Cohesive phycoremediation of pyrene by freshwater microalgae Selenastrum sp. and biodiesel production and its assessment.

In this study, the freshwater microalgae Selenastrum sp. was assessed for the effective degradation of pyrene and simultaneous production of biodiesel from pyrene-tolerant biomass. The growth of algae was determined based on the cell dry weight, cell density, chlorophyll content, and biomass productivity under different pyrene concentrations. Further, lipids from pyrene tolerant culture were converted into biodiesel by acid-catalyzed transesterification, which was characterized for the total fatty acid profile by gas chromatography. Increased pyrene concentration revealed less biomass yield and productivity after 20 days of treatment, indicating potent pyrene biodegradation by Selenastrum sp. Biomass yield was unaffected till the 20 mg/L pyrene. A 95% of pyrene bioremediation was observed at 20 days of culturing. Lipid accumulation of 22.14%, as evident from the estimation of the total lipid content, indicated a marginal increase in corroborating pyrene stress in the culture. Fatty acid methyl esters yield of 63.06% (% per 100 g lipids) was noticed from the pyrene tolerant culture. Moreover, fatty acid profile analysis of biodiesel produced under 10 mg/L and 20 mg/L pyrene condition showed escalated levels of desirable fatty acids in Selenastrum sp., compared to the control. Further, Selenastrum sp. and other freshwater microalgae are catalogued for sustainable development goals attainment by 2030, as per the UNSDG (United Nations Sustainable Development Goals) agenda. Critical applications for the Selenastrum sp. in bioremediation of pyrene, along with biodiesel production, are enumerated for sustainable and renewable energy production and resource management.

Comparative transcriptomics revealed the mechanism of Stenotrophomonas rhizophila JC1 response and biosorption to Pb2.

Nowadays, there is limited research focusing on the biosorption of Pb2+ through microbial process, particularly at the level of gene expression. To overcome this knowledge gap, we studied the adsorption capacity of Stenotrophomonas rhizophila JC1 to Pb2+, and investigated the physiological mechanism by means of SEM, EDS, FTIR, membrane permeability detection, and investigated the molecular mechanism through comparative transcriptomics. The results showed that after 16 h of cultivation, the biosorption capacity of JC1 for 100 mg/L of Pb2+ reached at 79.8%. The main mechanism of JC1 adsorb Pb2+ is via intracellular accumulation, accounting for more than 90% of the total adsorption. At the physiological level, Pb2+ can precipitate with anion functional groups (e.g., -OH, -NH) on the bacterial cell wall or undergo replacement reaction with cell component elements (e.g., Si, Ca) to adsorb Pb2+ outside of the cell wall, thus accomplishing extracellular adsorption of Pb2+ by strains. Furthermore, the cell membrane acts as a "switch" that inhibits the entry of metal ions into the cell from the plasma membrane. At the molecular level, the gene pbt specificity is responsible for the adsorption of Pb2+ by JC1. In addition, phosphate permease is a major member of the ABC transporter family involved in Pb2+, and czcA/cusA or Co2+/Mg2+ efflux protein plays an important role in the efflux of Pb2+ in JC1. Further, cellular macromolecule biosynthesis, inorganic cation transmembrane transport, citrate cycle (TCA) and carbon metabolism pathways all play crucial roles in the response of strain JC1 to Pb2+ stress.

Transcriptomics Reveals the Mechanism of Purpureocillium lilacinum GZAC18-2JMP in Degrading Keratin Material.

Microbial degradation of keratin is characterized by its inherent safety, remarkable efficiency, and the production of copious degradation products. All these attributes contribute to the effective management of waste materials at high value-added and in a sustainable manner. Microbial degradation of keratin materials remains unclear, however, with variations observed in the degradation genes and pathways among different microorganisms. In this study, we sequenced the transcriptome of Purpureocillium lilacinum GZAC18-2JMP mycelia on control medium and the medium containing 1% feather powder, analyzed the differentially expressed genes, and revealed the degradation mechanism of chicken feathers by P. lilacinum GZAC18-2JMP. The results showed that the chicken feather degradation rate of P. lilacinum GZAC18-2JMP reached 64% after 216 h of incubation in the fermentation medium, reaching a peak value of 148.9 µg·mL-1 at 192 h, and the keratinase enzyme activity reached a peak value of 211 U·mL-1 at 168 h, which revealed that P. lilacinum GZAC18-2JMP had a better keratin degradation effect. A total of 1001 differentially expressed genes (DEGs) were identified from the transcriptome database, including 475 upregulated genes and 577 downregulated genes. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis of the DEGs revealed that the metabolic pathways related to keratin degradation were mainly sulfur metabolism, ABC transporters, and amino acid metabolism. Therefore, the results of this study provide an opportunity to gain further insight into keratin degradation and promote the biotransformation of feather wastes.

Engineering natural microbiomes toward enhanced bioremediation by microbiome modeling.

Engineering natural microbiomes for biotechnological applications remains challenging, as metabolic interactions within microbiomes are largely unknown, and practical principles and tools for microbiome engineering are still lacking. Here, we present a combinatory top-down and bottom-up framework to engineer natural microbiomes for the construction of function-enhanced synthetic microbiomes. We show that application of herbicide and herbicide-degrader inoculation drives a convergent succession of different natural microbiomes toward functional microbiomes (e.g., enhanced bioremediation of herbicide-contaminated soils). We develop a metabolic modeling pipeline, SuperCC, that can be used to document metabolic interactions within microbiomes and to simulate the performances of different microbiomes. Using SuperCC, we construct bioremediation-enhanced synthetic microbiomes based on 18 keystone species identified from natural microbiomes. Our results highlight the importance of metabolic interactions in shaping microbiome functions and provide practical guidance for engineering natural microbiomes.

Pilot-scale field studies on activated microbial remediation of petroleum-contaminated soil.

Soil contamination by petroleum, including crude oil from various sources, is increasingly becoming a pressing global environmental concern, necessitating the exploration of innovative and sustainable remediation strategies. The present field-scale study developed a simple, cost-effective microbial remediation process for treating petroleum-contaminated soil. The soil treatment involves adding microbial activators to stimulate indigenous petroleum-degrading microorganisms, thereby enhancing the total petroleum hydrocarbons (TPH) degradation rate. The formulated microbial activator provided a growth-enhancing complex of nitrogen and phosphorus, trace elements, growth factors, biosurfactants, and soil pH regulators. The field trials, involving two 500 m3 soil samples with the initial TPH content of 5.01% and 2.15%, were reduced to 0.41% and 0.02% in 50 days, respectively, reaching the national standard for cultivated land category II. The treatment period was notably shorter than the commonly used composting and bioaugmentation methods (typically from 8 to 12 weeks). The results indicated that the activator could stimulate the functional microorganisms in the soil and reduce the phytotoxicity of the contaminated soil. After 40 days of treatment, the germination rate of rye seeds increased from 20 to 90%, indicating that the microbial activator could be effectively used for rapid on-site remediation of oil-contaminated soils.

How does the biochar-supported sulfidized nanoscale zero-valent iron affect the soil environment and microorganisms while remediating cadmium contaminated paddy soil?

In previous studies, iron-based nanomaterials, especially biochar (BC)-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC), have been widely used for the remediation of soil contaminants. However, its potential risks to the soil ecological environment are still unknown. This study aims to explore the effects of 3% added S-nZVI/BC on soil environment and microorganisms during the remediation of Cd contaminated yellow-brown soil of paddy field. The results showed that after 49 d of incubation, S-nZVI/BC significantly reduced physiologically based extraction test (PBET) extractable Cd concentration (P < 0.05), and increased the immobilization efficiency of Cd by 16.51% and 17.43% compared with S-nZVI and nZVI/BC alone, respectively. Meanwhile, the application of S-nZVI/BC significantly increased soil urease and sucrase activities by 0.153 and 0.446 times, respectively (P < 0.05), improving the soil environmental quality and promoting the soil nitrogen cycle and carbon cycle. The results from the analysis of the 16S rRNA genes indicated that S-nZVI/BC treatment had a minimal effect on the bacterial community and did not appreciably alter the species of the original dominant bacterial phylum. Importantly, compared to other iron-based nanomaterials, incorporating S-nZVI/BC significantly increased the soil organic carbon (OC) content and decreased the excessive release of iron (P < 0.05). This study also found a significant negative correlation between OC content and Fe(II) content (P < 0.05). It might originate from the reducing effect of Fe-reducing bacteria, which consumed OC to promote the reduction of Fe(III). Accompanying this process, the redistribution of Cd and Fe mineral phases in the soil as well as the generation of secondary Fe(II) minerals facilitated Cd immobilization. Overall, S-nZVI/BC could effectively reduce the bioavailability of Cd, increase soil nutrients and enzyme activities, with less toxic impacts on the soil microorganisms.

Heavy metal pollution indices in soil and plants within the vicinity of the Gosa Dumpsite in Abuja, Nigeria.

Heavy metal contamination in the soil and phytoremediation potential of the plants cultivated around the Gosa dumpsite were evaluated using pollution indices. The concentrations of heavy metals in the soil and plant samples were determined using an atomic absorption spectrophotometer (Agilent 280FS AA). The mean heavy metal contents in the upper and lower soil layers ranged from 0.37 to 1662.61 mg/kg and 0.32 to 1608.61 mg/kg, respectively, in ascending order of Cd < Cr < Cu < Ni < Pb < Co < Zn < Fe. The results revealed a steady depthwise decrease in heavy metal contents from the upper to lower soil layers. Co, Pb, Zn and Fe were introduced through geogenic and anthropogenic pathways, while Cr, Ni, Cu and Cd were derived mainly from anthropogenic sources. The mean soil enrichment in the heavy metals ranged from 0.96 to 237.04 in the ascending order of Fe > Co > Pb > Zn > Cu > Cd > Cr > Ni. The soil was moderately polluted with Co, Cu, Pb, Zn, Fe and Cd but heavily polluted with Cr and Ni. The results revealed that 37.5% of the sites studied had pollution load indices greater than 1.0, indicating gradual deterioration in overall soil quality. The concentrations of Pb, Cd and Fe exceeded the recommended limits for the five plant species assessed. The transfer factor (TF) values of okra plant 1 (0.7536), water hyacinth (1.3768), and Amaranthus hybridus (0.9783) indicated excellent Cd phytoremediation potential. Okra Plant, water hyacinth and Amaranthus hybridus had excellent potential for phytoremediation of Cu, Fe and Pb, respectively. The study area was strongly enriched in Fe, Cd, Cr, and Ni, suggesting some degree of soil pollution, while the plants demonstrated an excellent capacity to accumulate Cd, Cu, Fe and Pb. This dumpsite should be adequately monitored while proper remediation measures are adopted by government authorities.

The unexpected effect of the compound microbial agent NP-M2 on microbial community dynamics in a nonylphenol-contaminated soil: the self-stability of soil ecosystem.

Background: Nonylphenol (NP) is widely recognized as a crucial environmental endocrine-disrupting chemical and persistent toxic substance. The remediation of NP-contaminated sites primarily relies on biological degradation. Compound microbial products, as opposed to pure strains, possess a greater variety of metabolic pathways and can thrive in a wider range of environmental conditions. This characteristic is believed to facilitate the synergistic degradation of pollutants. Limited research has been conducted to thoroughly examine the potential compatibility of compound microbial agents with indigenous microflora, their ability to function effectively in practical environments, their capacity to enhance the dissipation of NP, and their potential to improve soil physicochemical and biological characteristics. Methods: In order to efficiently eliminate NP in contaminated soil in an eco-friendly manner, a simulation study was conducted to investigate the impact of bioaugmentation using the functional compound microbial agent NP-M2 at varying concentrations (50 and 200 mg/L) on the dynamics of the soil microbial community. The treatments were set as follows: sterilized soil with 50 mg/kg NP (CK50) or 200 mg/kg NP (CK200); non-sterilized soil with 50 mg/kg NP (TU50) or 200 mg/kg NP (TU200); non-sterilized soil with the compound microbial agent NP-M2 at 50 mg/kg NP (J50) or 200 mg/kg NP (J200). Full-length 16S rRNA analysis was performed using the PacBio Sequel II platform. Results: Both the indigenous microbes (TU50 and TU200 treatments) and the application of NP-M2 (J50 and J200 treatments) exhibited rapid NP removal, with removal rates ranging from 93% to 99%. The application of NP-M2 further accelerated the degradation rate of NP for a subtle lag period. Although the different treatments had minimal impacts on the soil bacterial α-diversity, they significantly altered the ß-diversity and composition of the bacterial community. The dominant phyla were Proteobacteria (35.54%-44.14%), Acidobacteria (13.55%-17.07%), Planctomycetes (10.78%-11.42%), Bacteroidetes (5.60%-10.74%), and Actinobacteria (6.44%-8.68%). The core species were Luteitalea_pratensis, Pyrinomonas_methylaliphatogenes, Fimbriiglobus_ruber, Longimicrobium_terrae, and Massilia_sp003590855. The bacterial community structure and taxon distribution in polluted soils were significantly influenced by the activities of soil catalase, sucrase, and polyphenol oxidase, which were identified as the major environmental factors. Notably, the concentration of NP and, to a lesser extent, the compound microbial agent NP-M2 were found to cause major shifts in the bacterial community. This study highlights the importance of conducting bioremediation experiments in conjunction with microbiome assessment to better understand the impact of bioaugmentation/biostimulation on the potential functions of complex microbial communities present in contaminated soils, which is essential for bioremediation success.

A polyethylene surrogate for microbial community enrichment and characterization.

Plastic pollution is a vast and increasing problem that has permeated the environment, affecting all aspects of the global food web. Plastics and microplastics have spread to soil, water bodies, and even the atmosphere due to decades of use in a wide range of applications. Plastics include a variety of materials with different properties and chemical characteristics, with polyethylene being a dominant fraction. Polyethylene is also an extremely persistent compound with slow rates of photodegradation or biodegradation. In this study, we developed a method to isolate communities of microbes capable of biodegrading a polyethylene surrogate. This method allows us to study potential polyethylene degradation over much shorter time periods. Using this method, we enriched several communities of microbes that can degrade the polyethylene surrogate within weeks. We also identified specific bacterial strains with a higher propensity to degrade compounds similar to polyethylene. We provide a description of the method, the variability and efficacy of four different communities, and key strains from these communities. This method should serve as a straightforward and adaptable tool for studying polyethylene biodegradation.

Synergistic biocementation: harnessing Comamonas and Bacillus ureolytic bacteria for enhanced sand stabilization.

Biocementation, driven by ureolytic bacteria and their biochemical activities, has evolved as a powerful technology for soil stabilization, crack repair, and bioremediation. Ureolytic bacteria play a crucial role in calcium carbonate precipitation through their enzymatic activity, hydrolyzing urea to produce carbonate ions and elevate pH, thus creating favorable conditions for the precipitation of calcium carbonate. While extensive research has explored the ability of ureolytic bacteria isolated from natural environments or culture conditions, bacterial synergy is often unexplored or under-reported. In this study, we isolated bacterial strains from the local eutrophic river canal and evaluated their suitability for precipitating calcium carbonate polymorphs. We identified two distinct bacterial isolates with superior urea degradation ability (conductivity method) using partial 16 S rRNA gene sequencing. Molecular identification revealed that they belong to the Comamonas and Bacillus genera. Urea degradation analysis was performed under diverse pH (6,7 and 8) and temperature (15 °C,20 °C,25 °C and 30 °C) ranges, indicating that their ideal pH is 7 and temperature is 30 °C since 95% of the urea was degraded within 96 h. In addition, we investigated these strains individually and in combination, assessing their microbially induced carbonate precipitation (MICP) in silicate fine sand under low (14 ± 0.6 °C) and ideal temperature 30 °C conditions, aiming to optimize bio-mediated soil enhancement. Results indicated that 30 °C was the ideal temperature, and combining bacteria resulted in significant (p ≤ 0.001) superior carbonate precipitation (14-16%) and permeability (> 10- 6 m/s) in comparison to the average range of individual strains. These findings provide valuable insights into the potential of combining ureolytic bacteria for future MICP research on field applications including soil erosion mitigation, soil stabilization, ground improvement, and heavy metal remediation.

Overexpressing CYP81D11 enhances 2,4,6-trinitrotoluene tolerance and removal efficiency in Arabidopsis.

Phytoremediation is a promising technology for removing the high-toxic explosive 2,4,6-trinitrotoluene (TNT) pollutant from the environment. Mining dominant genes is the key research direction of this technology. Most previous studies have focused on the detoxification of TNT rather than plants' TNT tolerance. Here, we conducted a transcriptomic analysis of wild type Arabidopsis plants under TNT stress and found that the Arabidopsis cytochrome P450 gene CYP81D11 was significantly induced in TNT-treated plants. Under TNT stress, the root length was approximately 1.4 times longer in CYP81D11-overexpressing transgenic plants than in wild type plants. The half-removal time for TNT was much shorter in CYP81D11-overexpressing transgenic plants (1.1 days) than in wild type plants (t1/2 = 2.2 day). In addition, metabolic analysis showed no difference in metabolites in transgenic plants compared to wild type plants. These results suggest that the high TNT uptake rates of CYP81D11-overexpressing transgenic plants were most likely due to increased tolerance and biomass rather than TNT degradation. However, CYP81D11-overexpressing plants were not more tolerant to osmotic stresses, such as salt or drought. Taken together, our results indicate that CYP81D11 is a promising target for producing bioengineered plants with high TNT removing capability.

Bottlenecks in biobased approaches to plastic degradation.

Plastic waste is an environmental challenge, but also presents a biotechnological opportunity as a unique carbon substrate. With modern biotechnological tools, it is possible to enable both recycling and upcycling. To realize a plastics bioeconomy, significant intrinsic barriers must be overcome using a combination of enzyme, strain, and process engineering. This article highlights advances, challenges, and opportunities for a variety of common plastics.

Experimental investigation on strengthening of Zea mays root fibres for biodegradable composite materials using potassium permanganate treatment.

Humans are the only species who generate waste materials that cannot be broken down by natural processes. The ideal solution to this waste problem would be to employ only compostable materials. Biodegradable materials play a key role in creating a safer and greener world. Biodegradability is the gift that keeps on giving, in the sense of creating an Earth worth living. The future is thus best served by green energy, sustainability, and renewable resources. To realize such goals, waste should be considered as a valuable resource. In this context, Zea mays (Zm) root fibres, which are normally considered as agricultural waste, can be used as reinforcing substances in polymer matrices to produce structural composite materials. Before being used in composites, such fibres must be analysed for their physical properties. Chemical treatments can be employed to improve the structural quality of fibres, and the changes due to such modification can be analysed. Therefore, the current work examines the effect of permanganate treatment on the surface properties of Zm fibres. The raw and potassium permanganate-treated samples were assayed for various properties. Physical analysis of the fibre samples yielded details concerning the physical aspects of the fibres. The thermal conductivity and moisture absorption behaviour of the samples were analysed. Chemical analysis was employed to characterize the composition of both treated and untreated samples. p-XRD was employed to examine the crystalline nature of the Zm fibres. Numerous functional groups present in each sample were analysed by FTIR. Thermogravimetric analysis was used to determine the thermal stability of Zm fibres. Elemental analysis (CHNS and EDS) was used to determine the elemental concentrations of both raw and treated samples. The surface alterations of Zm fibres brought on by treatment were described using SEM analysis. The characteristics of Zm roots and the changes in quality due to treatment were reviewed, and there were noticeable effects due to the treatment. Both samples would have applications in various fields, and each could be used as a potential reinforcing material in the production of efficient bio-composites.

Native desert plants have the potential for phytoremediation of phytotoxic metals in urban cities: implications for cities sustainability in arid environments.

Arid regions can benefit from using native desert plants, which require minimal freshwater and can aid in remediating soil phytotoxic metals (PTMs) from traffic emissions. In this study, we assessed the ability of three native desert plants-Pennisetum divisum, Tetraena qatarensis, and Brassica tournefortii-to accumulate phytotoxic metals (PTMs) in their different plant organs, including leaves, stems, and roots/rhizomes. The PTMs were analyzed in soil and plant samples collected from Dubai, United Arab Emirates (UAE). The results indicated significantly higher levels of PTMs on the soil surface than the subsurface layer. Brassica exhibited the highest concentrations of Fe and Zn, measuring 566.7 and 262.8 mg kg-1, respectively, while Tetraena accumulated the highest concentration of Sr (1676.9 mg kg-1) in their stems. In contrast, Pennisetum recorded the lowest concentration of Sr (21.0 mg kg-1), while Tetraena exhibited the lowest concentrations of Fe and Zn (22.5 and 30.1 mg kg-1) in their leaves. The roots of Pennisetum, Brassica, and Tetraena demonstrated the potential to accumulate Zn from the soil, with concentration factors (CF) of 1.75, 1.09, and 1.09, respectively. Moreover, Brassica exhibited the highest CF for Sr, measuring 2.34. Pennisetum, however, could not translocate PTMs from its rhizomes to other plant organs, as indicated by a translocation factor (TF) of 1. In contrast, Brassica effectively translocated the studied PTMs from its roots to the stem and leaves (except for Sr in the leaves). Furthermore, Pennisetum exclusively absorbed Zn from the soil into its leaves and stems, with an enrichment factor (EF) greater than 1. Brassica showed the ability to uptake the studied PTMs in its stem and leaves (except for Fe), while Tetraena primarily absorbed Sr and Zn into its stems. Based on the CF and TF results, Pennisetum appears to be a suitable species for phytostabilization of both Fe and Zn, while Brassica is well-suited for Sr and Zn polluted soils. Tetraena shows potential for Zn phytoremediation. These findings suggest that these plants are suitable for PTMs phytoextraction. Furthermore, based on the EF results, these plants can efficiently sequester PTMs.

Exploring the decolorization efficiency and biodegradation mechanisms of different functional textile azo dyes by Streptomyces albidoflavus 3MGH.

Efficiently mitigating and managing environmental pollution caused by the improper disposal of dyes and effluents from the textile industry is of great importance. This study evaluated the effectiveness of Streptomyces albidoflavus 3MGH in decolorizing and degrading three different azo dyes, namely Reactive Orange 122 (RO 122), Direct Blue 15 (DB 15), and Direct Black 38 (DB 38). Various analytical techniques, such as Fourier Transform Infrared (FTIR) spectroscopy, High-Performance Liquid Chromatography (HPLC), and Gas Chromatography-Mass Spectrometry (GC-MS) were used to analyze the degraded byproducts of the dyes. S. albidoflavus 3MGH demonstrated a strong capability to decolorize RO 122, DB 15, and DB 38, achieving up to 60.74%, 61.38%, and 53.43% decolorization within 5 days at a concentration of 0.3 g/L, respectively. The optimal conditions for the maximum decolorization of these azo dyes were found to be a temperature of 35 °C, a pH of 6, sucrose as a carbon source, and beef extract as a nitrogen source. Additionally, after optimization of the decolorization process, treatment with S. albidoflavus 3MGH resulted in significant reductions of 94.4%, 86.3%, and 68.2% in the total organic carbon of RO 122, DB 15, and DB 38, respectively. After the treatment process, we found the specific activity of the laccase enzyme, one of the mediating enzymes of the degradation mechanism, to be 5.96 U/mg. FT-IR spectroscopy analysis of the degraded metabolites showed specific changes and shifts in peaks compared to the control samples. GC-MS analysis revealed the presence of metabolites such as benzene, biphenyl, and naphthalene derivatives. Overall, this study demonstrated the potential of S. albidoflavus 3MGH for the effective decolorization and degradation of different azo dyes. The findings were validated through various analytical techniques, shedding light on the biodegradation mechanism employed by this strain.

Optimizing biochar, vermicompost, and duckweed amendments to mitigate arsenic uptake and accumulation in rice (Oryza sativa L.) cultivated on arsenic-contaminated soil.

The accumulation of arsenic (As) in rice (Oryza sativa L.) grain poses a significant health concern in Bangladesh. To address this, we investigated the efficacy of various organic amendments and phytoremediation techniques in reducing As buildup in O. sativa. We evaluated the impact of five doses of biochar (BC; BC0.1: 0.1%, BC0.28: 0.28%, BC0.55: 0.55%, BC0.82: 0.82% and BC1.0: 1.0%, w/w), vermicompost (VC; VC1.0: 1.0%, VC1.8: 1.8%, VC3.0: 3.0%, VC4.2: 4.2% and VC5.0: 5.0%, w/w), and floating duckweed (DW; DW100: 100, DW160: 160, DW250: 250, DW340: 340 and DW400: 400 g m- 2) on O. sativa cultivated in As-contaminated soil. Employing a three-factor five-level central composite design and response surface methodology (RSM), we optimized the application rates of BC-VC-DW. Our findings revealed that As contamination in the soil negatively impacted O. sativa growth. However, the addition of BC, VC, and DW significantly enhanced plant morphological parameters, SPAD value, and grain yield per pot. Notably, a combination of moderate BC-DW and high VC (BC0.55VC5DW250) increased grain yield by 44.4% compared to the control (BC0VC0DW0). As contamination increased root, straw, and grain As levels, and oxidative stress in O. sativa leaves. However, treatment BC0.82VC4.2DW340 significantly reduced grain As (G-As) by 56%, leaf hydrogen peroxide by 71%, and malondialdehyde by 50% compared to the control. Lower doses of BC-VC-DW (BC0.28VC1.8DW160) increased antioxidant enzyme activities, while moderate to high doses resulted in a decline in these activities. Bioconcentration and translocation factors below 1 indicated limited As uptake and translocation in plant tissues. Through RSM optimization, we determined that optimal doses of BC (0.76%), VC (4.62%), and DW (290.0 g m- 2) could maximize grain yield (32.96 g pot- 1, 44% higher than control) and minimize G-As content (0.189 mg kg- 1, 54% lower than control). These findings underscore effective strategies for enhancing yield and reducing As accumulation in grains from contaminated areas, thereby ensuring agricultural productivity, human health, and long-term sustainability. Overall, our study contributes to safer food production and improved public health in As-affected regions.

Influences of earthworm activity and mucus on Cd phytoremediation based on harvesting different leaf types of tall fescue (Festuca arundinacea).

To explore cost-effective and efficient phytoremediation strategies, this study investigated the distinct roles of earthworm activity and mucus in enhancing Cd phytoextraction from soils contaminated by Festuca arundinacea, focusing on the comparative advantages of selective leaf harvesting versus traditional whole-plant harvesting methods. Our study employed a horticultural trial to explore how earthworm activity and mucus affect Festuca arundinacea' s Cd phytoremediation in soils using control, earthworm, and mucus treatments to examine their respective effects on plant growth and Cd distribution. Earthworm activity increased the dry weight of leaves by 13.5% and significantly increased the dry weights of declining and senescent leaves, surpassing that of the control by more than 40%. Earthworm mucus had a similar, albeit less pronounced, effect on plant growth than earthworm activity. This study not only validated the significant role of earthworm activity in enhancing Cd phytoextraction by Festuca arundinacea, with earthworm activity leading to over 85% of Cd being allocated to senescent tissues that comprise only approximately 20% of the plant biomass, but also highlighted a sustainable and cost-effective approach to phytoremediation by emphasizing selective leaf harvesting supported by earthworm activity. By demonstrating that earthworm mucus alone can redistribute Cd with less efficiency compared to live earthworms, our findings offer practical insights into optimizing phytoremediation strategies and underscore the need for further research into the synergistic effects of biological agents in soil remediation processes.

Unravelling the halophyte Suaeda maritima as an efficient candidate for phytostabilization of cadmium and lead: Implications from physiological, ionomic, and metabolomic responses.

Cadmium (Cd) and lead (Pb) are among the most toxic heavy metals affecting human health and crop yield. Suaeda maritima (L.) Dumort is an obligate halophyte that is well adapted to saline soil. The inbuilt salinity tolerance mechanisms of halophytes help them to survive in heavy metal-contaminated rhizospheric soil. In the present study, growth and ionomic responses, reactive oxygen species (ROS) accumulation, modulations of phytochelatins, antioxidative defense, and metabolomic responses were studied in S. maritima imposed to Cd and Pb stresses with an aim to elucidate Cd and Pb tolerance mechanisms and phytoremediation potential of this halophyte. Our results showed a reduction of biomass in S. maritima, which may serve as an energy conservation strategy for survival under heavy metal stress. The increased accumulation of ROS with concomitant higher expression of various antioxidative enzymes suggests the efficient scavenging of ROS. The metabolite profiling revealed significant up-regulation of sugars, sugar alcohols, amino acids, polyphenols, and organic acids under Cd and Pb stresses suggesting their possible role in osmotic balance, ionic homeostasis, ROS scavenging, and signal transduction for stress tolerance. In S. maritima, the translocation factors (Tf) are <1 in both Cd and Pb treatments, which indicates that this halophyte has high phytostabilization potential for Cd and Pb in roots and through restricted translocation of heavy metal ions to the aboveground part. The findings of this study offer comprehensive information on Cd and Pb tolerance mechanisms in S. maritima and suggest that this halophyte can detoxify the HMs through physiological, ionic, antioxidative, and metabolic regulations.

Biohydrogen utilization in legume-rhizobium symbiosis reveals a novel mechanism of accelerated tetrachlorobiphenyl transformation.

Symbiosis between Glycine max and Bradyrhizobium diazoefficiens were used as a model system to investigate whether biohydrogen utilization promotes the transformation of the tetrachlorobiphenyl PCB77. Both a H2 uptake-positive (Hup+) strain (wild type) and a Hup- strain (a hupL deletion mutant) were inoculated into soybean nodules. Compared with Hup- nodules, Hup+ nodules increased dechlorination significantly by 61.1 % and reduced the accumulation of PCB77 in nodules by 37.7 % (p < 0.05). After exposure to nickel, an enhancer of uptake hydrogenase, dechlorination increased significantly by 2.2-fold, and the accumulation of PCB77 in nodules decreased by 54.4 % (p < 0.05). Furthermore, the tetrachlorobiphenyl transformation in the soybean root nodules was mainly testified to be mediated by nitrate reductase (encoded by the gene NR) for tetrachlorobiphenyl dechlorination and biphenyl-2,3-diol 1,2-dioxygenase (bphC) for biphenyl degradation. This study demonstrates for the first time that biohydrogen utilization has a beneficial effect on tetrachlorobiphenyl biotransformation in a legume-rhizobium symbiosis.