Reduction of antinutrients and off-flavour in kidney bean flour by acidic and alkaline reactive extrusion.

The presence of antinutrients and undesirable flavours in kidney bean flour poses challenges to consumer acceptance. Although extrusion can mitigate antinutrients to some extent, its impact on reducing beany flavour in bean flour remains underexplored. This study investigated the effects of injecting acetic acid or sodium carbonate solutions at three concentration levels (0.05, 0.1, 0.15 mol/L), in conjunction with three temperature profiles (40/60/80/80/90, 40/60/80/90/110, 50/70/90/110/130 °C) and two feed moisture levels (25, 30 %), on the removal of antinutrients (condensed tannins, trypsin inhibitor activity, phytic acid, raffinose family oligosaccharides) and reduction of volatile compounds that contribute to beany flavour in whole kidney bean flour. The results showed that all concentrations of acetic acid and sodium carbonate solutions effectively reduced condensed tannins compared to water, especially at 130 °C extrusion temperature. Introducing acetic acid and sodium carbonate solutions at a concentration of 0.15 mol/L led to 72 and 90 % reduction of total raffinose family oligosaccharide content, respectively, in contrast to the 17 % reduction observed with water alone. The incorporation of sodium carbonate solution reduced the total volatile compounds by 45-58 % as compared with water (23-33 %) and acetic acid (11-27 %). This reduction was primarily due to the reduction of aldehydes, alcohols, and aromatic hydrocarbons. These results indicate that injecting sodium carbonate solution during extrusion can effectively reduce antinutrients and beany flavour compounds in kidney bean flour.

Molecular mechanisms underlying sodium percarbonate treatment suppress the recovery and growth of Pseudanabaena sp. in early spring.

Increasing frequency and intensity of cyanobacterial blooms in water sources is a growing global issue. Algicides are usually implemented in summer or autumn when blooms break out, however, the blooms will form again when algicide's concentration declines to a certain extent. Preventing the recovery and growth of cyanobacteria in early spring may be conducive to abatement of the blooms in summer or autumn. In this study solid sodium percarbonate (SPC) was used as an algicide to suppress recovery and growth of Pseudanabaena sp., a common odour-producing cyanobacterium, in early spring (12 °C). Results showed that 3.0 and 6.0 mg/L SPC were able to kill most of the algal cells after 12 h treatment at 12 °C, and the residual cells gradually died during the re-cultivation period at 25 °C. As a control, although SPC also caused most of algal cells to lyse at 25 °C, regrowth of cells was found during the period of re-cultivation at 25 °C. Transcriptomic analysis revealed that the dysregulated genes were strongly associated with translation and photosynthesis after SPC treatment. All differentially expressed unigenes related to translation and photosynthesis were down-regulated after SPC oxidation at 12 °C, whereas key genes associated with translation and photosynthesis were upregulated after SPC treatment at 25 °C.

Molecular and geochemical basis of microbially induced carbonate precipitation for treating acid mine drainage: The case of a novel Sporosarcina genomospecies from mine tailings.

Microbially induced carbonate precipitation (MICP) immobilizes toxic metals and reduces their bioavailability in aqueous systems. However, its application in the treatment of acid mine drainage (AMD) is poorly understood. In this study, the genomes of Sporosarcina sp. UB5 and UB10 were sequenced. Urease, carbonic anhydrases, and metal resistance genes were identified and enzymatic assays were performed for their validation. The geochemical mechanism of precipitation in AMD was elucidated through geo-mineralogical analysis. Sporosarcina sp. UB5 was shown to be a new genomospecies, with an average nucleotide identity < 95 % (ANI) and DNA-DNA hybridization < 70 % (DDH) whereas UB10 is close to S. pasteurii. UB5 contained two urease operons, whereas only one was identified in UB10. The ureolytic activities of UB5 and UB10 were 122.67 ± 15.74 and 131.70 ± 14.35 mM NH4+ min-1, respectively. Both strains feature several carbonic anhydrases of the α, ß, or γ families, which catalyzed the precipitation of CaCO3. Only Sporosarcina sp. UB5 was able to immobilize metals and neutralize AMD. Geo-mineralogical analyses revealed that UB5 directly immobilized Fe (1-23 %), Mn (0.65-1.33 %) and Zn (0.8-3 %) in AMD via MICP and indirectly through adsorption to calcite and binding to bacterial cell walls. The MICP-treated AMD exhibited high removal rates (>67 %) for Ag, Al, As, Ca, Cd, Co, Cu, Fe, Mn, Pb, and Zn, and a removal rate of 15 % for Mg. This study provides new insights into the MICP process and its applications to AMD treatment using autochthonous strains.

Enhancing CO2 storage and marine carbon sink based on seawater mineral carbonation.

Human activities emitting carbon dioxide (CO2) have caused severe greenhouse effects and accelerated climate change, making carbon neutrality urgent. Seawater mineral carbonation technology offers a promising negative emission strategy. This work investigates current advancements in proposed seawater mineral carbonation technologies, including CO2 storage and ocean chemical carbon sequestration. CO2 storage technology relies on indirect mineral carbonation to fix CO2, involving CO2 dissolution, Ca/Mg extraction, and carbonate precipitation, optimized by adding alkaline substances or using electrochemical methods. Ocean chemical carbon sequestration uses natural seawater for direct mineral carbonation, enhanced by adding specific materials to promote carbonate precipitation and increase CO2 absorption, thus enhancing marine carbon sinks. This study evaluates these technologies' advantages and challenges, including reaction rates, costs, and ecological impacts, and analyzes representative materials' carbon fixation potential. Literature indicates that seawater mineral carbonation can play a significant role in CO2 storage and enhancing marine carbon sinks in the coming decades.

U(VI) sorption on illite in the Co-existence of carbonates and humic substances.

The presence of carbonates or humic substances (HS) will significantly affect the species and chemical behavior of U(VI) in solution, but lacking systematic exploration of the coupling effect of carbonates and HS under near real environmental conditions at present. Herein, the sorption behavior of U(VI) on illite was systematically studied in the co-existence of carbonates and HS including both humic acid (HA) and fulvic acid (FA) by batch technique. The distribution coefficients (Kd) increased as function of time and temperature but decreased with increasing concentrations of initial U(VI), Ca2+, and Mg2+, as well as ion strength. At pH 2.0-10.5, the Kd values first increased rapidly and then decreased visibly, with its maximum value appearing at pH 5.0, owning to the changes in the interaction between illite and the dominant species of U(VI) from electrostatic attraction to electrostatic repulsion. The sorption was a heterogeneous, spontaneous, and endothermic chemical process, which could be well described by pseudo-second-order kinetic and Flory-Huggins isotherm models. When carbonates and HA/FA coexisted, the Kd values always increased first and then decreased as a function of pH, with the only difference for HA and FA being the key pH (pHkey) at which the promoting and inhibiting effects on the sorption of U(VI) onto illite undergo a transition. The carbonates and HS have a synergistic inhibitory effect on the U(VI) sorption onto illite at pH 7.8. FTIR and XPS spectra demonstrated that the hydroxyl groups on the illite surface and in the HS were involved in U(VI) sorption on illite in the presence of carbonates. These results provide valuable data for a deeper understanding of U(VI) migration in geological media.

Percarbonate mediated advanced oxidation of irbesartan: A suitable alternative to chlorination?

This study aims to investigate the environmental fate of irbesartan when subjected to activated percarbonate treatment. The investigation delves into the formation of disinfection byproducts (DBPs) and evaluates their toxicity, and it seeks to draw comparisons with outcomes from treatment with sodium hypochlorite, already characterized in previous findings. The proposed treatment indicates the formation of at least 11 DBPs - eight identified for the first time - which have been isolated by various chromatographic techniques, identified by Nuclear Magnetic Resonance and Mass Spectrometry studies and for which a mechanism has been proposed to elucidate their formation. To evaluate irbesartan's biological impact during treatment with sodium percarbonate (SPC), a toxicity study of the DBPs was conducted using Daphnia magna, Aliivibrio fischeri, and Raphidocelis subcapitata, three model organisms. The ecotoxicity was evaluated using the Ecological Structure-Activity Relationships (ECOSAR) computer program and compared with experimental results. Compared to chlorination treatment, a lower mineralization percentage (-43 %) and amount of DBPs at least twice higher were observed. Toxicity assessment highlighted that DBPs formed during SPC treatment were more toxic than those from chlorination. ECOSAR predicted toxicity aligned with experimental findings. Additionally, the DBPs exhibited varying levels of toxicity, primarily attributable to the presence of aromatic and hydroxyl groups in their chemical structure, indicating that SPC treatment is not suitable for treatment of irbesartan polluted waters.

Variable and Large Losses of Diagnostic Biomarkers After Simulated Cosmic Radiation Exposure in Clay- and Carbonate-Rich Mars Analog Samples.

Mars has been exposed to ionizing radiation for several billion years, and as part of the search for life on the Red Planet, it is crucial to understand the impact of radiation on biosignature preservation. Several NASA and ESA missions are looking for evidence of ancient life in samples collected at depths shallow enough that they have been impacted by galactic cosmic rays (GCRs). In this study, we exposed a diverse set of Mars analog samples to 0.9 Megagray (MGy) of gamma radiation to mimic 15 million years of exposure on the Martian surface. We measured no significant impact of GCRs on the total organic carbon (TOC) and bulk stable C isotopes in samples with initial TOC concentration > 0.1 wt. %; however, diagnostic molecular biosignatures presented a wide range of degradation that didn't correlate to factors like mineralogy, TOC, water content, and surface area. Exposure dating suggests that the surface of Gale crater has been irradiated at more than five times our dose, yet using this relatively low dose and "best-case scenario" geologically recalcitrant biomarkers, large and variable losses were nevertheless evident. Our results empasize the importance of selecting sampling sites at depth or recently exposed at the Martian surface.

Microbial Ecology of an Arctic Travertine Geothermal Spring: Implications for Biosignature Preservation and Astrobiology.

Jotun springs in Svalbard, Norway, is a rare warm environment in the Arctic that actively forms travertine. In this study, we assessed the microbial ecology of Jotun's active (aquatic) spring and dry spring transects. We evaluated the microbial preservation potential and mode, as well as the astrobiological relevance of the travertines to marginal carbonates mapped at Jezero Crater on Mars (the Mars 2020 landing site). Our results revealed that microbial communities exhibited spatial dynamics controlled by temperature, fluid availability, and geochemistry. Amorphous carbonates and silica precipitated within biofilm and on the surface of filamentous microorganisms. The water discharged at the source is warm, with near neutral pH, and undersaturated in silica. Hence, silicification possibly occurred through cooling, dehydration, and partially by a microbial presence or activities that promote silica precipitation. CO2 degassing and possible microbial contributions induced calcite precipitation and travertine formation. Jotun revealed that warm systems that are not very productive in carbonate formation may still produce significant carbonate buildups and provide settings favorable for fossilization through silicification and calcification. Our findings suggest that the potential for amorphous silica precipitation may be essential for Jezero Crater's marginal carbonates because it significantly increases the preservation potential of putative martian organisms.

Carbonate chimneys at the highly productive point Dume methane seep: Fine-scale mineralogical, geochemical, and microbiological heterogeneity reflects dynamic and long-lived methane-metabolizing habitats.

Methane is a potent greenhouse gas that enters the marine system in large quantities at seafloor methane seeps. At a newly discovered seep site off the coast of Point Dume, CA, ~ meter-scale carbonate chimneys host microbial communities that exhibit the highest methane-oxidizing potential recorded to date. Here, we provide a detailed assessment of chimney geobiology through correlative mineralogical, geochemical, and microbiological studies of seven chimney samples in order to clarify the longevity and heterogeneity of these highly productive systems. U-Th dating indicated that a methane-driven carbonate precipitating system at Point Dume has existed for ~20 Kyr, while millimeter-scale variations in carbon and calcium isotopic values, elemental abundances, and carbonate polymorphs revealed changes in carbon source, precipitation rates, and diagenetic processes throughout the chimneys' lifespan. Microbial community analyses revealed diverse modern communities with prominent anaerobic methanotrophs, sulfate-reducing bacteria, and Anaerolineaceae; communities were more similar within a given chimney wall transect than in similar horizons of distinct structures. The chimneys represent long-lived repositories of methane-oxidizing communities and provide a window into how carbon can be transformed, sequestered, and altered over millennia at the Point Dume methane seep.

Primary to post-depositional microbial controls on the stable and clumped isotope record of shoreline sediments at Fayetteville Green Lake.

Lacustrine carbonates are a powerful archive of paleoenvironmental information but are susceptible to post-depositional alteration. Microbial metabolisms can drive such alteration by changing carbonate saturation in situ, thereby driving dissolution or precipitation. The net impact these microbial processes have on the primary δ18O, δ13C, and Δ47 values of lacustrine carbonate is not fully known. We studied the evolution of microbial community structure and the porewater and sediment geochemistry in the upper ~30 cm of sediment from two shoreline sites at Green Lake, Fayetteville, NY over 2 years of seasonal sampling. We linked seasonal and depth-based changes of porewater carbonate chemistry to microbial community composition, in situ carbon cycling (using δ13C values of carbonate, dissolved inorganic carbon (DIC), and organic matter), and dominant allochems and facies. We interpret that microbial processes are a dominant control on carbon cycling within the sediment, affecting porewater DIC, aqueous carbon chemistry, and carbonate carbon and clumped isotope geochemistry. Across all seasons and sites, microbial organic matter remineralization lowers the δ13C of the porewater DIC. Elevated carbonate saturation states in the sediment porewaters (Ω > 3) were attributed to microbes from groups capable of sulfate reduction, which were abundant in the sediment below 5 cm depth. The nearshore carbonate sediments at Green Lake are mainly composed of microbialite intraclasts/oncoids, charophytes, larger calcite crystals, and authigenic micrite-each with a different origin. Authigenic micrite is interpreted to have precipitated in situ from the supersaturated porewaters from microbial metabolism. The stable carbon isotope values (δ13Ccarb) and clumped isotope values (Δ47) of bulk carbonate sediments from the same depth horizons and site varied depending on both the sampling season and the specific location within a site, indicating localized (µm to mm) controls on carbon and clumped isotope values. Our results suggest that biological processes are a dominant control on carbon chemistry within the sedimentary subsurface of the shorelines of Green Lake, from actively forming microbialites to pore space organic matter remineralization and micrite authigenesis. A combination of biological activity, hydrologic balance, and allochem composition of the sediments set the stable carbon, oxygen, and clumped isotope signals preserved by the Green Lake carbonate sediments.

Microbially induced carbonate precipitation with Arthrobacter creatinolyticus: An eco-friendly strategy for mitigation of chromium contamination.

Chromium contamination from abandoned industrial sites and inadequately managed waste disposal areas poses substantial environmental threat. Microbially induced carbonate precipitation (MICP) has shown promising, eco-friendly solution to remediate Cr(VI) and divalent heavy metals. In this study, MICP was carried out for chromium immobilization by an ureolytic bacterium Arthrobacter creatinolyticus which is capable of reducing Cr(VI) to less toxic Cr(III) via extracellular polymeric substances (EPS) production. The efficacy of EPS driven reduction was confirmed by cellular fraction analysis. MICP carried out in aqueous solution with 100 ppm of Cr(VI) co-precipitated 82.21% of chromium with CaCO3 and the co-precipitation is positively correlated with reduction of Cr(VI). The organism was utilized to remediate chromium spiked sand and found that MICP treatment decreased the exchangeable fraction of chromium to 0.54 ±â€¯0.11% and increased the carbonate bound fraction to 26.1 ±â€¯1.15% compared to control. XRD and SEM analysis revealed that Cr(III) produced during reduction, influenced the polymorph selection of vaterite during precipitation. Evaluation of MICP to remediate Cr polluted soil sample collected from Ranipet, Tamil Nadu also showed effective immobilization of chromium. Thus, A. creatinolyticus proves to be viable option for encapsulating chromium contaminated soil via MICP process, and effectively mitigating the infiltration of Cr(VI) into groundwater and adjacent water bodies.

Shellfish CO2 excretion is modulated by seawater carbonate chemistry but largely independent of pCO2.

Four species of shellfish, blue mussel (Mytilus galloprovincialis), Pacific abalone (Haliotis discus hannai), zhikong scallops (Chlamys farreri), and Pacific oyster (Crassostrea gigas), were exposed to decoupled carbonate system variables to investigate the impacts of different seawater carbonate parameters on the CO2 excretion process of mariculture shellfish. Six experimental groups with two levels of seawater pH (pH 8.1 and pH 7.7) and three levels of total alkalinity (TA = 1000, 2300, and 3600 µmol/kg, respectively) were established, while pH 8.1 and TA = 2300 µmol/kg was taken as control. Results showed that the CO2 excretion rates of these tested shellfish were significantly affected by the change in carbonate chemistry (P < 0.05). At the same TA level, animals incubated in the acidified group (pH 7.7) had a lower CO2 excretion rate than those in the control group (pH 8.1). In comparison, at the same pH level, the CO2 excretion rate increased when seawater TA level was elevated. No significant correlation between the CO2 excretion rate and seawater pCO2 levels (P > 0.05) was found; however, a significant correlation (P < 0.05) between CO2 excretion rate and TA-DIC (the difference between total alkalinity and dissolved inorganic carbon) was observed. Blue mussel has a significantly higher CO2 excretion rate than the other three species in the CO2 excretions per unit mass of soft parts, with no significant difference observed among these three species. However, in terms of CO2 excretion rate per unit mass of gills, abalone has the highest CO2 excretion rate, while significant differences were found between each species. Our studies indicate that the CO2 buffering capacity impacts the CO2 excretion rate of four shellfish species largely independent of pCO2. Since CO2 excretion is related to acid-base balancing, the results imply that the effects of other carbonate parameters, particularly the CO2 buffering capacity, should be studied to fully understand the mechanism of how acidification affects shellfish. Besides, the species difference in gill to soft parts proportion may contribute to the species difference in responding to ocean acidification.

A pilot study of dimeticone oils versus sodium carbonate treatment for tungiasis: A randomized cohort trial in Homa Bay County, Kenya.

BACKGROUND: Tungiasis is a cutaneous parasitosis caused by the female flea Tunga penetrans. Two-component dimeticone (NYDA) is the only treatment for tungiasis recommended by the World Health Organization; however, this topical drug is not available in Kenya. In Western Kenya, sodium carbonate is commonly used in the treatment of tungiasis. This study evaluated the 7-day cure rates for tungiasis by comparing sodium carbonate and NYDA treatments in Homa Bay County, Kenya. METHODOLOGY/PRINCIPAL FINDINGS: This was a randomized, observer-blinded, parallel-treatment cohort trial. Twenty-three eligible children with 126 flea infections were matched and randomized. All participants received both treatments, with one treatment on each foot. We recorded all health conditions/information, including inflammation scores and adverse events. Observations were performed on days 3, 5, and 7 using a digital microscope to confirm dead or live fleas based on the viability signs. Twenty-three children aged 3-13 years were analyzed. The proportion of dead fleas on day 7 was higher after NYDA treatment than after 5% sodium carbonate treatment (87% versus 64%, respectively, P = 0.01) NYDA. Median survival was 5 days for both treatments; NYDA had significantly higher trend of flea non-viability rate than 5% sodium carbonate (P<0.01). There were no significant differences in the inflammation score or pain/itchiness between the two treatments. On the last day, 14 children indicated their preference for NYDA in future treatment of tungiasis, whereas nine children preferred the 5% sodium carbonate solution. CONCLUSIONS/SIGNIFICANCE: NYDA was significantly more effective than 5% sodium carbonate for tungiasis treatment. Both treatments were safe but the children preferred NYDA more. Future studies with more participants and an extended observation period are warranted to confirm our findings. The findings suggest that NYDA should be made more available in tungiasis endemic area. TRIAL REGISTRATION: UMIN-CTR; UMIN 000044320.

Effect of calcium sources on enzyme-induced carbonate precipitation to solidify desert aeolian sand.

Enzyme-induced carbonate precipitation (EICP) is a promising technique for soil reinforcement. To select a suitable calcium source and a suitable solution amount for aeolian sand stabilization using EICP, specimens treated with different solution amounts (1.5, 2, 2.5, 3, and 3.5 L/m2). Surface strength, crust thickness, calcium carbonate content (CCC) and water vapor adsorption tests were performed to evaluate the effect of two calcium sources (calcium acetate and calcium chloride) on aeolian sand solidification. The plant suitability of solidified sand was investigated by the sea buckthorn growth test. The suitable calcium source was then used for the laboratory wind tunnel test and the field test to examine the erosion resistance of solidified sand. The results demonstrated that Ca(CH3COO)2-treated specimens exhibited higher strength than CaCl2-treated specimens at the same EICP solution amount, and the water vapor equilibrium adsorption mass of Ca(CH3COO)2-treated specimens was less, indicating that Ca(CH3COO)2-solidified sand was more effective and had better long-term stability. In addition, plants grown in Ca(CH3COO)2-treated sand had greater seedling emergence percentage and higher average height, which indicated that calcium acetate is a more suitable calcium source for EICP treatment. Furthermore, the surface strength and crust thickness of solidified sand increased with increasing the solution amount. For sand treated with 3 L/m2 of solution, the excessive strength and thickness of the crust made plants growth difficult, and the performance of sand treated with more than 2 L/m2 of solution significantly improved. Thus, the solution amount of 2-3 L/m2 is suggested for engineering applications. The sand solidified using EICP in the field could effectively mitigate wind erosion and facilitate the growth of native plants. Therefore, EICP can be combined with vegetative method to achieve long-term wind erosion control in the future.

Improving membrane distillation performance by Fe(II) activated sodium percarbonate oxidation during the treatment of shale gas produced water.

Membrane distillation (MD) offers promise for recycling shale gas produced water (SGPW), while membrane fouling is still a major obstacle in standalone MD. Herein, sodium percarbonate (SPC) oxidation was proposed as MD pretreatment, and the performance of the single MD, SPC-MD hybrid process and Fe(II)/SPC-MD hybrid process for SGPW treatment were systematically evaluated. Results showed that compared to raw SGPW, the application of SPC and Fe(II)/SPC led to the decrease of the fluorescent organics by 28.54 % and 54.52 %, respectively. The hydrophobic fraction decreased from 52.75 % in raw SGPW to 37.70 % and 27.20 % for SPC and Fe(II)/SPC, respectively, and the MD normalized flux increased from 0.19 in treating raw SGPW to 0.65 and 0.81, respectively. The superiority of SPC oxidation in reducing the deposited membrane foulants and restoring membrane properties was further confirmed through scanning electron microscopy observation, attenuated total reflection fourier transform infrared, water contact angle and surface tension analyses of fouled membranes. Correlation analysis revealed that hydrophobic/hydrophilic matters and fluorescent organics in SGPW took a crucial role in MD fouling. The mechanism of MD fouling mitigation by Fe(II)/SPC oxidation was attributed to the decrease in concentrations and hydrophobicity of organic by synergistic oxidation, coagulation and adsorption.

Environmental microbiology explains the largest positive carbon isotope excursion in Earth history, the Lomagundi-Jatuli Event.

The geological record of stable carbon isotopes preserved in marine carbonate rocks spans nearly 4 billion years. Numerous perturbations mark this record, but one stands out for its magnitude, the Lomagundi-Jatuli Event, which spanned the transition of the Earth's surface from an anoxic to an oxic state. An Applied and Environmental Microbiology article by D. Y. Sumner (90:e00093-24, 2024, https://doi.org/10.1128/aem.00093-24) provides, for the first time, a biological explanation for its initiation, cessation, environmental specific restriction, and geological singularity.

Hematite enhances microbial autotrophic nitrate removal in carbonate and phosphate-rich environments by increasing Fe(II) activity.

Groundwater contamination by nitrates presents significant risks to both human health and the environment. In groundwater characterized as oligotrophic-low in organic carbon, but abundant in carbonate and phosphate-chemolithoautotrophic bacteria, including nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOB), play a vital role in denitrification. The chemoautotrophic nitrate reduction is sensitive to environmental factors, including widespread iron oxides like hematite in nature. However, the specific mechanisms of this influence remain unclear. We examined the mechanism of how hematite impacts autotrophic nitrate reduction in a model NRFeOB community known as culture KS. We found that hematite enhances the rate of autotrophic nitrate reduction by promoting Fe(II) oxidation. Mössbauer spectroscopy detected a significant amount of adsorbed Fe(II) when hematite was present, leading to a reduction in dissolved ferrous iron. In conjunction with XRD data, it can be inferred that the formation of vivianite decreased, thereby increasing the Fe(II) activity in the reaction system. Within the culture KS bacterial consortium, hematite fosters the proliferation of autotrophic microorganisms, specifically Gallionellaceae, and amplifies the presence of denitrifying microbes, notably Rhodanobacter. This dual enhancement improves Fe(II) utilization and nitrate reduction capabilities. Our findings highlight intricate interactions between hematite and a model NRFeOB community, offering insights into groundwater nitrate removal mechanisms and the ecological strategies of autotrophic bacteria in mineral-rich environments.

Sulfide-carbonate-mineralized functional bacterial consortium for cadmium removal in flue gas.

Sulfide-carbonate-mineralized functional bacterial consortium was constructed for flue gas cadmium biomineralization. A membrane biofilm reactor (MBfR) using the bacterial consortium containing sulfate reducing bacteria (SRB) and denitrifying bacteria (DNB) was investigated for flue gas cadmium (Cd) removal. Cadmium removal efficiency achieved 90%. The bacterial consortium containing Citrobacter, Desulfocurvus and Stappia were dominated for cadmium resistance-nitrate-sulfate reduction. Under flue gas cadmium stress, ten cadmium resistance genes (czcA, czcB, czcC, czcD, cadA, cadB, cadC, cueR, copZ, zntA), and seven genes related to sulfate reduction, increased in abundance; whereas others, nine genes related to denitrification, decreased, indicating that cadmium stress was advantageous to sulfate reduction in the competition with denitrification. A bacterial consortium could capable of simultaneously cadmium resistance, sulfate reduction and denitrification. Microbial induced carbonate precipitation (MICP) and biological adsorption process would gradually yield to sulfide-mineralized process. Flue gas cadmium could transform to Cd-EPS, cadmium carbonate (CdCO3) and cadmium sulfide (CdS) bioprecipitate. The functional bacterial consortium was an efficient and eco-friendly bifunctional bacterial consortium for sulfide-carbonate-mineralized of cadmium. This provides a green and low-carbon advanced treatment technology using sulfide-carbonate-mineralized functional bacterial consortium for the removal of cadmium or other hazardous heavy metal contaminants in flue gas.

Effect of sand minerals on microbially induced carbonate precipitation by denitrification.

Soil improvement techniques utilizing the metabolic functions of microorganisms, including microbially induced carbonate precipitation (MICP), have been extensively researched over the past few decades as part of bio-inspired geotechnical engineering research. Given that metabolic reactions in microorganisms produce carbonate minerals, an enhanced understanding of microbial interaction with soils could improve the effectiveness of MICP as a soil improvement technique. Therefore, this study investigated the effects of sands on MICP by denitrification to employ MICP for geotechnical soil improvement. Under the coexistence of natural sand and artificial silica sand, nitrate-reducing bacteria were cultured in a mixed liquid medium with nitrate, acetate, and calcium ions at 37 °C. Nitrate reduction occurred only in the presence of natural sand. However, the lack of chemical weathering of the composed minerals likely prevented the progress of bacterial growth and nitrate reduction in artificial silica sands. For natural sand, artificial chemical weathering by acid wash and ferrihydrite coating of the sand improved bacterial growth and accelerated nitrate reduction. The calcium carbonate formation induced by denitrification was also influenced by the state of the minerals in the soil and the nitrate reduction rate. The observed MICP enhancement is due to the involvement of coexisting secondary minerals like ferrihydrite with large specific surface areas and surface charges, which may improve the reaction efficiency by serving as adsorbents for bacteria and electron donors and acceptors in the solid phases, thereby promoting the precipitation and crystallization of calcium carbonate on the surfaces. This crystal formation in the minerals provides valuable insights for improving sand solidification via MICP. Considering the interactions between the target soil and microorganisms is essential to improving MICP processes for ground improvement.

Adsorption and recovery of phosphate using sodium carbonate as co-precipitant synthesized La&Zr dual-metal modified material: Adsorption mechanism and practical application.

Adsorption methods offer efficient recovery of phosphorus from water bodies. Modification adsorption materials combining lanthanum (La) and zirconium (Zr) dual-metal immobilized via co-precipitation method have been widely applied in the adsorption and recovery of phosphate. Meanwhile, sodium carbonate (Na2CO3) is gradually replacing sodium hydroxide (NaOH) as the mainstream co-precipitant for immobilizing metals into supporting matrices due to its excellent performance and environmental friendliness. However, the adsorption mechanisms of materials synthesized with different co-precipitants and the synergistic effects between dual-metal components are not well understood, which is not conducive to the further optimization of dual-metal adsorption materials. In this study, anion exchange resin was utilized as the supporting matrices, and La&Zr dual-metal-modified materials, La&Zr-CO32- and La&Zr-OH-, were prepared using Na2CO3 and NaOH as co-precipitants, respectively. The results indicate that La&Zr-CO32- exhibits superior performance in phosphate adsorption and recovery, with adsorption capacity and recovery efficiency reaching 36.28 mg/g and 82.59%, respectively. Additionally, this material demonstrates strong stability in reuse, phosphate selectivity, and a wide pH applicability range. La&Zr-CO32- achieves phosphate adsorption through surface electrostatic affinity, ligand exchange, and intraspherical complexation, whereas La&Zr-OH- primarily relies on electrostatic adsorption on the surface and interior of the material. Synergistic effects between La and Zr result in enhanced adsorption performance of the dual-metal material compared to individual metals. Specifically, phosphate adsorption is predominantly governed by La, while the presence of Zr further enhances ligand exchange between lattice oxygen and metals. Simultaneously, Zr doping enhances the phosphate recovery capacity and reusability of the materials. Continuous flow adsorption results from actual water bodies demonstrate that La&Zr-CO32- is more suitable for the removal and recovery of phosphate in water treatment engineering. This study provides a theoretical basis and technical support for the adsorption and recovery of phosphate using dual-metal-modified materials.