Higher Initial pH Research Articles

Influence of Loading Density and Gender on the Welfare and Meat Quality of Horses During Transport for Slaughter.

The aim of this study was to determine the effects of loading density and gender on blood welfare indicators, carcass bruises and horsemeat quality. Data were collected from twelve transports of 89 slaughter horses originating from the same collection centre. The transportation of slaughter horses at high loading densities (>200 kg/m2), especially stallions, resulted in increased levels of lactate (p = 0.021), glucose (p < 0.0001), ceruloplasmin (p < 0.0001) and AOPP (p < 0.0001), but lower GSH levels (p < 0.0001). Compared to stallions and mares, geldings subjected to high loading density (>200 kg/m2) during transport had lower levels of the aforementioned blood metabolites. In addition, stallions exposed to a high load density (>200 kg/m2) had the highest frequency of severe (p = 0.0002), large (p < 0.0001) and circular (p = 0.0001) carcass bruises, which were predominantly located on the abdominal (p = 0.0056) and thoracic (p = 0.0004) wall. In contrast, a higher percentage (p < 0.0001) of undamaged carcasses was found in slaughter horses exposed to a low loading density (≤200 kg/m2) during transport. Stallions exposed to high loading densities (>200 kg/m2) during transport had the highest initial pH (p < 0.0001) and ultimate pH (p = 0.005) in terms of m. longissimus lumborum and redness (p = 0.017), but the lowest drip loss (p = 0.050) and lightness (p < 0.0001), which, consequently, led to the highest (p = 0.0045) proportion of DFD-like defects in the meat quality. In conclusion, the results of this study showed that high loading densities (>200 kg/m2), regardless of gender, negatively affect horse welfare during transport. In addition, stallions were more sensitive to poor pre-slaughter conditions and produced the lowest meat quality, while geldings were the most resistant. To determine the optimal transport density, further research is needed to determine the effects of different loading densities on the behaviour, physiology, carcass and meat quality of slaughter horses.

Efficiency of heat-treated sepiolite in the adsorption of Cd, Zn, and Co from aqueous solutions: A low-cost approach for wastewater treatment

This study investigated the adsorption of Cd, Co, and Zn ions onto unmodified and heat-treated sepiolite, focusing on the effect of contact time, initial pH, and heat pretreatments. Kinetic experiments were conducted in triplicate, and equilibrium experiments indicated that Co2+ had the highest adsorption preference, followed by Zn2+ and Cd2+. The adsorption efficiency for Co2+ significantly increased with higher initial pH, whereas Zn2+ and Cd2+ showed optimal adsorption at lower pH levels. Heat-treated sepiolite at 250 ℃ exhibited a higher surface area and adsorption capacity in comparison with unmodified and 150 ℃-treated sepiolite, which indicated the importance of heat pretreatment. The pseudo-second-order kinetic model better described the adsorption process, and it was confirmed chemisorption as the rate-limiting step. By increasing the contact time, adsorption rates enhanced, with equilibrium achieved within 480 min for all systems. Higher initial solute concentrations led to an increase in adsorption processes, with Co ions consistently showing higher adsorption efficiency in competitive multi-ionic solutions. Adsorption percentages varied with pH and thermal treatment, indicating the importance of these parameters in optimizing sepiolite’s adsorption capacity for heavy metal removal.

Machine learning-assisted optimization of food-grade spirulina cultivation in seawater-based media: From laboratory to large-scale production

The shortage of food and freshwater sources threatens human health and environmental sustainability. Spirulina grown in seawater-based media as a healthy food is promising and environmentally friendly. This study used three machine learning techniques to identify important cultivation parameters and their hidden interrelationships and optimize the biomass yield of Spirulina grown in seawater-based media. Through optimization of hyperparameters and features, eXtreme Gradient Boosting, along with the recursive feature elimination (RFE) model demonstrated optimal performance and identified 28 important features. Among them, illumination intensity and initial pH value were critical determinants of biomass, which impacted other features. Specifically, high initial pH values (>9.0) mainly increased biomass but also increased nutrient sedimentation and ammonia (NH3) losses. Both batch and continuous additions could decrease nutrient losses by increasing their availability in the seawater-based media. When illumination intensity exceeded 200 μmol photons/m2/s, it amplified the growth of Spirulina by mitigating the light attenuation caused by a high initial inoculum level and counteracted the negative effect of low temperature (<25 °C). In large-scale cultivation, production efficiency would be reduced if illumination was not maintained at a high level. High salinity and sodium bicarbonate (NaHCO3) addition promoted carbohydrate accumulation, but suitable dilution could keep the required protein content in Spirulina with relatively low media and production costs. These findings reveal the interactive influence of cultivation parameters on biomass yield and help us determine the optimal cultivation conditions for large-scale cultivation of Spirulina-based seawater system based on a developed graphical user interface website.

Reagent-free phosphorus precipitation from a denitrified swine effluent in a batch electrochemical system

There is high interest in the recovery of phosphorus (P) from wastewater through crystallization processes. However, the addition of chemical reagents (e.g., sodium hydroxide) to raise the pH may result in high treatment costs and increased concentrations of undesired metal ions (e.g., sodium). As an alternative, in this research we considered electrochemical mediated precipitation at low current densities (0.4–1.2 A m−2) without using chemical reagents. For that purpose, a two-chamber electrochemical system was operated in batch for treating denitrified swine effluent (48 mg P L−1). By applying current at 1.2 A m−2, and targeting pH 11.5, a maximum P removal rate of 33.4 mmol P (L·d−1) was obtained while the P removal efficiency was above 90 %. New solids that formed mostly remained suspended in the catholyte. Before discharge, the catholyte effluent was recirculated to the anodic compartment to neutralize the pH, achieving a final pH of 6.4 ± 0.1. Chlorine (Cl2) production in the anodic compartment was favored by a small anode surface and a high initial pH of the catholyte. Although the production of chlorine achieved was limited (the highest concentration was 8.6 ± 0.1 mg Cl2 L−1) these findings represent a new opportunity for the recovery and onsite use of this side-product. Electrochemical impedance spectroscopy tests confirmed that the deposition of solids inside the cathodic compartment during the experimental period was limited. Membrane analysis revealed significant scaling of carbonate compounds. The electrochemical treatment described above was shown as a promising alternative to sodium hydroxide and sulfuric acid dosage for pH adjustment when crystallizing phosphate salts.

Insights into selective leaching of rare earths from weathered crust elution-deposited rare earth ore using magnesium sulfate

In this paper, a multi-stage leaching process for the weathered crust elution-deposited rare earth ore was proposed using MgSO4 as a leaching agent. The results indicate that with increasing the concentration of MgSO4 from 0.5 wt%–1.0 wt% to 2.0 wt%–4.0 wt%, the peak concentrations of rare earths increase from 1.87–3.59 to 5.49–10.21 g/L, and the collection periods of leach solution are shortened from 0.85–1.54 to 0.31–0.47 (liquid-to-ore ratio). When the rare earth ore is leached with leaching agent solution with high initial pH (3.0–5.0), the rare earths and aluminum are predominantly leached by Mg2+ instead of H+. However, H+ participate in the leaching process of rare earths and aluminum at lower initial pH (1.5–3.0) of the leaching agent solution. Especially, when the initial pH of leaching agent solution is 2.0, a large amount of aluminum is leached when the liquid-to-ore ratio is greater than 1.2. Based on the above insights, increasing the initial pH (3.0–5.0) of leaching agent solution in the injection stage using high-concentration MgSO4 (>1.0 wt%) can increase the peak concentration of rare earths in the leach solution and shorten the collection period. However, in the injection stage using low MgSO4 concentration (<1.0 wt%), an initial pH of leaching agent solution of 2.0 is selected to reduce the leaching amount of aluminum and the consumption of MgSO4. Comparing to the leaching process using constant MgSO4 concentration (2.0 wt%, initial pH of 5.0), the leaching efficiency of rare earths using a multi-stage leaching process is approximately equal (about 94.6%) under optimal conditions. The leaching amount of aluminum is reduced by 16.9%. The consumption of MgSO4 is reduced by 67.1%.

Effects of plasma treatment of digestates on pH, nitrification and nitrogen turnover during storage and after soil application

Acidification through plasma treatment technology presents a potential solution to mitigate nitrogen losses throughout the manure management chain, offering a dual benefit of atmospheric nitrogen incorporation into manures while inducing acidification. This study evaluated the use and effectiveness of plasma treatment technology as a one-time acidification strategy for digested slurry during long-term storage, its effects on slurry nitrogen (N) availability and subsequent release in the soil. A digestate from a full-scale anaerobic digester was separated using a decanter centrifuge, and the resultant liquid fraction (LF) was plasma treated to achieve three different initial pH levels (4.27, 5.03 and 5.42). After that, a storage experiment was set up for 180 days to monitor the evolution in pH and changes in NH4+, NO3- and NO2-. Concurrently, a soil incubation experiment was conducted to study the N turnover for 80 days after incorporating the organic materials (Liquid fraction, plasma-treated liquid fractions, digestate and raw slurry). Plasma treatment significantly increased total N and the proportion of inorganic N in the slurries by fixing atmospheric N as NO3- and NO2- and reduced the slurry pH depending on the treatment duration. After six months of storage, pH increased by 0.91 pH units in the plasma-treated liquid fraction with the highest initial pH (LFpH-5.42). Plasma treatment significantly increased net inorganic N release in soil by 5–14 % compared to a non-treated liquid fraction. Unexpected prolonged inhibition of NH4+ nitrification in soil for over 80 days after applying plasma-treated slurries was observed. In conclusion, plasma treatment emerges as a promising alternative to acid- and bio-acidification strategies, offering prolonged low slurry pH stabilisation, improved fertiliser value and delayed NH4+-N nitrification in soil.

The relationship between the initial pH and neurological outcome in patients with out-of-hospital cardiac arrest is affected by the status of recovery of spontaneous circulation on hospital arrival.

The early prediction of neurological outcomes is useful for out-of-hospital cardiac arrest (OHCA). The initial pH was associated with neurological outcomes, but the values varied among the studies. Patients admitted to our division with OHCA of cardiac origin between January 2015 and December 2022 were retrospectively examined (N = 199). A good neurological outcome was defined as a Glasgow-Pittsburgh cerebral performance category (CPC) of 1-2 at discharge. Patients were divided according to the achievement of recovery of spontaneous circulation (ROSC) on hospital arrival, and the efficacy of pH in predicting good neurological outcomes was compared. In patients with ROSC on hospital arrival (N = 100), the initial pH values for good and poor neurological outcomes were 7.26 ± 0.14 and 7.09 ± 0.18, respectively (p < 0.001). In patients without ROSC on hospital arrival (N = 99), the initial pH values for good and poor neurological outcomes were 7.06 ± 0.23 and 6.92 ± 0.15, respectively (p = 0.007). The pH associated with good neurological outcome was much lower in patients without ROSC than in those with ROSC on hospital arrival (P = 0.003). A higher initial pH is associated with good neurological outcomes in patients with OHCA. However, the pH for a good or poor neurological outcome depends on the ROSC status on hospital arrival.

Phosphorus recovery as struvite from wastewater by using seawater, brine and natural brine

Struvite crystallization is a widely employed technique for phosphorus recovery from wastewater. The accessibility and availability of cost-effective magnesium alternatives pose challenges for this process. This paper is a comparative study of struvite precipitation from synthetic wastewater using seawater, brine and natural brine as a low-cost magnesium sources. The impact of initial pH and Mg/P molar ratio on phosphate recovery was assessed and compared with Visual MINTEQ to determine its suitability for simulating P removal efficiencies. For the three magnesium sources, the findings indicated an improvement in phosphate removal efficiency with higher initial pH and Mg/P molar ratio. Nonetheless, at lower pH values and Mg/P molar ratios, the model calculations yielded higher removal efficiencies than the experimental results, attributed to its inability to consider system kinetics. Additionally, the analysis of precipitates showed the concurrent precipitation of magnesium phosphates when using natural brine. The Ca/Mg molar ratio in brine affects the morphology and the purity of the crystal product. Overall, alternative magnesium ions collected from sebkhat Ezzemoul can be a potential candidate for sustainable phosphorus recovery from wastewater as well as seawater and brine. Further studies are recommended to control the product properties.

A new hydration kinetic model based on boundary nucleation and growth mechanism with time-dependent growth rate: Application to quantitively characterize the influence of alkali on the early hydration of cement

In this study, a boundary nucleation and growth model with a time-dependent growth rate was proposed to quantitively characterize the precipitation of CSH. The newly constructed model was typically applied to quantitively analyse the influence of alkali content on the growth of CSH, and the value-taking equations of the time-dependent growth rate of CSH in various alkali content systems were proposed and verified. The experimental and simulation results proved that a high soluble alkali content stimulated early hydration (within the initial several hours) and inhibited the late growth of CSH (>20 h) in cement paste. The time-varying ion concentrations in cement solutions were the main driving force for the change in the growth rate of CSH with time. Likewise, the variation in the aqueous phase properties of cement pastes also explains the influence of alkali content on the growth rate of CSH, i.e., the high initial pH of the solution with high soluble alkali led to the high supersaturation degree and high growth rate of CSH, consuming large amounts of calcium ions and in turn reducing the later supersaturation degree and growth rate. The newly constructed model is also expected to precisely characterize the factors that have a significant influence on the precipitation of cement hydrates.

Is green manure a viable substitute for inorganic fertilizer to improve grain yields and advance carbon neutrality in paddy agriculture?

Green manure is a widely applied to increase grain yield, while it also attributes to greenhouse gas (GHG) emissions in agriculture ecosystems. Combining green manure with inorganic fertilizer inputs is a common practice that can influence soil GHG emissions and grain yield, however, its impacts on grain yield and global warming potential (GWP) under different initial soil conditions before rotating experiments and agronomic management in paddy fields remain unclear. We synthesized 508 data pairs to evaluate the responses of CO2 emissions, CH4 emissions, N2O emissions, and grain yield to combined inputs of green manure plus inorganic fertilizer compared with only inorganic fertilizer application. Our findings indicate that both inorganic fertilizer plus extra green manure (GM-E) and green manure substitutes for inorganic fertilizer (GM-S) could increase CO2 emissions (22.5 %−76.8 %), CH4 emissions (100 %−103 %), N2O emissions (29.8 %−50.9 %), and yield (2.21 %−19.6 %). Except for GM-E, which showed a non-significant increase in grain yield. The initial soil properties before rotating experiments, the types and timing of green manure application were key drivers of GHG emissions and yield, and extra green manure applied in areas with low initial soil pH and high C:N can increase GWP and yield. Overall, the mixed green manure application had greater impact than leguminous or non-leguminous green manure applied alone. The responses of GHG emissions and yield to GM-S were modulated by mean annual precipitation and initial soil properties before rotating experiments, and green manure substitutes for inorganic fertilizer in areas with high initial soil pH and low C:N can increase GWP and yield. Meanwhile, excessive precipitation caused a reduction in yield and a significant increase in GWP intensity. Our results showed that extra green manure applications of less than 68.1 kg N ha−1 would not significantly increase GWP. Therefore, an effective green manure strategy can achieve a win-win situation for the dual challenge of agricultural production and climate change mitigation.

Experimental alteration of allanite at 200°C: the role of pH and aqueous ligands

Abstract Allanite is a major host of rare earth elements (REEs) in the continental crust. In this study, reaction mechanisms behind allanite alteration are investigated through batch experiment runs on natural allanite grains in carbonate-bearing hydrothermal fluids at 200°C, with initial acidic (pH = 4) or alkaline (pH = 8) conditions and with different aqueous ligands (120 mmol kg −1 of F, Cl, P or S). Time-series experiment runs in F-doped systems at different durations between 15 and 180 days reached a steady state at 120 days. The pH efficiently controls the allanite alteration process, with initial high pH, alkaline conditions being more reactive (75% alteration compared with 25% under acidic conditions). The ligand also significantly influences the alteration process under initial acidic conditions with the P-doped system (70%) almost non-reactive for the Cl- and S-doped systems (&lt;5%). In the alteration rim, REEs are mainly redistributed in REE-bearing phases either as carbonates (F-doped) or phosphates (P-doped). The relatively flat REE-normalized patterns of the recovered experimental fluids suggest a fractionation of light rare earth elements (LREEs) over heavy rare earth elements (HREEs) during the course of the alteration reactions. It is proposed that secondary REE mineral precipitation at the reaction front creates a local disequilibrium in the solution and a steep chemical gradient promoting allanite dissolution and thus its alterability.

Strength performance of low-bearing-capacity clayey soils stabilized with ladle furnace slag

In this paper, the performance of ladle furnace slag (LFS), a by-product of secondary steel refining, is evaluated as a binder to stabilize clayey soils of low bearing capacity. The aim is to define whether additions of this by-product to clayey soil can stabilize the soil in accordance with the technical specifications of Spanish standards. To do so, three different soils stabilized with 5% LFS were compared with the same soils stabilized with 2% lime and with no stabilization, in order to investigate their different behaviors. The chemical and mineralogical characterizations of all the soil mixes were conducted using X-ray fluorescence, X-ray diffraction, and scanning electron microscopy. The Atterberg limit test was used to study the plastic behavior of the soils, and the results of compaction, bearing capacity, unconfined compressive strength, and direct shear strength (cohesion and friction angle) tests defined their strength characteristics. The analysis was completed with the pH monitoring of the mixes along the curing time in order to relate the pH changes with the strength evolution. The addition of LFS to the soils has resulted in an increase in the liquid limit and plastic limit, causing therefore a slight decrease in the plasticity index. All the soils showed increases between 30% and 70% in their California Bearing Ratios immediately after mixing with 5% LFS, and after 90 days of curing, improvements of 30–188% in their unconfined compressive strength were noted in comparison with untreated soil, which were higher than the lime-stabilized soils. The cohesion of soils stabilized with LFS at 28 days of curing obtained improvements ranging from 40 to 300% depending on the type of soil. However, the friction angle showed a slight increase of 10% in two of the soils and zero in another. The high initial pH in LFS-stabilized soils was maintained during the curing time, which favored the development of pozzolanic reactions that improve the soil strength. These results confirmed that the substitution of lime with LFS is a feasible option for soil stabilization.

Potential Use of Agricultural Waste—Carob Kibbles (Ceratonia siliqua L.) as a Biosorbent for Removing Boron from Wastewater

The release of boron (B) into the environment as a result of anthropogenic activity modifies sustainable natural conditions, thus affecting ecosystems. To meet water quality regulations, commercial and natural boron adsorbents are available to reduce its concentrations in industrial effluents, with the former being not only more expensive but also less sustainable. In the publication, the biosorption parameters of carob kibbles (Ceratonia siliqua L.) were optimized in order to remove boron from aqueous solutions using batch experiments. The biosorbent used in the present research was agro-waste biomass provided by the local locust-beam gum industry. Boron removal by carob kibbles was favored at high initial pH values, and this capacity was found to be a function of boron initial concentration, biosorbent content in the solution, and particle size. The change in temperature did not affect the potential of biomass to remove boron. The highest boron removal efficiency (55.1%) was achieved under the following optimal conditions: 50 g/L biosorbent dose (Cs), with particle size range 0.025–0.106 mm, for the initial concentration (C0) of boron in the solution of 100 mg/L, at an initial pH of 11.5, for 5 h at 25 °C. This investigation suggests that carob kibble agro-waste can be valorized as a biosorbent to remove boron from wastewater, and the boron-loaded residue may eventually be explored as a new boron-fertilizer.

Oxidative power loss control in ozonation: Nanobubble and ultrasonic cavitation

Nanobubble and ultrasonic cavitation were applied to support and prolong oxidation reactions of ozonation. Nanobubbles increased ozone dissolution by a factor of 16 due to low buoyancy, high surface area, and stability in water. Hydroxyl radicals generated by ultrasonic cavitation produced hydrogen peroxide rather than recombining due to additional oxygen atoms supplied by the nanobubbles. The generated hydrogen peroxide formed hydroperoxyl ions that reacted with ozone to generate hydroxyl radicals. The process achieved improvements in both the loss of emitted ozone and radical recombination. Rhodamine B decomposition was used to gauge the effectiveness of the process, with the highest rhodamine B decomposition evident at a high initial pH and power and a frequency of 132 kHz as revealed in ultrasonic experiments. The process achieved more than 99% of the rhodamine B decomposition in 20 min under the most efficient conditions. The generation of hydrogen peroxide exhibited tendencies similar to those of rhodamine B decomposition, supporting the proposed mechanism. An ozonation process combined with nanobubble and ultrasonic cavitation can therefore sustain oxidizing power using continuous dissolution by nanobubbles and successive radical generation caused by hydrogen peroxide generated by cavitation.

Short and Long-Term Solubility, Alkalizing Effect, and Thermal Persistence of Premixed Calcium Silicate-Based Sealers: AH Plus Bioceramic Sealer vs. Total Fill BC Sealer.

This study aimed to investigate the short- and long-term solubility, alkalizing potential, and suitability for warm-vertical compaction of AH Plus Bioceramic Sealer (AHBC), and Total Fill BC Sealer (TFBC) compared to the epoxy-resin sealer AH Plus (AHP). A solubility test was performed according to ISO specification 6876 and further similar to ISO requirements over a period of 1 month in distilled water (AD) and 4 months in phosphate-buffered saline (PBS). The pH of the immersion solution was determined weekly. Sealers were exposed to thermal treatment at 37, 57, 67, and 97 °C for 30 s. Furthermore, heat treatment at 97 °C was performed for 180 s to simulate inappropriate implementation of warm vertical filling techniques. Physical properties (setting time, flow, film thickness according to ISO 6876) and chemical properties (Fourier transformed infrared spectroscopy) were assessed. AHBC and TFBC were associated with significantly higher solubility than AHP over 1 month in AD and 4 months in PBS (p < 0.05). AHBC and TFBC both reached high initial alkaline pH, while TFBC was associated with a longer-lasting alkaline potential than AHBC. Initial pH of AHBC and TFBC was higher in AD than in PBS. None of the sealers were compromised by thermal treatment.

Phosphate solubilization and indole acetic acid production by rhizosphere yeast Torulaspora globosa: improvement of culture conditions for better performance in vitro.

The rhizosphere yeast Torulaspora globosa is known to produce indole acetic acid (IAA) and to solubilize minerals. Due to the prospective use of this yeast as a biostimulant for agricultural applications, this work aimed to optimize the cultural conditions for both IAA production and phosphate solubilization. For phosphate solubilization, the temperature (20, 25 and 30°C), initial medium pH (3.0, 5.0, and 7.0), and shaker speed (without mixing, 100rpm, 150rpm, and 200rpm) were considered using the one-factor-at-a-time (OFAT) design. Temperature of 25°C, initial medium pH 7.0, and static cultures were the conditions of greatest phosphate solubilization, with 40% of the total phosphorus content solubilized from calcium phosphate (419.86mg L-1) after 48h. By using the response surface methodology, the maximum IAA production (217.73µgmL-1) was obtained with the highest initial pH 7.0, the lowest nitrogen, and glucose concentrations (5g L-1 and 10g L-1, respectively) and the lowest agitator speed (100rpm). Further tests indicated that nitrogen affected significantly IAA production and the absence of nitrogen in the medium promoted higher IAA production (457µgmL-1). The results obtained here may contribute to the scaling up for industrial and agricultural applications of a yeast-based product with T. globosa.

Effects of process conditions on simultaneous removal and recovery of boron from boron-laden wastewater using improved bipolar membrane electrodialysis (BMED)

The anthropogenic emission of boron to the environment has posed a serious risk to human and animal health due to its non-biodegradability and the resulting accumulation in the body. Bipolar membrane electrodialysis (BMED) has been proven to be an economical and effective process to remove and recover boron from wastewater. In this work, we verified multiple process parameters to evaluate the efficiency of boron removal and recovery using intermittent and continuous BMED modes. Higher initial boron concentrations appeared to reduce the boron processing rate, but this reduction may be ameliorated by increasing current density. Similarly, higher initial pH was observed to retard the removal rate of boron with increasing mass transfer rate. When solution pH was controlled from 9.5 to 10.5 and the current density was 6.36 A/m2 under maximum allowable voltage of 12 V, boron removal and recovery efficiencies were 98.6% and 86.5%, respectively. During the pH-control process, current variation pattern indicated that current density was associated with initial boron concentrations in salt apartment. When the current variation pattern was applied to a five-cycle sequential feed-batch BMED process, it accurately reflected the timing of complete boron removal and recovery on a batch fill-and-draw process. The overall boron removal and recovery efficiencies were 98.53% and 81.2%, respectively, with an energy consumption of 31.5 Wh/g. Under these conditions, the final boron concentrations in effluent were less than 10 mg/L, as required by the Taiwan Environmental Protection Administration (EPA). Overall, BMED is a cost-effective treatment process for boron-containing wastewater. The proposed process indicator reflecting sequential BMED process progression based on process information will further elucidate the automatic process control in industrial applications.

Flow cytometric analysis reveals culture condition dependent variations in phenotypic heterogeneity of Limosilactobacillus reuteri

Optimisation of cultivation conditions in the industrial production of probiotics is crucial to reach a high-quality product with retained probiotic functionality. Flow cytometry-based descriptors of bacterial morphology may be used as markers to estimate physiological fitness during cultivation, and can be applied for online monitoring to avoid suboptimal growth. In the current study, the effects of temperature, initial pH and oxygen levels on cell growth and cell size distributions of Limosilactobacillus reuteri DSM 17938 were measured using multivariate flow cytometry. A pleomorphic behaviour was evident from the measurements of light scatter and pulse width distributions. A pattern of high growth yielding smaller cells and less heterogeneous populations could be observed. Analysis of pulse width distributions revealed significant morphological heterogeneities within the bacterial cell population under non-optimal growth conditions, and pointed towards low temperature, high initial pH, and high oxygen levels all being triggers for changes in morphology towards cell chain formation. However, cell size did not correlate to survivability after freeze-thaw or freeze-drying stress, indicating that it is not a key determinant for physical stress tolerance. The fact that L. reuteri morphology varies depending on cultivation conditions suggests that it can be used as marker for estimating physiological fitness and responses to its environment.

Reductive degradation of perfluorooctanoic acid in complex water matrices by using the UV/sulfite process

Hydrated electrons (e-aq,E= -2.9 V) generated by advanced reduction processes (ARPs) have been proved to be a promising approach to eliminate various per- and polyfluoroalkyl substances (PFASs) in water. In this study, the decomposition of perfluorooctanoic acid (PFOA) in a complex water matrix by e-aq generated from the UV/sulfite process was investigated. The effect of pH (9–12) and co-existing compounds (chloride, nitrate, phosphate, carbonate and humic acid) on PFOA degradation efficiency was studied. In addition, the intermediates and possible degradation pathways were analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS). The results showed that the concentration of PFOA was below the detection limit (10 μg/L) after 1 h (conditions: C0 10 mg/L, initial pH = 10, sulfite 10 mM) while 89% defluorination was achieved after 24 h. Using a higher initial pH (pH = 12) greatly enhanced the PFOA degradation as 100% degradation and 98% defluorination were achieved after 24 h. The presence of carbonate (> 5 mM), nitrate (> 2 mM) and humic acid (> 25 mg/L) showed a significant negative effect on PFOA degradation via a UV blocking effect or quenching of hydrated electrons while the presence of chloride and phosphate had a smaller effect on PFOA degradation. Even at extremely high concentrations of chloride (1.709 M, pH = 11.25), the defluorination ratio reached 97% after 24 h of reaction time. During the process, short-chain perfluorinated carboxylic acids (PFCAs, C < 7) and hydrogen substituted compounds were detected, which implies that chain-shortening and H/F change reactions had occurred. Moreover, this confirmed the generation of sulfonated and unsaturated intermediates during the process, which disclosed valuable new mechanistic insights into PFOA degradation.

Self-enhanced and efficient removal of As(III) from water using Fe–Cu–Mn composite oxide under visible-light irradiation: Synergistic oxidation and mechanisms

Here, we prepared a novel nanostructured Fe–Cu–Mn composite oxide (FCMOx) adsorbent using an ultrasonic coprecipitation method. The maximum adsorption capacity of As(III) and As(V) reached 158.5 and 115.2 mg/g under neutral conditions, respectively. The effects of several environmental factors (coexisting ions, solution pH, etc.) on the removal of inorganic arsenic using FCMOx were studied through batch experiments. The results showed that except for PO43– and high initial pH, it was not significantly affected by ionic strength and other existing anions, implying a higher selectivity and adaptability. Combined with EPR, FTIR, and XPS analysis, we concluded that the Cu component and the reactive oxygen species (ROS) it generates played a decisive role in maintaining the stability of the redox cycle between Mn(IV)/Mn(III)/Mn(II) and enhancing the oxidation efficiency of As(III). Meanwhile, the adsorption mechanism of As(V) was mainly through the replacement of the FCMOx surface –OH to form stable inner-sphere arsenic complexes, while the removal mechanism of As(III) may involve the process of synergistic oxidation and chemisorption coupling. Additionally, the effective removal of As from the simulated As-contaminated water and its satisfactory reuse performance make FCMOx adsorbents favorable candidates for the removal of As-contaminated water in the future.