Optimization of heavy metal (lead) remedial activities of fungi Aspergillus penicillioides (F12) through extra cellular polymeric substances

Bioremoval of tannins and heavy metals using immobilized tannase and biomass of Aspergillus glaucus

BACKGROUND

The presence of inorganic pollutants and heavy metals in industrial effluents has become a serious threat and environmental issues. Fungi have a remarkable ability to exclude heavy metals from wastewater through biosorption in eco-friendly way. Tannase plays an important role in bioconversion of tannin, a major constituent of tannery effluent, to gallic acid which has great pharmaceutical applications. Therefore, the aim of the current study was to exploit the potential of tannase from Aspergillus glaucus and fungal biomass waste for the bioremediation of heavy metals and tannin.

RESULTS

Tannase from A. glaucus was partially purified 4.8-fold by ammonium sulfate precipitation (80%). The enzyme was optimally active at pH 5.0 and 40 °C and stable at this temperature for 1 h. Tannase showed high stability at different physiological conditions, displayed about 50% of its activity at 60 °C and pH range 5.0-6.0. Immobilization of tannase was carried out using methods such. as entrapment in Na-alginate and covalent binding to chitosan. The effects of Na-alginate concentrations on the beads formation and enzyme immobilization revealed that maximum immobilization efficiency (75%) was obtained with 3% Na-alginate. A potential reusability of the immobilized enzyme was showed through keeping 70% of its relative activity up to the fourth cycle. The best bioconversion efficiency of tannic acid to gallic acid by immobilized tannase was at 40 °C with tannic acid concentration up to 50 g/l. Moreover, bioremediation of heavy metal (Cr3+, Pb2+, Cu2+, Fe3+, and Mn2+) from aqueous solution using A. glaucus biomass waste was achieved with uptake percentage of (37.20, 60.30, 55.27, 79.03 and 21.13 respectively). The biomass was successfully used repeatedly for removing Cr3+ after using desorbing agent (0.1 N HCl) for three cycles.

CONCLUSION

These results shed the light on the potential use of tannase from locally isolated A. glaucus in the bioremediation of industrial tanneries contained heavy metals and tannin.

Lead removal from the aqueous solution by extracellular polymeric substances produced by the marine diatom Navicula salinicola

Microbial extracellular polymeric substances (EPS) have recently emerged as significant contributors in diverse biotechnological applications. Extracellular polymeric substances (EPS), produced by a Navicula salinicola strain, have been studied for potential applications in a specific heavy metal (lead (Pb II)) removal from wastewater. The optimisation of operational parameters, mainly pH, Pb and EPS concentrations, using the Box-Behnken design (BBD) was undertaken to enhance lead uptake. The higher Pb adsorption capacity reached 2211.029 mg/g. Hydroxyl, carbonyl, carboxyl, phosphoric, and sulfhydryl groups were identified quantitatively as potential sites for Pb adsorption. EPS exhibited a notable flocculation rate of 70.20% in kaolin clay at a concentration of 15 mg/L. They demonstrated an emulsifying activity greater than 88%, showcasing their versatile potential for both sedimentation processes and stabilising liquid-liquid systems. EPS could be excellent nonconventional renewable biopolymers for treating water and wastewater.

Comprehensive review on recent trends and perspectives of natural exo-polysaccharides: Pioneering nano-biotechnological tools

Exopolysaccharides (EPSs), originating from various microbes, and mushrooms, excel in their conventional role in bioremediation to showcase diverse applications emphasizing nanobiotechnology including nano-drug carriers, nano-excipients, medication and/or cell encapsulation, gene delivery, tissue engineering, diagnostics, and associated treatments. Acknowledged for contributions to adsorption, nutrition, and biomedicine, EPSs are emerging as appealing alternatives to traditional polymers, for biodegradability and biocompatibility. This article shifts away from the conventional utility to delve deeply into the expansive landscape of EPS applications, particularly highlighting their integration into cutting-edge nanobiotechnological methods. Exploring EPS synthesis, extraction, composition, and properties, the discussion emphasizes their structural diversity with molecular weight and heteropolymer compositions. Their role as raw materials for value-added products takes center stage, with critical insights into recent applications in nanobiotechnology. The multifaceted potential, biological relevance, and commercial applicability of EPSs in contemporary research and industry align with the nanotechnological advancements coupled with biotechnological nano-cleansing agents are highlighted. EPS-based nanostructures for biological applications have a bright future ahead of them. Providing crucial information for present and future practices, this review sheds light on how eco-friendly EPSs derived from microbial biomass of terrestrial and aquatic environments can be used to better understand contemporary nanobiotechnology for the benefit of society.

Heavy Metal Remediation by Dry Mycelium Membranes: Approaches to Sustainable Lead Remediation in Water

Lead contamination poses significant and lasting health risks, particularly in children. This study explores the efficacy of dried mycelium membranes, distinct from live fungal biomass, for the remediation of lead (Pb(II)) in water. Dried mycelium offers unique advantages, including environmental resilience, ease of handling, biodegradability, and mechanical reliability. The study explores Pb(II) removal mechanisms through sorption and mineralization by dried mycelium hyphae in aqueous solutions. The sorption isotherm studies reveal a high Pb(II) removal efficiency, exceeding 95% for concentrations below 1000 ppm and ∼63% above 1500 ppm, primarily driven by electrostatic interactions. The measured infrared peak shifts and the pseudo-second-order kinetics for sorption suggests a correlation between sorption capacity and the density of interacting functional groups. The study also explores novel surface functionalization of the mycelium network with phosphate to enhance Pb(II) removal, which enables remediation efficiencies >95% for concentrations above 1500 ppm. Scanning electron microscopy images show a pH-dependent formation of Pb-based crystals uniformly deposited throughout the entire mycelium network. Continuous cross-flow filtration tests employing a dried mycelium membrane demonstrate its efficacy as a microporous membrane for Pb(II) removal, reaching remediation efficiency of 85-90% at the highest Pb(II) concentrations. These findings suggest that dried mycelium membranes can be a viable alternative to synthetic membranes in heavy metal remediation, with potential environmental and water treatment applications.

Fungal bioremediation approaches for the removal of toxic pollutants: Mechanistic understanding for biorefinery applications

Pollution is a global menace that poses harmful effects on all the living ecosystems and to the Earth. As years pass by, the available and the looming rate of pollutants increases at a faster rate. Although many treatments and processing strategies are waged for treating such pollutants, the by-products and the wastes or drain off generated by these treatments further engages in the emission of hazardous waste. Innovative and long-lasting solutions are required to address the urgent global issue of hazardous pollutant remediation from contaminated environments. Myco-remediation is a top-down green and eco-friendly tool for pollution management. It is a cost-effective and safer practice of converting pernicious substances into non-toxic forms by the use of fungi. But these pollutants can be transformed into useable products along with multiple benefits for the environment such as sequestration of carbon emissions and also to generate high valuable bioactive materials that fits as a sustainable economic model. The current study has examined the possible applications of fungi in biorefineries and their critical role in the transformation and detoxification of pollutants. The paper offers important insights into using fungal bioremediation for both economically and environmentally sound solutions in the domain of biorefinery applications by combining recent research findings.

Bioremoval of heavy metals from aqueous solution using dead biomass of indigenous fungi derived from fertilizer industry effluents: isotherm models evaluation and batch optimization

The present work investigated the utilization of dead biomass of the highly multi-heavy metals tolerant indigenous fungal strain NRCA8 isolated from the mycobiome of fertilizer industry effluents that containing multiple heavy metal ions at high levels to remove Pb2+, Ni2+, Zn2+, and Mn2+ as multiple solutes from multi-metals aqueous solutions for the first time. Based on morphotype, lipotype and genotype characteristics, NRCA8 was identified as Cladosporium sp. NRCA8. The optimal conditions for the bioremoval procedure in the batch system were pH 5.5 for maximum removal (91.30%, 43.25%, and 41.50%) of Pb2+, Zn2+ and Mn2+ but pH 6.0 supported the maximum bioremoval and uptake of Ni2+ (51.60% and 2.42 mg/g) by NRCA8 dead biomass from the multi-metals aqueous solution, respectively. The 30 min run time supported the highest removal efficiency and uptake capacity of all heavy metals under study. Moreover, the equilibrium between the sorbent NRCA8 fungal biomass and sorbates Ni2+, Pb2+ and Zn2+ was attained after increasing the dead biomass dose to 5.0 g/L. Dead NRCA8 biomass was described by scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectrometer before and after biosorption of Pb2+, Ni2+, Zn2+ and Mn2+ under multiple metals system. The Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich isotherms were applied to characterize the adsorption equilibrium between Pb2+, Ni2+, Mn2+ and Zn2+ and the adsorbent NRCA8. By comparing the obtained coefficient of regression (R2) by Freundlich (0.997, 0.723, 0.999, and 0.917), Langmiur (0.974, 0.999, 0.974, and 0.911) and Dubinin-Radushkevich (0.9995, 0.756, 0.9996 and 0.900) isotherms values for Pb2+, Zn2+, Ni2+ and Mn2+ adsorption, respectively, it was found that the isotherms are proper in their own merits in characterization the possible of NRCA8 for removal of Pb2+, Zn2+, Ni2+ and Mn2+. DKR isotherm is the best for Pb2+ and Ni2+ (0.9995 and 0.9996) while Langmiur isotherm giving a good fit to the Zn2+ sorption (0.9990) as well as Freundlich isotherm giving a good fit to the Mn2+ sorption (0.9170). The efficiencies of Cladosporium sp. NRCA8 dead biomass for bioremoval of heavy metals from real wastewater under the optimized conditions were Pb2+, Ag+, Mn2+, Zn2+ and Al3+ ˃ Ni2+ ˃ Cr6+ ˃ Co2+ ˃ Fe3+ ˃ Cu2+ ˃ Cd2+. Dead NRCA8 biomass showed efficient ability to adsorb and reduce harmful components in the industrial effluents to a level acceptable for discharge into the environment.

Gravity-driven membrane system treating heavy metals-containing secondary effluent: Improved removal of heavy metals and mechanism

This study aimed at investigating the removal performance of the gravity-driven membrane (GDM) system in treating the heavy metals-containing secondary effluent, as well as evaluating the respective roles of Fe and Mn addition on the removal of heavy metals. GDM process with the formation of biocake layer exerted effective removals of Cr, Pb and Cd, with an average removal efficiency of 98%, 95% and 40%, respectively, however, after removing the biocake layer, the removal efficiencies of Cr, Pb and Cd reduced to 59%, 85% and 19%, respectively, indicating that the biocake layer played a fundamental role in removing heavy metals. With the assistance of Fe, the removal efficiency of heavy metals increased, and exhibited a positive response to the Fe dosage, due to the adsorption by the freshly generated iron oxides. On the contrary, the Mn involvement would result in the reduction of Cd removal due to the competitive adsorption of residual dissolved Mn2+ and Cd. Furthermore, the addition of a high dosage of Fe increased the diversity of eukaryotic communities and facilitated the elimination of heavy metals, however, the involvement of Mn would lead to a reduction in microbial diversity, resulting in a decrease of heavy metal removal efficiency. These findings are expected to develop new tactics to enhance heavy metal removal and promote widespread application of GDM technology in the fields of deep treatment of heavy metals-containing wastewater and reclamation of secondary effluent.

Multimetal bioremediation from aqueous solution using dead biomass of Mucor sp. NRCC6 derived from detergent manufacturing effluent

Among ten metal-tolerant fungal isolates obtained from the microbiomes of detergent industry effluent, Mucor sp. NRCC6 showed the highest tolerance and an adaptive behavior toward the heavy metals Ni2+, Pb2+, Mn2+, and Zn2+. It gave the highest growth rates 0.790 ± 0.59, 0.832 ± 0.32, 0.774 ± 0.40, and 0.741 ± 1.06 mm/h along with the lowest growth inhibition 9.19, 4.37, 11.04, and 14.83% in the presence of Pb2+, Zn2+, Ni2+, and Mn2+, respectively, at a concentration of 5.0 g/L. Then, Mucor sp. NRCC6 was selected as a biotrap for the removal of these heavy metals. The optimized operating conditions were detected to be pH 6.0 for Pb2+, Zn2+, and Mn2+ and pH 5.5 for Ni2+ at 30 °C; agitation speed 150 rpm; contact time 30 min for Mn2+ and Ni2+, 30-60 min for Pb2+, and 90-180 min for Zn2+; NRCC6 biomass dosage 5.0 g/L for Ni2+ and Pb2+ and 10.0 g/L for Mn2+ and Zn2+; and initial concentration 12 mg/L of each ion in the multimetal aqueous solutions. Under these optimized conditions, the adsorption capacity for Pb2+, Ni2+, Mn2+, and Zn2+ reached 98.75, 59.25, 58.33, and 50.83%. The Langmuir isotherm was the best for describing the adsorption of Zn2+ (0.970) and Mn2+ (0.977). The Freundlich isotherm significantly giving a good fit to the adsorption of Pb2+ (0.998) while the adsorption of Ni2+ onto NRCC6 biomass can follow DKR (0.998). Furthermore, the current study revealed that Mucor sp. NRCC6 fungus is a new efficient and eco-friendly method that revealed a maximum removal of 100% for Pb2+ and Zn2+ as well as 97.39, 88.70, 78.95, 74.0, 70.22, 68.57, and 60.0% for Ni2+, Mn2+, Cd2+, Cu2+, Fe3+, As2+, and Cr6+ from the industrial wastewater, respectively.

Roles and significance of chelating agents for potentially toxic elements (PTEs) phytoremediation in soil: A review

Phytoremediation is a biological remediation technique known for low-cost technology and environmentally friendly approach, which employs plants to extract, stabilise, and transform various compounds, such as potentially toxic elements (PTEs), in the soil or water. Recent developments in utilising chelating agents soil remediation have led to a renewed interest in chelate-induced phytoremediation. This review article summarises the roles of various chelating agents and the mechanisms of chelate-induced phytoremediation. This paper also discusses the recent findings on the impacts of chelating agents on PTEs uptake and plant growth and development in phytoremediation. It was found that the chelating agents have increased the rate of metal absorption and translocation up to 45% from roots to the aboveground plant parts during PTEs phytoremediation. Besides, it was also explored that the plants may experience some phytotoxicity after adding chelating agents to the soil. However, due to the leaching potential of synthetic chelating agents, the use of organic chelants have been explored to be used in PTEs phytoremediation. Finally, this paper also presents comprehensive insights on the significance of using chelating agents through SWOT analysis to discuss the advantages and limitations of chelate-induced phytoremediation.

Exopolysaccharides of Serratia fonticola CPSE11 can alleviate the toxic effect of Cd2+ on Codonopsis pilosula

In order to study the detoxification effect of microbial exopolysaccharides (EPS) on the heavy metal cadmium (Cd2+), this study took an EPS-producing Serratia fonticola CPSE11 (NZ_CP050171.1) isolated from Codonopsis pilosula root as the research object. The whole genome and EPS synthesis gene clusters of this strain were predicted and analyzed, the adsorption kinetics of EPS on Cd2+ were studied by using pseudo-first-order and second-order kinetic equations, the isothermal adsorption curves were simulated and analyzed by using the Langmuir isothermal adsorption equation, and the effects of Cd2+ and EPS on the growth of C. pilosula were explored by seed germination experiment and hydroponic experiment. The analysis revealed that this strain contained three gene clusters related to EPS synthesis, and the metabolic pathway for EPS synthesis was obtained on the basis of the whole genome analysis and microbial physiological metabolism. The molecular weight and monosaccharide composition of EPS were determined by HPLC analysis, which showed that EPS consisted of mannose, glucosamine, rhamnose, galactosamine, glucose, and galactose with a molar ratio of 1:1.74:4.57:3.96:14.04:10.28, with the molecular weight of 366,316.09 kDa. The adsorption process of EPS on Cd2+ was in accordance with the second-order kinetic model, and the results of seed germination experiments showed that EPS could promote seed germination and improve seed activity. In the hydroponic experiment, high concentration of Cd2+ (15 mg/L) caused toxic symptoms in C. pilosula, while the addition of EPS reduced the toxic effect of Cd2+ on C. pilosula, and the plant growth was significantly improved.

Insight into the roles of soluble, loosely bound and tightly bound extracellular polymeric substances produced by Enterobacter sp. in the Cd2+ and Pb2+ biosorption process: Characterization and mechanism

Extracellular polymeric substances (EPSs) are macromolecular polymers formed by metabolic secretion, and they have great potential for removing heavy metal (HM) ions from the aquatic phase. In this study, the contributions of soluble EPSs (S-EPSs), loosely bound EPSs (LB-EPSs) and tightly bound EPSs (TB-EPSs) secreted by Enterobacter sp. to Cd²⁺ and Pb²⁺ adsorption were analyzed. The results indicated that in a solution containing both Cd²⁺ and Pb²⁺, pH= 6.0 was best suited for the adsorption process, and adsorption equilibrium was reached in approximately 120 min. Moreover, the mechanism for adsorption of Cd²⁺ and Pb²⁺ by the different layers of EPSs involved spontaneous chemical processes. However, Cd²⁺ adsorption by the three layers of the EPSs was an exothermic process (∆H⁰ <0), but Pb²⁺ adsorption by the three layers of the EPSs was an endothermic process (∆H⁰ >0). The variations in zeta potentials indicated that ion exchange occurred during Cd²⁺ and Pb²⁺ adsorption. FT-IR, XPS and 3D-EEM analyses indicated that the functional groups of the EPSs involved in adsorption were mainly the CO, C-O and C-O-C groups of the polysaccharides; furthermore, fulvic acid-like substances, humic-like substances and tyrosine-like proteins played important roles in the adsorption of Cd²⁺ and Pb²⁺ by the different EPS layers.

Cadmium/lead tolerance of six Dianthus species and detoxification mechanism in Dianthus spiculifolius

Toxic heavy metal contaminants seriously affect plant growth and human health. Reducing the accumulation of toxic metals by phytoremediation is an effective way to solve this environmental problem. Dianthus spiculifolius Schur is an ornamental plant with strong cold and drought tolerance. Because of its fast growth, well-developed root system, and large accumulation of biomass, D. spiculifolius has potential applications as a heavy metal hyperaccumulator. Therefore, the aim of this study was evaluate the ability of D. spiculifolius and other Dianthus species to remediate heavy metals, with an ultimate goal to identify available genetic resources for toxic metal removal. The cadmium (Cd) and lead (Pb) tolerance and accumulation of six Dianthus species were analyzed comparatively in physiological and biochemical experiments. Compared with the other Dianthus species, D. spiculifolius showed higher tolerance to, and greater accumulation of, Cd and Pb. Second-generation transcriptome analysis indicated that glutathione transferase activity was increased and the glutathione metabolism pathway was enriched with genes encoding antioxidant enzymes (DsGST, DsGST3, DsGSTU10, DsGGCT2-1, and DsIDH-2) that were up-regulated under Cd/Pb treatment by RT-qPCR in D. spiculifolius. When expressed in yeast, DsGST, DsGST3, DsGSTU10 and DsIDH-2 enhanced Cd or Pb tolerance. These results indicate that D. spiculifolius has potential applications as a new ornamental hyperaccumulator plant, and that antioxidant enzymes might be involved in regulating Cd/Pb accumulation and detoxification. The findings of this study reveal some novel genetic resources that can be used to breed new plant varieties that tolerate and accumulate heavy metals.