Removal of Cd(II), Cu(II) and Zn(II) from aqueous solutions by live Phanerochaete chrysosporium

Trade-offs and adaptation to metalliferous soils: The role of soil microbiome in metal tolerance and uptake in Arabidopsis halleri ecotypes from a reciprocal transplant experiment

Soil contamination with trace metal elements is a worldwide issue, prompting research on plant species capable of hyperaccumulating metals to reduce soil toxicity. Previous research suggests that both plant species and their populations can affect soil microbial communities, yet little is known about how different populations of hyperaccumulator species influence these microbial communities to enhance metal-uptake and tolerance. This study evaluated the effect of soil origin, soil microbiome, and plant population on phytoextraction efficiencies of Cd and Zn among four A. halleri populations: two each from metalliferous and non-metalliferous sites. In a controlled transplant experiment, clonal replicates of A. halleri were grown in native and three non-native soils for six months. Biogeochemical analyses of plants and soils were conducted, alongside sequencing of root-associated soil bacterial/archaeal and fungal DNA. Soil treatments primarily differed in pH, total Cd, Pb, and Zn, as well as acid and alkaline phosphatase enzyme activities. A combined effect of soil origin and population was noted for arylsulfatase and β-glucosidase activities, as well as ammonium and nitrate concentrations. Both non-metallicolous and metallicolous populations accumulated high levels of Cd and Zn in metalliferous soils with the non-metallicolous population NM_PL14 outperforming the metallicolous populations in Zn hyperaccumulation. Interestingly, non-metallicolous populations grown in metalliferous soils exhibited no trade-offs in plant performance despite higher Cd and Zn accumulation. Soil origin had a stronger effect on the bacterial/archaeal and fungal community composition than plant ecotype. Partial least square regression models explained 66 % and 79 % of the variability in A. halleri Cd and Zn hyperaccumulation. There was a positive association between Zn-uptake and specific microbial taxa (e.g., Cornebacteriales, Microbacteriaceae, Propionibacteriales, Rhizobiaceae, Basidiomycota, Oidiodendron, Phallaceae) and functional activity (e.g., arylsulfatase, S oxidation) in metalliferous soils. Taken together, our findings suggest that non-metallicolous A. halleri populations may be better suited for Zn phytoextraction applications.

Biosorption of Cu2+ on magnetic calcium alginate immobilized Phanerochaete chrysosporium

Phanerochaete chrysosporium were immobilized in magnetic Fe3O4 nanoparticles and calcium alginate to form MC microspheres. The obtained MC microsphere was characterized by SEM, EDS, XRD, BET, VSM and TGA. The results indicated that MC microsphere was a three-dimensional structure with relatively large specific surface area and good porosity. MC microspheres had excellent magnetic recovery performance and thermal stability. The characteristics and performance of MC microspheres on adsorption of Cu2+ were evaluated based on batch adsorption experiments. The maximum adsorption capacity of Cu2+ by MC microspheres was 35.07 mg g-1 at pH of 5.0, temperature of 35 °C and adsorption time of 8 h. MC microspheres can still effectively adsorb Cu2+ at 400 mg L-1. Integrating simulation results from pseudo-second-order kinetic model, Intra-particle diffusion model and Freundlich model, the process was mainly dominated by chemical adsorption, and it is a multi-molecular layer adsorption. The results of XPS and FTIR showed that complexation, ion replacement, and reduction are important mechanisms for adsorption of Cu2+ on MC microspheres. -OH and C-O/C=O mainly complexes with Cu2+ in the biosorption process. After five adsorption-desorption cycles, the adsorption efficiency can still reach 32.40 %. Therefore, MC microspheres are a potential adsorbent that can achieve effective recovery.

Zinc and copper supplements enhance trichloroethylene removal by Pseudomonas plecoglossicida in water

The effects of two microelements, zinc and copper, on the aerobic co-metabolic removal of trichloroethylene (10 mg/L) by the isolate Pseudomonas plecoglossicida were investigated. The strain was previously isolated from a petroleum-contaminated site using toluene (150 mg/L) as substrate. Different concentrations (1, 10 and 100 mg/L) of microelements provided with SO42- and Cl- were tested. The results showed the supplement of Zn2+ and Cu2+ at the low concentration (1 mg/L) significantly enhanced cell growth. The removal efficiencies for toluene and trichloroethylene were also enhanced at the low concentration (1 mg/L) of Zn2+ and Cu2+. Compared to the control without zinc supplement, higher concentrations of zinc (10 and 100 mg/L) enhanced the removal efficiencies for both toluene and trichloroethylene in the first three days but showed some inhibitory effect afterward. However, the higher concentrations of Cu2+ (10 and 100 mg/L) always showed inhibitory to the toluene removal while showing inhibitory to the TCE removal after three days. For both Zn2+ and Cu2+, the anions SO42- and Cl- did not show significant difference in their effects on the toluene removal. A possible mechanism for Zn2+ and Cu2+ to enhance the removal of toluene and trichloroethylene would be their involvement in toluene oxygenase-based transformation processes. In addition, high concentrations of Zn2+ and Cu2+ ions could be removed from the liquid by the cells accordingly. The results imply a potential of supplementing low concentrations of zinc and copper to enhance bioremediation of the sites co-contaminated with toluene and trichloroethylene.

Assembly processes of bacterial and fungal communities in metal(loid)s smelter soil

There are few studies on concurrent bacterial and fungal community assembly processes that govern the metal(loid)s biogeochemical cycles at smelters. Here, a systematic investigation combined geochemical characterization, co-occurrence patterns, and assembly mechanisms of bacterial and fungal communities inhabiting soils around an abandoned arsenic smelter. Acidobacteriota, Actinobacteriota, Chloroflexi, and Pseudomonadota were dominant in bacterial communities, whereas Ascomycota and Basidiomycota dominated fungal communities. The random forest model indicated the bioavailable fractions of Fe (9.58%) were the main positive factor driving the beta diversity of bacterial communities, and the total N (8.09%) was the main negative factor for fungal communities. Microbe-contaminant interactions demonstrate the positive impact of the bioavailable fractions of certain metal(loid)s on bacteria (Comamonadaceae and Rhodocyclaceae) and fungi (Meruliaceae and Pleosporaceae). The fungal co-occurrence networks exhibited more connectivity and complexity than the bacterial networks. The keystone taxa were identified in bacterial (including Diplorickettsiaceae, norank_o_Candidatus_Woesebacteria, norank_o_norank_c_AT-s3-28, norank_o_norank_c_bacteriap25, and Phycisphaeraceae) and fungal (including Biatriosporaceae, Ganodermataceae, Peniophoraceae, Phaeosphaeriaceae, Polyporaceae, Teichosporaceae, Trichomeriaceae, Wrightoporiaceae, and Xylariaceae) communities. Meanwhile, community assembly analysis revealed that deterministic processes dominated the microbial community assemblies, which were highly impacted by pH, total N, and total and bioavailable metal(loid) content. This study provides helpful information to develop bioremediation strategies for the mitigation of metal(loid)s-polluted soils.

Identification of Cd-resistant microorganisms from heavy metal-contaminated soil and its potential in promoting the growth and Cd accumulation of bermudagrass

Phytoremediation has been increasingly used as a green technology for the remediation of heavy metal contaminated soils. Microorganisms could enhance phytoremediation efficiency by solubilizing heavy metal and improve plant growth by producing phytohormones in the heavy metal contaminated soils. In this study, we investigated the abundance and composition of soil microbial communities in heavy metal contaminated soils. Furthermore, we identified a Cd-resistant fungal strain Penicillium janthinellum ZZ-2 and assessed its potential in improving plant growth, Cd accumulation and Cd tolerance in bermudagrass. The results indicated that long-term heavy metal pollution decreased microbial biomass and activity by inhibiting microbial community diversity, but did not significantly affect community composition. Mainly, the relative abundance of some specific bacterial and fungal taxa, such as Actinobacteria, Chloroflexi, Bacteroidetes, Ascomycota and Basidiomycota, changes under metal pollution. Furthermore, at genus level, certain microbial taxa, such as Pseudonocardiaceae, AD3, Latescibacteria, Apiotrichum and Paraboeremia, only exist in polluted soil. One Cd-resistant fungus ZZ-2 was isolated and identified as Penicillium janthinellum. Further characterization revealed that ZZ-2 had a greater capacity for Cd²⁺ absorption, produced indole-3-acid (IAA), and facilitated plant growth in the presence of Cd. Interestingly, ZZ-2 inoculation significantly increased Cd uptake in the stem and root of bermudagrass. Thus, ZZ-2 could improve plant growth under Cd stress by reducing Cd-toxicity, increasing Cd uptake and producing IAA. This study suggests a novel fungus-assisted phytoremediation approach to alleviate Cd toxicity in heavy metals contaminated soils.

Biosorption of Mercury Ion (Hg2+) using Live and Dead Cells of Rhizopus oryzae and Aspergillus niger : Characterization, Kinetic and Isotherm Studies

Mercury ions (Hg2+) are usually being discharged into water bodies without proper treatment. It is toxic, non-biodegradable and persistent naturally which leads to serious environmental problems. Through microbial approach, this study compares the efficiency of two types of fungi: R. oryzae and A. niger of common biosorption fungi in absorbing Hg2+ based on FTIR analysis, kinetic and isotherm studies. Both fungi were prepared into two forms which are live and dead biomass; and the Hg2+ was prepared at 10 and 100 ppm. FTIR analysis has identified existing functional group of hydroxyl, carboxylic and amino functional groups from both fungi, which are important in attracting Hg2+ ion. On average, 60-90% of Hg2+ was removed by both live and dead biomass of R. oryzae and A. niger at 10 and 100 ppm. Meanwhile, the highest sorption was achieved by dead cells of R. oryzae which is up to 90.38% at 100 ppm. In terms of kinetic studies, experimental data fitted to the Pseudo-second-order kinetic model, with correlation coefficient, R2 (0.9997), and Langmuir isotherm, which means the absorption process occurs on the homogenous surface that corresponds to the monolayer formation. Through these findings, the dead cells of A. niger and R. oryzae are better in sorption of Hg2+ compared to the live cells. Meanwhile, the rate of biosorption by R. oryzae is higher compared to A. niger. However, both fungi are excellent in biosorption of Hg2+ ions and could be an alternative to current physico-chemical methods used.

Potentiality of white-rot fungi in biosorption of nickel and cadmium: Modeling optimization and kinetics study

The present study aimed to analyze simultaneous biosorption of Cd⁺² and Ni⁺² by living Phanerochaete chrysosporium as low-cost and eco-friendly biosorbent following optimization by applying a central composite design. The effect of operating parameters such as solution pH (4.0-8.0), temperature (20-40 °C), contact time (3-15 h), initial Cd⁺² and Ni⁺² concentrations (15-35, 5-25 mg L^-1, respectively) was evaluated by response surface methodology (RSM) for optimizing biosorption process. The Cd⁺² and Ni⁺² ions at 25 and 16 mg L^-1 were accumulated in P. chrysosporium with the efficiency of 96.23% and 89.48%, respectively, at pH of 6 and 36 °C after around 9 h under well mixing. The equilibrium data were fitted well with Langmuir isotherm model with maximum biosorption capacity of 71.43 and 46.50 mg g^-1 for Cd⁺² and Ni⁺², respectively. In addition, the pseudo-second order kinetic model could describe the kinetic data adequately. Further, possible interaction pathway among metals and P. chrysosporium functional groups were studied by Fourier transform infrared (FT-IR) spectroscopy. Furthermore, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) techniques were applied for morphology investigation and semi elemental analysis.

Utilization of Pleurotus eryngii biosorbent as an environmental bioremedy for the decontamination of trace cadmium(II) ions from water system

In many parts of the world, cadmium metal concentration in drinking water is higher than some international guideline values. To reduce its level below the safety limit, a sustainable and environmental friendly approach is crucial. Thereby, present article introduce an efficient, non-pathogenic and a novel fungal biosorbent Pleurotus eryngii for the removal of Cd(II) ions from aqueous system. The efficiency of P. eryngii were improved and optimized by investigating many significant factors such as; pH, biosorbent dose, initial Cd(II) ion concentration, temperature and contact time. Maximum Cd(II) ions removal (99.9%) was achieved at pH 5.0, biosorbent dosage 0.2 g/10 mL, concentration 20 mg L^-1, time 10 min and temperature 50 °C. The isotherm and kinetic models revealed bioremediation of Cd(II) ions as monolayer coverage with biosorption capacity of 1.51 mg g^-1 following pseudo second order reaction. Moreover, thermodynamic parameters such as ΔG°, ΔH°, and ΔS° showed that the removal of Cd(II) ions is spontaneous and endothermic in nature. Batch elution process revealed that the complete elution of Cd(II) ions from the biomass were achieved using 0.1 N HNO₃ solution. The sorption efficiency decreased from 99.99 to 56.89% as the biomass were recycled up to five times. The efficiency of Cd(II) ions removal from real water samples lies between 85 and 90%. Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopic (EDS) and atomic force microscopic (AFM) analysis of fungal biomass confirmed that the Cd(II) ions were the most abundant species on the biomass surface after the sorption process.

Effects of cadmium on calcium homeostasis in the white-rot fungus Phanerochaete chrysosporium

Due to the widespread application of white-rot fungi for the treatment of pollutants, it's crucial to exploit the special effects of pollutants on the microbes. Here, we studied the effects of cadmium on calcium homeostasis in the most studied white-rot fungus Phanerochaete chrysosporium. The response of P. chrysosporium to cadmium stress is concentration-dependent. A high concentration of cadmium caused the release of calcium from P. chrysosporium, while a hormesis effect was observed at a lower cadmium concentration (10 μM), which resulted in a significant increase in calcium uptake and reversed the decrease in cell viability. Calcium (50 μM) promoted cell viability (127.2% of control), which reflects that calcium can protect P. chrysosporium from environmental stress. Real-time changes in the Ca²⁺ and Cd²⁺ fluxes of P. chrysosporium were quantified using the noninvasive microtest technique. Ca²⁺ influx decreased significantly under cadmium exposure, and the Ca²⁺ channel was involved in Ca²⁺ and Cd²⁺ influx. The cadmium and/or calcium uptake results coupled with the real-time Ca²⁺ and Cd²⁺ influxes microscale signatures can enhance our knowledge of the homeostasis of P. chrysosporium with respect to cadmium stress, which may provide useful information for improving the bioremediation process.

Applications of white rot fungi in bioremediation with nanoparticles and biosynthesis of metallic nanoparticles

White rot fungi (WRF) are important environmental microorganisms that have been widely applied in many fields. To our knowledge, the application performance of WRF in bioremediation can be greatly improved by the combination with nanotechnology. And the preparation of metallic nanoparticles using WRF is an emerging biosynthesis approach. Understanding the interrelation of WRF and nanoparticles is important to further expand their applications. Thus, this mini-review summarizes the currently related reports mainly from the two different point of views. We highlight that nanoparticles as supports or synergistic agents can enhance the stability and bioremediation performance of WRF in wastewater treatment and the biosynthesis process and conditions of several important metallic nanoparticles by WRF. Furthermore, the potential toxicity of nanoparticles on WRF and challenges encountered are also discussed. Herein, we deem that this mini-review will strengthen the basic knowledge and provide valuable insight for the applications of WRF and nanoparticles.

Marine fungi isolated from Chilean fjord sediments can degrade oxytetracycline

Salmon farming is the main economic activity in the fjords area of Southern Chile. This activity requires the use of antibiotics, such as oxytetracycline, for the control and prevention of diseases, which have a negative impact on the environment. We analyzed the abilities of endemic marine fungi to biodegrade oxytetracycline, an antibiotic used extensively in fish farming. We isolated marine fungi strains from sediment samples obtained from an area of fish farming activity. The five isolated strains showed an activity on oxytetracycline and were identified as Trichoderma harzianum, Trichoderma deliquescens, Penicillium crustosum, Rhodotorula mucilaginosa, and Talaromyces atroroseus by a scanning electron microscopy and characterized by molecular techniques. Results showed significant degradation in the concentration of oxytetracycline at the first 2 days of treatment for all strains analyzed. At 21 days of treatment, the concentration of oxytetracycline was decreased 92 % by T. harzianum, 85 % by T. deliquescens, 83 % by P. crustosum, 73 % by R. mucilaginosa, and 72 % by T. atroroseus, all of which were significantly higher than the controls. Given these results, we propose that fungal strains isolated from marine sediments may be useful tools for biodegradation of antibiotics, such as oxytetracycline, in the salmon industry.

An evaluation of the major factors influencing the removal of copper ions using the egg shell (Dromaius novaehollandiae): chitosan (Agaricus bisporus) composite

Rapid industrialisation, technological development, urbanization and increase in population in the recent past coupled with unplanned and unscientific disposal methods led to increased heavy metal levels in water. Realizing the need for development of eco-friendly and cost effective methods, the present investigation was done for the adsorptive removal of copper from aqueous solutions with Dromaius novaehollandiae eggshell and chitosan composite. By one variable at a time method, the optimum contact time was found to be 60 min with an adsorbent dosage of 8 g/L at pH 6, initial adsorbate concentration of 20 mg/L and temperature 30 °C. The equilibrium data followed Langmuir and Freundlich isotherm models and pseudo second-order kinetics. The equilibrium adsorption capacity determined from Langmuir isotherm was 48.3 mg/g. From the Van't Hoff equation, thermodynamic parameters such as enthalpy (ΔH°), entropy (ΔS°) and Gibb's free energy (ΔG°) were calculated and inferred that the process was spontaneous, irreversible and endothermic. To know the cumulative effects of operating parameters, a three level full factorial design of Response Surface Methodology (RSM) was applied and the suggested optimum conditions were 7.90 g/L of adsorbent dosage, 20.2651 mg/L of initial adsorbate concentration and 5.9 pH. Maximum percentage of copper adsorption attained was 95.25 % (19.05 mg/L) and the residual concentration of the metal after sorption corresponded to 0.95 mg/L, which is below the permissible limits (1.3 mg/L) of copper in drinking water. The adsorbent was characterized before and after adsorption by SEM-EDS, FTIR and XRD. The FTIR analysis showed the involvement of carboxyl, hydroxyl and amino groups while XRD analysis revealed the predominantly amorphous nature of the composite post-adsorption and the peaks at 2θ angles characteristic for copper and copper oxide. The mechanisms involved in the adsorption of copper onto the adsorbent are chemisorption, complexation and ion exchange.

Hybrid materials from agro-waste and nanoparticles: implications on the kinetics of the adsorption of inorganic pollutants

This study is a first-hand report of the immobilization of Nauclea diderrichii seed waste biomass (ND) (an agro-waste) with eco-friendly mesoporous silica (MS) and graphene oxide-MS (GO + MS) nanoparticles, producing two new hybrid materials namely: MND adsorbent for agro-waste modified with MS and GND adsorbent for agro-waste modified with GO + MS nanoparticles showed improved surface area, pore size and pore volume over those of the agro-waste. The abstractive potential of the new hybrid materials was explored for uptake of Cr(III) and Pb(II) ions. Analysis of experimental data from these new hybrid materials showed increased initial sorption rate of Cr(III) and Pb(II) ions uptake. The amounts of Cr(III) and Pb(II) ions adsorbed by MND and GND adsorbents were greater than those of ND. Modification of N. diderrichii seed waste significantly improved its rate of adsorption and diffusion coefficient for Cr(III) and Pb(II) more than its adsorption capacity. The rate of adsorption of the heavy metal ions was higher with GO + MS nanoparticles than for other adsorbents. Kinetic data were found to fit well the pseudo-second-order and the diffusion-chemisorption kinetic models suggesting that the adsorption of Cr(III) and Pb(II) onto these adsorbents is mainly through chemisorption mechanism. Analysis of kinetic data with the homogeneous particle diffusion kinetic model suggests that particle diffusion (diffusion of ions through the adsorbent) is the rate-limiting step for the adsorption process.