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

The Synergistic Effect of Biosynthesized Silver Nanoparticles and Phytocompound as a Novel Approach to the Elimination of Pathogens

Due to the wide applications of silver nanoparticles (AgNPs), research on their ecological synthesis has been extensive in recent years. In our study, biogenic silver nanoparticles were synthesized extracellularly using the white rot fungus Trametes versicolor via two cultivation methods: static and shaking. The cell filtrate of the fungus was used as a reducing agent in the process of nanoparticle synthesis. Characterization of the obtained nanoparticles was carried out using UV-VIS spectroscopy and scanning electron microscopy. The biosynthesized nanoparticles have antimicrobial potential against pathogenic bacteria, particularly in Gram-negative strains. The bactericidal effect was obtained for E. coli at a concentration of 7 µg/mL. The use of higher concentrations of compounds was necessary for Gram-positive bacteria. Taking into account the problem of the risk of cytotoxicity of AgNPs, combined therapy using a phytochemical was used for the first time, which was aimed at reducing the doses of nanoparticles. The most representative synergistic effect was observed in the treatment of 5 µg/mL silver nanoparticles in combination with 15 µg/mL ursolic acid against E. coli and P. aeruginosa with a bactericidal effect. Moreover, the coadministration of nanoparticles considerably reduced the growth of both Staphylococcus strains, with a bactericidal effect against S. aureus. The viability test confirmed the strong synergistic effect of both tested compounds. Silver nanoparticles synthesized using the T. versicolor showed excellent antibacterial potential, which opens perspectives for future investigations concerning the use of the nanoparticles as antimicrobials in the areas of health.

Optimizing the microbial synthesis of silver nanoparticles using Gloeophyllum striatum and their antimicrobial potential evaluation

The search for new sources of silver nanoparticles (AgNPs) is highly relevant in many fields. Mycosynthesis seems to be advantageous for large-scale production, and using brown rot fungi might be a promising solution. In this study, AgNP synthesis using Gloeophyllum striatum DSM 9592 was performed under various process conditions. The resulting AgNPs were characterized using UV/Vis, FT-IR, SEM and NTA techniques and their biological activities were determined. It was found that different synthesis conditions changed the production efficiency, which was the highest in 28 s AgNPs. Moreover, temperature and shaking conditions slightly affected the activity of the resulting AgNP types. Gram-negative bacteria were generally more susceptible to the action of AgNPs with MIC values two- or three-fold lower compared to Gram-positive strains. Pseudomonas aeruginosa was the most sensitive among tested strains with a MIC value of 1.56 µg/ml. The research was additionally extended by the biofilm formation assay for this strain. It was found that AgNPs of all types led to a reduction in biofilm-forming capability of P. aeruginosa over the tested concentration range. Haemolytic and cytotoxic activity assays showed that synthesis conditions also affected AgNP toxicity. For instance, 4 ns AgNPs were the least cytotoxic and cause less than 50% reduction of fibroblast viability in the concentration that inhibits the growth of P. aeruginosa completely. These results highlight the possible utility of mycogenic silver nanoparticles as an antibacterial agent in antiseptics or other external treatments.

The potential of white-rot fungi for algal control: Mechanisms, Strategies, and Challenges

As human society and industrialization have progressed, harmful algal blooms have contributed to global ecological pollution which makes the development of a novel and effective algal control strategy imminent. This is because existing physical and chemical methods for dealing with the problem have issues like cost and secondary pollution. Benefiting from their environmentally friendly and biocompatible properties, white-rot fungi (WRF) have been studied to control algal growth. WRF control algae by using algae for carbon or nitrogen, antagonism, and enhancing allelopathies. It can be better applied to practice by immobilization. This paper reviews the mechanism for WRF control of algae growth and its practical application. It demonstrates the limitations of WRF controlling algae growth and aids the further study of biological methods to regulate eutrophic water in algae growth research. In addition, it provides theoretical support for the fungi controlling algae growth.

Tanning Wastewater Sterilization in the Dark and Sunlight Using Psidium guajava Leaf-Derived Copper Oxide Nanoparticles and Their Characteristics

Employing Psidium guajava (P. guajava) extract from leaves, copper oxide nanoparticles (CuO NPs), likewise referred to as cupric oxide and renowned for their sustainable and harmless biogenesis, have the possibility of being useful for the purification of pollutants as well as for medicinal purposes. The current study examined the generated CuO NPs and their physical qualities by using ultraviolet-visible (UV) spectroscopy. The distinctive peak at 265 nm of the CuO NP production was originally seen. Additionally, an X-ray diffraction (XRD) investigation was conducted to identify the crystalline arrangement of the produced CuO NPs, and a Fourier transform infrared (FTIR) spectroscopy examination was performed to validate the functional compounds of the CuO NPs. Additionally, the synthesized nanoparticles' catalytic activities (wastewater treatment) were analyzed in dark and sunlight modes. The catalytic properties of CuO NPs in total darkness resulted in 64.21% discoloration, whereas exposure to sunshine increased the nanomaterials' catalyst performance to 92.31%. By lowering Cr(VI), Ni, Pb, Co, and Cd in sewage by proportions of 91.4, 80.8, 68.26, 73.25, and 72.4% accordingly, the CuO NP demonstrated its effectiveness as a nanosorbent. Total suspended solids (TSS), total dissolved solids (TDS), chemical oxygen demand (COD), biological demand for oxygen (BOD), and conductance were all successfully reduced by nanotreatment of tanning effluents, with proportion reductions of 93.24, 88.62, 94.21, 87.5, and 98.3%, correspondingly.

Tramates trogii biomass in carboxymethylcellulose-lignin composite beads for adsorption and biodegradation of bisphenol A

Tramates trogii biomass was immobilized in carboxymethyl cellulose-lignin composite beads via cross-linking with Fe(III) ions (i.e., Fe(III)-CMC@Lig(1-4)@FB). The composite beads formulations were used for the adsorption and degradation of bisphenol A (BPA) using the free fungal biomass as a control system. The maximum adsorption capacity of the free fungal biomass and Fe(III)-CMC@Lig-3@FB for BPA was found to be 57.8 and 95.6, mg/g, respectively. The degradation rates of BPA were found to be 87.8 and 89.6% for the free fungal biomass and Fe(III)CMC@Lig-3@FB for 72 h in a batch reactor, respectively. Adsorption of BPA on the free fungal biomass and Fe(III)CMC@Lig-3@FB fungal preparations described by the Langmuir and Temkin isotherm models, and the pseudo-second-order kinetic model. The values of Gibbs free energy of adsorption (ΔG°) were - 20.7 and - 25.8 kJ/mol at 298 K for BPA on the free fungal biomass and Fe(III)-CMC@Lig-3@FB beads, respectively. Moreover, the toxicities of the BPA and degradation products were evaluated with three different test organisms: (i) a freshwater micro-crustacean (Daphnia magna), (ii) a freshwater algae (Chlamydomonas reinhardti), and (iii) a Turkish winter wheat seed (Triticum aestivum L.). After treatment with the Fe(III)CMC@Lig-3@FB formulation, the degradation products had not any significant toxic effect compared to pure BPA. This work shows that the prepared composite bioactive system had a high potential for degradation of BPA from an aqueous medium without producing toxic end-products. Thus, it could be a good candidate for environmentally safe biological methods.

Diversity of Biogenic Nanoparticles Obtained by the Fungi-Mediated Synthesis: A Review

Fungi are very promising biological objects for the green synthesis of nanoparticles. Biogenic synthesis of nanoparticles using different mycological cultures and substances obtained from them is a promising, easy and environmentally friendly method. By varying the synthesis conditions, the same culture can be used to produce nanoparticles with different sizes, shapes, stability in colloids and, therefore, different biological activity. Fungi are capable of producing a wide range of biologically active compounds and have a powerful enzymatic system that allows them to form nanoparticles of various chemical elements. This review attempts to summarize and provide a comparative analysis of the currently accumulated data, including, among others, our research group's works, on the variety of the characteristics of the nanoparticles produced by various fungal species, their mycelium, fruiting bodies, extracts and purified fungal metabolites.

Microalgae Harvesting after Tertiary Wastewater Treatment with White-Rot Fungi

Tertiary wastewater treatment with microalgae incorporates environmental sustainability with future technologies and high exploitation costs. Despite the apparent ecological benefits of microalgae-assisted wastewater treatment/biomass-based resource production, technological improvements are still essential to compete with other technologies. Bio-flocculation instead of mechanical harvesting has been demonstrated as an alternative cost-effective approach. So far, mostly filamentous fungi of genus Aspergillus have been used for this purpose. Within this study, we demonstrate a novel approach of using white-rot fungi, with especially high potential of algae-Irpex lacteus complex that demonstrates efficiency with various microalgae species at a broad range of temperatures (5-20 °C) and various pH levels. Harvesting of microalgae from primary and secondary wastewater resulted in 73-93% removal efficiencies within the first 24 h and up to 95% after 48 h. The apparent reuse potential of the algae-I. lacteus pellets further complements the reduced operating costs and environmental sustainability of bio-flocculation technology.

Insights into the recent advances in nano-bioremediation of pesticides from the contaminated soil

In the present scenario, the uncontrolled and irrational use of pesticides is affecting the environment, agriculture and livelihood worldwide. The excessive application of pesticides for better production of crops and to maintain sufficient food production is leading to cause many serious environmental issues such as soil pollution, water pollution and also affecting the food chain. The efficient management of pesticide use and remediation of pesticide-contaminated soil is one of the most significant challenges to overcome. The efficiency of the current methods of biodegradation of pesticides using different microbes and enzymes depends on the various physical and chemical conditions of the soil and they have certain limitations. Hence, a novel strategy is the need of the hour to safeguard the ecosystem from the serious environmental hazard. In recent years, the application of nanomaterials has drawn attention in many areas due to their unique properties of small size and increased surface area. Nanotechnology is considered to be a promising and effective technology in various bioremediation processes and provides many significant benefits for improving the environmental technologies using nanomaterials with efficient performance. The present article focuses on and discusses the role, application and importance of nano-bioremediation of pesticides and toxic pollutants to explore the potential of nanomaterials in the bioremediation of hazardous compounds from the environment.

Leachate treatment potential of nanomaterial based assemblies: a systematic review on recent development

Rapid development of the population has brought about a serious problem of waste generation and management. Open dumping and land filling are two of the preferred options for waste management and treatment. As a consequence of this, the accumulation of leachates has become one of the concerns for environmental sustainability. In this regard, various treatment methodologies have been developed in recent decades. Among them, the nanomaterial-based approaches are the emerging ones in the current scenario due to their various unique properties. Furthermore, nanomaterial-based assemblies (i.e., nanomaterials combined with microbes, chemical catalysts, enzymes, and so on) have been introduced as a novel modification for leachate treatment. This work, therefore, has been dedicated to comprehensively reviewing all nanomaterial based leachate treatment techniques. In this regard, the first part of this review will discuss the nano catalyst, nano adsorbent along with their synthesis and mechanistic view of pollutant removal potential. In the second part, the nanomaterial-based microbial conjugates applied in the leachate treatments have been discussed. Apart from this, various other nanomaterial-based methods have been discussed in the third part of the review. Hence this review is providing an insight of all the recent developments pertaining to the nano material based leachate treatment techniques.

Enhanced degradation capability of white-rot fungi after short-term pre-exposure to silver ion: Performance and selectively antimicrobial mechanisms

Azo dyes in wastewater have great threats to environment and human health. White-rot fungi (WRF) have broad-spectrum potential for such refractory organics bioremediation; however, their applications are largely restrained by the poor viability owning to microbial invasion under non-sterile conditions. In this study, short-term pre-exposure to silver ion (Ag⁺) was demonstrated to be a practical, economic, and green method to enhance the perdurability of azo dyes decoloration by WRF Phanerochaete chrysosporium under non-sterile conditions. In control (without Ag⁺ pre-exposure), decoloration deactivated since cycle 7 (<10%), whereas in Ag⁺ pre-exposure groups, the decoloration ratios remained 91.5%-94.7% after 7 cycles. Variations in decoloration-related extracellular lignin enzyme activities were consistent with the decoloration effectiveness. The enhanced decoloration capability in Ag⁺ pre-exposure groups under non-sterile conditions could be ascribed to the selectively antimicrobial action by Ag⁺. The released Ag⁺ from the self-assembled silver nanoparticles (AgNPs) could selectively "stimulate" the proliferation and viability of P. chrysosporium, and simultaneously inhibit the growths of invasive microorganisms. The pyrosequencing results indicated that genus Sphingomonas (24.1%-31.3%) was the main invasive bacteria in Ag⁺ pre-exposure groups after long-term operation owing to the AgNPs passivation. As control, the invasive fungi (Asterotremella humicola) and bacteria (Burkholderia spp.) occurred in control after short-term operation, and genus Burkholderia (74.9%) dominated after long-term operation, leading to decoloration deactivation. Overall, these findings offer a new insight into the bio-nano interactions between WRF and invasive microorganisms in response to Ag⁺ or biogenic AgNPs, and could extend WRF application perspective under non-sterile conditions in future.

Bibliometric analysis of global research on white rot fungi biotechnology for environmental application

In recent years, white rot fungi (WRFs) have received tremendous attention as a biotechnological tool for environmental pollution control. In order to systematically and comprehensively describe the progress, trends, and hotspots of WRF biotechnology in the field of environmental pollution control, the 3967 related publications from 2003 to 2020 were collected from Web of Science Core Collection database, and the bibliometric characteristics including publication output, country, institution, journal, author, citation frequency, h-index, and research focus were evaluated by using Excel 2007, CiteSpace V, and VOSviewer. The results indicated that the number of research publications increased rapidly before 2009, but after that, the number of publications fluctuated in a certain range. China and USA were the most productive countries and the most active country in international cooperation. In this field, most authors tend to cooperate within a small group. The journal and subject category with the largest number of publications are "International Biodeterioration & Biodegradation" and "Biotechnology Applied Microbiology", respectively. The analysis of high-frequency keywords revealed that "laccase", "biodegradation", "decolorization", and "Phanerochaete chrysosporium" were the most cited terms among all publications. The pretreatment of biomass waste, decolorization of dye wastewater, and bioremediation of polluted environment are the key research directions of WRF biotechnology. Finally, the frontier topics and active authors in this research field were identified using burst detection. We believe that this bibliometric study provides a comprehensive and systematic overview and promoted the future cooperative research and knowledge exchange in this field of WRF biotechnology for environmental applications.

Detection and remediation of pollutants to maintain ecosustainability employing nanotechnology: A review

Environmental deterioration due to anthropogenic activities is a threat to sustainable, clean and green environment. Accumulation of hazardous chemicals pollutes soil, water and air and thus significantly affects all the ecosystems. This article highlight the challenges associated with various conventional techniques such as filtration, absorption, flocculation, coagulation, chromatographic and mass spectroscopic techniques. Environmental nanotechnology has provided an innovative frontier to combat the aforesaid issues of sustainable environment by reducing the non-requisite use of raw materials, electricity, excessive use of agrochemicals and release of industrial effluents into water bodies. Various nanotechnology based approaches including surface enhance scattering, surface plasmon resonance; and distinct types of nanoparticles like silver, silicon oxide and zinc oxide have contributed significantly in detection of environmental pollutants. Biosensing technology has also gained significant attention for detection and remediation of pollutants. Furthermore, nanoparticles of gold, ferric oxide and manganese oxide have been used for the on-site remediation of antibiotics, organic dyes, pesticides, and heavy metals. Recently, green nanomaterials have been given more attention to address toxicity issues of chemically synthesized nanomaterials. Hence, nanotechnology has provided a platform with tremendous applications to have sustainable environment for present as well as future generations. This review article will help to understand the fundamentals for achieving the goals of sustainable development, and healthy environment.

Antimicrobial activity and toxicological risk assessment of silver nanoparticles synthesized using an eco-friendly method with Gloeophyllum striatum

Recently, nanomaterials synthesized ecologically using microorganisms have attracted much interest. In the present study, the ability of Gloeophyllum striatum to synthesize silver nanoparticles is described for the first time. Nanoparticles were formed in an eco-friendly extracellular manner and characterized by UV-Vis, FT-IR, MADLS and SEM techniques. The obtained nanoparticles showed excellent activity against gram-positive and gram-negative bacteria. The MIC values for gram-negative bacteria were 15 µM, while for gram-positive strains they reached 30 µM. The haemolytic and cytotoxic activities of the synthesized nanoparticles towards mammalian cells were also determined. The addition of AgNPs at the concentrations above 30 µM caused 50% haemolysis of red blood cells after they 24-hour incubation. A decrease in the viability of fibroblasts by over 50% was also found in the samples treated with nanoparticles at the concentrations above 30 µM. The ecotoxicological risk of silver nanoparticles was assessed using A. franciscana and D. magna crustaceans as well as L. sativum plants. The EC₅₀ values for A. franciscana and D. magna were 61.97 and 0.275 µM, respectively. An about 20% reduction in the length of L. sativum shoots and roots was noted after the treatment with AgNPs at the concentration of 100 µM.

Applications of Fusarium solani YMM20 in bioremediation of heavy metals via enhancing extracellular green synthesis of nanoparticles

A novel technique for removing metals from water, by converting them into nanoparticles using the culture filtrate of Fusarium solani YMM20, followed by their removal by centrifugation was developed in this study. It is a promising, simple, and eco-friendly process for the bioremediation of wastewater. This method is built on the reduction of metal ions by cell-free fungal filtrate protein(s). The chitosan and chitosan nanoparticles were used as adsorbents for the removal of Cu²⁺ , Pb²⁺ , Co²⁺ , Cd²⁺ , Ni²⁺ , and Fe²⁺ , separately. In addition, fungal filtrate and chitosan nanoparticles loaded with fungal filtrate were used for the biosynthesis of metal nanoparticles of Cu²⁺ , Pb²⁺ , Co²⁺ , Cd²⁺ , Ni²⁺ , and Fe²⁺ , separately for their removal. The fungal filtrate approach has the highest metal removal (%) for most metals. Among the six metal ions, the fungal filtrate, chitosan nanoparticles loaded with fungal filtrate, chitosan, and chitosan nanoparticles showed the highest removal (%) for Pb²⁺ and the lowest removal (%) for Co²⁺ . Techniques such as transmission electron microscopy, scanning electron microscopy, and Zeta potential measurements were used to characterize the obtained nanoparticles. The average size of the spherical nanoparticles observed by transmission electron microscopy was from 18.938 ± 2.269 nm to 60.175 ± 4.973 nm.

White-rot fungus mediated green synthesis of zinc oxide nanoparticles and their impregnation on cellulose to develop environmental friendly antimicrobial fibers

An economic, eco-friendly and efficient synthesis route for Zinc oxide (ZnO) nanoparticles (NPs) using fungus Phanerochaete chrysosporium has been explored along with the single-step impregnation of these nanoparticles on cellulose fibers. The transmission electron microscopy confirmed 50 nm as an average size of ZnO NPs and showed the presence of hexagonal phases. ZnO NPs-cellulose composite was fabricated by amending sugarcane bagasse-extracted cellulose in the reaction mixture during the nanoparticle synthesis. The composite was characterized using Fourier transform infrared, X-ray diffraction patterns, Scanning electron microscopy, and Energy dispersive spectroscopy, thermogravimetric analysis, and also evaluated for its antimicrobial potential. The analyses revealed that well-dispersed hexagonal wurtzite ZnO NPs were present on the surface of the cellulose fibers. ZnO NPs-cellulose demonstrated antibacterial activity against Staphylococcus aureus and Escherichia coli, and antifungal activity against Aspergillus niger , Geotrichum candidum, and Phanerochaete chrysosporium. Thus, the study demonstrated an environmental friendly synthesis of ZnO NPs-cellulose composite using an economic and efficient method, which can be used for developing antimicrobial cellulosic fabric for numerous applications.

Insights into nanomycoremediation: Secretomics and mycogenic biopolymer nanocomposites for heavy metal detoxification

Our environment thrives on the subtle balance achieved by the forever cyclical nature of building and rebuilding life through natural processes. Fungi, being the evident armor of bioremediation, is the indispensable element of the soil food web, contribute to be the nature's most dynamic arsenal with non-specific enzymes like peroxidase (POX), glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), non-enzymatic compounds like thiol (-SH) groups and non-protein compounds such as glutathione (GSH) and metallothionein (MT). Recently, the area of nanomycoremediation has been gaining momentum as a powerful tool for environmental clean-up strategies with its ability to detoxify heavy metals with its unique characteristics to adapt mechanisms such as biosorption, bioconversion, and biodegradation to harmless end products. The insight into the elaborate secretomic processes provides us with huge opportunities for creating a magnificent living bioremediation apparatus. This review discusses the scope and recent advances in the lesser understood area, nanomycoremediation, the state-of-the-art, innovative, cost-effective and promising tool for detoxification of heavy metal pollutants and focuses on the metabolic capabilities and secretomics with nanobiotechnological interventions.

Synthesis of silver nanoparticles using white-rot fungus Anamorphous Bjerkandera sp. R1: influence of silver nitrate concentration and fungus growth time

Currently, silver nanoparticles (AgNPs) constitute an interesting field of study in medicine, catalysis, optics, among others. For this reason, it has been necessary to develop new methodologies that allow a more efficient production of AgNPs with better antimicrobial and biological properties. In this research growth time effects Anamorphous Bjerkandera sp. R1 and the silver nitrate (AgNO₃) concentration over AgNPs synthesis were studied. Through the protocol used in this work, it was found that the action of the capping proteins on the surface of the mycelium played a determining role in the reduction of the Ag⁺ ion to Ag⁰ nanoparticles producing a particle size that oscillated between 10 and 100 nm. The progress of the reaction was monitored using visible UV-Vis spectroscopy and the synthesized AgNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared radiation (FTIR) spectroscopy. The best synthetic properties were found at 1 mM of AgNO₃ concentration, growth time of 8 days, and reaction time of 144 h. Nanometals obtention from microorganisms could be considered as a new method of synthesis, due to reducing abilities of metal ions through its enzymatic system and represents low-cost synthesis that reduces the generation of harmful toxic wastes.

Effect of interactions between various humic acid fractions and iron nanoparticles on the toxicity to white rot fungus

Humic acid plays an important role in controlling the toxicity of nanoparticles to organisms. However, little is known about the influence of different fractions of dissolved humic acid (DHA) from soil on the toxicity of nanoparticles to organisms. The concentration of γ-Fe₂O₃ and the exposure time affected the malondialdehyde (MDA) content, reactive oxygen species (ROS) production and lactate dehydrogenase (LDH) activity in P. chrysosporium cells and were inversely proportional to the relative activities of the cells. P. chrysosporium was exposed to γ-Fe₂O₃ and DHA₁ for 3 h, 6 h and 12 h. Catalase (CAT) and peroxidase (POD) activities were generally higher than control. Particularly, under the influence of 50 mg/L DHA₁ and different concentrations of γ-Fe₂O₃ (10 and 50 mg/L), the CAT and POD activities were higher than those of cells exposed to γ-Fe₂O₃ alone. Conversely, both activities of P. chrysosporium exposed to DHA₄ combined with γ-Fe₂O₃ for 12 h were lower than those of cells exposed to γ-Fe₂O₃ alone and gradually decreased with increasing DHA₄ concentration (0, 10 and 50 mg/L). The μ-XAFS normalized spectrum indicated that Fe³⁺ entering the cells tended to transform into Fe²⁺ as the stress time prolonged. TEM analysis confirmed the toxicity of high concentrations of γ-Fe₂O₃ to P. chrysosporium. The comet assay showed that DHA₄ in soil enhanced the toxicity of γ-Fe₂O₃ to P. chrysosporium more than DHA₁ did. Namely, compared to DHA₁, DHA₄ made it easier for nano-Fe₂O₃ to enter P. chrysosporium cells, causing more toxicity of γ-Fe₂O₃ to P. chrysosporium.

Antimicrobial efficacy and mechanisms of silver nanoparticles against Phanerochaete chrysosporium in the presence of common electrolytes and humic acid

In this study, influences of cations (Na⁺, K⁺, Ca²⁺, and Mg²⁺), anions (NO₃^-, Cl^-, and SO₄^2-), and humic acid (HA) on the antimicrobial efficacy of silver nanoparticles (AgNPs)/Ag⁺ against Phanerochaete chrysosporium were investigated by observing cell viability and total Ag uptake. K⁺ enhanced the antimicrobial toxicity of AgNPs on P. chrysosporium, while divalent cations decreased the toxicity considerably, with preference of Ca²⁺ over Mg²⁺. Impact caused by a combination of monovalent and divalent electrolytes was mainly controlled by divalent cations. Compared to AgNPs, however, Ag⁺ with the same total Ag content exhibited stronger antimicrobial efficacy towards P. chrysosporium, regardless of the type of electrolytes. Furthermore, HA addition induced greater microbial activity under AgNP stress, possibly originating from stronger affinity of AgNPs over Ag⁺ to organic matters. The obtained results suggested that antimicrobial efficacy of AgNPs was closely related to water chemistry: addition of divalent electrolytes and HA reduced the opportunities directly for AgNP contact and interaction with cells through formation of aggregates, complexes, and surface coatings, leading to significant toxicity reduction; however, in monovalent electrolytes, the dominating mode of action of AgNPs could be toxic effects of the released Ag⁺ on microorganisms due to nanoparticle dissolution.

Iron-rich microorganism-enabled synthesis of magnetic biocarbon for efficient adsorption of diclofenac from aqueous solution

Microorganisms in nature have been suggested as effective synthetic platform for functional materials construction. In this study, we cultured a typical white rot fungus of Phanerochaete chrysosporium in iron-containing medium to obtain iron-rich biomass, serving as sole precursor for magnetic biocarbon synthesis. The accumulated iron in biomass reached to 4.6 wt%. After carbonization and activation, microporous magnetic biocarbon (Fe/BC) with high specific surface area of 1986 m² g^-1 was obtained. When applied as adsorbent for a model pharmaceutical (diclofenac sodium, DCF) removal from aqueous solution, a high adsorption capacity of 361.25 mg g^-1 was found for the developed Fe/BC. Systematic isotherm, kinetic, thermodynamic and recycle studies were conducted to investigate adsorption behaviors of DCF onto Fe/BC. This work not only provides a novel strategy for magnetic biocarbon construction, but also envisions new perspective on the utilization of a variety of microorganisms in nature for functional materials preparation.

Alleviation of heavy metal and silver nanoparticle toxicity and enhancement of their removal by hydrogen sulfide in Phanerochaete chrysosporium

Hydrogen sulfide (H₂S), an important cellular signaling molecule, plays vital roles in mediating responses to biotic/abiotic stresses. Influences of H₂S on metal removal, cell viability, and antioxidant response of Phanerochaete chrysosporium upon exposure to heavy metals and silver nanoparticles (AgNPs) in the present study were investigated. An enhancement in Pb(ΙΙ) removal with an increase in concentration of the H₂S donor sodium hydrosulfide (NaHS) was observed, and the maximum removal efficiencies increased by 31% and 17% under 100 and 200 mg/L Pb(ΙΙ) exposure, respectively, in the presence of 500 μM NaHS. Application of 500 μM NaHS increased the cell viability by 15%-39% under Pb(II) stress (10-200 mg/L) with relative to the untreated control. Increase in total Ag uptake and cell survival was also elicited by NaHS in a concentration-dependent manner under AgNP stress. Meanwhile, activities of superoxide dismutase and catalase were significantly enhanced with the introduction of NaHS under stresses of Pb(II), Cd(II), Cu(II), Zn(II), Ni(II), and AgNPs. The inhibition in lipid peroxidation and oxidative stress was observed in P. chrysosporium cells exposed to these toxicants following NaHS pretreatment, which could be attributed to the upregulation in antioxidant enzymes. The results obtained suggest that H₂S can alleviate heavy metals and AgNP-induced toxicity to P. chrysosporium and improve the removal efficiency of these toxicants from wastewater.

Differential behaviors of silver nanoparticles and silver ions towards cysteine: Bioremediation and toxicity to Phanerochaete chrysosporium

Potential transformations of silver nanoparticles (AgNPs) upon interaction with naturally ubiquitous organic ligands in aquatic environments influence their transport, persistence, bioavailability, and subsequent toxicity to organisms. In this study, differential behaviors of AgNPs and silver ions (Ag⁺) towards cysteine (Cys), an amino acid representative of thiol ligands that easily coordinate to Ag⁺ and graft to nanoparticle surfaces, were investigated in the aspects of bioremediation and their toxicity to Phanerochaete chrysosporium. Total Ag removal, 2,4-dichlorophenol (2,4-DCP) degradation, extracellular protein secretion, and cellular viability were enhanced to some extent after supplement of various concentrations of cysteine under stress of AgNPs and Ag⁺. However, an obvious decrease in total Ag uptake was observed after 5-50 μM cysteine addition in the groups treated with 10 μM AgNPs and 1 μM Ag⁺, especially at a Cys:Ag molar ratio of 5. More stabilization in uptake pattern at this ratio was detected under Ag⁺ exposure than that under AgNP exposure. Furthermore, in the absence of cysteine, all Ag⁺ treatments stimulated the generation of reactive oxygen species (ROS) more significantly than high-dose AgNPs did. However, cysteine supply under AgNP/Ag⁺ stress aggravated ROS levels, albeit alleviated at 100 μM Ag⁺, indicating that the toxicity profiles of AgNPs and Ag⁺ to P. chrysosporium could be exacerbated or marginally mitigated by cysteine. The results obtained were possibly associated with the lability and bioavailability of AgNP/Ag⁺-cysteine complexes.

Silver ion-enhanced particle-specific cytotoxicity of silver nanoparticles and effect on the production of extracellular secretions of Phanerochaete chrysosporium

This study investigated the influence of silver ions (Ag⁺) on the cytotoxicity of silver nanoparticles (AgNPs) in Phanerochaete chrysosporium and noted the degree of extracellular secretions in response to the toxicant's stress. Oxalate production was elicited with moderate concentrations of 2,4-dichlorophenol (2,4-DCP) and AgNPs reaching a plateau at 10 mg/L and 10 μM, respectively. Increased oxalate accumulation was accompanied by higher activities of manganese peroxidase (MnP) and lignin peroxidase (LiP). However, the secretion of oxalate, MnP and LiP was significantly inhibited owing to Ag⁺ incorporation into AgNP solution. Production of extracellular polymeric substances (EPS) significantly elevated with an increase in 2,4-DCP concentrations; however, after 24 h of exposure to 100 mg/L 2,4-DCP, an obvious decrease in EPS occurred, indicating that part of EPS could be consumed as carbon and energy sources to ameliorate biological tolerance to toxic stress. Furthermore, AgNP-induced "particle-specific" cytotoxicity was substantially enhanced with additional Ag⁺ as evidenced by its significant negative impact on cellular growth, plasma membrane integrity, and morphological preservation compared with AgNPs at equal Ag concentration.

Use of non-living lyophilized Phanerochaete chrysosporium cultivated in various media for phenol removal

The biosorption of phenol on non-living lyophilized mycelial pellets of Phanerochaete chrysosporium cultivated in liquid medium of various compositions was studied in batch biosorption system. The fungal cell surfaces were characterized by FTIR spectroscopy and specific surface charge determination. The sorption kinetics and equilibrium were evaluated using linear and non-linear regression. For adsorption equilibrium, a comparative evaluation is also presented using non-linear least-square estimation and linearization of the Langmuir and anti-Langmuir equations. The presence of mineral and vitamin materials in the liquid medium enhanced the adsorption capacity of fungal biomass for phenol. At optimum pH 5-6, the values of specific surface charge were 0.023 and 0.069 meq g^-1 for various cultivations, and the maximum amounts of phenol can be adsorbed at these pH values. The maximum adsorbed phenol amounts by cells cultivated in simple and complex media were 4.53 and 13.48 mg g^-1, respectively, at an initial phenol concentration of 100 mg l^-1. Graphical abstract ᅟ.