Efficient removal of total arsenic (As3+/5+) from contaminated water by novel strategies mediated iron and plant extract activated waste flowers of marigold

Optimization of polyamine and mycorrhiza in sorghum plant for removal of hazardous cadmium

Eco-friendly and sustainable practices must be followed while using the right plants and microbes to remove harmful heavy metals from the soil. The goal of the current study was to ascertain how effectively sorghum plants removed cadmium (Cd) from the soil using polyamines and mycorrhiza. Plant-biochemicals such as free amino acids, ascorbic acids, anthocyanin, proline, and catalase, APX, peroxidase activities were considered as markers in this study which revealed the adverse plant growth performance under 70 and 150 ppm of Cd concentration (w/w) after 30,60, and 90 days of treatment. The plants showed a mitigating effect against high Cd-concentration with exogenous use of mycorrhiza and putrescine. The treatment T17 (mycorrhiza +5 mM putrescine) showed a substantial decrease in the content of total free amino acid, ascorbic acid, catalase, APX, peroxidase by 228.36%, 39.79%, 59.06%, 182.79% 106.97%, respectively after 90 days as compared to T12 (150 ppm Cd). Anthocyanin content was negatively correlated (-0.503, -0.556, and -0.613) at p < 0.01 with other studied markers, with an increase by 10.52% in T17 treated plant as compared to T12. The concentration of Cd in root increased by 49.6% (141 ppm) and decreased in the shoot by 71% (17.8 ppm) in T17 treated plant as compared to T12 after 90 days. The application of mycorrhiza and putrescine significantly increased BCF (>1) and decreased TF (<1) for Cd translocation. The administration of mycorrhiza and putrescine boosted the Cd removal efficiency of sorghum plants, according to FTIR, XRD, and DSC analysis. As a result, this study demonstrates novel approaches for induced phytoremediation activity of plants via mycorrhiza and putrescine augmentation, which can be a promising option for efficient bioremediation in contaminated sites.

Some remarks on "Efficient removal of total arsenic (As3+/5+) from contaminated water by novel strategies mediated iron and plant extract activated waste flowers of marigold"

We explain here that the authors of the article cited in the title have misrepresented the species of As(III) and As(V) in solutions and, in particular, have neglected their speciation as a function of pH. Their discussion of (ad)sorption mechanisms is therefore unsatisfactory, especially since organic matter (flower waste) and the presence of iron oxyhydroxides should be taken into account. Furthermore, the modeling of (ad)sorption kinetics and isotherms was based on linearized equations, whereas the corresponding nonlinear equations should have been used. Therefore, we believe that the authors of the original article should make corrections and additions to it. This Letter to the Editor is motivated by a concern to avoid the dissemination of approximate or even incorrect concepts in the scientific literature, which could mislead novice researchers.

Recent advancement of nano-biochar for the remediation of heavy metals and emerging contaminants: Mechanism, adsorption kinetic model, plant growth and development

Even though researches have shown that biochar can improve soil-health and plant-growth even in harsh environments and get rid of harmful heavy metals and new contaminants, it is still not sustainable, affordable, or effective enough. Therefore, scientists are required to develop nanomaterials in order to preserve numerous aquatic and terrestrial species. The carbonaceous chemical known as nano-biochar (N-BC) can be used to get rid of metal contamination and emerging contaminants. However, techniques to reduce hetero-aggregation and agglomeration of nano-biochar are needed that lead to the emergence of emerging nano-biochar (EN-BC) in order to maximise its capacity for adsorption of nano-biochar. To address concerns in regards to the expanding human population and sustain a healthy community, it is imperative to address the problems associated with toxic heavy metals, emerging contaminants, and other abiotic stressors that are threatening agricultural development. Nano-biochar can provide an effective solution for removal of emerging contaminants, toxic heavy metals, and non-degradable substance. This review provides the detailed functional mechanistic and kinetics of nano-biochar, its effectiveness in promoting plant growth, and soil health under abiotic stress. Nonetheless, this review paper has comprehensively illustrated various adsorption study models that will be employed in future research.

Impact of Bacillus cereus SPB-10 on Growth Promotion of Wheat (Triticum aestivum L.) Under Arsenic-Contaminated Soil

This study investigates the impact of bacteria on arsenic reduction in wheat plants, highlighting the potential of microbe-based eco-friendly strategies for plant growth. In the present study, bacterial isolate SPB-10 was survived at high concentration against both form of arsenic (As3+ and As5+). SPB-10 produced 5.2 g/L and 11.3 g/L of exo-polysaccharide at 20 ppm of As3+ and As5+, respectively, whereas qualitative examination revealed the highest siderophores ability. Other PGP attributes such as IAA production were recorded 52.12 mg/L and 95.82 mg/L, phosphate solubilization was 90.23 mg/L and 129 mg/L at 20 ppm of As3+ and As5+, respectively. Significant amount of CAT, APX, and Proline was also observed at 20 ppm of As3+ and As5+ in SPB-10. Isolate SPB-10 was molecularly identified as Bacillus cereus through 16S rRNA sequencing. After 42 days, wheat plants inoculated with SPB-10 had a 25% increase in shoot length and dry weight, and 26% rise in chlorophyll-a pigment under As5+ supplemented T4 treatment than control. Reducing sugar content was increased by 24% in T6-treated plants compared to control. Additionally, SPB-10 enhanced the content of essential nutrients (NPK), CAT, and APX in plant's-leaf under both As3+ and As5+ stressed conditions after 42 days. The study found that arsenic uptake in plant roots and shoots decreased in SPB-10-inoculated plants, with the maximum reduction observed in As5+ treated plants. Bio-concentration factor-BCF was reduced by 90.89% in SPB-10-inoculated treatment T4 after 42 days. This suggests that Bacillus cereus-SPB-10 may be beneficial for plant growth in arsenic-contaminated soil.

Dual metal ion (Fe3+ and As3+) sensing and cell bioimaging using fluorescent carbon quantum dots synthesised from Cynodon dactylon

In this study, water dispersible fluorescent carbon quantum dot (CQD) has been synthesised, having an average size of 8.6 ± 0.4 nm using Cynodon dactylon (CD) following microwave assisted green synthetic one-step method. As-prepared CQD fluoresces strongly at 444 nm having a quantum yield of 1% in water when excited at 350 nm. This fluorescence of CQD is sensitive toward As3+ and Fe3+ metal ions. These CQD are utilized for dual metal ion fluorescence sensing; turn-on fluorescence sensing for As3+ and turn-off fluorescence sensing for Fe3+ ions. Limit of detection for As3+ and Fe3+ ions has been found to be 19 nM and 0.10 μM respectively, which is the lowest value reported for As3+ without any functionalization. The adsorption kinetics of As3+ and Fe3+ ions on CQD have been examined using pseudo-first-order-kinetic model revealing that physical adsorption is dominant over chemical processes in this work. For 0.41 g/L and 1.90 g/L dose of CQD, the equilibrium adsorption capacity was found to be 1.57 × 10-6 mg/g, 2.91 × 10-7 mg/g, and 1.01 × 10-5 mg/g, 1.69 × 10-6 mg/g respectively for As3+ and Fe3+ ions. Despite having low quantum yield in water, as-prepared CQD showed low cytotoxicity and good tolerance against photodegradation of biological cells at concentrations lower than 62.5 μg/mL and when the cells are illuminated up to 12 h. Owing to this, the synthesised CQD have been utilized as fluorescent probes for in itro cell imaging.

Study on diversity, nitrogen-fixing capacity, and heavy metal tolerance of culturable Pongamia pinnata rhizobia in the vanadium-titanium magnetite tailings

Introduction

The diversity, nitrogen-fixing capacity and heavy metal tolerance of culturable rhizobia in symbiotic relationship with Pongamia pinnata surviving in vanadium (V) - titanium (Ti) magnetite (VTM) tailings is still unknown, and the rhizobia isolates from the extreme barren VTM tailings contaminated with a variety of metals would provide available rhizobia resources for bioremediation.

Methods

P. pinnata plants were cultivated in pots containing the VTM tailings until root nodules formed, and then culturable rhizobia were isolated from root nodules. The diversity, nitrogen-fixing capacity and heavy metal tolerance of rhizobia were performed.

Results

Among 57 rhizobia isolated from these nodules, only twenty strains showed different levels of tolerance to copper (Cu), nickel (Ni), manganese (Mn) and zinc (Zn), especially strains PP1 and PP76 showing high tolerance against these four heavy metals. Based on the phylogenetic analysis of 16S rRNA and four house-keeping genes (atpD, recA, rpoB, glnII), twelve isolates were identified as Bradyrhizobium pachyrhizi, four as Ochrobactrum anthropic, three as Rhizobium selenitireducens and one as Rhizobium pisi. Some rhizobia isolates showed a high nitrogen-fixing capacity and promoted P. pinnata growth by increasing nitrogen content by 10%-145% in aboveground plant part and 13%-79% in the root. R. pachyrhizi PP1 showed the strongest capacity of nitrogen fixation, plant growth promotion and resistance to heavy metals, which provided effective rhizobia strains for bioremediation of VTM tailings or other contaminated soils. This study demonstrated that there are at least three genera of culturable rhizobia in symbiosis with P. pinnata in VTM tailings.

Discussion

Abundant culturable rhizobia with the capacity of nitrogen fixation, plant growth promotion and resistance to heavy metals survived in VTM tailings, indicating more valuable functional microbes could be isolated from extreme soil environments such as VTM tailings.

A review on simultaneous heavy metal removal and organo-contaminants degradation by potential microbes: Current findings and future outlook

Industrial processes result in the production of heavy metals, dyes, pesticides, polyaromatic hydrocarbons (PAHs), pharmaceuticals, micropollutants, and PFAS (per- and polyfluorinated substances). Heavy metals are currently a significant problem in drinking water and other natural water bodies, including soil, which has an adverse impact on the environment as a whole. The heavy metal is highly poisonous, carcinogenic, mutagenic, and teratogenic to humans as well as other animals. Multiple polluted sites, including terrestrial and aquatic ecosystems, have been observed to co-occur with heavy metals and organo-pollutants. Pesticides and heavy metals can be degraded and removed concurrently from various metals and pesticide-contaminated matrixes due to microbial processes that include a variety of bacteria, both aerobic and anaerobic, as well as fungi. Numerous studies have examined the removal of heavy metals and organic-pollutants from different types of systems, but none of them have addressed the removal of these co-occurring heavy metals and organic pollutants and the use of microbes to do so. Therefore, the main focus of this review is on the recent developments in the concurrent microbial degradation of organo-pollutants and heavy metal removal. The limitations related to the simultaneous removal and degradation of heavy metals and organo-pollutant pollutants have also been taken into account.

Mechanism of lead adsorption by a Bacillus cereus strain with indole-3-acetic acid secretion and inorganic phosphorus dissolution functions

BACKGROUND

Heavy metal pollution has become a major source of environmental pollution because of increasing industrialization. Microbial remediation is a promising approach to remediate lead-contaminated environments owing to its cost-effective, environment-friendly, ecologically sustainable, and highly efficient properties. In this study, the growth-promoting functions and lead-adsorption ability of Bacillus cereus SEM-15 were examined, and the functional mechanism of the strain was preliminarily identified using scanning electron microscopy, energy spectrum, infrared spectrum, and genome analyses, providing theoretical support for utilization of B. cereus SEM-15 in heavy metals remediation.

RESULTS

B. cereus SEM-15 showed strong ability to dissolve inorganic phosphorus and secrete indole-3-acetic acid. The lead adsorption efficiency of the strain at lead ion concentration of 150 mg/L was more than 93%. Single factor analysis revealed the optimal conditions for heavy metal adsorption by B. cereus SEM-15 (adsorption time, initial lead ion concentration, pH, and inoculum amount were 10 min, 50-150 mg/L, 6-7, and 5 g/L, respectively) in nutrient-free environment, with the lead adsorption rate reaching 96.58%. Scanning electron microscopy of B. cereus SEM-15 cells before and after lead adsorption showed adherence of a large number of granular precipitates to the cell surface after lead adsorption. X-Ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results indicated the characteristic peaks of Pb-O, Pb-O-R (R = functional group), and Pb-S bonds after lead adsorption, and a shift in the characteristic peaks of bonds and groups related to C, N, and O. Genome annotation results showed the presence of genes related to heavy metals tolerance and plant growth promotion in B. cereus SEM-15, providing a molecular basis for the strain's heavy metals tolerance and plant growth promotion functions.

CONCLUSIONS

This study analyzed the lead adsorption characteristics of B. cereus SEM-15 and the associated influencing factors, and discussed the adsorption mechanism and related functional genes, providing a basis for clarifying the underlying molecular mechanism and offering a reference for further research on plant-microorganisms combined remediation of heavy metals polluted environments.

Bacteria assisted green synthesis of copper oxide nanoparticles and their potential applications as antimicrobial agents and plant growth stimulants

Copper oxide nanoparticles (CuO-NPs) have piqued the interest of agricultural researchers due to their potential application as fungicides, insecticides, and fertilizers. The Serratia sp. ZTB29 strain, which has the NCBI accession number MK773873, was a novel isolate used in this investigation that produced CuO-NPs. This strain can survive concentrations of copper as high as 22.5 mM and can also remove copper by synthesizing pure CuO-NPs. UV-VIS spectroscopy, DLS, Zeta potential, FTIR, TEM, and XRD techniques were used to investigate the pure form of CuO-NPs. The synthesized CuO-NPs were crystalline in nature (average size of 22 nm) with a monoclinic phase according to the XRD pattern. CuO-NPs were found to be polydisperse, spherical, and agglomeration-free. According to TEM and DLS inspection, they ranged in size from 20 to 40 nm, with a typical particle size of 28 nm. CuO-NPs were extremely stable, as demonstrated by their zeta potential of -15.4 mV. The ester (C=O), carboxyl (C=O), amine (NH), thiol (S-H), hydroxyl (OH), alkyne (C-H), and aromatic amine (C-N) groups from bacterial secretion were primarily responsible for reduction and stabilization of CuO-NPs revealed in an FTIR analysis. CuO-NPs at concentrations of 50 μg mL^-1 and 200 μg mL^-1 displayed antibacterial and antifungal activity against the plant pathogenic bacteria Xanthomonas sp. and pathogenic fungus Alternaria sp., respectively. The results of this investigation support the claims that CuO-NPs can be used as an efficient antimicrobial agent and nano-fertilizer, since, compared to the control and higher concentrations of CuO-NPs (100 mg L^-1) considerably improved the growth characteristics of maize plants.