A study on nickel application methods for optimizing soybean growth.

Fertilization with nickel (Ni) can positively affect plant development due to the role of this micronutrient in nitrogen (N) metabolism, namely, through urease and NiFe-hydrogenase. Although the application of Ni is an emerging practice in modern agriculture, its effectiveness strongly depends on the chosen application method, making further research in this area essential. The individual and combined effects of different Ni application methods-seed treatment, leaf spraying and/or soil fertilization-were investigated in soybean plants under different edaphoclimatic conditions (field and greenhouse). Beneficial effects of the Soil, Soil + Leaf and Seed + Leaf treatments were observed, with gains of 7 to 20% in biological nitrogen fixation, 1.5-fold in ureides, 14% in shoot dry weight and yield increases of up to 1161 kg ha-1. All the Ni application methods resulted in a 1.1-fold increase in the SPAD index, a 1.2-fold increase in photosynthesis, a 1.4-fold increase in nitrogenase, and a 3.9-fold increase in urease activity. Edaphoclimatic conditions exerted a significant influence on the treatments. The integrated approaches, namely, leaf application in conjunction with soil or seed fertilization, were more effective for enhancing yield in soybean cultivation systems. The determination of the ideal method is crucial for ensuring optimal absorption and utilization of this micronutrient and thus a feasible and sustainable management technology. Further research is warranted to establish official guidelines for the application of Ni in agricultural practices.

Phase-separated droplets swim to their dissolution.

Biological macromolecules can condense into liquid domains. In cells, these condensates form membraneless organelles that can organize chemical reactions. However, little is known about the physical consequences of chemical activity in and around condensates. Working with model bovine serum albumin (BSA) condensates, we show that droplets swim along chemical gradients. Active BSA droplets loaded with urease swim toward each other. Passive BSA droplets show diverse responses to externally applied gradients of the enzyme's substrate and products. In all these cases, droplets swim toward solvent conditions that favor their dissolution. We call this behavior "dialytaxis", and expect it to be generic, as conditions which favor dissolution typically reduce interfacial tension, whose gradients are well-known to drive droplet motion through the Marangoni effect. These results could potentially suggest alternative physical mechanisms for active transport in living cells, and may enable the design of fluid micro-robots.

Targeting bacterial nickel transport with aspergillomarasmine A suppresses virulence-associated Ni-dependent enzymes.

Microbial Ni2+ homeostasis underpins the virulence of several clinical pathogens. Ni2+ is an essential cofactor in urease and [NiFe]-hydrogenases involved in colonization and persistence. Many microbes produce metallophores to sequester metals necessary for their metabolism and starve competing neighboring organisms. The fungal metallophore aspergillomarasmine A (AMA) shows narrow specificity for Zn2+, Ni2+, and Co2+. Here, we show that this specificity allows AMA to block the uptake of Ni2+ and attenuate bacterial Ni-dependent enzymes, offering a potential strategy for reducing virulence. Bacterial exposure to AMA perturbs H2 metabolism, ureolysis, struvite crystallization, and biofilm formation and shows efficacy in a Galleria mellonella animal infection model. The inhibition of Ni-dependent enzymes was aided by Zn2+, which complexes with AMA and competes with the native nickelophore for the uptake of Ni2+. Biochemical analyses demonstrated high-affinity binding of AMA-metal complexes to NikA, the periplasmic substrate-binding protein of the Ni2+ uptake system. Structural examination of NikA in complex with Ni-AMA revealed that the coordination geometry of Ni-AMA mimics the native ligand, Ni-(L-His)2, providing a structural basis for binding AMA-metal complexes. Structure-activity relationship studies of AMA identified regions of the molecule that improve NikA affinity and offer potential routes for further developing this compound as an anti-virulence agent.

Thermal accelerated urease-driven hyaluronan-targeted melanin nano-missile for bio-radar detection and chemodrug-free phototherapy.

Polymer-based nanomotors are attracting increasing interest in the biomedical field due to their microscopic size and kinematic properties which support overcoming biological barriers, completing cellular uptake and targeted blasting in limited spaces. However, their applications are limited by the complex viscous physiological environment and lack of sufficient biocompatibility. This manuscript firstly reports a natural melanin nano-missile of MNP@HA-EDA@Urease@AIE PS (MHUA) based on photothermally accelerated urease-driven to achieve chemodrug-free phototherapy. Compared to conventional nano-missiles that only provide driving force, this photothermally accelerated urease-driven nanomotor is independent of chemodrug to maximise biocompatibility, and achieve ideal therapeutic effect through targeted PTT/PDT. In particular, the thermal effect can not only boost the catalytic activity of urease but also achieve ideally anti-tumor effect. In addition, guided by and AIE PS, the nanomotor can generate 1O2 to achieve PDT and be traced in real time serving as an effective fluorescent bio-radar for intracellular self-reporting during cancer treatment. Finally, the targeting ability of MUHA is provided by hyaluronan. Taken together, this MHUA platform provides a simple and effective strategy for target/fluorescence radar detective-guided PTT/PDT combination, and achieves good therapeutic results without chemodrug under thermal accelerated strategy, providing a new idea for the construction of chemodrug-free nanomotor-therapy system.

Deterioration phenomenon of Pb-contaminated aqueous solution remediation and enhancement mechanism of nano-hydroxyapatite-assisted biomineralization.

Modern metallurgical and smelting activities discharge the lead-containing wastewater, causing serious threats to human health. Bacteria and urease applied to microbial-induced carbonate precipitation (MICP) and enzyme-induced carbonate precipitation (EICP) are denatured under high Pb2+ concentration. The nano-hydroxyapatite (nHAP)-assisted biomineralization technology was applied in this study for Pb immobilization. Results showed that the extracellular polymers and cell membranes failed to secure the urease activity when subjected to 60 mM Pb2+. The immobilization efficiency dropped to below 50% under MICP, whereas it due to a lack of extracellular polymers and cell membranes dropped to below 30% under EICP. nHAP prevented the attachment of Pb2+ either through competing with bacteria and urease or promoting Ca2+/Pb2+ ion exchange. Furthermore, CO32- from ureolysis replaced the hydroxyl (-OH) in hydroxylpyromorphite to encourage the formation of carbonate-bearing hydroxylpyromorphite of higher stability (Pb10(PO4)6CO3). Moreover, nHAP application overcame an inability to provide nucleation sites by urease. As a result, the immobilization efficiency, when subjected to 60 mM Pb2+, elevated to above 80% under MICP-nHAP and to some 70% under EICP-nHAP. The findings highlight the potential of applying the nHAP-assisted biomineralization technology to Pb-containing water bodies remediation.

Microbial-induced carbonate precipitation effectively prevents Pb2+ migration through the soil profile: Lab experiment and model simulation.

Due to the inappropriate disposal of waste materials containing lead (Pb) and irrigation with sewage containing Pb, the migration of Pb2+ within the soil profile has been extensively investigated. The conventional Pb2+ block method is challenging to implement due to its complex operational procedures and high construction costs. To address this issue, this study introduces the microbial-induced carbonate precipitation (MICP) technique as a novel approach to impede the migration of Pb2+ in the soil profile. Soil acclimatization with urea resulted in an increased proportion of urease-producing microorganisms, including Bacillus, Paenibacillus, and Planococcaceae, along with heightened expression of urea-hydrolyzing genes (UreA, UreB, UreC, and UreG). This indicates that urea-acclimatized soil (Soil-MICP) possesses the potential to induce carbonate precipitation. Batch Pb2+ fixation experiments confirmed that the fixation efficiency of Soil-MICP on Pb2+ exceeded that of soil without MICP, attributed to the MICP process within the Soil-MICP group. Dynamic migration experiments revealed that the MICP reaction transformed exchangeable lead into carbonate-bound Pb, effectively impeding Pb2+ migration in the soil profile. Additionally, the migration rate of Pb2+ in Soil-MICP was influenced by varying urea amounts, pH levels, and pore flow rates, leading to a slowdown in migration. The Two-site sorption model aptly described the Pb2+ migration process in the Soil-MICP column. This study aims to elucidate the MICP biomineralization process, uncover the in-situ blocking mechanism of MICP on lead in soil, investigate the impact of Pb on key genes involved in urease metabolism, enhance the comprehension of the chemical morphology of lead mineralization products, and provide a theoretical foundation for MICP technology in preventing the migration of Pb2+ in soil profiles.

Ecotoxicological impact of butisanstar and clopyralid herbicides on soil microbial respiration and the enzymatic activities.

The application of herbicides in soil has been noted for its detrimental effect on the soil microbial community, crucial for various biochemical processes. This study provides a comprehensive assessment of the impact of butisanstar and clopyralid herbicides, both individually and in combination at different dosage (recommended field dose (RFD), ½, 2 and 5-times RFD). The assessment focuses on soil basal respiration (SBR), cumulative microbial respiration (CMR), and the activities dehydrogenase (DH), catalase (CAT), urease, acid and alkaline phosphatases (Ac-P and Alk-P) enzymes, along with their variations on days 10, 30, 60, and 90 post-herbicide application. Results indicate that, although herbicides, even at lower doses of RFD, demonstrate inhibitory effects on DH, CAT, and microbial respiration, they paradoxically lead to a significant enhancement in urease and phosphatase activities, even at higher doses. The inhibitory/enhancing intensity varies based on herbicide type, incubation period, and dosage. Co-application of herbicides manifests synergistic effects compared to individual applications. The most notable inhibitory effects on DH, CAT, and SBR are observed on the 30th day, coinciding with the highest activities of urease and phosphatases on the same day. The persistent inability to restore respiration and enzyme activities to initial soil (control) levels emphasizes the lasting adverse and inhibitory effects of herbicides, especially clopyralid, over the long term. It becomes apparent that soil microorganisms require an extended duration to decompose and acclimate to the presence of herbicides. Consequently, these agrochemical compounds pose a potential risk to crucial biochemical processes, such as nutrient cycling, ultimately impacting crop production.

In vitro anti-Helicobacter pylori activity and antivirulence activity of cetylpyridinium chloride.

The primary treatment method for eradicating Helicobacter pylori (H. pylori) infection involves the use of antibiotic-based therapies. Due to the growing antibiotic resistance of H. pylori, there has been a surge of interest in exploring alternative therapies. Cetylpyridinium chloride (CPC) is a water-soluble and nonvolatile quaternary ammonium compound with exceptional broad-spectrum antibacterial properties. To date, there is no documented or described specific antibacterial action of CPC against H. pylori. Therefore, this study aimed to explore the in vitro activity of CPC against H. pylori and its potential antibacterial mechanism. CPC exhibited significant in vitro activity against H. pylori, with MICs ranging from 0.16 to 0.62 µg/mL and MBCs ranging from 0.31 to 1.24 µg/mL. CPC could result in morphological and physiological modifications in H. pylori, leading to the suppression of virulence and adherence genes expression, including flaA, flaB, babB, alpA, alpB, ureE, and ureF, and inhibition of urease activity. CPC has demonstrated in vitro activity against H. pylori by inhibiting its growth, inducing damage to the bacterial structure, reducing virulence and adherence factors expression, and inhibiting urease activity.

Freeze-thaw aged polyethylene and polypropylene microplastics alter enzyme activity and microbial community composition in soil.

In cold regions, microplastics (MPs) in the soil undergo freeze-thaw (FT) aging process. Little is known about how FT aged MPs influence soil physico-chemical properties and microbial communities. Here, two environmentally relevant concentrations (50 and 500 mg/kg) of 50 and 500 µm polyethylene (PE) and polypropylene (PP) MPs treated soils were subjected to 45-day FT cycles (FTCs). Results showed that MPs experienced surface morphology, hydrophobicity and crystallinity alterations after FTCs. After 45-day FTCs, the soil urease (SUE) activity in control (MPs-free group that underwent FTCs) was 33.49 U/g. SUE activity in 50 µm PE group was reduced by 19.66 %, while increased by 21.16 % and 37.73 % in 500 µm PE and PP groups compared to control. The highest Shannon index was found in 50 µm PP-MPs group at 50 mg/kg, 2.26 % higher than control (7.09). Compared to control (average weighted degree=8.024), all aged MPs increased the complexity of network (0.19-1.43 %). Bacterial biomarkers of aged PP-MPs were associated with pollutant degradation. Aged PP-MPs affected genetic information, cellular processes, and disrupted the biosynthesis of metabolites. This study provides new insights into the potential hazards of MPs after FTCs on soil ecosystem in cold regions.

Genomic characterization of a novel ureolytic bacteria, Lysinibacillus capsici TSBLM, and its application to the remediation of acidic heavy metal-contaminated soil.

Soil heavy metal contamination is an essential challenge in ecological and environmental management, especially for acidic soils. Microbially induced carbonate precipitation (MICP) is an effective and environmentally friendly remediation technology for heavy metal contaminated sites, and one of the key factors for its realization lies in the microorganisms. In this study, Lysinibacillus capsici TSBLM was isolated from heavy metal contaminated soil around a gold mine, and inferred to be a novel ureolytic bacteria after phylogenomic inference and genome characterization. The urease of L. capsici TSBLM was analyzed by genetic analysis and molecular docking, and further applied this bacteria to the remediation of Cu and Pb in solution and acidic soils to investigate its biomineralization mechanism and practical application. The results revealed L. capsici TSBLM possessed a comprehensive urease gene cluster ureABCEFGD, and the encoded urease docked with urea at the lowest binding energy site (ΔG = -3.43 kcal/mol) connected to three amino acids threonine, aspartic, and alanine. The urease of L. capsici TSBLM is synthesized intracellularly but mainly functions extracellularly. L. capsici TSBLM removes Cu/Pb from the solution by generating heavy metal carbonates or co-precipitating with CaCO3 vaterite. For acidic heavy metal-contaminated soil, the carbonate-bound states of Cu and Pb increased significantly from 7 % to 16 % and from 23 % to 35 % after 30 days by L. capsici TSBLM. Soil pH improved additionally. L. capsici TSBLM maintained the dominant status in the remediated soil after 30 days, demonstrating good environmental adaptability and curing persistence. The results provided new strain resources and practical application references for the remediation of acidic heavy metal contaminated soil based on MICP.

Response of plants and soils to inundation duration and construction of the plant‒soil association mode in the hydro‒fluctuation belt of the reservoir wetland.

Hydro-Fluctuation Belt (HFB), a periodically exposed bank area formed by changes in water level fluctuations, is critical for damaging the reservoir wetland landscape and ecological balance. Thus, it is important to explore the mechanism of hydrological conditions on the plant-soil system of the HFB for protection of the reservoir wetland and landscape restoration. Here, we investigated the response of plant community characteristics and soil environment of the HFB of Tonghui River National Wetland Park (China), is a typical reservoir wetland, to the duration of inundation, as well as the correlation between the distribution of dominant plants and soil pH, nutrient contents, and enzyme activity by linear regression and canonical correlation analyses. The results show that as the duration of inundation decreases, the vegetation within the HFB is successional from annual or biennial herbs to perennial herbs and shrubs, with dominant plant species prominent and uneven distribution of species. Soil nutrient contents and enzyme activities of HFB decreased with increasing inundation duration. Dominant species of HFB plant community are related to soil environment, with water content, pH, urease, and available potassium being principle soil environmental factors affecting their distribution. When HFB was inundated for 0-30 days, soil pH was strongly acidic, with available potassium content above 150 mg kg-1 and higher urease activity, distributed with Arundo donax L., Polygonum perfoliatum L., Alternanthera philoxeroides (Mart.) Griseb., and Daucus carota L. communities. When inundated for 30-80 days, soil pH was acidic, with lower available potassium content (50-150 mg kg-1) and urease activity, distributed with Beckmannia syzigachne (Steud.) Fern.+ Polygonum lapathifolium L., Polygonum lapathifolium L., Medicago lupulina L. + Dysphania ambrosioides L. and Leptochloa panicea (Retz.) Ohwi communities. Using the constructed HFB plant-soil correlation model, changes in the wetland soil environment can be quickly judged by the succession of plant dominant species, which provides a simpler method for the monitoring of the soil environment in the reservoir wetland, and is of great significance for the scientific management and reasonable protection of the reservoir-type wetland ecosystem.

Machine Learning-Driven Classification of Urease Inhibitors Leveraging Physicochemical Properties as Effective Filter Criteria.

Urease, a pivotal enzyme in nitrogen metabolism, plays a crucial role in various microorganisms, including the pathogenic Helicobacter pylori. Inhibiting urease activity offers a promising approach to combating infections and associated ailments, such as chronic kidney diseases and gastric cancer. However, identifying potent urease inhibitors remains challenging due to resistance issues that hinder traditional approaches. Recently, machine learning (ML)-based models have demonstrated the ability to predict the bioactivity of molecules rapidly and effectively. In this study, we present ML models designed to predict urease inhibitors by leveraging essential physicochemical properties. The methodological approach involved constructing a dataset of urease inhibitors through an extensive literature search. Subsequently, these inhibitors were characterized based on physicochemical properties calculations. An exploratory data analysis was then conducted to identify and analyze critical features. Ultimately, 252 classification models were trained, utilizing a combination of seven ML algorithms, three attribute selection methods, and six different strategies for categorizing inhibitory activity. The investigation unveiled discernible trends distinguishing urease inhibitors from non-inhibitors. This differentiation enabled the identification of essential features that are crucial for precise classification. Through a comprehensive comparison of ML algorithms, tree-based methods like random forest, decision tree, and XGBoost exhibited superior performance. Additionally, incorporating the "chemical family type" attribute significantly enhanced model accuracy. Strategies involving a gray-zone categorization demonstrated marked improvements in predictive precision. This research underscores the transformative potential of ML in predicting urease inhibitors. The meticulous methodology outlined herein offers actionable insights for developing robust predictive models within biochemical systems.

Honeycomb-Inspired Surface-Enhanced Raman Scattering Microarray for Large-Area Automated Testing of Urease in Saliva Samples.

Surface-enhanced Raman scattering (SERS) technology, as an important analytical tool, has been widely applied in the field of chemical and biomedical sensing. Automated testing is often combined with biochemical analysis technologies to shorten the detection time and minimize human error. The present SERS substrates for sample detection are time-consuming and subject to high human error, which are not conducive to the combination of SERS and automated testing. Here, a novel honeycomb-inspired SERS microarray is designed for large-area automated testing of urease in saliva samples to shorten the detection time and minimize human error. The honeycomb-inspired SERS microarray is decorated with hexagonal microwells and a homogeneous distribution of silver nanostars. Compared with the other four common SERS substrates, the optimal honeycomb-inspired SERS microarray exhibits the best SERS performance. The RSD of 100 SERS spectra continuously collected from saliva samples is 6.56%, and the time of one detection is reduced from 5 min to 10 s. There is a noteworthy linear relationship with a R2 of 0.982 between SERS intensity and urease concentration, indicating the quantitative detection capability of the urease activity in saliva samples. The honeycomb-inspired SERS microarray, combined with automated testing, provides a new way in which SERS technology can be widely used in biomedical applications.

Epiberberine: a potential rumen microbial urease inhibitor to reduce ammonia release screened by targeting UreG.

Rumen microbial urease inhibitors have been proposed for regulating nitrogen emission and improving nitrogen utilization efficiency in ruminant livestock industry. However, studies on plant-derived natural inhibitors of rumen microbial urease are limited. Urease accessory protein UreG, plays a crucial role in facilitating urease maturation, is a new target for design of urease inhibitor. The objective of this study was to select the potential effective inhibitor of rumen microbial urease from major protoberberine alkaloids in Rhizoma Coptidis by targeting UreG. Our results showed that berberine chloride and epiberberine exerted superior inhibition potential than other alkaloids based on GTPase activity study of UreG. Berberine chloride inhibition of UreG was mixed type, while inhibition kinetics type of epiberberine was uncompetitive. Furthermore, epiberberine was found to be more effective than berberine chloride in inhibiting the combination of nickel towards UreG and inducing changes in the second structure of UreG. Molecular modeling provided the rational structural basis for the higher inhibition potential of epiberberine, amino acid residues in G1 motif and G3 motif of UreG formed interactions with D ring of berberine chloride, while interacted with A ring and D ring of epiberberine. We further demonstrated the efficacy of epiberberine in the ruminal microbial fermentation with low ammonia release and urea degradation. In conclusion, our study clearly indicates that epiberberine is a promising candidate as a safe and effective inhibitor of rumen microbial urease and provides an optimal strategy and suitable feed additive for regulating nitrogen excretion in ruminants in the future. KEY POINTS: • Epiberberine is the most effective inhibitor of rumen urease from Rhizoma Coptidis. • Urease accessory protein UreG is an effective target for design of urease inhibitor. • Epiberberine may be used as natural feed additive to reducing NH3 release in ruminants.

Feeding strategies for Sporosarcina pasteurii cultivation unlock more efficient production of ureolytic biomass for MICP.

The bacterium Sporosarcina pasteurii is the most commonly used microorganism for Microbial Induced Calcite Precipitation (MICP) due to its high urease activity. To date, no proper fed-batch cultivation protocol for S. pasteurii has been published, even though this cultivation method has a high potential for reducing costs of producing microbial ureolytic biomass. This study focusses on fed-batch cultivation of S. pasteurii DSM33. The study distinguishes between limited fed-batch cultivation and extended batch cultivation. Simply feeding glucose to a S. pasteurii culture does not seem beneficial. However, it was exploited that S. pasteurii is auxotrophic for two vitamins and amino acids. Limited fed-batch cultivation was accomplished by feeding the necessary vitamins or amino acids to a culture lacking them. Feeding nicotinic acid to a nicotinic acid deprived culture resulted in a 24% increase of the specific urease activity compared to a fed culture without nicotinic acid limitation. Also, extended batch cultivation was explored. Feeding a mixture of glucose and yeast extract results in OD600 of ≈70 at the end of cultivation, which is the highest value published in literature so far. These results have the potential to make MICP applications economically viable.

Synthetic DNA-based Swimmers Driven by Enzyme Catalysis.

Here, we report DNA-based synthetic nanostructures decorated with enzymes (hereafter referred to as DNA-enzyme swimmers) that self-propel by converting the enzymatic substrate to the product in solution. The DNA-enzyme swimmers are obtained from tubular DNA structures that self-assemble spontaneously by the hybridization of DNA tiles. We functionalize these DNA structures with two different enzymes, urease and catalase, and show that they exhibit concentration-dependent movement and enhanced diffusion upon addition of the enzymatic substrate (i.e., urea and H2O2). To demonstrate the programmability of such DNA-based swimmers, we also engineer DNA strands that displace the enzyme from the DNA scaffold, thus acting as molecular "brakes" on the DNA swimmers. These results serve as a first proof of principle for the development of synthetic DNA-based enzyme-powered swimmers that can self-propel in fluids.

Simple enzyme based fluorimetric biosensor for urea in human biofluids.

As an important biomarker for renal related diseases, detection of urea is playing a vital role in human biofluids on clinical diagnosis concern. In this work, a synthetic salicyaldehyde based imine fluorophore was synthesized using sonication method and conjugated with urease which was used as fluorescent biosensor for the detection of urea in serum samples. This enzyme based biosensor has shown a good selectivity and sensitivity towards urea with the linear range from 2 to 80 mM and the detection limit of 73 µM. The sensing response obtain is highly agreeing with existing analytical technique for urea detection which strongly recommends this biosensor for clinical application.

Bacterial diversity in agricultural drainage ditches shifts with increasing urea-N concentrations.

Urea-based fertilizers applied to crop fields can enter the surface waters of adjacent agricultural drainage ditches and contribute to the nitrogen (N) loading in nearby watersheds. Management practices applied in drainage ditches promote N removal by the bacterial communities, but little is known about the impacts of excess urea fertilizer from crop fields on the bacterial diversity in these ditches. In 2017, sediments from drainage ditches next to corn and soybean fields were sampled to determine if fertilizer application and high urea-N concentrations alters bacterial diversity and urease gene abundances. A mesocosm experiment was paired with a field study to determine which bacterial groups respond to high urea-N concentrations. The bacterial diversity in the ditch next to corn fields was significantly different from the other site. The bacterial orders of Rhizobiales, Bacteroidales, Acidobacteriales, Burkholderiales, and Anaerolineales were most abundant in the ditch next to corn and increased after the addition of urea-N (0.5 mg N L-1) during the mesocosm experiment. The results of our study suggests that urea-N concentrations >0.07 mg N L-1, which are higher than concentrations associated with downstream harmful algal blooms, can lead to shifts in the bacterial communities of agricultural drainage ditches.

Influence of enzyme activity on domestic wastewater amelioration in a hybrid subsurface flow constructed wetland.

Wastewater treatment in a constructed wetland is achieved by the presence of plant species, the metabolism of microorganisms, and the enzyme activities. Three small-scale hybrid subsurface flow constructed wetlands (HSFCWs) planted with Arundo donax and one unplanted HSFCW were constructed near a water resource recovery facility at Guru Gobind Singh Indraprastha University. The purpose of the study was to determine the correlation between soil enzymatic activities and the removal of contaminants from domestic wastewater. Enzyme activity of phosphatase, protease, urease, and cellulase increased with an increase in temperature. A strong correlation between enzyme activities and TKN and surfactant removal was observed, whereas moderate correlation was observed with phosphate in planted HSFCW during the study. The correlation between COD removal and enzyme activities was low to moderate. In unplanted HSFCW, the correlation between enzyme activities and COD removal was negative, negligible to moderate to strong in the case of TKN, low to moderate in the case of phosphate, and negligible to low in the case of surfactants. The increased removal efficiency of the planted system compared with that of the unplanted system indicated a positive impact on enzyme activities with the growth of plants and their roots. PRACTITIONER POINTS: Protease, urease, and cellulase activities: Planted HSFCW exhibited higher protease, urease, and cellulase activities than unplanted, signifying enhanced breakdown. July displayed maximum enzyme activities, correlating with heightened biological breakdown in both systems. Fluctuations in enzyme activities reflected seasonal changes, influencing nutrient degradation rates. Planted HSFCW consistently showed higher enzymatic activities across protease, urease, and cellulase than unplanted.

Treatment of low-pH rubber wastewater using ureolytic bacteria and the production of calcium carbonate precipitate for soil stabilization.

Rubber wastewater contains variable low pH with a high load of nutrients such as nitrogen, phosphorous, suspended solids, high biological oxygen demand (BOD), and chemical oxygen demand (COD). Ureolytic and biofilm-forming bacterial strains Bacillus sp. OS26, Bacillus cereus OS36, Lysinibacillus macroides ST13, and Burkholderia multivorans DF12 were isolated from rubber processing centres showed high urease activity. Microscopic analyses evaluated the structural organization of biofilm. Extracellular polymeric substances (EPS) matrix of the biofilm of the strains showed the higher abundance of polysaccharides and lipids which help in the attachment and absorption of nutrients. The functional groups of polysaccharides, proteins, and lipids present in EPS were revealed by ATR-FTIR and 1H NMR. A consortium composed of B. cereus OS36, L. macroides ST13, and B. multivorans DF12 showed the highest biofilm formation, and efficiently reduced 62% NH3, 72% total nitrogen, and 66% PO43-. This consortium also reduced 76% BOD, 61% COD, and 68% TDS. After bioremediation, the pH of the remediated wastewater increased to 11.19. To reduce the alkalinity of discharged wastewater, CaCl2 and urea were added for calcite reaction. The highest CaCO3 precipitate was obtained at 24.6 mM of CaCl2, 2% urea, and 0.0852 mM of nickel (Ni2+) as a co-factor which reduced the pH to 7.4. The elemental composition of CaCO3 precipitate was analyzed by SEM-EDX. XRD analysis of the bacterially-induced precipitate revealed a crystallinity index of 0.66. The resulting CaCO3 precipitate was used as soil stabilizer. The precipitate filled the void spaces of the treated soil, reduced the permeability by 80 times, and increased the compression by 8.56 times than untreated soil. Thus, CaCO3 precipitated by ureolytic and biofilm-forming bacterial consortium through ureolysis can be considered a promising approach for neutralization of rubber wastewater and soil stabilization.