) and pharmaceuticals and personal care products (PPCPs) from urban sewage. MTF and ASP resulted in >1 log unit reduction in the abundance of ARB, while for ARGs, the removal was observed in the range of 0.1 to 1.7 log units. In MTF, ARGs were substantially removed in the aerobic zone compared to the anoxic zone. The relative abundance of most of the ARGs either decreased or remained unchanged during MTF and ASP operations. However, the relative abundance of most of the ARGs increased in the secondary sludge generated from ASP. The concentration of PPCPs such as atenolol, sulfamethazine, triclosan, and ranitidine was reduced by MTF by >80 %. Overall, the results indicated that MTF followed by ozonation is the most effective combination for removing emerging contaminants from municipal sewage.

Biofilm microenvironment response nanoplatform synergistically degrades biofilm structure and relieves hypoxia for efficient sonodynamic therapy

Treatment of bacterial biofilms remains a great challenge in the clinic. Recently, ultrasound (US)-driven antimicrobial sonodynamic therapy (aSDT) has been considered as an emerging therapeutic strategy for the treatment of biofilm infections. However, the hypoxic microenvironment and restricted diffusion of sonosensitizers within biofilms substantially reduce the therapeutic efficacy of aSDT. Herein, a biofilm microenvironment-responsive nanoplatform was proposed to promote biofilm degradation and sonosensitizer penetration, and relieve the hypoxic microenvironment, thereby augmenting aSDT efficiency against bacterial biofilm infections. This nanoplatform was prepared by modifying manganese dioxide nanosheets (MNS) with α-amylase, polyethylene glycol (PEG), and chlorin e6 (Ce6) to form MNS-α-amylase/PEG-Ce6 nanosheets (MAPC). After delivery into biofilm-infected tissues, MAPC decompose in the acidic biofilm microenvironment to locally release α-amylase and Ce6. The α-amylase degrades the extracellular polymeric substances of biofilms to promote Ce6 penetration. In addition, the MNS catalyze the conversion of endogenously overproduced H2O2 into O2 in infected tissue and relieve the hypoxic microenvironment to further enhance antibiofilm efficacy of aSDT. Such biofilm degradation and hypoxia-relief enhanced aSDT show approximately 6.9 log units (99.99998%) reduction of bacteria within biofilms in vitro, and efficiently treat methicillin-resistant Staphylococcus aureus (MRSA) biofilms-infected mice. Overall, biofilm degradation improves sonosensitizer penetration and relieves the hypoxic biofilm microenvironment to enhance the effects of aSDT by MAPC. Thus, the use of this nanoplatform provides a promising strategy for combating bacterial biofilm-associated infections.

Cecropin A Improves the Antibacterial Activity of Hen Egg White Lysozyme against Challenging Salmonella enterica Serovars.

The prevalence of multidrug-resistant Salmonella enterica among animal- and plant-derived food products threatens global healthcare and economic sectors. Hen egg white lysozyme is widely exploited as a food preservative against Gram-positive pathogens. Nevertheless, its limited penetration of the outer membrane renders it ineffective against Gram-negative bacteria. Herein, we present a safe and effective approach to facilitate HEWL access to peptidoglycan layers using cecropin A. In silico analysis of cecropin A peptide revealed an amphipathic α-helical peptide with potential outer membrane permeabilizing activity through its interaction with both hydrophobic and ionic stabilizing forces. Evaluation of HEWL/cecropin A combination showed a cecropin A dose-dependent bacterial count reduction up to 4.16 and 3.18 ± 0.26 log units against Salmonella enterica ATCC 35664 at the logarithmic and stationary growth phases, respectively. Moreover, the combination displayed antibacterial activity of 2.1 ± 0.31 and ~1 log-unit reductions against Salmonella enterica serovars Kentucky, Typhimurium, and Enteritidis, respectively, whereas Hato and Shangani were found irresponsive. The cytotoxicity assay revealed compatibility of cecropin A with oral epithelial cells. These observations suggest HEWL/cecropin A combination as an effective and safe alternative to lysozyme against Salmonella enterica.

Plasma treatment effects on destruction and recovery of Porphyromonas gingivalis biofilms.

The objective of this study was to investigate the treatment effects of non-thermal atmospheric gas plasmas (NTAP) on destruction and the recovery (or re-colonization) of Porphyromonas gingivalis (P. gingivalis) in biofilms. P. gingivalis is a well-known keystone periodontal pathogen strongly associated with periodontal diseases, especially periodontitis. P. gingivalis biofilms were formed on stainless steel coupons and treated for 1, 2, and 5 minutes by NTAP of pure argon gas and argon+oxygen gas mixture. MTT assay, colony forming unit (CFU) counting assay and confocal laser scanning microscopy (CLSM) were used to assess the destruction efficiency. In addition, the plasma treated biofilms were re-cultured in the medium supplemented with antibiotics and oxidative stress sources to determine the synergy of the NTAP with other antimicrobial agents. The results showed the plasma treatment could result in 2.7 log unit reduction in bacterial load. The recovered biofilm CFU with NTAP treatment combined with sub minimal inhibition concentration of amoxicillin was 0.33 log units less than the biofilm treated with amoxicillin alone. The recovered biofilm CFU in NTAP groups was about 2.0 log units less than that in the untreated controls under H2O2 treatment. There was approximately 1.0 log unit reduction of biofilm CFU in plasma treated biofilm compared with untreated control under paraquat treatment. The plasma treated biofilms exhibited less resistance to amoxicillin and greater susceptibility to hydrogen peroxide (H2O2) and paraquat, suggesting that NTAP may enhance biofilm susceptibility to host defense. These in vitro findings suggested that NTAP could be a novel and effective treatment method of oral biofilms that cause periodontal diseases.

Effects of ruminal protozoa on methane emissions in ruminants—A meta-analysis

The effects of different ruminal protozoa (RP) on CH4 emissions from ruminants were evaluated in a meta-analysis, using 64 publications reporting data from 79 in vivo experiments. Experiments included in the database reported CH4 emissions (g/d) and total RP (TRP, log10 cells/mL) from the same group of animals. The relationship between CH4 emissions and RP (TRP, entodiniomorphids, and isotrichids), and TRP-, entodiniomorphid-, and isotrichid-based CH4 emission prediction models, were evaluated as mixed models with experiment as a random effect and weighted by the reciprocal of the standard error of the mean and centered around one. Positive associations existed between TRP and isotrichids with CH4 emissions but not between entodiniomorphids and CH4 emissions. A reduction in CH4 emissions was observed, averaging 7.96 and 4.25 g/d, per log unit reduction in TRP and isotrichid concentrations, respectively. Total RP and isotrichids were important variables in predicting CH4 emissions from ruminants. Isotrichid CH4 prediction model was more robust than the TRP, evidenciated by lower predicted sigma hat study (%), and error (%), and with higher concordance correlation coefficient. Both TRP and isotrichid models can accurately predict CH4 emissions across different ruminant types, as shown by the low square root of the mean square prediction error, with 6.59 and 4.08% of the mean of root of the mean square prediction error in the TRP and isotrichid models, respectively. Our results confirm that isotrichids are more important than entodiniomorphids in methanogenesis. Distinguishing these 2 populations yielded a more robust CH4 prediction model than combining them as total protozoa.

The use of bacteriophage-based edible coatings for the biocontrol of Salmonella in strawberries

The physicochemical quality and the effectiveness of antimicrobial activity against Salmonella and phage stability of dip-coated strawberries were investigated in this study by using bacteriophage cocktail with four different biopolymers for a period of 5 day at +4°Ϲ. The biopolymers used in this study were whey protein concentrate (WPC), carboxymethyl cellulose (CMC), chitosan (CH), and sodium alginate (SA). The phage cocktail was prepared using S. Enteritidis and S. Typhimurium obtained from the phages isolated from different environmental sources as host bacteria. Uncoated fruit was used as a control. The color, pH, and titratable acidity (TA) of strawberry samples and the stability and antimicrobial activity of bacteriophages during storage were also investigated. Amongst all the biopolymers, WPC coating showed the least escalation in pH and the least decrease in TA. During storage, 0.7 log-unit (PFU/g) reduction in WPC coating with the bacteriophage cocktail was observed. The highest antimicrobial effect was observed in WPC with a reduction of 3.1 log (CFU/g) after 5 days when the multiplicity of infection was 1000. In the light of the results, it was concluded that the phage loaded WPC coating had much better physicochemical and microbiological quality during refrigerated storage; therefore, it could be used effectively to extend the postharvest life of strawberries.

Active Composite Packaging Reinforced with Nisin-Loaded Nano-Vesicles for Extended Shelf Life of Chicken Breast Filets and Cheese Slices.

To meet the demands for more effective and ecofriendly food packaging strategies, the potential of nisin-loaded rhamnolipid functionalized nanofillers (rhamnosomes) has been explored after embedding in hydroxypropyl-methylcellulose (HPMC) and κ-carrageenan (κ-CR)-based packaging films. It was observed that intrinsically active rhamnosomes based nanofillers greatly improved the mechanical and optical properties of nano-active packaging (NAP) films. Incorporation of rhamnosomes resulted in higher tensile strength (5.16 ± 0.06 MPa), Young’s modulus (2777 ± 0.77 MPa), and elongation (2.58 ± 0.03%) for NAP than active packaging containing free nisin (2.96 ± 0.03 MPa, 1107 ± 0.67 MPa, 1.48 ± 0.06%, respectively). NAP demonstrated a homogenous distribution of nanofillers in the biopolymer matrix as elucidated by scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) confirmed that NAP prepared with nisin-loaded rhamnosomes was thermally stable even above 200 °C. Differential scanning calorimetry (DSC) analyses revealed that addition of nisin in nanofillers resulted in a slight increase in Tg (108.40 °C), indicating thermal stability of NAP. Fourier transform infrared spectroscopy (FTIR) revealed slight shift in all characteristic bands of nano-active packaging, which indicated the embedding of rhamnosomes inside the polymer network without any chemical interaction. Finally, when tested on chicken breast filets and cheese slices under refrigerated storage conditions, NAP demonstrated broad-spectrum antimicrobial activity (up to 4.5 log unit reduction) and inhibited the growth of Listeria monocytogenes, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. These results suggest that HPMC and κ-CR-based NAP containing functionalized nanofillers can serve as an innovative packaging material for the food industry to improve the safety, quality, and shelf-life of dairy and meat products.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11947-022-02815-2.

An extraordinary dairy phage and its properties: Occurrence, growth, inactivation, survival

Lactococcus lactis phages can be very heat resistant and phage P680 survive pasteurisation. In this work, phage growth, thermal and non-thermal as well as chemical methods were presented together and re-evaluated in the elimination of P680. A fermentation failure within 2 h can occur under the presence of phage P680, which survived heating at 95 °C for 5 min. Up to 4 log units of reduction could be achieved using membrane filtration (cut-off 100 nm). In case of ultraviolet-C treatment, doses up to 0.05 J cm−2 and 4 J cm−2 were required for phage P680 to achieve 6 log units reduction in water and 8 log units reduction in filtered whey. Phage P680 was mostly resistant at pH levels of 3 and 10 (<0.5 log reduction), however, a significant drop of the phage levels was observed at pH values of 2 and 12 (∼6 log units of reduction).

Anti-Colonization Effect of Au Surfaces with Self-Assembled Molecular Monolayers Functionalized with Antimicrobial Peptides on S. epidermidis.

Medical devices with an effective anti-colonization surface are important tools for combatting healthcare-associated infections. Here, we investigated the anti-colonization efficacy of antimicrobial peptides covalently attached to a gold model surface. The gold surface was modified by a self-assembled polyethylene glycol monolayer with an acetylene terminus. The peptides were covalently connected to the surface through a copper-catalyzed [3 + 2] azide-acetylene coupling (CuAAC). The anti-colonization efficacy of the surfaces varied as a function of the antimicrobial activity of the peptides, and very effective surfaces could be prepared with a 6 log unit reduction in bacterial colonization.

Orthogonal processing strategies to create “phage-free” whey – Membrane filtration followed by thermal or ultraviolet C treatment for the reduction of Lactococcus lactis bacteriophages

Lactococcal bacteriophages can cause fermentation failures in the cheese production (e.g., Cheddar), especially when the by-product whey (≤109 plaque-forming units mL−1 of bacteriophages) is recycled and added to new batches. Using membrane filtration, the bacteriophage titre in whey can be reduced by 4 log units without protein denaturation. To achieve higher bacteriophage reduction (≥9 log units), we attempted an orthogonal process strategy (combination of different technologies supporting each other). Three representative bacteriophages were inactivated in membrane filtered whey by (i) UV-C irradiation and (ii) heat treatment to achieve additional 5 log units reduction. Thermal treatment was only partially successful, as the varying degrees of heat resistance required, in the worst-case, temperature-time combinations above pasteurisation conditions. In contrast, UV-C treatment required doses of maximally 2.25 J cm−2 for successful inactivation, thus representing a promising avenue for the establishment of a novel process for the production of “phage-free” whey.

Surface chemistry-dependent antiviral activity of silver nanoparticles

The toxicity towards viruses of silver nanoparticles (AgNPs) has been reported to be dependent on several factors such as particle concentration, size, and shape. Although these factors may indeed contribute to the toxicity of AgNPs, the results presented in this work demonstrate that surface chemistry and especially surface charge is a crucial factor governing their antiviral activity. Here, this work investigated the influence of capping agents representing various surface charges ranging from negative to positive. These AgNPs were capped with citrate, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) mercaptoacetic acid (MAA) and (branched polyethyleneimine (BPEI). We show that AgNPs exhibited surface charge-dependent toxicity towards MS2 bacteriophages. Among the capping agents under investigation, BPEI capped AgNPs (Ag/BPEI) exhibited the highest reduction of MS2 resulting in ≥6 log10-units reductions, followed by 4–5 log10-units reductions with PVP and PEG capping’s and 3–4 log10-units with MAA and citrate cappings. Bare nanoparticles reported a mere 1–2 log10-units reduction. Electrostatic interaction between the positively charged BPEI-coating and the negatively charged virus surface played a significant role in bringing the MS2 closer to toxic silver ions (Ag+). Further results obtained from TEM showed that Ag/BPEI nanoparticles could directly damage the structure of the MS2 bacteriophages. AgNPs and cationic capping agents’ observed synergy can lead to much lower and much more efficient dosing of AgNPs for antiviral applications.