Cell lysis in sludge pretreatment by advanced oxidation process (AOP) has a great effect on sludge dewaterability. Cell lysis caused by reactive radicals (e.g. hydroxyl radical) was dependent on the ...reaction site of AOP. However, little is known about the accurate radical generation site of AOP in sludge pretreatment. In this study, two kinds of oxidation behaviors from different oxidants (HOCl vs. H2O2) catalyzed by ferrous iron were comparatively investigated. Higher amount of living cells (84.3%) and hydroxyl radicals (9.86 × 10−5 M), and more fragmentized sludge flocs (particle sizes of D50 was 50.1 vs. 57.3 μm of RS) were detected in sludge conditioned by Fe2+/H2O2, which implied that Fenton reaction mainly happened at surface and outside of sludge flocs (such as EPS layer and liquid phase). Thus, it could be regarded as “extracellular oxidation”. Fewer living cells (undetectable), fewer amount of hydroxyl radicals (undetectable in sludge), and more integrated sludge flocs (particle size of D50 was 56.1 vs. 57.3 μm of RS) were determined in sludge conditioned by Fe2+/Ca(ClO)2. Hence, it could be regarded as “Intracellular oxidation”.
In addition, sludge pretreatment based on Fe2+/Ca(ClO)2 could achieve simultaneous deep-dewatering performance and total coliforms inactivation. Based on response surface methodology, the optimal dosages of Fe2+ and Ca(ClO)2 were proposed as 106.1 and 234.5 mg/g volatile solids respectively, without any acidification of sludge. Under these optimal dosages, the water content of dewatered sludge cake was 51.9 ± 0.1 wt% and the pH of the final filtrate was 5.8 ± 0.2. Total coliforms of sludge could be inactivated in 10 s after Fe2+/Ca(ClO)2 addition.
Display omitted
•Catalyzed hypochlorite achieved deep-dewatering and Escherichia coli inactivation.•Optimal dosages of 106.1 mg Fe2+/g VS and 234.5 mg Ca(ClO)2/g VS were proposed.•Extracellular and intracellular oxidations were investigated in sludge pretreatment.•Hypochlorite attacked inner cell components, resulting in intracellular oxidation.•Fenton oxidation occurred at surface of sludge flocs as extracellular oxidation.
The bacterial inactivation mechanisms by solar light and the photo-Fenton process is still a matter of debate. In this study, we bring evidence towards the elucidation of the mechanisms that govern ...photo-Fenton disinfection at near-neutral pH. With the use of porin-deficient and catalase over-producing E. coli strains, in conjunction with measurements of cell wall oxidation and permeability, we are able to i) highlight the role of the aforementioned components in bacterial inactivation and ii) localize the damages in the intracellular domain, despite the addition of the Fenton reagents in the bulk. We report that H2O2 oxidizes cell walls but under light the process is of low significance; UVA initiated an intracellular oxidation process based on excess accumulated H2O2, while the UVA+H2O2 and UVA+H2O2+Fe2+ processes have the same effect with light, albeit enhanced, as shown by malondialdehyde (MDA) production and ONPG hydrolysis rates. Finally, compared to the UVA-assisted photo-Fenton process, its solar counterpart is enhanced by the direct UVB effects on bacterial DNA. In conclusion, we have sufficient evidence to postulate that the photo-Fenton process is intracellular and propose the pathways that form the integrated bacterial inactivation mechanism by photo-Fenton.
Display omitted
•Evidence for the intracellular bacterial inactivation by the photo-Fenton process are presented.•The use of porin- and catalase mutants reveals key aspects of H2O2 transport and elimination.•Porinless mutants presented lower inactivation rates than the parent bacterial strains.•H2O2-scavenging enzymes are incapacitated by light exposure, even at over-expression.•A mechanistic proposal is provided based on the localization of oxidative damages on E. coli.
•Fe2+/Ca(ClO)2 conditioning simultaneously promoted sludge dewatering and ARG removal.•Fe2+/Ca(ClO)2 conditioning was even better than Fenton treatment to eliminate ARGs.•HOCl could penetrate the ...cell and induce direct oxidation of intracellular ARGs.•ARG removal was achieved by reducing potential hosts and related metabolic pathways.•Fe2+/Ca(ClO)2 conditioning oxidized intracellular ARGs without bacterial cell lysis.
Pre-acidification has been shown to be crucial in attenuating antibiotic resistance genes (ARGs) during the conditioning of sewage sludge. However, it is of great significance to develop alternative conditioning approaches that can effectively eliminate sludge-borne ARGs without relying on pre-acidification. This is due to the high investment costs and operational complexities associated with sludge pre-acidification. In this study, the effects of Fe2+/Ca(ClO)2 conditioning treatment on the enhancement of sludge dewaterability and the removal of ARGs were compared with other conditioning technologies. The dose effect and the associated mechanisms were also investigated. The findings revealed that Fe2+/Ca(ClO)2 conditioning treatment had the highest potential, even surpassing Fenton treatment with pre-acidification, in terms of eliminating the total ARGs. Moreover, the effectiveness of the treatment was found to be dose-dependent. This study also identified that the •OH radical reacted with extracellular polymeric substance (EPS) and extracellular ARGs, and the HOCl, the production of which was positively correlated with the dose of Fe2+/Ca(ClO)2, could infiltrate the EPS layer and diffuse into the cell of sludge flocs, inducing the oxidation of intracellular ARGs. Furthermore, this study observed a significant decrease in the predicted hosts of ARGs and MGEs in sludge conditioned with Fe2+/Ca(ClO)2, accompanied by a significant downregulation of metabolic pathways associated with ARG propagation, thereby contributing to the attenuation of sludge-borne ARGs. Based on these findings, it can be concluded that Fe2+/Ca(ClO)2 conditioning treatment holds great potential for the removal of sludge-borne ARGs while also enhancing sludge dewaterability, which mainly relies on the intracellular oxidation by HOCl.
Display omitted
Aim
To understand the underlying cellular mechanisms during inactivation of Escherichia coli in response to antimicrobial solution of nonthermal plasma‐activated N‐acetylcysteine (NAC).
Methods and ...Results
The recommended techniques were used to demonstrate E. coli cellular and transcriptomic changes caused associated with peroxynitrite and compared with plasma‐treated NAC solution. The findings demonstrate that E. coli cells respond to plasma‐treated NAC and undergo severe oxidative and nitrosative stress, and leading to stress‐induced damages to different components of bacterial cells, which includes loss of membrane potential, formation of oxidized glutathione (GSSG), formation of nitrotyrosine (a known marker of nitrosative stress), DNA damage, and generated a prominent pool of peroxynitrite. Reverse‐transcriptase (RT)‐polymerase chain reaction analysis of reactive nitrogen species (RNS) responsive genes indicated their differential expressions.
Conclusion
For the first time, we report that the plasma‐treated NAC solution activates predominantly nitrosative stress‐responsive genes in E. coli and is responsible for cell death.
Significance and Impact of the Study
The reactive species generated in solutions by nonthermal plasma treatment depends on the type of solution or solvent used. The plasma‐treated NAC solution rapidly inactivates E. coli, mostly involving highly RNS generated in NAC solution, and has high potential as disinfectant.
Gel filtration of black berry (
Rubus fruticosus sp) ethanolic extracts was employed to obtain an anthocyanin-enriched extract. The anthocyanin profile identified cyanidin-3-glucoside as the primary ...(e.g., 90% of total) anthocyanin present in blackberry. Gel filtration of crude extracts resulted in a 20-fold increase in total anthocyanin content, with no change in the proportion of cyanidin-3-glucoside. Antioxidant activities of both the crude and anthocyanin-enriched blackberry extracts were determined using cell-free (ORAC) and cell-based (INT-407 intracellular) antioxidant assays. Antioxidant activity, assessed by the ORAC assay, indicated a 7-fold increase in activity for the anthocyanin-enriched fraction. Similar results were obtained for the anthocyanin-enriched extract using the intracellular antioxidant assay with INT-407 cells. Our results indicate that the anthocyanin content, and more specifically the presence of cyanidin-3-glucoside, in blackberry, contributes a major part of the antioxidant ability to suppress both peroxyl radical-induced chemical and intracellular oxidation.
The effect of four esters of caffeic acid, caffeic acid methanol ester (CAME), caffeic acid ethanol ester (CAEE), caffeic acid isopropyl ester (CAIPE) and caffeic acid phenethyl ester (CAPE) on ...intracellular oxidation, vitality and viability of the yeast Saccharomyces cerevisiae as a model eukaryotic organism was investigated. Results showed that each ester showed its own behavior at the concentrations tested. For CAPE, CAIPE and CAEE decreased intracellular oxidation and simultaneously increased cellular vitality with no changes in cellular viability compared to the control were determined. Additionally, a combination of CAIPE or CAPE with ethanolic propolis extract was observed to be more effective in decreasing intracellular oxidation compared to propolis extract alone.
The yeast Saccharomyces cerevisiae has been used as a model organism to investigate responses to different environmental stressors. The importance of their conclusions has been expanded to human ...cells. The experiments were done with exponentially growing cells, which do not resemble human cells. Human and other eukaryotic cells spend the greater part of their lives in a quiescent state, known as G0 corresponding to the yeast stationary phase. Providing energy, which comes from mitochondrial respiration, is also common. Thus, in the present study S. cerevisiae was used in the stationary phase for characterization at the cellular and proteome levels. At the cellular level, optical density, cell viability, glycogen content, intracellular oxidation and cell energy metabolic activity were measured, while at the proteome level, protein profiles were analyzed using two-dimensional electrophoresis. The data obtained at both levels provide better insight into quiescence program state, which still remains poorly understood. At their base, optimal time period reflecting a stable metabolic and oxidative state of the yeast was determined. Consequently, this period is the appropriate to study changes in cell oxidant status and energy metabolic activity in response to different environmental stressors.
Display omitted
► S. cerevisiae in the stationary phase was characterized at the cellular and proteome level. ► At the cellular level, optical density, cell viability, glycogen content, intracellular oxidation and cell energy metabolic activity were measured, while at the proteome level, protein profiles were analyzed using two-dimensional electrophoresis. ► The data obtained at both levels provide better insight into quiescence program state, which still remains poorly understood. ► Optimal time period reflecting a stable metabolic and oxidative state of the yeast was determined (2 to 8days in PBS buffer-plateau 1). ► As such, this yeast system shows potential for studying changes in cell oxidant status as well as for energy metabolic activity in response to different environmental stressors.
The eukaryotic cell contains a multitude of pathways coupling environmental stimuli to the specific regulation of gene expression. Two early response transcriptional complexes, NF-κB and AP-1, appear ...to respond to environmental stressors by inducing the expression of response specific downstream genes. Both are well-characterized transcriptional regulatory factors that are induced by a wide variety of seemingly unrelated exogenous and endogenous agents and serve important roles in cell growth and differentiation, immunity, inflammation, and other preprogrammed cellular genetic processes. The activities of NF-κB and AP-1 are also affected following exposure to chemicals, drugs, or other agents that appear to alter the cellular oxidation/reduction (redox) status. From these observations, it has been suggested that changes in cellular oxidation/reduction status, communicated via a series of cellular redox-sensitive signaling circuitry employing metal- and thiol-containing proteins, serve as common mechanisms linking environmental stressors to adaptive cellular responses. As such, these transcription factors are ideal paradigms to study the mechanism and possible physiological significance of early response genes in the cellular response to changes in cellular redox status. In this article we summarize the evidence suggesting that cellular redox regulates these transcription factors.
Royal jelly is a bee product, secreted from the hypopharingeal and mandibular glands of worker bees. There are many reports on pharmacological activities of royal jelly in experimental animals, but ...there are few about its antioxidative properties connected to aging. The aim of the work was to investigate the antioxidative action of royal jelly in the cell of the yeast
Saccharomyces cerevisiae as a model organism. Yeast was cultivated in YEPD medium enriched with different concentrations of royal jelly like 1, 2 and 5
g/L. Yeast growth was monitored by measuring optical density. At different time points cell energy metabolic activity was measured using the cell energy metabolism indicator resazurin, and 2′,7′-dichlorofluorescein was applied to estimate intracellular oxidation. Additionally, protein profile of cell extract was analyzed by 2-D electrophoresis. Results showed that royal jelly decreased intracellular oxidation in a dose dependent manner. Additionally it affected growth and cell energy metabolic activity in a growth phase dependent manner. Protein profile analysis showed that royal jelly in the cell does not act only as a scavenger of reactive oxygen species, but it also affects protein expression. Differentially expressed proteins were identified.
Mammalian electron transfer flavoproteins comprise a mitochondrial matrix heterodimer, and an electron transfer flavoprotein dehydrogenase localized in the mitochondrial inner membrane. Electrons ...from primary acyl-CoA dehydrogenases, of mitochondrial metabolism of fatty acids and amino acids, are transferred to the matricial heterodimer and, subsequently, to the electron transfer flavoprotein dehydrogenase, which transfers electrons to ubiquinone of the mitochondrial electron transport chain. Several evidences suggest that these proteins may convey electrons directly to molecular oxygen, yielding reactive oxygen species. In this work, we investigated phenotypes of the yeast mutants affected in the orthologous genes of the matrix heterodimer (AIM45 and YGR207c/CIR1) and of the electron transfer flavoprotein dehydrogenase (YOR356w/CIR2). The mutant strains aim45 and yor356w/cir2 displayed better growth on several non-fermentable carbon sources, which depended on the component of the electron transport chain that accepts the electrons resulting from its mitochondrial oxidation. Furthermore, upon heat shock, the mutant strains presented decreased intracellular oxidation, suggesting that these flavoproteins are a source of reactive oxygen species. Other phenotypes identified suggest that AIM45, YGR207c/CIR1 and YOR356w/CIR2 can protect cells from oxidative and heat stress, which encompass increased heat stress sensitivity, superoxide sensitivity, both only on non-fermentable carbon sources.
PDF
