Oxidation Rate Research Articles

Aging delays the suppression of lipolysis and fatty acid oxidation in the postprandial period.

Plasma glycerol and free fatty acid concentrations decrease following oral glucose consumption, but changes in the rate of lipolysis during an oral glucose tolerance test (OGTT) have not been documented in conjunction with changes in fatty acid (FA) oxidation or reesterification rates in healthy individuals. After a 12-h overnight fast, 15 young (21-35 yr; 7 men and 8 women) and 14 older (60-80 yr; 7 men and 7 women) participants had the forearm vein catheterized for primed continuous infusion of [1,1,2,3,3-2H]glycerol. A contralateral hand vein was catheterized for arterialized blood sampling. Indirect calorimetry was performed simultaneously to determine total FA and carbohydrate (CHO) oxidation rates (Rox). Total FA reesterification rates (Rs) were estimated from tracer-measured lipolytic and FA oxidation rates. After a 90-min equilibration period, participants underwent a 120-min, 75-g OGTT. Glycerol rate of appearance (Ra), an index of lipolysis, decreased significantly from baseline 5 min postchallenge in young participants and 30 min in older participants. At 60 min, FA Rox decreased in both groups, but was significantly higher in older participants. Between 5 and 90 min, CHO Rox was significantly lower in older participants. In addition, FA Rs was significantly lower in older participants at 60 and 90 min. The area under the curve (AUC) for FA Rox was greater than that for FA Rs in older, but not in young participants. Our results indicate that, in aging, the postprandial suppression of lipolysis and FA oxidation are delayed such that FA oxidation is favored over CHO oxidation and FA reesterification.NEW & NOTEWORTHY To our knowledge, our investigation is the first to demonstrate changes in lipolysis during an oral glucose tolerance test (OGTT) in healthy young and older individuals. Plasma glycerol and free fatty acid concentrations changed after glycerol rate of appearance (Ra), indicating that plasma concentrations are incomplete surrogates of the lipolytic rate. Moreover, simultaneous determinations of substrate oxidation rates are interpreted to indicate that metabolic inflexibility in aging is characterized by delayed changes in postprandial substrate utilization related to the lipolytic rate.

Regulation of Microlocalization of Antioxidants by Surfactant Micelles in Oil-in-Water Emulsions.

The mass transport effect of aqueous micelles on antioxidants and oxidation products in emulsions may alter the rate, degree, and pathway of lipid oxidation. In this study, the dynamic mass transport of oxidation products and endogenous tocopherol during storage at different micelle concentrations was monitored by UV-vis spectrophotometry and high-performance liquid chromatography. Furthermore, the microlocalization of tocopherol in micelles was investigated using 1H nuclear magnetic resonance and nuclear Overhauser effect spectroscopy, fluorescence measurements, and molecular dynamics simulation. It was demonstrated that high-concentration micelles enhanced the emulsion stability by promoting the mass transport of hydroperoxides and endogenous antioxidants. The enhancement of micelles was a superposition effect of concentration, interaction sites, and binding force between tocopherols and Tween 20 molecules. Tween 20 concentration-induced favorable changes of microlocalization of tocopherol and dynamic mass transport demonstrated a new integrated perspective to control lipid oxidation.

Combined transcriptome and proteome profiling reveal cell-type-specific functions of Drosophila garland and pericardial nephrocytes

Drosophila nephrocytes are specialised cells that share critical functional, morphological, and molecular features with mammalian podocytes. Accordingly, nephrocytes represent a preferred invertebrate model for human glomerular disease. Here, we established a method for cell-specific isolation of the two types of Drosophila nephrocytes, garland and pericardial cells, from animals of different developmental stages and ages. Mass spectrometry-based proteomics and RNA-Seq-based transcriptomics were applied to characterise the proteome and transcriptome of the respective cells in an integrated and complementary manner. We observed characteristic changes in the proteome and transcriptome due to cellular ageing. Furthermore, functional enrichment analyses suggested that larval and adult nephrocytes, as well as garland and pericardial nephrocytes, fulfil distinct physiological functions. In addition, the pericardial nephrocytes were characterised by transcriptomic and proteomic profiles suggesting an atypical energy metabolism with very low oxidative phosphorylation rates. Moreover, the nephrocytes displayed typical signatures of extensive immune signalling and showed an active antimicrobial response to an infection. Factor-specific comparisons identified novel candidate proteins either expressed and secreted by the nephrocytes or sequestered by them. The data generated in this study represent a valuable basis for a more specific application of the Drosophila model in analysing renal cell function in health and disease.

Synergistic effects of Pt and Y addition in (Ni, Pt)CrAlY bond coat on oxide spallation resistance and growth of interdiffusion zone between bond coat and Ni-based single crystal superalloy

This study shows the beneficial effect of Pt addition to the (β+γ)-NiCrAlY coating. Adding Y in NiCrAl increases oxide growth kinetics but improves spallation resistance. Pt with Y does not change the oxidation rate compared to only adding Y but significantly reduces spallation when cooled to room temperature. Continuous layers of Al2O3 and Cr2O3, along with other oxides such as YAlO3, NiCr2O4, and NiAl2O4, are observed. Moreover, Pt addition reduces the thickness of the interdiffusion zone where Al goes through an uphill diffusion profile, minimizing Al loss and significantly decreasing the growth of deleterious TCP phases.

Application of bacterial nanocellulose film loaded with sodium nitrite, sumac, and black carrot extracts to reduce sodium nitrite, extend shelf life, and inhibit Clostridium perfringens in cooked beef ham

This study aimed to develop innovative bacterial nanocellulose (BNC) films incorporated with sodium nitrite (SN), sumac extract (SE), and black carrot extract (BCE) to reduce sodium nitrite, extend shelf life, and inhibit Clostridium perfringens in cooked beef ham. The ham covered with BNC film immersed in SE (10 % w/v) + BCE (5 % w/v) + SN (125 ppm) (SE10BCE5SN125) exhibited the lowest microbial load (4.39, 4.32, 3.83, and 4.6 log cycles reductions in total viable count, lactic acid bacteria, Enterobacteriaceae, and C. perfringens, respectively) and the lowest oxidation rate (70 % reduction compared to control) on day 28 of storage. The samples covered with SE10BCE5SN125 film had also the lowest level of residual nitrite (64 % lower compered to positive control). Positive control (ham containing 120 ppm SN) and ham covered with SE10BCE5SN125 film had the highest redness. It was concluded that the films developed in this study have the potential to reduce the use of sodium nitrite in beef ham production.

Effects of the Aerobic Exercise Types of the Same Amount of Exercise on the Energy Metabolism During Exercise and Recovery Phase

OBJECTIVES The purpose of this study was to investigate the effects of aerobic exercise types on energy metabolism during and after exercise under the same exercise volume conditions.METHODS Ten healthy men were randomly assigned to interval(IV), intermittent(IM), and continuous(CO) exercise, and the experiment was conducted at intervals of one week and consumed 300 kcal. The data were verified by repeated measurement one-way ANOVA, and contrast was conducted. The statistical significance level was set at α=0.05.RESULTS As a result of the study, first, among the energy metabolism variables during exercise, oxygen intake(VO2) was statistically significantly higher in the IM and CO exercise than in the IV exercise(p<0.001). The respiratory exchange rate(RER, p<0.001), energy consumption per minute(ECM, p<0.001), and carbohydrate consumption amount(CCA, p=0.013) were significantly higher in the IM exercise, but there was no statistically significant difference in the fat oxidation rate(FOR), fat consumption amount(FCA), and carbohydrate consumption rate(CCR). Second, there were statistically significant differences in EPOC(p<0.001), RER(p<0.001), and ECM(p<0.001) in the post-exercise recovery phase, among them, the highest in the IM exercise. In terms of FOR(p=0.002) and FCA(p=0.007), IV and CO exercise were significantly higher than IM exercise, and on the contrary, in terms of CCR(p=0.002) and CCA(p<0.001), IM exercise was higher than IV and CC exercise.CONCLUSIONS In conclusion, considering not only during exercise but also the recovery period after exercise, the intermittent exercise seems to have an advantage in increasing energy consumption while having a shorter exercise time than the other two under the condition of the same exercise amount.

Fish oil-containing edible films with active film incorporated with extract of Psidium guajava leaves: preparation and characterization of double-layered edible film

The utilization of zein and gum arabic has grown in an attempt to formulate wall materials based on protein–polysaccharide complexes. This mixture provides a versatile delivery system for hydrophilic (guava leaf extract, GLE) or lipophilic (fish oil, FO) bioactive compounds, and it can be used as an edible film-forming polymer. This study was undertaken to characterize FO-containing edible films that were double-layered with a film containing GLE. Modified zein and gum arabic solutions (MG complex) were mixed at a ratio of 1:1.5 (v/v), adjusted to pH 5, added with glycerol (20% of the complex) and FO (5% of the complex), and finally adjusted to pH 5. This was prepared as the bottom/lower layer. The upper/active layer was prepared by mixing MG complex, glycerol, and GLE (1, 3, and 5% w/v of the complex). The total phenolic and flavonoid contents in GLE were 15.81 mg GAE/g extract and 6.99 mg QE/g extract, respectively. The IC50 of the DPPH radical scavenging activity of GLE was 26.86 ppm with antibacterial activity against Bacillus subtilis and Escherichia coli of 9.83 and 12.55 mm. The total plate counts of double-layered films containing GLE were retained below 3 log CFU/g during 28-day storage. The peroxide values of these films were dimmed for no more than 9.08 meq/kg sample on day 28 of storage. Thickness (872.00-971.67 μm), water vapor transmission rate (12.99-17.04 g/m2/day), tensile strength (1.56-2.02 kPa), elongation at break (61.53-75.41%), glass transition (52.74-57.50°C), melting peak (131.59-142.35°C), inhibition against B. subtilis (33.67-40.58 mm), and inhibition against E. coli (2.05-9.04 mm) were obtained by double-layered films. GLE can be successfully incorporated into the active layer of a double-layer film to improve its characteristics while significantly slowing down the microbial contamination and oxidation rate. MG complex and FO can also contribute to the performance of the edible film.

Homogeneous Catalysts of RedOx Processes Based on Heteropolyacid Solutions. VI: Developing a Process for Low-Temperature Oxidation of CO with Oxygen

Research on the development of a homogeneous process for low-temperature oxidation of carbon monoxide in the presence of a “platinum group metal + vanadium-containing heteropolyacid (HPA)” catalytic system has been presented. The optimal reaction conditions, ensuring the maximum rate of CO oxidation to CO2, have been determined; for this reaction the kinetic features have been established, and its mechanism has been proposed. It has been shown that homogeneous systems based on PdII complex exhibit high activity and productivity, but have low stability and operate only at pH below 1,5. The stability of the catalyst can be increased by simultaneous introduction of σ- and π-donor ligands into the system; however, it is more effective to use the PtIV complex in the presence of catalytic amounts of palladium salt at a ratio of 100/1. The transition from HPA solutions with a low content of vanadium atoms (H7PMo8V4O40) to solutions of modified compositions (H10P3Mo18V7O84) ensures an increase in the activity and productivity of the system, with the kinetics of CO oxidation being maintained. The combined homogeneous catalyst PtIV + PdII + H10P3Mo18V7O84 remains stable during multi-cycle use without reducing activity, operates without an induction period and can be used at pH range of 1,7–2,0, which simplifies the process equipment.

An Innovative Fuel Design for HTGRs: Evaluating a 10-Hour High-Temperature Oxidation of the SiC Fuel Matrix During Air Ingress Accident Conditions

Preventing severe corrosion incidents caused by air ingress accidents in high-temperature gas-cooled reactors (HTGRs) while improving heat removal efficiency from the core is of paramount importance. To enhance both safety and efficiency, a sleeveless silicon carbide (SiC)-matrix fuel compact has been proposed. This study evaluates the 10-hour oxidation of reaction-sintered SiC (RS-SiC)-matrix fuel compact under the conditions of an air ingress accident within the temperature range of 1000 to 1400 °C. The oxidation tests were conducted in a stagnant air environment without flow. As a result, it is demonstrated that RS-SiC exhibits exceptional resistance to air oxidation up to 1400 °C, as shown by the thermogravimetric analysis (TGA), with minimal mass loss due to the oxidation of free carbon. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) analysis reveals that the morphology and thickness of the SiO2 layer formed on the RS-SiC surface vary with temperature. At 1400 °C, uniform oxide layer thickness ranging from 1.59 to 4.10 μm and localized nodule-like oxide formations of approximately 10 μm are observed. In contrast, at 1000–1200 °C, thinner oxide layers are identified, indicating that oxide growth accelerates at higher temperatures. The oxidation rates measured provide insights into the mechanisms of oxide growth.

High-Temperature Steam Oxidation and Surface Microstructure Evolution of Fe13Cr6Al(1–4)Mo0.15Y Alloys

The current study investigated the microstructure evolution and anti-corrosion behavior of low Y doping alloys of Fe13Cr6Al(1–4)Mo0.15Y subjected to high-temperature steam (800 °C to 1300 °C). The results indicate that steam oxidation induces the growth of high-quality oxidation film that is thermodynamically driven, with rapid increases in the thickness from 800 °C to 1300 °C without film convolution and spallation. The film convolution and spallation were successfully suppressed through on-site formation of the high-temperature stable ternary crystalline phase (Y2Mo3O12) and decreasing of the thickness of α-Al2O3 oxidation film during the fabrication and oxidation scenario. The on-site steam oxidation rate has been significantly suppressed, with lower weight gain and less oxidizing film convolution than monolithic FeCrAlMo alloy, through the addition of a low concentration of Y.

Influence of composition and temperature on oxide film formation for Fe-Cr-Ni alloys in simulated PWR primary water

ABSTRACT The growth of oxide films on Fe-Cr-Ni alloys in simulated pressurized water reactor (PWR) primary system environments was investigated, with focus on the influence of alloy composition and temperature. Oxide film thicknesses were measured for 90 specimens prepared from compact tension (CT) test pieces. Cross-sectional observations were also conducted on coupon specimens using scanning transmission electron microscopy (STEM). The behavior of Ni-based alloys, specifically Alloy 600, and Fe-based alloys, specifically Type 316 stainless steel, were compared. Ni-based alloys exhibit superior corrosion resistance due to slower Fe diffusion kinetics compared to Fe-based alloys, leading to the formation of a nickel-enriched protective layer at the metal-oxide interface. The oxidation rates of Ni-based alloys follow an Arrhenius-type temperature dependence. In contrast, Fe-based alloys show a more complex temperature-dependent behavior, with reduced oxidation rates at higher temperatures that are likely due to changes in oxide dissolution. Higher chromium concentrations in both alloy types improve the protectiveness of the oxide film towards corrosion by forming a more compact inner oxide layer. The study identifies three primary factors influencing oxide film growth: reactions at the metal-oxide interface, diffusion within the oxide layer, and processes at the oxide-solution interface. The relative significance of these processes varies depending on the alloy composition and temperature.

The Effect of Pre-Exercise Caffeine and Glucose Ingestion on Endurance Capacity in Hypoxia: A Double-Blind Crossover Trial

The impact of caffeine and glucose supplementation in a hypoxic environment on endurance exercise performance remains inconclusive. The current study examined the effect of pre-exercise carbohydrate and caffeine supplementation on endurance exercise performance in an acute hypoxic environment. Eight healthy active young males participated in this double-blind, within-subjects crossover study. Participants ingested the test drink 60 min before exercising at 50% Wmax for 90 min on a cycle ergometer (fatiguing preload); there followed an endurance performance test at 85% Wmax until exhaustion in a hypoxic chamber (~15%O2). Participants completed four experimental trials in a randomized order: caffeine (6 mg·kg−1; Caff), glucose (1 g·kg−1; CHO), caffeine (6 mg·kg−1) + glucose (1 g·kg−1; Caff−CHO), and taste- and color-matched placebo with no caffeine or CHO (PLA). Blood samples were collected during fasting, pre-exercise, every 30 min throughout the exercise, and immediately after exhaustion. The caffeine and glucose trials significantly enhanced endurance capacity in hypoxic conditions by Caff, 44% (68.8–31.5%, 95% confidence interval), CHO, 31% (44.7–15.6%), and Caff−CHO, 46% (79.1–13.2%). Plasma-free fatty-acid and glycerol concentrations were higher in Caff and PLA than in CHO and Caff−CHO (p < 0.05). The estimated rate of fat oxidation was higher in Caff and PLA than in CHO and Caff−CHO (p < 0.05). There were no significant differences in ratings of perceived exertion between trials. In conclusion, the ingestion of caffeine, glucose, or caffeine + glucose one hour before exercising in hypoxic conditions significantly improved 85% Wmax endurance performance after prolonged exercise.

Kinetics of Oxidation of an Al2O3–SiC–C‐Based Blast Furnace Trough Refractory in Air

During tapping of liquid hot‐metal from the blast‐furnace, the blast‐furnace main trough gets exposed to air and the blast‐furnace‐trough refractory becomes prone to oxidation. In this work, isothermal oxidation kinetics of an Al2O3–SiC–C‐based BFT (Blast‐Furnace‐Trough) refractory castable using a high‐temperature vertical tubular furnace equipped with a microbalance is investigated. Herein, it is observed that up to about 800 °C, carbon only oxidizes, resulting in weight loss in the refractory. Around 900 °C, SiC also starts to oxidize via the passive‐oxidation mechanism, leading to the formation of a mullite phase as a result of the reaction between SiO2 generated via passive oxidation and Al2O3 already present in the refractory. This causes a volume expansion and weight gain, both having a beneficial effect on the refractory performance, which is further validated from apparent porosity measurements. Thus, above 900 °C, simultaneous oxidation of C and passive oxidation of SiC occurs, which eventually stabilizes the weight of the refractory. Around 1100 °C, the oxidation process of the refractory is practically complete, with no further increase in the oxidation rate beyond 1100 °C. The activation energy for the oxidation process is obtained as 37.2 ± 5 kJ mol−1 in the temperature range 600–1150 °C.

Influence of BN microstructure on oxidation of SiC/BN/SiC composites

AbstractThis study investigates the effects of boron nitride (BN) coating characteristics on the subsurface oxidation behavior of SiC/SiC composites in high‐temperature, water‐rich environments. Three types of coatings were examined: a crystalline stoichiometric BN, an amorphous BN, and a Si‐doped amorphous BN, the latter two containing 5–10 at% of oxygen and carbon. High‐resolution imaging and chemical analysis techniques were used to probe microstructural changes after oxidation at 1000°C for 1 or 12 h in flowing 20 vol% H2O, focusing on effects of coating thickness. Complementary chemical thermodynamic calculations and models for reaction‐ and transport‐controlled recession were used to interpret the experimental findings. Crystalline BN coatings produce open recession channels without forming borosilicate glass, a consequence of carbothermal reduction arising from C/CO produced through concomitant SiC oxidation. The combination of active oxidation and the relatively thick coatings in this system (ca. 1 µm) leads to a recession rate controlled by the intrinsic BN volatilization rate rather than the rate of gas transport. In contrast, amorphous coatings, both undoped and Si‐doped, readily oxidize to form borosilicate glasses that replace the BN. Broadly, the recession lengths increase with coating thickness. In the early stages, while the glass is boria‐rich and thus permeable to environmental oxidants, recession is controlled by the BN oxidation rate. As boria volatilizes, the silica concentration in the glass increases, eventually reaching the saturation limit and precipitating solid silica on the internal surfaces, essentially arresting further recession.

Improving In Situ Combustion for Heavy Oil Recovery: Thermal Behavior and Reaction Kinetics of Mn(acac)3 and Mn-TO Catalysts

In this research work, the catalytic performances of two manganese-based catalysts, manganese (III) acetylacetonate (Mn(acac)3) and manganese tallate (Mn-TO), were studied during the process of Ashalcha heavy oil oxidation under in situ combustion conditions. DSC analysis shows distinct thermal behavior of both ligated catalysts during low- and high-temperature oxidation phases (LTO and HTO); for example, the shifting in peak temperature (Tp) in the HTO at a heating rate of 10 °C/min was reduced by approximately 5.3% for Mn-TO and 2.24% for Mn(acac)3 when compared with uncatalyzed heavy oil. Combined isothermal kinetic analyses using the Friedman and Kissinger–Akahira–Sunose analytic methods have provided insights about activation energies and frequency factors over the whole conversion range, where the catalytic performance of Mn-TO showed low activation energies in both LTO and HTO (Eα of Mn-TO was approximately 13.33% (LTO) and 7.68% (HTO) less than with the heavy oil alone). In addition, calculations of the effective rate constant confirmed the increased oxidation rate trend of both catalysts, with Mn-TO exhibiting the highest values. The findings highlight the potential of these manganese-based catalysts, the Mn-TO catalyst in particular, in optimizing heavy oil oxidation processes. The overall results further contribute to developing more efficient ligand catalyst complexes for sustainable heavy oil recovery while continuously improving their efficient application during in situ combustion in the petroleum industry.

The Impact of Metal Ions on MXene Membranes: Critical Role of Titanium Vacancies.

Two-dimensional transition metal carbides and nitrides (MXenes) and MXene-based membranes hold promise for applications including water purification and seawater desalination; however, their environmental behavior and fate in these matrices remain unknown. In this study, we systematically assessed the reaction efficiencies of Ti3C2Tx at varying important environmental conditions. Our experiments revealed that copper and iron ions accelerated the oxidation rate of Ti3C2Tx 55.4 and 33.4 times, respectively. TiO2 and amorphous carbon were identified as the primary solid products. Based on in situ water-phase atomic force microscopy, atomic high-angle annular dark-field scanning transmission electron microscopy, and theoretical results, we postulate that metal ions enhance Ti3C2Tx oxidation by spontaneously migrating and anchoring at Ti vacancies, which then become active sites for this reaction. This process increases the adsorption of H2O and oxygen, making the Ti vacancy-rich surface convex area the most vulnerable site to attack. The findings in this study provide useful information for a comprehensive understanding of the interaction between MXene structural defects and metal ions as well as for the design and modification of MXene membranes resistant to metal ion impact.

Electric arc synthesis of titanium carbide using carbon obtained from thermal conversion of waste from the power industry

The work presents for the first time the results of obtaining titanium carbide using a vacuum-free electric arc method using various types of biocarbon obtained by classical pyrolysis of biomass waste, such as tangerine peel, pomelo peel, banana peel, pine nut shells, walnut shells. Analysis of X-ray diffraction patterns of the synthesized materials showed the repeatability of the experiment with the receipt of diffraction maxima indicating the formation of a cubic structure of titanium carbide. An analysis of the thermal oxidation of the resulting powders showed that up to a thousand degrees the process proceeds quite slowly, but with increasing temperature the oxidation rate increases significantly. It has been established that during thermal heating in an oxidizing environment, the mass of the studied titanium carbide powders obtained using various types of carbon increases, which is confirmed by thermogravimetric analysis.

Electrochemical and bioelectrochemical sulphide removal: A review

AbstractThe increased demand for energy worldwide and the focus on the green shift have raised interest in renewable energy sources such as biogas. During biogas production, sulphide (H2S, HS− and S2−) is generated as a byproduct. Due to its corrosive, toxic, odorous, and inhibitory nature, sulphide is problematic in various industrial processes. Therefore, several techniques have been developed to remove sulphide from liquid and gaseous streams, including chemical absorption, chemical dosing, bioscrubbers, and biological oxidation. This review aims to elucidate electrochemical and bioelectrochemical sulphide removal methods, which are gaining increasing interest as possible supplements to existing technologies. In these systems, the sulphide oxidation rate is affected by the reactor design and operational parameters, including electrode materials, anodic potential, pH, temperature and conductivity. Anodic and bioanodic materials are highlighted here, focusing on recent material developments and surface modification techniques. Moreover, the review focuses on sulphide generation and inhibition in biogas production processes and introduces the prospect of removing sulphide and producing methane in one single bioelectrochemical reactor. This could introduce BESs for combined biogas upgrading and cleaning, thereby increasing the methane content and removing pollutants such as sulphide and ammonia in one unit.

Macrokinetics of ammonium sulfite oxidation inhibited by sodium thiosulfate in wet ammonium flue gas desulfurization

AbstractThe oxidation of ammonium sulfite must be inhibited to improve the economy and cycle performance of the ammonia flue gas desulfurization process. A stirred bubbling reactor was used to investigate the macrokinetics of oxidation inhibition of ammonium sulfite by sodium thiosulfate in wet ammonia desulfurization. The effects of initial concentration, Na2S2O3 concentration, pH value, gas flow rate, and temperature on the oxidation rate were discussed. The results show that the apparent activation energy of the reaction is 37.3 kJ/mol. The macrokinetics equation of sodium thiosulfate inhibiting sulfite oxidation in the ammonia desulfurization process was established. Combined with the kinetic model, it is inferred that the rate of sodium thiosulfate inhibiting ammonium sulfite oxidation is controlled by the intrinsic chemical reaction. The results can provide a reference for the regeneration of ammonium sulfite in the wet ammonia desulfurization process.

Microalgae Enhance the Resistance of Pond-Dwelling Ammonia-Oxidizing Bacteria to Light Irradiation

Pond aquaculture is an important aquacultural model worldwide in which ammonia-oxidizing bacteria (AOB) are crucial for the removal of ammonia from water. The influence of light irradiation on AOB in an aquaculture pond was studied using artificial simulation wastewater under dark/light cycles of 24 h/0 h (L0), 12 h/12 h (L12), and 0 h/24 h (L24). The ammonia oxidation rates (AORs) in groups L0, L12, and L24 were 9.88 ± 0.19 mg h−1, 6.01 ± 0.32 mg h−1, and 1.85 ± 0.09 mg h−1, respectively. Long-term exposure to light had a serious impact on the AOR and decreased the abundance of Nitrosomonas spp. and their ammonia monooxygenase genes. To determine the protective effect of microalgae on AOB, different doses of freeze-dried Chlorella spp. powder were added to the nitrifying bacteria community. The photoinhibition rate of chlorophyll a (Chla) in the groups with 300 and 1300 µg L−1 of added Chlorella were 32.85% and 28.77%, respectively, while the Chla in the 2200 µg L−1 Chlorella-added group was only 0.01%, with no significant differences (p > 0.05) in AOR between the dark/light treatment subgroups. Fluorescence in situ hybridization showed that AOB, nitrite-oxidizing bacteria, and algae coexist and grow together without free AOB in the nitrifying bacterial community. It was suggested that microalgae enhance the resistance of AOB to light irradiation in a pond through the shading effect provided by algal chlorophyll and the close symbiotic relationship between microalgae and AOB.