Bioleaching of tellurium from mine tailings by indigenous Acidithiobacillus ferrooxidans

Bioremediation of hazardous heavy metals by marine microorganisms: a recent review

Heavy metals (HMs) like Zn, Cu, Pb, Ni, Cd, and Hg, among others, play a role in several environmental problems. The marine environment is polluted by several contaminants, such as HMs. A variety of physico-chemical methods usually available for sanitation HMs remediation suffer from either limitation. Bioremediation is a promising way of dealing with HMs pollution. Microbes have the ability with various potencies to resist HMs tension. The current review discusses the main sources and influences of HMs, the role of marine microorganisms in HMs bioremediation, as well as the microbial mechanisms for HMs detoxification and transformation. This review paper aims to provide an overview of the bioremediation technologies that are currently available for the removal of HMs ions from industrial and urban effluent by aquatic organisms such as bacteria, fungi, and microalgae, particularly those that are isolated from marine areas. The primary goals are to outline various studies and offer helpful information about the most important aspects of the bioelimination techniques. The biotreatment practices have been primarily divided into three techniques based on this topic. They are biosorption, bioaccumulation, bioleaching, and biotransformation. This article gives the brief view on the research studies about bioremediation of HMs using marine microorganisms. The current review also deals with the critical issues and recent studies based on the HMs biodetoxification using aquatic microorganisms.

The cryptic step in the biogeochemical tellurium (Te) cycle: Indirect elementary Te oxidation mediated by manganese-oxidizing bacteria Bacillus sp. FF-1

Tellurium (Te) is a rare element within the chalcogen group, and its biogeochemical cycle has been studied extensively. Tellurite (Te(IV)) is the most soluble Te species and is highly toxic to organisms. Chemical or biological Te(IV) reduction to elemental tellurium (Te0) is generally considered an effective detoxification route for Te(IV)-containing wastewater. This study unveils a previously unnoticed Te0 oxidation process mediated by the manganese-oxidizing bacterium Bacillus sp. FF-1. This bacterium, which exhibits both Mn(II)-oxidizing and Te(IV)-reducing abilities, can produce manganese oxides (BioMnOx) and Te0 (BioTe0) when exposed to Mn(II) and Te(IV), respectively. When 5 mM Mn(II) was added after incubating 0.1 mM or 1 mM Te(IV) with strain FF-1 for 16 h, BioTe0 was certainly re-oxidized to Te(IV) by BioMnOx. Chemogenic and exogenous biogenic Te0 can also be oxidized by BioMnOx, although at different rates. This study highlights a new transformation process of tellurium species mediated by manganese-oxidizing bacteria, revealing that the environmental fate and ecological risks of Te0 need to be re-evaluated.

A comprehensive review of bioleaching optimization by statistical approaches: recycling mechanisms, factors affecting, challenges, and sustainability

A serious environmental problem is associated with the accumulation of solid waste on the Earth. Researchers are encouraged to find an efficient and sustainable method to recover highly profitable heavy metals and precious and base metals. Bioleaching is a green method of recovering valuable metals from solid waste. Optimizing the variables and conditions of the bioleaching process is crucial to achieving maximum metal recovery most cost-effectively. The conventional optimization method (one factor at a time) is well-studied. However, it has some drawbacks, such as the necessity of more experiments, the need to spend more time, and the inability to illuminate the synergistic effect of the variables. Optimization studies are increasingly utilizing response surface methodology (RSM) because it provides details about the interaction effects of variables with fewer experiments. This review discusses the application of RSM for bioleaching experiments from other solid wastes. It discusses the Central Composite and Box-Behnken designs as the most commonly used designs for optimizing bioleaching methods. The most influential factors for increasing the heavy metal recovery rate in applying RSM using the bioleaching process are recognized, and some suggestions are made for future research.

Microbial mechanisms to transform the super-trace element tellurium: a systematic review and discussion of nanoparticulate phases

Tellurium is a super-trace metalloid on Earth. Owing to its excellent physical and chemical properties, it is used in industries such as metallurgy and manufacturing, particularly of semiconductors and - more recently - solar panels. As the global demand for tellurium rises, environmental issues surrounding tellurium have recently aroused concern due to its high toxicity. The amount of tellurium released to the environment is increasing, and microorganisms play an important role in the biogeochemical cycling of environmental tellurium. This review focuses on novel developments on tellurium transformations driven by microbes and includes the following sections: (1) history and applications of tellurium; (2) toxicity of tellurium; (3) microbial detoxification mechanisms against soluble tellurium anions including uptake, efflux and methods of reduction, and reduced ability to cope with oxidation stress or repair damaged DNA; and (4) the characteristics and applications of tellurium nanoparticles (TeNPs) produced by microbes. This review raises the awareness of microorganisms in tellurium biogeochemical cycling and the growing applications for microbial tellurium nanoparticles.