Preparation and Formation Mechanism Study of Antibiofilm Coating Based on Phase Transition of Glutenin.

The endoplasmic reticulum (ER) has a strict protein quality control system. Misfolded proteins generated in the ER are degraded by the ER-associated degradation (ERAD). Yeast Mnl1p consists of an N-terminal mannosidase homology domain and a less conserved C-terminal domain and facilitates the ERAD of glycoproteins. We found that Mnl1p is an ER luminal protein with a cleavable signal sequence and stably interacts with a protein-disulfide isomerase (PDI). Analyses of a series of Mnl1p mutants revealed that interactions between the C-terminal domain of Mnl1p and PDI, which include an intermolecular disulfide bond, are essential for subsequent introduction of a disulfide bond into the mannosidase homology domain of Mnl1p by PDI. This disulfide bond is essential for the ERAD activity of Mnl1p and in turn stabilizes the prolonged association of PDI with Mnl1p. Close interdependence between Mnl1p and PDI suggests that these two proteins form a functional unit in the ERAD pathway.

In Drosophila, phototransduction is mediated by G(q)-activation of phospholipase C and is a well studied model system for understanding the kinetics of signal initiation, propagation and termination controlled by G proteins. The proper intracellular targeting and spatial arrangement of most proteins involved in fly phototransduction require the multi-domain scaffolding protein InaD, composed almost entirely of five PDZ domains, which independently bind various proteins including NorpA, the relevant phospho lipase C-beta isozyme. We have determined the crystal structure of the N-terminal PDZ domain of InaD bound to a peptide corresponding to the C-terminus of NorpA to 1.8 A resolution. The structure highlights an intermolecular disulfide bond necessary for high affinity interaction as determined by both in vitro and in vivo studies. Since other proteins also possess similar, cysteine-containing consensus sequences for binding PDZ domains, this disulfide-mediated 'dock-and-lock' interaction of PDZ domains with their ligands may be a relatively ubiquitous mode of coordinating signaling pathways.

A systematic characterization of the distribution, biofilm-forming potential and the resistance of the biofilms to the CIP processes of the bacteria in a milk powder processing factory

Effect of WC content on laser cladding Ni-based coating on the surface of stainless steel

Graphical Abstract Highlight Research The biofilm formation of Raoultella ornithinolytica on a stainless steel surface was analyzed Longer duration of hot water immersion leading to a higher reduction of Raoultella ornithinolytica biofilm on stainless steel surface. Longer duration of nanochitosan exposure leading to a higher reduction of Raoultella ornithinolytica biofilm on stainless steel surface The combination treatment of hot water immersion and nanochitosan shows higher efficacy to reduce Raoultella ornithinolytica biofilm on stainless steel surface compare to sodium hypochlorite treatment. Abstract The equipment surfaces in food processing industries have the potential to contaminate products. Bacteria on a surface are able to form a biofilm. This study aimed to determine the effect of a combination treatment using hot water immersion and nanochitosan on the reduction of R. ornithinolytica’s biofilm on stainless steel surfaces. R. ornithinolytica was applied to a stainless steel surface, incubated at 30oC for 48 hours, and tested for its reduction using hot water immersion treatment with different times. The best result from this treatment was when it was used in combination. The viability of cells was determined using a swab and the total plate count method. A scanning electron microscope was used for qualitative observations of biofilm formed on stainless steel before and after sanitation. The result showed that 10 minutes of hot water immersion resulted in significant R. ornithinolytica biofilm reduction compared to 5 minutes of treatment (p<0.05). Furthermore, the combination treatment of 10 minutes of hot water with 15 minutes of nanochitosan (0.1%) immersion showed the highest percent reduction of R. ornithinolytica biofilm (p<0.05). The ability of the combination treatment to eliminate R. ornithinolytica biofilms is equivalent to or even better than sodium hypochlorite treatment.

In our laboratory, we have been studying the reductive processes that occur during matrix-assisted laser desorption/ionization (MALDI) experiments. Recently, we have finished an analysis of the DHB matrix effect on the azo group in cyclic peptides. However, deep understanding of disulfide bond behaviour during a mass spectrometry (MS) experiment is much more important in proteomics as its reduction can cause serious errors in protein spectra interpretation. Therefore, we have focused on intra- and intermolecular disulfide bonds as well as disulfide bonds connecting cysteine and 2-thio-5-nitrobenzoic acid (TNB, Ellman's reagent modification) in model peptides during MALDI MS measurements. While the reduction was not observed for intra- and intermolecular cysteine-cysteine disulfide bonds, the disulfide connection between cysteine and TNB was always affected. It was proved that TNB and Ellman's reagent can act as a matrix itself. The results obtained enabled us to propose a reaction mechanism model which is able to describe the phenomena observed during the desorption/ionization process of disulfide-containing molecules.

The GP64 envelope glycoprotein of the Autographa californica nucleopolyhedrovirus (AcMNPV) is a class III viral membrane fusion protein that is triggered by low pH during entry. Unlike most other viral fusion protein trimers, the monomers of GP64 are covalently linked to each other within the trimer by a single intermolecular disulfide bond (Cys24 Cys372). Single or paired alanine substitutions for Cys24 and Cys372 resulted in lower-efficiency transport of GP64 to the cell surface. Surprisingly, these mutated GP64s induced syncytium formation, and normalized fusion activities were approximately 30% of that from wild-type (WT) GP64. Heat treatment (37 degrees C) did not further reduce fusion activity of GP64 constructs with a disrupted intermolecular disulfide bond, suggesting that the GP64 trimers were relatively thermostable in the absence of the intermolecular disulfide bond. In addition, analysis of binding by a conformation-specific monoclonal antibody (MAb) suggested that the low-pH-induced refolding of those GP64 constructs was generally similar to that of WT GP64. In addition to its critical role in membrane fusion, GP64 is also necessary for efficient budding. When GP64 constructs containing a disrupted intermolecular disulfide bond (Cys24 Cys372) were displayed at the cell surface at levels comparable to those of WT GP64, virion budding efficiency ranged from approximately 39 to 88%, indicating that the intermolecular disulfide bond is not required for virion budding. However, GP64 proteins with a disrupted intermolecular disulfide could not rescue a GP64-null bacmid. We also examined the 6 conserved intramolecular disulfide bonds using single and paired alanine substitution mutations. None of the GP64 constructs with disrupted intramolecular disulfide bonds were capable of mediating pH-triggered membrane fusion, indicating that the intramolecular disulfide bonds are all necessary for membrane fusion. Thus, while the intramolecular disulfide bonds of GP64 appear to serve critical roles in membrane fusion, the unusual intermolecular disulfide bond was not critical for membrane fusion or virion budding yet appears to play an unknown role in viral infectivity.

Almost every metal and alloy corrodes when used in high-temperature applications. To combat this problem, ceramic coatings on the metals can be deposited for better thermal and corrosion behavior. The present study applies an alumina-titania (Al2O3-TiO2) ceramic coating to the stainless steel (SS) surface using a detonation spray process. The surface of the coated SS is probed by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The clear differences between coated and uncoated SS have been observed based on the SEM images. The XRD pattern indicates that the Al2O3-TiO2 coating on SS has been successfully deposited. The hardness of coated and uncoated SS surfaces is determined by using the Micro Vickers hardness tester, which claims that the hardness of the SS surface has decreased after coating. Salt spray tests were used to examine the corrosion behavior of coated and uncoated SS after 12 and 24 hours. After 12 hours, no corrosion was observed on the SS. After 24 hours, however, significant corrosion of uncoated SS is observed, and the coated SS shows negligible corrosion. Based on the study, it is claimed that an Al2O3-TiO2 coating on SS has improved its corrosion behavior significantly.

Organic residues on equipment surfaces in poultry processing plants can generate cross contamination and increase the risk of unsafe food for consumers. This research was aimed to investigate the potential of LED-induced fluorescence imaging technique for rapid inspection of organic residues on poultry processing equipment surfaces. High-power blue LEDs with a spectral output at 410 nm were used as the excitation source for a line-scanning hyperspectral imaging system. Common chicken residue samples including fat, blood, and feces from ceca, colon, duodenum, and small intestine were prepared on stainless steel sheets. Fluorescence emission images were acquired from 120 samples (20 for each type of residue) in the wavelength range of 500-700 nm. LED-induced fluorescence characteristics of the tested samples were determined. PCA (principal component analysis) was performed to analyze fluorescence spectral data. Two SIMCA (soft independent modeling of class analogy) models were developed to differentiate organic residues and stainless steel samples. Classification accuracies using 2-class ('stainless steel' and 'organic residue') and 4-class ('stainless steel', 'fat', 'blood', and 'feces') SIMCA models were 100% and 97.5%, respectively. An optimal single-band and a band-pair that are promising for rapid residue detection were identified by correlation analysis. The single-band approach using the selected wavelength of 666 nm could generate false negative errors for chicken blood inspection. Two-band ratio images using 503 and 666 nm (F503/F666) have great potential for detecting various chicken residues on stainless steel surfaces. This wavelength pair can be adopted for developing a LED-based hand-held fluorescence imaging device for inspecting poultry processing equipment surfaces.

Polyethylene glycol (PEG) structures were deposited onto stainless steel (SS) surfaces by spin coating and argon radio frequency (RF)‐plasma mediated crosslinking. Electron spectroscopy for chemical analysis (ESCA) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) indicated the presence of CH2CH2O structure and CCC linkage, as a result of the plasma crosslinking, on PEG‐modified SS surfaces. Scanning electron microscopy (SEM) indicated complete deposition, and water contact angle analysis revealed higher hydrophilicity on PEG‐modified surfaces compared to unmodified SS surfaces. Surface morphology and roughness analysis by atomic force microscopy (AFM) revealed smoother SS surfaces after PEG modification. The evaluation of antifouling ability of the PEG‐modified SS surfaces was carried out. Compared to the unmodified SS, PEG‐modified surfaces showed about 81–96% decrease in Listeria monocytogenes attachment and biofilm formation (p < 0.05). This cold plasma mediated PEG crosslinking provided a promising technique to reduce bacterial contamination on surfaces encountered in food‐processing environments. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 485–497, 2005

Study of heat-denatured whey protein removal from stainless steel surfaces in clean-in-place systems

In order to develop strategies for preventing biofilm formation in the dairy industry, a deeper understanding of the interaction between different species during biofilm formation is necessary. Bacterial strains of the P. fluorescens group are known as the most important biofilm-formers on the surface of dairy processing equipment that may attract and/or shelter other spoilage or pathogenic bacteria. The present study used different strains of the P. fluorescens group as background microbiota of milk, and evaluated their interaction with Staphylococcus aureus, Bacillus cereus, Escherichia coli O157:H7, and Salmonella Typhimurium during dual-species biofilm formation on stainless steel surfaces. Two separate scenarios for dual-species biofilms were considered: concurrent inoculation of Pseudomonas and pathogen (CI), and delayed inoculation of pathogen to the pre-formed Pseudomonas biofilm (DI). The gram-positive pathogens used in this study did not form dual-species biofilms with P. fluorescens strains unless they were simultaneously inoculated with Pseudomonas strains. E. coli O157:H7 was able to form dual-species biofilms with all seven P. fluorescens group strains, both in concurrent (CI) and delayed (DI) inoculation. However, the percentage of contribution varied depending on the P. fluorescens strains and the inoculation scenario. S. Typhimurium contributed to biofilm formation with all seven P. fluorescens group strains under the CI scenario, with varying degrees of contribution. However, under the DI scenario, S. Typhimurium did not contribute to the biofilm formed by three of the seven P. fluorescens group strains. Overall, these are the first results to illustrate that the strains within the P. fluorescens group have significant differences in the formation of mono-or dual-species biofilms with pathogenic bacteria. Furthermore, the possibility of forming dual-species biofilms with pathogens depends on whether the pathogens form the biofilm simultaneously with the P. fluorescens group strains or whether these strains have already formed a biofilm.

Redox regulation of nuclear factor kappaB (NF-kappaB) has been described, but the molecular mechanism underlying such regulation has remained unclear. We recently showed that a novel disulfide reductase, TRP14, inhibits tumor necrosis factor alpha (TNFalpha)-induced NF-kappaB activation, and we identified the dynein light chain LC8, which interacts with the NF-kappaB inhibitor IkappaBalpha, as a potential substrate of TRP14. We now show the molecular mechanism by which NF-kappaB activation is redox-dependently regulated through LC8. LC8 inhibited TNFalpha-induced NF-kappaB activation in HeLa cells by interacting with IkappaBalpha and thereby preventing its phosphorylation by IkappaB kinase (IKK), without affecting the activity of IKK itself. TNFalpha induced the production of reactive oxygen species, which oxidized LC8 to a homodimer linked by the reversible formation of a disulfide bond between the Cys(2) residues of each subunit and thereby resulted in its dissociation from IkappaBalpha. Butylated hydroxyanisol, an antioxidant, and diphenyleneiodonium, an inhibitor of NADPH oxidase, attenuated the phosphorylation and degradation of IkappaBalpha by TNFalpha stimulation. In addition LC8 inhibited NF-kappaB activation by other stimuli including interleukin-1beta and lipopolysaccharide, both of which generated reactive oxygen species. Furthermore, TRP14 catalyzed reduction of oxidized LC8. Together, our results indicate that LC8 binds IkappaBalpha in a redox-dependent manner and thereby prevents its phosphorylation by IKK. TRP14 contributes to this inhibitory activity by maintaining LC8 in a reduced state.

In the food industry, the surfaces of processing equipment are considered to be major factors in the risk of food contamination. The cleaning process of solid surfaces is essential, but it requires a significant amount of water and chemicals. Herein, we report the use of foam flows based on alkyl polyglucosides (APGs) to remove spores of Bacillus subtilis on stainless-steel surfaces as the model-contaminated surface. Sodium dodecyl sulfate (SDS) was also studied as an anionic surfactant. Foams were characterized during flows by measuring the foam stability and the bubble size. The efficiency of spores’ removal was assessed by enumerations. We showed that foams based on APGs could remove efficiently the spores from the surfaces, but slightly less than foams based on SDS due to an effect of SDS itself on spores removal. The destabilization of the foams at the end of the process and the recovery of surfactant solutions were also evaluated by using filtration. Following a life cycle assessment (LCA) approach, we evaluated the impact of the foam flow on the global environmental footprint of the process. We showed significant environmental impact benefits with a reduction in water and energy consumption for foam cleaning. APGs are a good choice as surfactants as they decrease further the environmental impacts.

This study analyzed biofilms composed of Escherichia coli and Staphylococcus aureus on a stainless steel surface, in the presence of food residues (milk and meat exudate), at 25 and 35 °C, with the objective of simulating the real conditions of industrial processing of these foods. The biofilm formed on the surface was determined by quantifying the colonies and scanning electron microscopy. In addition to milk and meat exudate, three different culture media were used, one specific for each bacterium and a common environment for the growth of both bacteria (Mueller Hinton agar, MH). Such conditions were favorable for the biofilm formation of both bacteria, with predominance of the Gram-negative species in the multispecies biofilm. The food residues favored the formation of the biofilm in both temperatures, especially the meat exudate at 35 °C, when compared to the MH broth. Therefore, substrate and temperature directly influenced the microbial composition of the biofilm. Practical applications This study demonstrates the influence of industrial residue (substrate) on temperature in the composition of a biofilm. As it was evaluated two distinct bacteria, one Gram-positive and another Gram-negative, that can be present in several industrial food processing, it can be observed that the substrate and the temperature may favor the development of a species. This fact is extremely relevant so that a correct hygiene process can be applied and it is necessary to know the composition of the biofilm on a certain surface to combat it more effectively.