Steel Coupons Research Articles

Corrosion of carbon steel in artificial soil: Processes occurring during wet/dry transitions studied with a multi-coupon electrode

A multi-coupon electrode, composed of 16 square (5 mm × 5 mm) carbon steel coupons, was buried at room temperature during 125 days in an artificial silt loam soil. The soil was initially set at 75% of the saturation with a 0.01 M NaCl + 0.01 M NaHCO3 solution in a specific electrochemical cell. The experimental cell was hermetically closed for 32 days before to be opened so that the effects induced by the progressive drying of the soil could be studied. The OCP and the soil electrolyte resistance Rs, determined by electrochemical impedance spectroscopy, were then monitored over time for each coupon. During the drying process, different behaviors were observed for the various coupons, demonstrating the heterogeneity of this process. XRD analysis of the corrosion product layer covering each coupon at the end of the experiment revealed significant variations of composition from one coupon to another. The composition of the corrosion product layers could be interpreted in link with the OCP and Rs measured values.

Multi-functional Flow Assurance Chemicals: Corrosion and Kinetic Hydrate Inhibition from Maleic Anhydride:N-Vinyl Caprolactam Copolymers and Synergists

Water-based flow assurance issues include corrosion, scale, and gas hydrate formation. Chemical solutions to mitigate these issues usually require separate inhibitors, which sometimes can lead to compatibility difficulties. Herein, we report studies on maleic-based copolymers to combat hydrate and corrosion with a view to optimizing for scale inhibition also. The product of maleic anhydride:N-vinyl caprolactam copolymer reacted with 3-dibutylaminopropylamine (MA:VCap-DBAPA) and its amine oxide derivative (MA:VCap-DBAPA-AO) were the kinetic hydrate inhibitor (KHI) polymers investigated. Due to limited CO2 corrosion inhibition (CI) by the polymers alone, various oxygen-, sulfur-, and nitrogen-based additives were screened for improved CO2 CI and possible KHI synergy. KHI performance screening tests were conducted under high pressure with a structure II-forming natural gas mixture in steel rocking cells using the slow (1 °C/h) constant cooling method. CO2 corrosion inhibition was measured by linear polarization resistance in a stirred 1 L CO2 bubble test apparatus using C1018 steel coupons and 3.6 wt % brine at 20.5 °C. Several sulfur-based additives improved the CI efficiency of the maleic polymers, especially butyl thioglycolate and 2-aminoethanethiol, without a negative effect on the KHI performance. For example, 2500 ppm MA:VCap-DBAPA plus 1000 ppm butyl thioglycolate gave an average hydrate onset temperature (To) of 4.4 °C (12.7 °C below the To for no additive) and 99.7% CI efficiency. In contrast to a classic fatty acid imidazoline surfactant corrosion inhibitor, butyl thioglycolate was also found to greatly enhance the CI efficiency of industrial KHIs, poly(N-vinyl caprolactam) (PVCap) and N-vinyl pyrrolidone:N-vinyl caprolactam copolymer, with no antagonism to the KHI performance of the polymer. In addition, butyl thioglycolate boosted the KHI performance of PVCap. The use of small synergists such as butyl thioglycolate avoids the use of classical surfactant corrosion inhibitors which can lead to tighter emulsions and poor overboard oil-in-water quality.

Chemical Solution Deposition of Protective Er2O3 and Y2O3 Coatings onto Stainless Steel for Molten Metal Casting using Metal-Nitrate Precursors.

Chemical solution deposition (CSD) methods involving the thermal decomposition of 5.0 M Er(NO3)3·5H2O and Y(NO3)3·6H2O precursor solutions were employed to fabricate protective erbia and yttria coatings onto stainless steel (SS304/SS316) coupons. The two techniques tested were dip and spray coating, which were then compared to a commercial yttria spray (ZYP Coatings). It was determined that solution concentration, solvent choice, injection of Er2O3 and Y2O3 micropowder, and the annealing temperature/ramp profile were critical to the coatings' physical properties. For dip coatings, thicknesses were 1-20 μm after two dipping/annealing cycles, and adhesion strength was ∼1000 psi, increasing up to ∼1300 psi if the SS coupons had preliminary sandblasting. Spray coatings from precursor solutions were reported to have thicknesses of 20-80 μm and adhesion strength less than 500 psi (regardless of the coupon surface finish). Cross-sectional views of the coatings confirmed subsurface porosity, and XRD results indicated that the coatings were polycrystalline, with patterns typical to that of cubic Er2O3 and Y2O3.

Comparison of a standard environmental surface sampling method and a composite approach for select healthcare pathogens

Background: Hospital surfaces are known to contribute to the spread of healthcare-associated infections (HAIs). Environmental sampling is often performed to locate a reservoir or to evaluate intervention strategies in healthcare facilities. Composite sampling is commonly practiced in other fields of environmental sampling and involves collection of multiple samples combined entirely or partially to form a new sample. We compared a standard CDC surface whole-tool sampling method with a composite sampling approach. Methods:Acinetobacter baumannii (AB), Klebsiella pneumoniae that produce K. pneumoniae carbapenemase (KPC), vancomycin-resistant Enterococcus faecalis (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and Clostridioides difficile spores were suspended in an artificial soil and deposited as 40 µL droplets (~104 CFU total) onto steel coupons of surface areas 323 cm2, 645 cm2, or 1,290 cm2 and dried for 2 hours. The surfaces were sampled with a single pass of a cellulose sponge— either the larger side of the sponge (face) or the smaller side of the sponge (edge)—and the optimal surface area was determined. Recovery from the optimal surface area with a single pass sampling was compared to the recovery using a standard CDC method in which all sides were used (ie, whole-tool method) to sample a standard area (645 cm2). Recovery was determined by culture and total CFU were determined for each optimal surface area. Theoretical composites were constructed using the mean total CFU of optimal surface area; 2×((face) + (edge)). Significance was set at P ≤ .05. Results: Total CFU recovery using the whole-tool method was significantly greater than the single pass sample recovery for MRSA (18,300 vs 16,600 CFU) and VRE (27,600 vs 26,400 CFU) (P < .05). When comparing the theoretical composite method to the standard whole-tool area (625 cm2), the theoretical composite total CFU was significantly greater than the whole-tool method for all organisms. For example, VRE recovery with the standard CDC whole-tool method was 27,600 CFU from 625 cm2, yet a theoretical composite approach recovered 79,800 CFU from an area of 1,290 cm2. Conclusions: Many factors influence recovery when sampling the environment, and composite sampling is a promising approach when sampling large surface areas. Using a theoretical composite of single-pass samples, the potential for improved detection with composite sampling was demonstrated. A composite sampling approach will reduce time and resources for sampling and sample processing, allowing larger surface areas to be investigated which will improve infection control strategies.Disclosures: None

Long-term aqueous contamination of stainless steel in simulant nuclear reprocessing environments

Stainless steels are contaminated with a wide range of radionuclides over time when exposed to the harsh acidic environments in nuclear reprocessing facilities. Existing research into the contamination of stainless steel with problematic radionuclides has predominantly focused on single-contaminant systems. Hence a more comprehensive understanding is a necessity for the development and optimisation of decontamination and decommissioning strategies, thus minimising waste volumes and associated costs. This work aims to understand contaminant uptake behaviour on AISI 304 stainless steel in a mixed element system (Cs, Sr) over extended time periods (up to 420 days) and the effects of temperature and surface finish on contaminant uptake over shorter time periods (up to 28 days). Steel coupons were immersed in 12 M HNO3 to accelerate corrosion with both caesium and strontium ions (1 mM) and maintained at 50 °C. The extent of uptake was assessed through solution analysis using ICP-OES, identifying that strontium uptake exceeded caesium's in all tested scenarios, with maximum uptake values of 0.208 g m−2 and 0.170 g m−2 obtained at 50 °C for strontium and caesium, respectively. Kinetic modelling confirmed that uptake followed pseudo-second order behaviour. Stainless steel coupons were characterised after exposure, which found grain dropping and bulk dissolution had occurred after 420 days, leading to reduced levels of surface uptake. X-ray Photoelectron Spectroscopy found evidence of caesium and strontium chromates formed via co-precipitation with chromium corrosion products, confirming observations by previous studies. Furthermore, depth profiling with LA-ICP-MS found evidence of contaminants diffusing into the bulk substrate (by 30 - 40 nm), which has significant implications for the development and optimisation of decontamination approaches which can minimise excess waste generation.

Testing protective coatings for metal conservation: the influence of the application method

The lack of a standardised methodology for the application of coatings on heritage metals can lead to non-comparable results. A careful and meaningful study requires considering the different application variables involved, especially in the preparation of the coupons. In this work, the effect that these application variables can have on the protective capacity of the coatings used has been studied. The influence of the thickness, number of layers and drying time (between layers and final) of Paraloid B-72, C80 microcrystalline wax and Incralac has been evaluated. Coatings have been applied on bare steel coupons, thickness measured with an induction probe, and subject to artificial ageing on UV light/water condensation cycles. The performance of the coatings has been studied by visual inspection and electrochemical impedance spectroscopy (EIS). Morphology of the layers has been characterised by optical microscopy and the composition of the corrosion products by Raman spectroscopy. Results show that the number of layers is not always proportional to the final thickness of the coating, and that drying time is a critical factor affecting the thickness and the protective properties of the coatings. After accelerated ageing, some coatings that had been left to dry for 14 days have a much better protective capacity than those that were left to dry for less time. Without taking into account these factors, performance measured can be wrong and comparison between materials misleading.

Roughness-controlled cell-surface interactions mediate early biofilm development in drinking water systems

Bacterial colonization onto interior pipe walls is ubiquitous in drinking water systems, with the inevitable consequences on water quality safety. However, the mechanisms of how physicochemical properties of pipe materials interfering with cell-surface interactions and subsequent biofilm colonization in drinking water systems have not been fully unveiled. In this study, we investigated initial biofilm colonization onto polyvinyl chloride (PVC), polyethylene (PE) and stainless steel (STS) coupons having various surface roughness during one week incubation in bench reactors. Results display that increased surface roughness encouraged biofilm formation particularly on plastic materials. With the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) modeling analysis, the increment in surface roughness enlarged superficial area and hydrophobicity that reinforced van der Waals force and acid-base bacteria-surface interactions, thereof facilitating biofilm initialization and consequent accumulation. Meanwhile, the PVC and PE coupons attracted around six-fold and four-fold adhesive cells in contrast to the STS ones with the roughness of ∼1.50 µm, respectively. Unlike the STS that induced hydrophilic (repulsive) interactions, plastic materials encouraged hydrophobic (attractive) acid-base interactions and bacterial surface adhesion, accordingly contributing to ensuing colonization. Increasing ionic strength (1–100 mM) further stimulated initial colonization associated with compressed electrical double layer and decreased electrokinetic potential that reduced the energy barriers for bacterial cells. These findings reveal that early biofilm development is a pipe material and roughness-controlled process, which provide new insights into the mechanistic understanding of the ever-growing biofilms in drinking water systems.

Impact of gas ultrafine bubbles on the efficacy of antimicrobials for eliminating fresh and aged Listeria monocytogenes biofilms on dairy processing surfaces

AbstractUltrafine bubbles (UFB) are a novel concept that has the potential to enhance the potency of antimicrobials to eliminate biofilms. This study investigated the impact of incorporating gas (air, CO2, and N2) UFB on the potency of chlorine (Cl2; 50, 100, and 200 ppm) and peracetic acid (PAA; 20, 40, and 80 ppm) antimicrobial (AM) solutions against fresh (3 days) and aged (30 days) Listeria monocytogenes biofilms on polypropylene, silicone, and stainless steel surfaces. Listeria monocytogenes biofilms were statically grown on polypropylene, silicone, and stainless steel coupons (7.62 × 2.54 cm) at 25°C for 3 or 30 days, by immersing in a three‐strain cocktail of L. monocytogenes in brain heart infusion (BHI) broth. The coupons were treated by submerging in AM solutions with or without UFB for 1 min, then swabbed into Dey‐Engley neutralizing broth and enumerated on BHI agar. Incorporation of air, CO2, and N2 UFB in AM solutions resulted in significantly increased log reductions (0.4–1.5 logs) of fresh and aged L. monocytogenes biofilms on polypropylene and stainless steel surfaces, whereas incorporation of CO2 UFB in AM solutions resulted in ~1 log greater reductions of fresh and aged L. monocytogenes biofilms on silicone surfaces compared with AM solutions without UFB. This study also demonstrated that 200 ppm Cl2 was most effective against fresh and aged L. monocytogenes biofilms on polypropylene, silicone, and stainless steel surfaces compared with 50 ppm Cl2, 20 ppm PAA, and 40 ppm PAA.

Two metabolic stages of SRB strain Desulfovibrio bizertensis affecting corrosion mechanism of carbon steel Q235

Desulfovibrio bizertensis (D. bizertensis), an SRB isolated and cultured from the rust layer of the South China Sea, is widespread in the corrosive microbial communities on steel surface. Although the corrosion mechanism of SRB was widely studied, the mechanism of different metabolic stages inducing corrosion was still unclear. In this work, D. bizertensis was used to study the corrosion process of carbon steel Q235 at different metabolic stages by surface analysis and electrochemical methods. Combined with the metabolic process of SRB, corrosion pits of carbon steel could be influenced by two stages. In the first stage, the rapid growth of planktonic D. bizertensis cells in culture medium was accompanied by quick consumption of the electron donor (lactate) till complete consumption. D. bizertensis cells began to adhere to Q235 surface and promote anodic dissolution of iron. In the second stage, the growth of planktonic cells was suppressed, thus the colonized D. bizertensis cell in the pitting could obtain energy directly from Fe(0) through DET, which would further aggravate pitting corrosion and the maximum depth of the pits approached 15.7 µm. Sulfides produced by D. bizertensis metabolism would accumulate on steel coupon and form FeS coverage. Thus D. bizertensis could survive for a long time in this conductive FeS particles network. Electrochemical results showed the promotion effect of D. bizertensis on cathodic reaction, and the values of Rct in the SRB medium were much lower than that in the sterile medium.

Stability of SARS-CoV-2 variants of concern (Delta and Omicron) on surfaces at room temperature

Surfaces contaminated with infectious SARS-CoV-2 particles have the potential to cause human infection and any increase in surface survivability of a SARS-CoV-2 variant may increase its prevalence over other variants. This study investigated whether there were differences in surface persistence between Delta and Omicron variants leading to Omicron's dominance globally.Stainless steel coupons were inoculated with suspensions of either Delta or Omicron variant and exposed to typical environmental conditions within a containment level 3 laboratory. Coupons were recovered at different timepoints and enumerated using plaque assay.Both variants were recoverable for >48 h on the coupons. Omicron showed a greater reduction of viability after 48 h compared to Delta with a 20-fold decrease versus 15-fold respectively, but this difference was not statistically significant (p = 0.424). These results indicate that Omicron's surface persistence is unlikely to contribute to it becoming the dominant variant over Delta.

Role of Microbial Interactions across Food-Related Bacteria on Biofilm Population and Biofilm Decontamination by a TiO2-Nanoparticle-Based Surfactant.

Microbial interactions play an important role in initial cell adhesion and the endurance of biofilm toward disinfectant stresses. The present study aimed to evaluate the effect of microbial interactions on biofilm formation and the disinfecting activity of an innovative photocatalytic surfactant based on TiO2 nanoparticles. Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli, Leuconostoc spp., Latilactobacillus sakei, Serratia liquefaciens, Serratia proteomaculans, Citrobacter freundii, Hafnia alvei, Proteus vulgaris, Pseudomonas fragi, and Brochothrix thermosphacta left to form mono- or dual-species biofilms on stainless steel (SS) coupons. The effectiveness of the photocatalytic disinfectant after 2 h of exposure under UV light on biofilm decontamination was evaluated. The effect of one parameter i.e., exposure to UV or disinfectant, was also determined. According to the obtained results, the microbial load of a mature biofilm depended on the different species or dual species that had adhered to the surface, while the presence of other species could affect the biofilm population of a specific microbe (p < 0.05). The disinfectant strengthened the antimicrobial activity of UV, as, in most cases, the remaining biofilm population was below the detection limit of the method. Moreover, the presence of more than one species affected the resistance of the biofilm cells to UV and the disinfectant (p < 0.05). In conclusion, this study confirms that microbial interactions affected biofilm formation and decontamination, and it demonstrates the effectiveness of the surfactant with the photocatalytic TiO2 agent, suggesting that it could be an alternative agent with which to disinfect contaminated surfaces.

Investigation of the Photoinduced Antimicrobial Properties of N-Doped TiO2 Nanoparticles under Visible-Light Irradiation on Salmonella Typhimurium Biofilm

The aim of the present study was to investigate the photoinduced properties of nitrogen-doped titanium dioxide (N-TiO2) against the Salmonella ser. Typhimurium bacterial biofilm, under visible-light irradiation. The capability of N-TiO2 nanoparticles working as multipurpose materials with antimicrobial applications, as well as environmental ones, was therefore investigated. The sol–gel method was used to synthesize N-TiO2 particles, which were then characterized by Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), Brunauer–Emmett–Teller (BET) analysis of surface area, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), and transmission electron microscopy (TEM). The results showed that the particles formed were nano-sized and had the expected Ti-O bonds and the presence of elemental N. The as-produced N-TiO2 nanoparticles (NPs) were tested for their antimicrobial activity. The antibacterial photocatalytic testing was performed under visible-light irradiation, on Salmonella Typhimurium biofilm. To form the biofilm, stainless steel (ss) coupons were incubated with three different strains of Salmonella Typhimurium bacteria for 48 h at 15 °C in tryptone soy broth (TSB). After the biofilm’s formation, the coupons were placed on a horizontal, rectangular, batch, equipped with a vis-LED irradiation source reactor in the presence of N-TiO2 NPs. After 1, 2, and 3 h of irradiation, sampling of the bacterial population was assessed. The results showed an evident inhibition of proliferation under light irradiation when the N-TiO2 was present, compared to the non-irradiated NPs. It is noteworthy that, during the first 2 h, the TiO2 NPs specimens tended to attract more bacteria on their surface then the control specimens, due to their higher available surface area, which worked as a shelter. There were ~6% viable (remaining) Salmonella cells after the first hour of visible-light irradiation with N-TiO2 NPs.

Biofilm Formation of Escherichia coli on Hydrophobic Steel Surface Provided by Laser-Texturing

Lozenge-patterned surfaces obtained with laser texturing can reduce the risk of infection by preventing or delaying biofilm formation of Escherichia coli. To investigate this aspect, the biofilm formation ability of E. coli on both lozenge-patterned and untreated surfaces of 630 stainless steel coupons was examined over 48 h. Biofilm on the coupons was analysed for bacterial enumeration and total carbohydrates concentration and was observed using scanning electron microscopy (SEM). The surface modification by texturing caused a 6 h delay in the attachment of E. coli and an approximately 99% decrease in the number of adhered bacteria. However, it was determined that E. coli produced more extracellular polymeric substances (EPS) (p&lt;0.01) to attach to the lozenge-patterned surface and formed a multi-layered biofilm. In conclusion, lozenge-patterned surfaces can be applied to reduce bacterial count and induce a delay in attachment, but the increased amount of EPS limits its use.

Corrosion barrier alumina/zirconia bilayer stack on low Cr steel by direct liquid injection metalorganic chemical vapor deposition

Numerous industrial fields necessitate the development of advanced metallic materials presenting high corrosion resistance in aqueous media and being less expensive than classical high chromium steels. In the present work, amorphous zirconia, alumina and alumina/zirconia coatings have been deposited on 2 wt% chromium steel coupons using an innovative direct liquid injection metal organic chemical vapor deposition process. Scanning electron microscopy and X-ray diffraction reveal that the alumina sublayer acts as an efficient barrier against steel oxidation occurring during the amorphous zirconia deposition performed under O2 at 400 °C. They also show that the steel oxidation occurring concomitantly to the zirconia coating modifies the film morphology by increasing its roughness and thickness, in comparison with the same zirconia coating on alumina. The anticorrosive properties of the thin films have been studied by an immersion test of the bare and coated coupons in deionized water at 80 °C during 6 days and by electrochemical impedance spectroscopy in aqueous sodium chloride solution for 48 h. They reveal that, in contrast to alumina and zirconia monolayers alone, the alumina/zirconia stack acts as a corrosion protection coating in pure water through a synergetic barrier effect against (i) oxidation by alumina and (ii) aqueous corrosion by zirconia.

Palmitic acid-based amide as a corrosion inhibitor for mild steel in 1M HCl

Due to growing environmental concerns and regulations limiting the use of harmful and toxic synthetic corrosion inhibitors, there is a high demand for sustainable corrosion inhibitors. In this study, a green and rapid technique was used to synthesize amide N-(4-aminobutyl)palmitamide (BAPA) which yielded 91.17% of the product within 2 min, compared to a low yield of 75–80% and a very long 8–10 h reaction time with the conventional thermal condensation method. The chemical structure of BAPA was analyzed by FT-IR, 1HNMR and 13CNMR spectra, as well as CHNS elemental analysis. When applied to mild steel exposed to 1 M HCl, BAPA delayed and reduced corrosion by adsorbing to the steel surface to form a protective layer. The inhibition efficiency increased with increasing amide concentration, and maximal inhibition of 91.5% was observed at 0.5 mM BAPA. The adsorption of BAPA on mild steel in an acidic solution was studied and inhibition performance was correlated with the calculated adsorption-free energy ΔGads, indicating good agreement between the experimental and adsorption findings. Surface morphology of untreated and treated mild steel coupons was evaluated by SEM, and based on density functional theory (DFT) computations and atomic charges analysis, a stronger interaction was observed between BAPA and mild steel surface leading to the formation of a compact protective film on the metallic surface. This protective film is attributed to the presence of nitrogen atoms and carbonyl group in the chemical structure of BAPA.

Survival of livestock-associated methicillin-resistant Staphylococcus aureus CC398 on different surface materials

BackgroundZoonotic livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is widely spread in pig herds in many countries. However, the knowledge regarding the survival of LA-MRSA in the pig farm environment is currently limited. The aim of this study was to assess the survival of LA-MRSA on different surface materials found in the farm environment. The study investigated the survival of two different LA-MRSA strains belonging to the clonal complex (CC) 398 on four different surfaces: stainless steel, polypropylene plastic, K30 concrete and commercial concrete disk coupons. The survival of the bacteria over time was determined by the viable count method and, where possible, fitting a model to the observed data by using nonlinear least squares method to calculate the half-life ({t}_{1/2}) for different strain and material combinations.ResultsThe study showed that the half-life of the bacteria was longer on polypropylene plastic ({t}_{1/2}=11.08–15.78 days) than on stainless steel ({t}_{1/2}=2.45–7.83 days). On these materials, both LA-MRSA strains survived through the 14 week observation period. The bacterial decay was fastest on the concrete surfaces, where LA-MRSA became undetectable after 3–9 weeks.ConclusionsThe survival of LA-MRSA in the pig farm environment may be affected by different surface materials. A more frequent sampling protocol (< 7 days) is needed to determine the half-life on concrete surfaces.

Bacterial biofilm reduction by 275 and 455 nm light pulses emitted from light emitting diodes

AbstractEradication of biofilms from the food contact surfaces is a challenging task, owing to their increased resistance to sanitizers and regular cleaning practices. The treatment with the light pulses emitted from the light emitting diode (LED) is an emerging surface decontamination technology, that can produce the antibiofilm effect by photodynamic inactivation. The objective of this study was to understand the antibiofilm efficacy of the 275 (Ultraviolet‐C [UV‐C]) and 455 nm (Blue) light pulses emitted from the LEDs against single and dual‐species biofilms of Salmonella Typhimurium ATCC13311 and Aeromonas australiensis 03‐09 on stainless steel (SS) coupons formed at different time. The biofilm formation by S. Typhimurium was improved when grown with A. australiensis in dual‐species culture. Both 275 and 455 nm light pulses showed significant antibiofilm activity against S. Typhimurium and A. australiensis in single and dual‐species biofilms. For instance, the 275 nm LED treatment of surfaces of SS coupons with 1.8 J/cm2 dose on each surface, produced reductions of 4.24 and 3.9 log (CFU/cm2) in single (cell attachment) and dual‐species biofilms of S. Typhimurium, and reductions of 4.45 and 4.99 log (CFU/cm2) in single and dual‐species biofilms of A. australiensis. However, the susceptibility of A. australiensis toward 455 nm LED treatments was influenced by the presence of S. Typhimurium in the dual‐species biofilm. The confocal laser scanning microscopy images revealed significant cell membrane damage in the dual‐species biofilms by the LED treatments with 275 and 455 nm light pulses. Overall, several factors like surface temperature increase, strains used, treatment dose, treatment time, and incubation period of biofilms influenced the inactivation efficacy of the 275 and 455 nm LED treatments against the biofilms formed on SS coupons. This study provides an insight into the inactivation efficacy of LED light pulses against bacterial biofilms on food grade SS surfaces.

Evaluating the impact of organic matter and sample processing techniques on RNA detection using environmental samples

This study evaluated sample processing methods and the presence of organic matter on detection of porcine epidemic diarrhea virus (PEDV) from environmental samples using real-time reverse transcriptase-polymerase chain reaction (qRT-PCR). Steel coupons were inoculated with PEDV and different types of organic material contamination. Surface samples were collected and processed in one of four ways: none, centrifugation, syringe filtration, or combination of centrifugation and syringe filtration, then submitted for PEDV qRT-PCR. There was a surface inoculation type by processing method interaction (P &lt; .001) that impacted the sample cycle threshold value. Centrifugation resulted in the most consistent detection of PEDV RNA.

Safranin-O-Mediated Photodynamic Inactivation of Microorganisms Reduces Milk Contaminating Bacteria Count and Prevented New Cases of Mastitis

The objectives of this study were to evaluate the antimicrobial capacity of the photosensitizer (PS) safranin-O (Sf), through antimicrobial photodynamic therapy (PDTa), against strains of Pseudomonas fluorescens (PV1, PVh, and PC3) and Staphylococcus aureus (SV1, SV3, SV5, SC5, SC6, and SC8) isolated from milk from cows and goats and the biofilm formation on equipment. To evaluate the effectiveness of the formulation, studies were carried out through in situ applications of the Sf hydrogel as post-dipping in lactating cows and goats. Antibiogram tests showed the resistance of Staphylococcus aureus isolates to ampicillin, trimethoprim, and tetracycline. In the in vitro assays in bovine milk, the PDTa reduced the P. fluorescens (PV1) counts by 17.4% (p<0.05). In goat milk, the PDTa reduced the growth of S. aureus by up to 24.43% (SC8) (p<0.05), and for P. fluorescens (PC3), the inactivation was 50.25%. In biofilm formation, there were reduction of 66.66% (SV1) and 38.27% (SC5) in the adhesion of S. aureus to stainless steel coupons. For in situ applications, photoactivated Sf maintained bacterial counts in bovine milk similar to the control treatment (lactic acid). During the experimental period (28 days), there were reductions of 23.23% and 28.85% in staphylococci and Pseudomonas spp. in cow’s milk and 76.13% for Pseudomonas spp. in goat milk (p<0.05). There was no significant difference in goat milk’s somatic cell count (CCS). These results indicate that photoactivated Sf can help reduce milk contamination and maintain the health of the mammary gland.

Utilization of Piper betle L. Extract for Inactivating Foodborne Bacterial Biofilms on Pitted and Smooth Stainless Steel Surfaces.

Biofilms are a significant concern in the food industry. The utilization of plant-derived compounds to inactivate biofilms on food contact surfaces has not been widely reported. Also, the increasing negative perception of consumers against synthetic sanitizers has encouraged the hunt for natural compounds as alternatives. Therefore, in this study we evaluated the antimicrobial activities of ethanol extracts, acetone extracts, and essential oils (EOs) of seven culinary herbs against Salmonella enterica serotype Typhimurium and Listeria innocua using the broth microdilution assay. Among all tested extracts and EOs, the ethanol extract of Piper betle L. exhibited the most efficient antimicrobial activities. To evaluate the biofilm inactivation effect, S. Typhimurium and L. innocua biofilms on pitted and smooth stainless steel (SS) coupons were exposed to P. betle ethanol extract (12.5 mg/ml), sodium hypochlorite (NaClO; 200 ppm), hydrogen peroxide (HP; 1100 ppm), and benzalkonium chloride (BKC; 400 ppm) for 15 min. Results showed that, for the untreated controls, higher sessile cell counts were observed on pitted SS versus smooth SS coupons. Overall, biofilm inactivation efficacies of the tested sanitizers followed the trend of P. betle extract ≥ BKC > NaClO > HP. The surface condition of SS did not affect the biofilm inactivation effect of each tested sanitizer. The contact angle results revealed P. betle ethanol extract could increase the surface wettability of SS coupons. This research suggests P. betle extract might be utilized as an alternative sanitizer in food processing facilities.