Biosorbents for heavy metals removal and their future

Microbes play key geoactive roles in the biosphere, particularly in the areas of element biotransformations and biogeochemical cycling, metal and mineral transformations, decomposition, bioweathering, and soil and sediment formation. All kinds of microbes, including prokaryotes and eukaryotes and their symbiotic associations with each other and 'higher organisms', can contribute actively to geological phenomena, and central to many such geomicrobial processes are transformations of metals and minerals. Microbes have a variety of properties that can effect changes in metal speciation, toxicity and mobility, as well as mineral formation or mineral dissolution or deterioration. Such mechanisms are important components of natural biogeochemical cycles for metals as well as associated elements in biomass, soil, rocks and minerals, e.g. sulfur and phosphorus, and metalloids, actinides and metal radionuclides. Apart from being important in natural biosphere processes, metal and mineral transformations can have beneficial or detrimental consequences in a human context. Bioremediation is the application of biological systems to the clean-up of organic and inorganic pollution, with bacteria and fungi being the most important organisms for reclamation, immobilization or detoxification of metallic and radionuclide pollutants. Some biominerals or metallic elements deposited by microbes have catalytic and other properties in nanoparticle, crystalline or colloidal forms, and these are relevant to the development of novel biomaterials for technological and antimicrobial purposes. On the negative side, metal and mineral transformations by microbes may result in spoilage and destruction of natural and synthetic materials, rock and mineral-based building materials (e.g. concrete), acid mine drainage and associated metal pollution, biocorrosion of metals, alloys and related substances, and adverse effects on radionuclide speciation, mobility and containment, all with immense social and economic consequences. The ubiquity and importance of microbes in biosphere processes make geomicrobiology one of the most important concepts within microbiology, and one requiring an interdisciplinary approach to define environmental and applied significance and underpin exploitation in biotechnology.

http://dzumenvis.nic.in/Physiology/pdf/Metals,%20minerals%20and%20microbes.pdf

Metals, minerals and microbes: geomicrobiology and bioremediation

The loss of carbon from roots (rhizodeposition) and the consequent proliferation of microorganisms in the surrounding soil, coupled with the physical presence of a root and processes associated with nutrient uptake, gives rise to a unique zone of soil called the rhizosphere. In this review, we bring together evidence to show that roots can directly regulate most aspects of rhizosphere C flow either by regulating the exudation process itself or by directly regulating the recapture of exudates from soil. Root exudates have been hypothesized to be involved in the enhanced mobilization and acquisition of many nutrients from soil or the external detoxification of metals. With few exceptions, there is little mechanistic evidence from soil-based systems to support these propositions. We conclude that much more integrated work in realistic systems is required to quantify the functional significance of these processes in the field. We need to further unravel the complexities of the rhizosphere in order to fully engage with key scientific ideas such as the development of sustainable agricultural systems and the response of ecosystems to climate change. Contents I. Introduction 460 II. What is rhizodeposition? 460 III. Regulation of rhizodeposition 460 IV. How large is the root exudation C flux? 463 V. How responsive is the root exudation C flux? 463 VI. How responsive is the microbial community to root exudation? 464 VII. The role of root exudates in nutrient acquisition 464 VIII. Mycorrhizal fungi and rhizodeposition 471 IX. Future thoughts 474 Acknowledgements 474 References 474.

https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/j.1469-8137.2004.01130.x

Plant and mycorrhizal regulation of rhizodeposition

Biosorption of heavy metals by Saccharomyces cerevisiae: a review.

Polycyclic Hydrocarbons Vol. 1. Pp. xxvi + 487. 126S. (With a chapter on carcinogenesis by Regina Schoental.) Vol. 2. Pp. lvii + 487. 140s. By E. Clar. (London and New York: Academic Press; Berlin: Springer-Verlag, 1964.)

Polycyclic Aromatic Hydrocarbons

An interactive metal-based potentiometric titration method has been developed using an ion selective electrode for studying the sorption of metal cations The accuracy of this technique was verified by analyzing the metal sorption mechanism for the biomass of Rhizopus arrhizus fungus and diatomite, two dissimilar materials (organic and mineral, strong sorbent and weak sorbent) of a different order of cation exchange capacity The problem of the initial electrochemical potential was addressed identifying the usefulness of a Na-sulfonic resin as a strong chelating agent applied before the beginning of sorption titration experiments so that the titration curves and the sorption uptake could be quantitatively compared The resin stabilized the initial electrochemical potential to � 405 ± 5 mV corresponding to 2 l gl � 1 of lead concentration in solution The amounts of lead sorbed by R arrhizus biomass and diatomite were 09 mmol g � 1 (Ce = 516 · 10 � 2 mM) and 0052 mmol g � 1 (Ce = 597 · 10 � 2 mM), respectively Lead sorption by the fungal biomass was pinpointed to at least two types of chemical active sites The first type was distinguished by high reactivity and a low number of sites whereas the other was characterized by their higher number and lower reactivity � 2005 Elsevier Ltd All rights reserved

Short Communication Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process

Une technique originale pour suivre l'oxydation bactérienne d'une pyrite : les électrodes en sachets

Pyrite by Thiobacillus ferrooxidans Corrosion and Electrochemical Oxidation of a

In the saline paddy soils of Thailand, four bacterial consortia (S1, S2, S6, and S8) were isolated in paddy soils and then selected for their abilities and efficiencies to reduced iron oxyhydroxyde (goethite) at different concentration of salt in culture medium. In this study, the effect of salinity on the structure and activities of bacterial consortia involved in iron reduction process were studied at two saline concentrations (0 and 3% NaCl). The results show that the bacterial consortia presented different behaviors in the presence or absence of salt. The bacterial consortia S1 and S2 were not affected by the presence of salt. Bacterial consortium S6 had a higher iron-reducing activity under saline conditions than in a non-saline environment. The iron reducing activity of the bacterial consortium S8 was inhibited by the presence of salt but not fermentation processes. In this rice fields, the presence of diverse halosensitive to slightly halophilic bacterial groups and also of bacteria presenting both fermentative and iron-respiring metabolisms are able to maintain a strong ability in iron-reduction and dissolution under changing saline environmental conditions.

Jacques Berthelin

Papers

Short Communication Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process

Une technique originale pour suivre l'oxydation bactérienne d'une pyrite : les électrodes en sachets

Pyrite by Thiobacillus ferrooxidans Corrosion and Electrochemical Oxidation of a

Structure and Activity of Fe(III)-Reducing Microorganism Occurring in Paddy Fields of Thailand