Anionically reinforced hydrogel network entrapped fungal cells for retention of cadmium in the contaminated aquatic media

Revisiting biochemical pathways for lead and cadmium tolerance by domain bacteria, eukarya, and their joint action in bioremediation

With the advent rise is in urbanization and industrialization, heavy metals (HMs) such as lead (Pb) and cadmium (Cd) contamination have increased considerably. It is among the most recalcitrant pollutants majorly affecting the biotic and abiotic components of the ecosystem like human well-being, animals, soil health, crop productivity, and diversity of prokaryotes (bacteria) and eukaryotes (plants, fungi, and algae). At higher concentrations, these metals are toxic for their growth and pose a significant environmental threat, necessitating innovative and sustainable remediation strategies. Bacteria exhibit diverse mechanisms to cope with HM exposure, including biosorption, chelation, and efflux mechanism, while fungi contribute through mycorrhizal associations and hyphal networks. Algae, especially microalgae, demonstrate effective biosorption and bioaccumulation capacities. Plants, as phytoremediators, hyperaccumulate metals, providing a nature-based approach for soil reclamation. Integration of these biological agents in combination presents opportunities for enhanced remediation efficiency. This comprehensive review aims to provide insights into joint action of prokaryotic and eukaryotic interactions in the management of HM stress in the environment.

Mycoremediation of heavy metals: processes, mechanisms, and affecting factors

Industrial processes and mining of coal and metal ores are generating a number of threats by polluting natural water bodies. Contamination of heavy metals (HMs) in water and soil is the most serious problem caused by industrial and mining processes and other anthropogenic activities. The available literature suggests that existing conventional technologies are costly and generated hazardous waste that necessitates disposal. So, there is a need for cheap and green approaches for the treatment of such contaminated wastewater. Bioremediation is considered a sustainable way where fungi seem to be good bioremediation agents to treat HM-polluted wastewater. Fungi have high adsorption and accumulation capacity of HMs and can be potentially utilized. The most important biomechanisms which are involved in HM tolerance and removal by fungi are bioaccumulation, bioadsorption, biosynthesis, biomineralisation, bioreduction, bio-oxidation, extracellular precipitation, intracellular precipitation, surface sorption, etc. which vary from species to species. However, the time, pH, temperature, concentration of HMs, the dose of fungal biomass, and shaking rate are the most influencing factors that affect the bioremediation of HMs and vary with characteristics of the fungi and nature of the HMs. In this review, we have discussed the application of fungi, involved tolerance and removal strategies in fungi, and factors affecting the removal of HMs.

Sonochemical synthesis of ZnS nanolayers on the surface of microbial cells and their application in the removal of heavy metals

In order to improve the adsorption performance of microorganisms, we synthesized a novel material - phanerochaete chrysosporium cells covered with a layer of ZnS nanoparticles (ZnS-cells). The preparation of the ZnS-cells is based on the Sonochemical method to synthesize the ZnS nanoparticle layer on the surface of the microbial cells. The ZnS-cells were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). Characterization results showed that wurtzite ZnS was coated on the cell surface in the form of nanoclusters by sonochemical reaction, and the formation of ZnS was related to the carboxyl group on the cell surface. Batch experiments showed that the ZnS-cells exhibited high adsorption efficiency for Pb²⁺and Cd²⁺, the removal rate of Pb²⁺ and Cd²⁺ by ZnS-cells was 140 % and 160 % higher than that of pure P. chrysosporium, respectively. Studies on the adsorption mechanism showed that the removal of heavy metals by ZnS-cells mainly depended on the complexation of surface functional groups on the surface of the cells and the ion exchange of ZnS nanofilms.

Fungal cell with artificial metal container for heavy metals biosorption: Equilibrium, kinetics study and mechanisms analysis

White-rot fungi show low-cost superiority as a promising biosorbent in heavy metal removal, but limited by its poor biosorption capacity. Herein, a novel biosorbent, functionalized Phanerochaete chrysosporium with intracellular mineral scaffold, was prepared for the biosorption of heavy metal ions. The functionalized fungi cells with intracellular mineral scaffold that serve as internal metal container exhibiting high biosorption efficiency for Pb(II) and Cd(II) ions. Adsorption isotherm models were employed to investigate the biosorption isotherm and determine the biosorption equilibrium. The Freundlich model shows better fit with the experimental data of both metal ions (R² = 0.9866 and 0.9897 for Pb(II) and Cd(II) respectively). Three kinetic models, pseudo-first-order, pseudo-second-order and intra-particle diffusion models, were used to determine the biosorption kinetics. The pseudo-second-order model shows the better fit with the experimental data, and we suggests the rate-limiting step of the biosorption could be a chemisorption step which involves sharing or exchanging of electrons between adsorbent and adsorbate. Intra-particle diffusion model study result shows the biosorption process could be divided into three steps: a fast surface adsorption stage, a slow transfer stage from external to internal, and a stage of andante reaching equilibrium. The biosorption mechanism was carefully analyzed by various characterization methods.