Role of oxidants and disinfectants on the removal,masking and generation of tastes and odours

This paper summarises theadvantages and disadvantages effects of themost commonly used oxidants and disinfectants:chlorine, ozone, advanced oxidation withozone/hydrogen peroxide, chlorine dioxide,potassium permanganate and chloramines, ontastes and odours present in natural anddrinking waters. Case studies are presentedwhich illustrate the generation of odorousby-products such as chlorophenols, iodinatedtrihalomethanes, aldehydes, the masking effectbetween earthy-musty and chlorinous odours andthe removal of odorous algal metabolites oranthropogenic pollutants by ozone alone orozone coupled with hydrogen peroxide.     

Oxidation of thymidylate synthase by inorganic compounds

Thymidylate synthase from methotrexate-resistant Lactobacillus casei was rapidly and completely inactivated by low concentrations of permanganate, periodate, or potassium triiodide at 0 degree C. The enzyme was not inactivated to any appreciable extent by iodate, iodide, ferricyanate, iodosobenzoate, or hydrogen peroxide. The inactivation by permanganate was retarded by the substrate 2'-deoxyuridylate and, to a lesser extent, by phosphate. Titration of enzyme activity with permanganate showed that two moles of permanganate were required to completely inactivate one mole of thymidylate synthase.     

The oxidative generation of sulfonic acid groups in neuromelanin and lipofuscin in the human brain

Sulfonic acid groups were oxidatively generated in the soluble lipid-free lipofuscin component of neuromelanin of human substantia nigra and in lipofuscin of human inferior olive. Exposure of these oxidized, intraneuronal pigments to low pH Alcian blue or aldehyde fuchsin demonstrated an intensity of staining that related to the type of oxidant and the conditions of its use. Utilization of the following oxidants generated increasingly strong staining reactions as signified by the following sequence; periodic acid under mild conditions, bromine in carbon tetrachloride, hydrogen peroxide, periodic acid under drastic conditions, potassium permanganate followed by oxalic acid, hydrogen peroxide followed by bromine in carbon tetrachloride, potassium permanganate followed by metabisulfite or bisulfite, and performic acid. Neither Alcian blue nor aldehyde fuchsin revealed oxidatively generated aldehyde as judged by 1) their failure or near failure to stain inferior olive lipofuscin following mildly applied periodic acid, and 2) the increase in staining intensity, from moderate to strong, displayed by the soluble lipid-free lipofuscin component of neuromelanin and by inferior olive lipofuscin when potassium permanganate was followed by a rinse with metabisulfite or bisulfite in place of one with oxalic acid.     

Effect of organic N-halamines on selected membrane functions in intact Staphylococcus aureus cells.

Two N-halamine compounds, 3-chloro-4,4-dimethyl-2-oxazolidinone and 1,3-dichloro-4,4,5,5-tetramethyl-2-imidazolidinone, were compared with free chlorine as to their effects on selected membrane functions of intact Staphylococcus aureus cells. Free chlorine was found to cause a loss of permeability control, as measured by the efflux of potassium from the cells and a dramatic increase in hydrogen ion permeability, and to affect cell respiration in a nonreversible fashion, as measured by oxygen uptake. The two N-halamines were found to have very little effect on permeability to either potassium or hydrogen ions but were both found to dramatically inhibit respiration in a reversible manner. It is proposed that the first step in the disinfection process by these N-halamines is an inhibition of respiratory enzymes that, if not reversed, ultimately leads to a loss of cell viability.     

Effect of organic N-halamines on selected membrane functions in intact Staphylococcus aureus cells

Two N-halamine compounds, 3-chloro-4,4-dimethyl-2-oxazolidinone and 1,3-dichloro-4,4,5,5-tetramethyl-2-imidazolidinone, were compared with free chlorine as to their effects on selected membrane functions of intact Staphylococcus aureus cells. Free chlorine was found to cause a loss of permeability control, as measured by the efflux of potassium from the cells and a dramatic increase in hydrogen ion permeability, and to affect cell respiration in a nonreversible fashion, as measured by oxygen uptake. The two N-halamines were found to have very little effect on permeability to either potassium or hydrogen ions but were both found to dramatically inhibit respiration in a reversible manner. It is proposed that the first step in the disinfection process by these N-halamines is an inhibition of respiratory enzymes that, if not reversed, ultimately leads to a loss of cell viability.     

Optimization of hydrogen peroxide in totally chlorine free bleaching of cellulose pulp from olive tree residues

The influence of the operating conditions used in the bleaching of olive wood trimmings pulp (viz. hydrogen peroxide concentration and time) on the yield, kappa index and viscosity of the resulting pulp and on strength-related properties of paper sheets was studied to determine the optimal bleaching conditions of this pulp. Hydrogen peroxide bleached pulps at different sequences (oxygen, ozone, chlorine dioxide and alkaline extractions) were compared. Hydrogen peroxide bleaching proved to be suitable for this pulp. Considerable improvements in viscosity were obtained with respect to other bleaching sequences such as oxygen, ozone and chlorine dioxide. Hydrogen peroxide bleaching decreased the kappa index 51.3% less than ozone bleaching, 25.0% less than chlorine dioxide (D) and 6.3% less combined chlorine dioxide-alkaline extraction (DE). To obtain kappa indices 50.9% and 37.9% lower than the index achieved by hydrogen peroxide, oxygen (LaO(p)) and ozone (LaO(LaZ)R) sequences respectively were needed. Lower-medium levels of hydrogen peroxide concentrations (1-3%) and high reaction times (210 min) proved to be suitable for bleaching of pulp olive trimming residues. This approach could be used on this residue to produce adequately bleached pulp.     

Inactivation of possible micromycete food contaminants using the low-temperature plasma and hydrogen peroxide

The inhibition effect of hydrogen peroxide aerosol, low-temperature plasma and their combinations has been studied on several micromycetes spores. The low-temperature plasma was generated in corona discharges in the open air apparatus with hydrogen peroxide aerosol. Micromycete spores were inoculated on the surface of agar plates, exposed solely to the hydrogen peroxide aerosol, corona discharge or their combination. After incubation the diameter of inhibition zone was measured. The solely positive corona discharge exhibits no inactivation effect, the solely negative corona discharge and solely hydrogen peroxide aerosol exhibit the inactivation effect, however their combinations exhibit to be much more effective. Low-temperature plasma and hydrogen peroxide aerosol present a possible alternative method of microbial decontamination of food, food packages or other thermolabile materials.     

Oxygen protection of bacteriophage T1 against ionizing radiations

Bacteriophage T1 was suspended in distilled water and in phosphate buffer, saturated with oxygen, nitrogen, hydrogen, and carbon monoxide, and irradiated with gamma rays and x-rays. Under the same conditions phage was exposed to hydrogen peroxide. Oxygen acted as a protective agent against both irradiation and hydrogen peroxide inactivation. As a protective agent against irradiation, oxygen was more efficient in distilled water than in buffer. The phage was much more sensitive to irradiation in the presence of hydrogen or nitrogen than in the presence of oxygen. Survivals of phage irradiated in suspensions saturated with hydrogen and with nitrogen did not differ significantly. From this it was concluded that oxygen did not protect T1 by removing atomic hydrogen from the irradiated medium, since the hydrogen-saturated medium increased the yield of atomic hydrogen but did not increase the yield of inactivated phage. It was presumed, therefore, that phage is sensitive to OH radicals and this was confirmed by irradiating phage with UV in the presence of hydrogen peroxide and comparing this survival with the survivals obtained from hydrogen peroxide alone and from UV alone. The combined effect of hydrogen peroxide and UV acting simultaneously was greater than the effect attributable to hydrogen peroxide and UV acting separately. Evidence for sensitivity to HO₂ radicals was considered, and the effect was attributed chiefly to an oxidizing action since phage sensitivity is greater at higher hydrogen ion concentrations, which favor oxidation by HO₂ radicals. Since the OH radical is a more efficient oxidizing agent than O^-, the former being favored in an acid medium, the latter in an alkaline medium, and since the phage is more sensitive in the first situation than in the second, the present tests proved the importance of oxidation as the mechanism of inactivation. Since some inactivation was encountered when phage was exposed to reducing agents, independently of irradiation, it was concluded that phage is somewhat sensitive to reducing agents, but the inactivation attributable to ionizing radiations is due chiefly to oxidation, against which these reducing agents are very efficient protectors. Under no circumstances did hydrogen peroxide protect T1, whether produced by irradiation in the medium or added beforehand to the medium to be irradiated. The first point was investigated by irradiating T1 in the presence of hydrogen and oxygen combined; this produced a higher yield of hydrogen peroxide but a lower survival of T1. In all these tests phage survival under irradiation was directly correlated with oxygen content of the medium rather than with production of hydrogen peroxide. It is proposed that the protective effect of oxygen is due to a reaction between the phage and oxygen, and this complex confers stability upon the phage.     

Exogenous catalase introduced in CHO cells by electroporation does not protect against chromosome damage induced by ionizing radiation.

The relative importance of hydrogen peroxide generated as a consequence of irradiation with X-rays for the production of chromosomal aberrations has been studied in cultured CHO cells. Catalase introduced into cells by electroporation protected DNA from strand breakage induced by hydrogen peroxide given 4h later, and the yield of chromosome aberrations was also reduced. Nevertheless, when the cells were irradiated after treatment with catalase following a similar protocol and the yield of chromosomal aberrations analyzed at metaphase, no protective effect was observed as compared with cells treated with X-rays alone. These observations seem to support the hypothesis that hydroxyl radicals generated from hydrogen peroxide are not a major factor responsible for chromosome damage induced by ionizing radiation.     

Efficacy of standard disinfectant test methods for contact lens-care solutions

Two disinfection systems based on hydrogen peroxide (0.5, 1.5 and 3%) and chlorhexidine gluconate (0.004%) were challenged in suspension tests using a modification of a standard method, with inocula containing 10⁶ or 10⁸ cfu/ml of the standard organisms Serratia marcescens, Pseudomonas aeruginosa and Staphylococcus warneri. The effect of an organic load on the shapes of microbial inactivation curves was also investigated. Although there were rapid declines in viability of 1–2 log units (cfu/ml) within the first minute of challenge in all cases, declines in viability subsequently levelled out rapidly, and with hydrogen peroxide viable counts increased slightly thereafter. These increases are unexplained, but may in part be attributable to disruption of cell clumps during challenge.     

Escherichia coli small heat shock proteins, IbpA and IbpB, protect enzymes from inactivation by heat and oxidants.

To examine functions of two small heat shock proteins of Escherichia coli, IbpA and IbpB, we constructed His-IbpA and His-IbpB, in which a polyhistidine tag was fused to the N-terminals. Both purified His-IbpA and His-IbpB formed multimers, which have molecular masses of about 2.0-3.0 MDa and consist of about 100-150 subunits. They suppressed the inactivation of several enzymes including citrate synthase and 6-phosphogluconate dehydrogenase by heat, potassium superoxide, hydrogen peroxide and freeze-thawing, but not the inactivation of glyceraldehyde-3-phosphate dehydrogenase by hydrogen peroxide. Both His-IbpA and His-IbpB suppressed enzyme inactivation by various treatments and were also found to be associated with their non-native forms. However, both His-IbpA and His-IbpB were not able to reactivate enzymes inactivated by heat, oxidants or guanidine hydrochloride. When heated to 50 degrees C, each multimeric form of His-IbpA or His-IbpB was dissociated to form a monomer for His-IbpA, and an oligomer of about one-quarter size for His-IbpB. These structural changes were reversible, as both heated proteins regained the multimeric structures after incubation at 25 degrees C. However, when exposed to hydrogen peroxide or potassium superoxide, the large multimeric forms of His-IbpA and His-IbpB were maintained. The results suggest that His-IbpA and His-IbpB suppress the inactivation of enzymes and bind non-native proteins to protect their structures from heat and oxidants.     

Kolaviron and selenium reduce hydrogen peroxide-induced alterations of the inflammatory response

The abilities of kolaviron and selenium (either separately or in combination) to prevent hydrogen peroxide-induced alterations in cell viability and activation were investigated. The cell line U937 was incubated with the antioxidants (i.e. kolaviron or selenium) for 24?h before exposure to hydrogen peroxide and cell viability was assessed via trypan blue dye exclusion assay. The U937 cells were also transformed to the macrophage form, incubated with the antioxidants before exposure to hydrogen peroxide. Subsequently, production of nitric oxide and pro-inflammatory cytokines were assessed as indices of macrophage activation. The myoblast cell line H9c2 was also incubated with Se and kolaviron for 24?h before exposure to hydrogen peroxide. Cell viability and generation of reactive oxygen species (ROS) were assessed via MTT and DCHF assays. The results revealed that hydrogen peroxide significantly reduced (p?<?0.05) the viability of U937 cells which was ameliorated by kolaviron and selenium. Kolaviron and selenium also reduced hydrogen peroxide-induced secretion of nitric oxide, TNF-α, IL-1 and IL-6 by transformed U937 cells. Hydrogen peroxide also significantly reduced (p?<?0.05) the viability of H9c2 cells which was significantly restored by kolaviron. Though selenium had no effect on the proliferation of H9c2 cells, co-treatment with kolaviron significantly reduced hydrogen peroxide-induced alterations. Both kolaviron and selenium also reduced hydrogen peroxide-mediated ROS production by H9c2 cells. In all cases, the combined action of kolaviron and selenium offered greater amelioration of the hydrogen peroxide-induced alterations than their separate effects (p?<?0.05) but may not be synergistic or additive.     

Enhanced inactivation of salmonella and pseudomonas biofilms on stainless steel by use of T-128, a fresh-produce washing aid, in chlorinated wash solutions

The effect of the washing aid T-128 (generally recognized as safe [GRAS] formulation, composed mainly of phosphoric acid and propylene glycol) on inactivation of Salmonella and Pseudomonas populations in biofilms on stainless steel was evaluated under conditions of increasing organic matter loads in chlorinated wash solutions dominated by hypochlorous acid. Biofilms were formed statically on stainless steel coupons suspended in 2% lettuce extract after inoculation with Salmonella enterica serovar Thompson or Newport or with Pseudomonas fluorescens. Coupons with biofilms were washed in chlorine solutions (0, 0.5, 1, 2, 5, 10, or 20 mg/liter at pH 6.5, 5.0 and 2.9), with or without T-128, and with increasing loads of organic matter (0, 0.25, 0.5, 0.75, or 1.0% lettuce extract). Cell populations on coupons were dispersed using intermittent, pulsed ultrasonication and vortexing and enumerated by colony counts on XLT-4 or Pseudomonas agars. Cell responses to fluorescent viability staining of biofilm treatment washing solutions were examined using confocal laser scanning microscopy. Results showed that 0.1% T-128 (without chlorine) reduced P. fluorescens biofilm populations by 2.5 log(10) units but did not reduce Salmonella populations. For both Salmonella and Pseudomonas, the sanitizing effect of free chlorine (1.0 to 5.0 mg/liter) was enhanced (P < 0.05) when it was combined with T-128. Application of T-128 decreased the free chlorine depletion rate caused by increasing organic matter in wash waters and significantly (P < 0.05) augmented inactivation of bacteria in biofilms compared to treatments without T-128. Image analysis of surfaces stained with SYTO and propidium iodide corroborate the cultural assay results showing that T-128 can aid in reducing pathogen viability in biofilms and thus can aid in sanitizing stainless steel contact surfaces during processing of fresh-cut produce.     

Impact of electrolyte solution on electrochemical oxidation treatment of Escherichia coli K-12 by boron-doped diamond electrodes

We studied the disinfection efficacy of boron-doped electrodes on Escherichia coli-contaminated water-based solutions in three different electrolytes, physiological solution (NaCl), phosphate buffer (PB), and phosphate buffer saline (PBS). The effect of the electrochemical oxidation treatment on the bacteria viability was studied by drop and spread plate cultivation methods, and supported by optical density measurements. We have found that bacterial suspensions in NaCl and PBS underwent a total inactivation of all viable bacteria within 10 min of the electrochemical treatment. By contrast, experiments performed in the PB showed a relatively minor decrease of viability by two orders of magnitude after 2 h of the treatment, which is almost comparable with the untreated control. The enhanced bacterial inactivation was assigned to reactive chlorine species, capable of penetrating the bacterial cytoplasmic membrane and killing bacteria from within.     

Hydrogen peroxide triggers the proteolytic cleavage and the inactivation of calcineurin

Increases in the levels of reactive oxygen species (ROS) are correlated with a decrease in calcineurin (CN) activity under oxidative or neuropathological conditions. However, the molecular mechanism underlying this ROS-mediated CN inactivation remains unclear. Here, we describe a mechanism for the inactivation of CN by hydrogen peroxide. The treatment of mouse primary cortical neuron cells with Abeta(1-42) peptide and hydrogen peroxide triggered the proteolytic cleavage of CN and decreased its enzymatic activity. In addition, hydrogen peroxide was found to cleave CN in different types of cells. Calcium influx was not involved in CN inactivation during hydrogen peroxide-mediated cleavage, but CN cleavage was partially blocked by chloroquine, indicating that an unidentified lysosomal protease is probably involved in its hydrogen peroxide-mediated cleavage. Treatment with hydrogen peroxide triggered CN cleavage at a specific sequence within its catalytic domain, and the cleaved form of CN had no enzymatic ability to dephosphorylate nuclear factor in activated T cells. Thus, our findings suggest a molecular mechanism by which hydrogen peroxide inactivates CN by proteolysis in ROS-related diseases.     

Efficacy of two peroxygen-based disinfectants for inactivation of Cryptosporidium parvum oocysts

Two commercial peroxygen-based disinfectants containing hydrogen peroxide plus either peracetic acid (Ox-Virin) or silver nitrate (Ox-Agua) were tested for their ability to inactivate Cryptosporidium parvum oocysts. Oocysts were obtained from naturally infected goat kids and exposed to concentrations of 2, 5, and 10% Ox-Virin or 1, 3, and 5% Ox-Agua for 30, 60, and 120 min. In vitro excystation, vital dyes (4',6'-diamidino-2-phenylindole and propidium iodide), and infectivity in neonatal BALB/c mice were used to assess the viability and infectivity of control and disinfectant-treated oocysts. Both disinfectants had a deleterious effect on the survival of C. parvum oocysts, since disinfection significantly reduced and in some cases eliminated their viability and infectivity. When in vitro assays were compared with an infectivity assay as indicators of oocyst inactivation, the excystation assay showed 98.6% inactivation after treatment with 10% Ox-Virin for 60 min, while the vital-dye assay showed 95.2% inactivation and the infectivity assay revealed 100% inactivation. Treatment with 3% Ox-Agua for 30 min completely eliminated oocyst infectivity for mice, although we were able to observe only 74.7% inactivation as measured by excystation assays and 24.3% with vital dyes (which proved to be the least reliable method for predicting C. parvum oocyst viability). These findings indicate the potential efficacy of both disinfectants for C. parvum oocysts in agricultural settings where soil, housing, or tools might be contaminated and support the argument that in comparison to the animal infectivity assay, vital-dye and excystation methods overestimate the viability of oocysts following chemical disinfection.     

Bactericidal properties of peracetic acid and hydrogen peroxide, alone and in combination, and chlorine and formaldehyde against bacterial water strains.

The bactericidal properties of peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were compared in vitro using a rapid micromethod. A combination of peracetic acid and hydrogen peroxide was also tested to assess interactions. The activities of these agents, which are widely used as disinfectants, were evaluated against water isolates and culture collection strains. Peracetic acid and chlorine exhibited an excellent antimicrobial activity, with a relatively rapid destruction of 10(5) bacteria/mL. The time-dependent bactericidal activities of hydrogen peroxide and formaldehyde were the lowest. The combination of peracetic acid and hydrogen peroxide, tested by a checkerboard micromethod, was found to be synergistic. The minimal bactericidal concentration was established in terms of time for a given mixture of peracetic acid and hydrogen peroxide. Determination of bactericidal concentrations showed that synergy was maintained with increasing contact time. Concentrations for minimal times of treatment by chemicals that provided interesting activities in vitro were tested for disinfection of ultrafiltration membranes. The bactericidal activities of peroxygen compounds were confirmed and synergism was maintained in working conditions. Chlorine showed a loss of efficacy when used on membranes.     

Esteblishment and characterization of the line of Fagopyrum tataricum morphogenic callus tolerant to aminotriazole

It is shown that the inhibitor of catalase 3-amino-1,2,4-triazole (AT) at the concentration of 2 mM affected differently growth of tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) callus lines differing in the morphogenecity. In some cases, AT induced the death of a great fraction of non-morphogenic callus cells; in other cases, it inhibited growth and reduced viability of morphogenic callus. The death of non-morphogenic callus cells may be related to the accumulation of hydrogen peroxide and the development of oxidative stress. After morphogenic callus treatment with AT, we obtained a modified line 1?C8 AT tolerant to AT and differing from the original line in morphology, cell sizes, proliferative activity, and some biochemical characteristics. In the 1?C8 AT line, catalase was sensitive to this inhibitor action. In this case, catalase inactivation with AT did not increase the content of hydrogen peroxide in the cells, which may indicate the compensatory functioning of another/others mechanism(s) destroying hydrogen peroxide.     

A Decrease of neuroprotective effect of ganglioside GM1 on PC12 cells under conditions of oxidative stress in the presence of inhibitor of tyrosine kinase of Trk-receptors

Effects of inhibitors of tyrosine kinases (K-252a, genistein) and of phospholipase A₂ (bromophenacyl bromide) on viability of PC12 cells are studied in the presence of hydrogen peroxide and ganglioside GM1. The degree of inhibition of hydrogen peroxide cytotoxic effects by ganglioside GM1 amounted to 52.8 ± 4.2%. However, in the presence in the medium of 0.1 and 1 μM inhibitors of tyrosine kinase of Trk-receptors (K-252a) it was as low as 32.7 ± 6.5% and 11.7 ± 9.8%, respectively. GM1 prevented Na⁺,K⁺-ATPase oxidative inactivation produced by H₂O₂, but in the presence of 1 μM K-252a this effect was practically not pronounced. In the presence of another inhibitor of tyrosine kinases-genistein, a tendency for a decrease of the GM1 protective effect was observed at its concentrations 0.1 and 1 μM, whereas at a higher concentration 10 μM, genistein depressed statistically significantly the GM1 neuroprotective effect. It was found that inhibitor of phospholipase A₂ bromophenacyl bromide did not affect the action of GM1 aimed at increasing the viability of cells under action of hydrogen peroxide on them. It seems that this enzyme is not involved in the cascade of reactions participating in realization of the ganglioside protective effect. Thus, inhibitor of tyrosine kinase of Trk-receptors K-252a decreases or practically prevents the ganglioside GM1 neuroprotective effect on PC12 cells under stress conditions; the same ability is characteristic of genistein—an inhibitor of tyrosine kinases of the wider spectrum of action.